Stable and rugged etalon for the Dynamics Explorer Fabry-Perot interferometer. I - Design and construction

NASA Astrophysics Data System (ADS)

Rees, D.; Fuller-Rowell, T. J.; Lyons, A.; Killeen, T. L.; Hays, P. B.

1982-11-01

The cemented etalons are shown to be rugged and highly stable for high-resolution spectroscopy and to be well suited to space applications. The etalons will be of considerable value as the tuning elements of dye laser systems and as the stable spectral disperser for pulse and CW laser spectroscopy. Even for etalons 15 cm in diameter, the strength of the cemented bond is greatly in excess of the maximum steady and impulsive forces experienced from the much larger etalon plate mass (2-4 kg rather than 200 g). It is thought that the small but systematic and significant positive increment in the thermal expansion coefficient which occurs when an etalon and its spacers are cemented may be linked to the cessation of the microscopic migration that occurs with an optically contacted bond under thermal or mechanical stress. The etalon comprises two flat plates of fused silica, with spacers constructed of Zerodur (a polycrystalline glass ceramic of extremely low expansion coefficient) which are cemented together using cyanoacrylic adhesives.

Design and Construction of Airport Pavements on Expansive Soils

DTIC Science & Technology

1976-06-01

Selection of the type anc amount of stabilizing agent (lime, cement , asphalt, only) (4) Test methods to determine the physical properties of sta...7 8.3 5.4 3.3 6.5 1 4.7 3-3, 1 (8) Investigate the effect of sulfate on cement -stabilized soils and establish...terested because the properties of soil/ cement mixtures and the relationships existing among these properties and various test values are discussed

The dynamic volume changes of polymerising polymethyl methacrylate bone cement.

PubMed

Muller, Scott D; Green, Sarah M; McCaskie, Andrew W

2002-12-01

The Swedish hip register found an increased risk of early revision of vacuum-mixed cemented total hip replacements. The influence of cement mixing technique on the dynamic volume change in polymerising PMMA is not well understood and may be relevant to this observation. Applying Archimedes' principle, we have investigated the dynamic volume changes in polymerising cement and determined the influence of mixing technique. All specimens showed an overall volume reduction: hand-mixed 3.4% and vacuum-mixed 6.0%. Regression analysis of sectional porosity and volume reduction showed a highly significant relationship. Hand-mixed porous cement showed a transient volume increase before solidification. However, vacuum-mixed cement showed a progressive volume reduction throughout polymerisation. Transient expansion of porous cement occurs at the critical time of micro-interlock formation, possibly improving fixation. Conversely, progressive volume reduction of vacuum-mixed cement throughout the formation of interlock may damage fixation. Stable fixation of vacuum-mixed cement may depend on additional techniques to offset the altered volumetric behaviour of vacuum-mixed cement.

Experimental constraints on phreatic eruption processes at Whakaari (White Island volcano)

NASA Astrophysics Data System (ADS)

Mayer, Klaus; Scheu, Bettina; Gilg, H. Albert; Heap, Michael J.; Kennedy, Ben M.; Lavallée, Yan; Letham-Brake, Mark; Dingwell, Donald B.

2015-09-01

Vigorous hydrothermal activity interspersed by sequences of phreatic and phreatomagmatic eruptions occur at Whakaari (White Island volcano), New Zealand. Here, we investigate the influence of sample type (hydrothermally altered cemented ash tuffs and unconsolidated ash/lapilli) and fragmentation mechanism (steam flashing versus gas expansion) on fragmentation and ejection velocities as well as on particle-size and shape. Our rapid decompression experiments show that fragmentation and ejection speeds of two ash tuffs, cemented by alunite and amorphous opal, increase with increasing porosity and that both are significantly enhanced in the presence of steam flashing. Ejection speeds of unconsolidated samples are higher than ejection speeds of cemented tuffs, as less energy is consumed by fragmentation. Fragmentation dominated by steam flashing results in increased fragmentation energy and a higher proportion of fine particles. Particle shape analyses before and after fragmentation reveal that both steam flashing and pure gas expansion produce platy or bladed particles from fracturing parallel to the decompression front. Neither fragmentation mechanisms nor sample type show a significant influence on the shape. Our results emphasize that, under identical pressure and temperature conditions, eruptions accompanied by the process of liquid water flashing to steam are significantly more violent than those driven simply by gas expansion. Therefore, phase changes during decompression and cementation are both important considerations for hazard assessment and modeling of eruptions in hydrothermally active environments.

Hygroscopic expansion of self-adhesive resin cements and the integrity of all-ceramic crowns.

PubMed

Kirsten, Magdalena; Matta, Ragai Edward; Belli, Renan; Lohbauer, Ulrich; Wichmann, Manfred; Petschelt, Anselm; Zorzin, José

2018-04-27

Low pH neutralization and subsequent remnant hydrophilicity can lead to hygroscopic expansion of self-adhesive resin cements (SARCs) after water storage. The aim of this in vitro study was to investigate the effects of hygroscopic expansion of SARCs, used as luting and partial core build-up material, on integrity and cement gap thickness increase of all-ceramic CAD/CAM crowns. Human third molars (n=48) were prepared and anatomical all-ceramic CAD/CAM crowns were manufactured (VITABLOCS Mark II, VITA Zahnfabrik). Crowns internal surfaces were HF etched and silanized. The prepared teeth with their respective crowns were divided into 6 groups (n=8). In groups 1, 3 and 5 the coronal dentin was removed to simulate a partial core build-up. Groups 1 and 2 were luted with iCEM (Heraeus Kulzer), 3 and 4 with RelyX Unicem 2 Automix (3M), 5 and 6 with Variolink Esthetic DC (Ivoclar Vivadent). All specimens were dual cured and stored in distilled water at 37°C. Crown integrity was controlled at baseline and in regular intervals until 180 days. Cement gap thickness was measured using an optical 3D scanner (ATOS Triple scan, GOM) at baseline and after 180 days. Crown integrity was statistically analysed using Kaplan-Meier survival analysis and cement gap thickness increase using two-way ANOVA (α=0.05). After 180 days storage, crack formation was observed in all specimens of group 1 (mean survival time of 85.5 days), in one specimen of group 2 and in two specimens of group 4. Two-way ANOVA analysis revealed a statistically significant interaction between material type and build-up on cement gap size increase for iCEM. Within the limits of this study, the application of SARCs with low pH neutralization as partial build-up material under CAD/CAM crowns is not recommended for clinical use. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design : technical summary report.

DOT National Transportation Integrated Search

2011-12-01

The coefficient of thermal expansion (CTE) has been widely considered as a fundamental property of : Portland cement concrete (PCC) pavement but has never played an important role in the thickness design : procedure for PCC pavement until recently. I...

Studies on the reuse of waste printed circuit board as an additive for cement mortar.

PubMed

Ban, Bong-Chan; Song, Jong-Yoon; Lim, Joong-Yeon; Wang, Soo-Kyoon; An, Kwang-Guk; Kim, Dong-Su

2005-01-01

The recent development in electronic industries has generated a drastic increase in production of printed circuit boards (PCB). Accordingly, the amount of waste PCB from electronic productions and waste electronics and its environmental impact such as soil and groundwater contamination have become a great concern. This study aims to propose a method for reuse of waste PCB as an additive for cement mortar. Although the expansibility of waste PCB powder finer than 0.08 mm in water was observed to be greater than 2.0%, the maximum expansion rates in water for 0.08 to approximately 0.15 and 0.15 to approximately 0.30 mm sized PCB powders were less than 2.0%, which satisfied the necessary condition as an alternative additive for cement mortar in place of sand. The difference in the compressive strength of standard mortar and waste PCB added mortar was observed to be less than 10% and their difference was expected to be smaller after prolonged aging. The durability of waste PCB added cement mortar was also examined through dry/wet conditioning cyclic tests and acidic/alkaline conditioning tests. From the tests, both weight and compressive strength of cement mortar were observed to be recovered with aging. The leaching test for heavy metals from waste PCB added mortar showed that no heavy metal ions such as copper, lead, or cadmium were detected in the leachate, which resulted from fixation effect of the cement hydrates.

Cement Type Influence on Alkali-Silica Reaction in Concrete with Crushed Gravel Aggregate

NASA Astrophysics Data System (ADS)

Rutkauskas, A.; Nagrockienė, D.; Skripkiūnas, G.

2017-10-01

Alkali-silica reaction is one of the chemical reactions which have a significant influence for durability of concrete. During alkali and silica reaction, silicon located in aggregates of the concrete, reacts with high alkali content. This way in the micropores of concrete is forming hygroscopic gel, which at wet environment, expanding and slowly but strongly destroying concrete structures. The goal of this paper- to determine the influence of cement type on alkali-silica reaction of mortars with crushed gravel. In the study crushed gravel with fraction 4/16 mm was used and four types of cements tested: CEM I 42.5 R; CEM I 42.5 SR; CEM II/A-S 42.5; CEM II/A-V 52.5. This study showed that crushed gravel is low contaminated on reactive particles containing of amorphous silica dioxide. The expansion after 14 days exceed 0.054 %, by RILEM AAR-2 research methodology (testing specimen dimension 40×40×160 mm). Continuing the investigation to 56 days for all specimens occurred alkaline corrosion features: microcracking and the surface plaque of gel. The results showed that the best resistance to alkaline corrosion after 14 days was obtained with cement CEM I 42.5 SR containing ash additive, and after 56 days with cement CEM II/A-V 52.5 containing low alkali content. The highest expansion after 14 and 56 days was obtained with cement CEM I 42.5 R without active mineral additives.

The influence of sugarcane bagasse ash as fly ash on cement quality

NASA Astrophysics Data System (ADS)

Rauf, N.; Damayanti, M. C.; Pratama, S. W. I.

2017-01-01

Fly ash often is used as the third material for cement. The fly ash from sugarcane bagasse is usually considered as industrial waste material that can be added to the base material of cement (clinker, trash, gypsum and lime stone) for economic and environment reason. The amount of fly ash usually up to 30 % of cement material, but in this research the percentage of sugarcane bagasse ash (SBA) is added to cement material is up to 15% total weight. Then the x-rays fluorescence (XRF) was used to determine its chemical composition of raw material and cement samples. The physical properties of cement such as fineness, setting time, expansion, and compressive strength were measured using Automatic Blaine, Vicat, Autoclave, respectively. The result show that the percentage of sugarcane bagasse ash influences the quality of cement and concrete, and this is confirmed with Indonesia National Standard (SNI). It is showed that the sugarcane bagasse ash could be use as material to improve the quality of cement and will solve the environment waste material

A study of surfactant interaction in cement-based systems and the role of the surfactant in frost protection

NASA Astrophysics Data System (ADS)

Tunstall, Lori Elizabeth

Air voids are deliberately introduced into concrete to provide resistance against frost damage. However, our ability to control air distribution in both traditional and nontraditional concrete is hindered by the limited amount of research available on air-entraining agent (AEA) interaction with both the solid and solution components of these systems. This thesis seeks to contribute to the information gap in several ways. Using tensiometry, we are able to quantify the adsorption capacity of cement, fly ash, and fly ash carbon for four commercial AEAs. These results indicate that fly ash interference with air entrainment is due to adsorption onto the glassy particles tucked inside carbon, rather than adsorption onto the carbon itself. Again using tensiometry, we show that two of the AEA show a stronger tendency to micellize and to interact with calcium ions than the others, which seems to be linked to the freezing behavior in mortars, since mortars made with these AEA require smaller dosages to achieve similar levels of protection. We evaluate the frost resistance of cement and cement/fly ash mortars by measuring the strain in the body as it is cooled and reheated. All of the mortars show some expansion at temperatures ≥ -42 °C. Many of the cement mortars are able to maintain net compression during this expansion, but none of the fly ash mortars maintain net compression once expansion begins. Frost resistance improves with an increase in AEA dosage, but no correlation is seen between frost resistance and the air void system. Thus, another factor must contribute to frost resistance, which we propose is the microstructure of the shell around the air void. The strain behavior is attributed to ice growth surrounding the void, which can plug the pores in the shell and reduce or eliminate the negative pore pressure induced by the ice inside the air void; the expansion would then result from the unopposed crystallization pressure, but this must be verified by future work. If the shell has numerous, tiny pores it is more difficult to eliminate suction, since more ice is needed to plug all the pores.

Combined Use of Shrinkage Reducing Admixture and CaO in Cement Based Materials

NASA Astrophysics Data System (ADS)

Tittarelli, Francesca; Giosuè, Chiara; Monosi, Saveria

2017-10-01

The combined addition of a Shrinkage-Reducing Admixture (SRA) with a CaO-based expansive agent (CaO) has been found to have a synergistic effect to improve the dimensional stability of cement based materials. In this work, aimed to further investigate the effect, mortar and self-compacting concrete specimens were prepared either without admixtures, as reference, or with SRA alone and/or CaO. Their performance was compared in terms of compressive strength and free shrinkage measurements. Results showed that the synergistic effect in reducing shrinkage is confirmed in the specimens manufactured with SRA and CaO. In order to clarify this phenomenon, the effect of SRA on the hydration of CaO as well as cement was evaluated through different techniques. The obtained results show that SRA induces a finer microstructure of the CaO hydration products and a retarding effect on the microstructure development of cement based materials. A more deformable mortar or concrete, due to the delay in microstructure development by SRA, coupled with a finer microstructure of CaO hydration products could allow higher early expansion, which might contribute in contrasting better the successive drying shrinkage.

Corrosion of aluminium metal in OPC- and CAC-based cement matrices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinoshita, Hajime, E-mail: h.kinoshita@sheffield.ac.uk; Swift, Paul; Utton, Claire

Corrosion of aluminium metal in ordinary Portland cement (OPC) based pastes produces hydrogen gas and expansive reaction products causing problems for the encapsulation of aluminium containing nuclear wastes. Although corrosion of aluminium in cements has been long known, the extent of aluminium corrosion in the cement matrices and effects of such reaction on the cement phases are not well established. The present study investigates the corrosion reaction of aluminium in OPC, OPC-blast furnace slag (BFS) and calcium aluminate cement (CAC) based systems. The total amount of aluminium able to corrode in an OPC and 4:1 BFS:OPC system was determined, andmore » the correlation between the amount of calcium hydroxide in the system and the reaction of aluminium obtained. It was also shown that a CAC-based system could offer a potential matrix to incorporate aluminium metal with a further reduction of pH by introduction of phosphate, producing a calcium phosphate cement.« less

The effect of calcium hydroxide, alkali dilution and calcium concentration in mitigating the alkali silica reaction using palm oil fuel ash

NASA Astrophysics Data System (ADS)

Asrah, Hidayati; Mirasa, Abdul Karim; Bolong, Nurmin

2018-02-01

This study investigated the mechanism of how POFA mitigated the ASR expansion. Two types of POFA; the UPOFA and GPOFA with different fineness were used to replace the cement at 20% and 40% and their effects on the mortar bar expansion, calcium hydroxide, alkali dilution, and calcium concentration were investigated. The results showed that UPOFA has a significant ability to mitigate the ASR, even at a lower level of replacement (20%) compared to GPOFA. The mechanism of UPOFA in mitigating the ASR expansion was through a reduction in the calcium hydroxide content, which produced low calcium concentration within the mortar pore solution. Low pore solution alkalinity signified that UPOFA had good alkali dilution effect. Meanwhile, a higher dosage of GPOFA was required to mitigate the ASR expansion. An increase in the pore solution alkalinity of GPOFA mortar indicated higher penetration of alkalis from the NaOH solution, which reduced the alkali dilution effect. However, this was compensated by the increase in the cement dilution effect at higher GPOFA replacement, which controlled the mortar bar expansion below the ASTM limit.

Multiscale characterization of chemical–mechanical interactions between polymer fibers and cementitious matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernández-Cruz, Daniel; Hargis, Craig W.; Bae, Sungchul

2014-04-01

Together with a series of mechanical tests, the interactions and potential bonding between polymeric fibers and cementitious materials were studied using scanning transmission X-ray microscopy (STXM) and microtomography (lCT). Experimental results showed that these techniques have great potential to characterize the polymer fiber-hydrated cement-paste matrix interface, as well as differentiating the chemistry of the two components of a bi-polymer (hybrid) fiber the polypropylene core and the ethylene acrylic acid copolymer sheath. Similarly, chemical interactions between the hybrid fiber and the cement hydration products were observed, indicating the chemical bonding between the sheath and the hardened cement paste matrix. Microtomography allowedmore » visualization of the performance of the samples, and the distribution and orientation of the two types of fiber in mortar. Beam flexure tests confirmed improved tensile strength of mixes containing hybrid fibers, and expansion bar tests showed similar reductions in expansion for the polypropylene and hybrid fiber mortar bars.« less

Modeling Self-Healing of Concrete Using Hybrid Genetic Algorithm–Artificial Neural Network

PubMed Central

Ramadan Suleiman, Ahmed; Nehdi, Moncef L.

2017-01-01

This paper presents an approach to predicting the intrinsic self-healing in concrete using a hybrid genetic algorithm–artificial neural network (GA–ANN). A genetic algorithm was implemented in the network as a stochastic optimizing tool for the initial optimal weights and biases. This approach can assist the network in achieving a global optimum and avoid the possibility of the network getting trapped at local optima. The proposed model was trained and validated using an especially built database using various experimental studies retrieved from the open literature. The model inputs include the cement content, water-to-cement ratio (w/c), type and dosage of supplementary cementitious materials, bio-healing materials, and both expansive and crystalline additives. Self-healing indicated by means of crack width is the model output. The results showed that the proposed GA–ANN model is capable of capturing the complex effects of various self-healing agents (e.g., biochemical material, silica-based additive, expansive and crystalline components) on the self-healing performance in cement-based materials. PMID:28772495

Radiation effects in concrete for nuclear power plants, Part II: Perspective from micromechanical modeling

DOE PAGES

Le Pape, Yann; Field, Kevin G.; Remec, Igor

2014-11-15

The need to understand and characterize the effects of neutron irradiation on concrete has become urgent because of the possible extension of service life of many nuclear power generating stations. Current knowledge is primarily based on a collection of data obtained in test reactors. These results are inherently difficult to interpret because materials and testing conditions are inconsistent. A micromechanical approach based on the Hashin composite sphere model is presented to derive a first-order separation of the effects of radiation on cement paste and aggregate, and, also, on their interaction. Although the scarcity of available data limits the validation ofmore » the model, it appears that, without negating a possible gamma-ray induced effect, the neutron-induced damage and swelling of aggregate plays a predominant role on the overall concrete expansion and the damage of the cement paste. Finally, the radiation-induced volumetric expansion (RIVE) effects can also be aided by temperature elevation and shrinkage in the cement paste.« less

Modeling Self-Healing of Concrete Using Hybrid Genetic Algorithm-Artificial Neural Network.

PubMed

Ramadan Suleiman, Ahmed; Nehdi, Moncef L

2017-02-07

This paper presents an approach to predicting the intrinsic self-healing in concrete using a hybrid genetic algorithm-artificial neural network (GA-ANN). A genetic algorithm was implemented in the network as a stochastic optimizing tool for the initial optimal weights and biases. This approach can assist the network in achieving a global optimum and avoid the possibility of the network getting trapped at local optima. The proposed model was trained and validated using an especially built database using various experimental studies retrieved from the open literature. The model inputs include the cement content, water-to-cement ratio (w/c), type and dosage of supplementary cementitious materials, bio-healing materials, and both expansive and crystalline additives. Self-healing indicated by means of crack width is the model output. The results showed that the proposed GA-ANN model is capable of capturing the complex effects of various self-healing agents (e.g., biochemical material, silica-based additive, expansive and crystalline components) on the self-healing performance in cement-based materials.

Analytic hierarchy process helps select site for limestone quarry expansion in Barbados.

PubMed

Dey, Prasanta Kumar; Ramcharan, Eugene K

2008-09-01

Site selection is a key activity for quarry expansion to support cement production, and is governed by factors such as resource availability, logistics, costs, and socio-economic-environmental factors. Adequate consideration of all the factors facilitates both industrial productivity and sustainable economic growth. This study illustrates the site selection process that was undertaken for the expansion of limestone quarry operations to support cement production in Barbados. First, alternate sites with adequate resources to support a 25-year development horizon were identified. Second, technical and socio-economic-environmental factors were then identified. Third, a database was developed for each site with respect to each factor. Fourth, a hierarchical model in analytic hierarchy process (AHP) framework was then developed. Fifth, the relative ranking of the alternate sites was then derived through pair wise comparison in all the levels and through subsequent synthesizing of the results across the hierarchy through computer software (Expert Choice). The study reveals that an integrated framework using the AHP can help select a site for the quarry expansion project in Barbados.

Formulation of portland composite cement using waste glass as a supplementary cementitious material

NASA Astrophysics Data System (ADS)

Manullang, Ria Julyana; Samadhi, Tjokorde Walmiki; Purbasari, Aprilina

2017-09-01

Utilization of waste glass in cement is an attractive options because of its pozzolanic behaviour and the market of glass-composite cement is potentially available. The objective of this research is to evaluate the formulation of waste glass as supplementary cementitious material (SCM) by an extreme vertices mixture experiment, in which clinker, waste glass and gypsum proportions are chosen as experimental variables. The composite cements were synthesized by mixing all of powder materials in jar mill. The compressive strength of the composite cement mortars after being cured for 28 days ranges between 229 to 268 kg/cm2. Composite cement mortars exhibit lower compressive strength than ordinary Portland cement (OPC) mortars but is still capable of meeting the SNI 15-7064-2004 standards. The highest compressive strength is obtained by shifting the cement blend composition to the direction of increasing clinker and gypsum proportions as well as reducing glass proportion. The lower compressive strength of composite cement is caused by expansion due to ettringite and ASR gel. Based on the experimental result, the composite cement containing 80% clinker, 15% glass and 5% gypsum has the highest compressive strength. As such, the preliminary technical feasibility of reuse of waste glass as SCM has been confirmed.

Comparing the use of sewage sludge ash and glass powder in cement mortars.

PubMed

Chen, Zhen; Poon, Chi Sun

2017-06-01

This study explored the suitability of using sewage sludge ash (SSA) and mixed-colored glass powder (MGP) as construction materials in cement mortars. Positive findings from this study may help promote the recycling of waste SSA and MGP in construction works. The results indicated that the SSA decreased while MGP improved the mortar workability. The SSA exhibited very low pozzolanic activity, but the cement mortar prepared with 20% SSA yielded strength values slightly superior to those of the glass mortars due to its water absorption ability. MGP can serve as a pozzolan and when 20% of cement was replaced by MGP, apparent compressive strength gains were found at later curing ages. The SSA could be used to mitigate ASR expansion while the MGP was superior in resisting drying shrinkage.

Scaling and saturation laws for the expansion of concrete exposed to sulfate attack.

PubMed

Monteiro, Paulo J M

2006-08-01

Reinforced concrete structures exposed to aggressive environments often require repair or retrofit even though they were designed to last >50 years. This statement is especially true for structures subjected to sulfate attack. It is critical that fundamental models of life prediction be developed for durability of concrete. Based on experimental results obtained over a 40-year period, scaling and saturation laws were formulated for concrete exposed to sulfate solution. These features have not been considered in current models used to predict life cycle of concrete exposed to aggressive environment. The mathematical analysis shows that porous concrete made with high and moderate water-to-cement ratios develops a definite scaling law after an initiation time. The scaling coefficient depends on the cement composition but does not depend on the original water-to-cement ratio. Dense concrete made with low water-to-cement ratios develops a cyclic saturation curve. An index for "potential of damage" is created to allow engineers to design concrete structures with better precision and cement chemists to develop portland cements with optimized composition.

Early-age monitoring of cement structures using FBG sensors

NASA Astrophysics Data System (ADS)

Wang, Chuan; Zhou, Zhi; Zhang, Zhichun; Ou, Jinping

2006-03-01

With more and more broad applications of the cement-based structures such as neat cement paste, cement mortar and concrete in civil engineering, people hope to find out what their performances should like. The in-service performances of cement-based structures are highly affected by their hardening process during the early-age. But it is still a big problem for traditional sensors to be used to monitor the early curing of cement-based structures due to such disadvantages as difficulties to install sensors inside the concrete, limited measuring points, poor durability and interference of electromagnetic wave and so on. In this paper, according to the sensing properties of the Fiber Bragg Grating sensors and self-characters of the cement-based structures, we have successfully finished measuring and monitoring the early-age inner-strain and temperature changes of the neat cement paste, concrete with and without restrictions, mass concrete structures and negative concrete, respectively. Three types of FBG-based sensors have been developed to monitor the cement-based structures. Besides, the installation techniques and the embedding requirements of FBG sensors in cement-based structures are also discussed. Moreover, such kind of technique has been used in practical structure, 3rd Nanjing Yangtze Bridge, and the results show that FBG sensors are well proper for measuring and monitoring the temperature and strain changes including self-shrinkage, dry shrinkage, plastic shrinkage, temperature expansion, frost heaving and so on inside different cement-based structures. This technique provides us a new useful measuring method on early curing monitoring of cement-based structures and greater understanding of details of their hardening process.

Assessment of Pb-slag, MSWI bottom ash and boiler and fly ash for using as a fine aggregate in cement mortar.

PubMed

Saikia, Nabajyoti; Cornelis, Geert; Mertens, Gilles; Elsen, Jan; Van Balen, Koenraad; Van Gerven, Tom; Vandecasteele, Carlo

2008-06-15

Three types of wastes, metallurgical slag from Pb production (SLG), the sand-sized (0.1-2 mm) fraction of MSWI bottom ash from a grate furnace (SF), and boiler and fly ash from a fluidised bed incinerator (BFA), were characterized and used to replace the fine aggregate during preparation of cement mortar. The chemical and mineralogical behaviour of these wastes along with the reactivities of the wastes with lime and the hydration behaviour of ordinary Portland cement paste with and without these wastes added were evaluated by various chemical and instrumental techniques. The compressive strengths of the cement mortars containing waste as a partial substitution of fine aggregates were also assessed. Finally, leaching studies of the wastes and waste containing cement mortars were conducted. SLG addition does not show any adverse affect during the hydration of cement, or on the compressive strengths behaviours of mortars. Formation of expansive products like ettringite, aluminium hydroxide and H2 gas due to the reaction of some constituents of BFA and SF with alkali creates some cracks in the paste as well as in the cement mortars, which lower the compressive strength of the cement mortars. However, utilization of all materials in cement-based application significantly improves the leaching behaviour of the majority of the toxic elements compared to the waste as such.

Cork is used to make tooling patterns and molds

NASA Technical Reports Server (NTRS)

Hoffman, F. J.

1965-01-01

Sheet and waste cork are cemented together to provide a tooling pattern or mold. The cork form withstands moderately high temperatures under vacuum or pressure with minimum expansion, shrinkage, or distortion.

The use of by-products from metallurgical and mineral industries as filler in cement-based materials.

PubMed

Moosberg, Helena; Lagerblad, Björn; Forssberg, Eric

2003-02-01

This investigation has been made in order to make it possible to increase the use of by-products in cement-based materials. Use of by-products requires a screening procedure that will reliably determine their impact on concrete. A test procedure was developed. The most important properties were considered to be strength development, shrinkage, expansion and workability. The methods used were calorimetry, flow table tests, F-shape measurements, measurements of compressive and flexural strength and shrinkage/expansion measurements. Scanning electron microscopy was used to verify some results. Twelve by-products were collected from Swedish metallurgical and mineral industries and classified according to the test procedure. The investigation showed that the test procedure clearly screened out the materials that can be used in the production of concrete from the unsuitable ones.

Development of the Use of Alternative Cements for the Treatment of Intermediate Level Waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, M.; Godfrey, I.H.

2007-07-01

This paper describes initial development studies undertaken to investigate the potential use of alternative, non ordinary Portland cement (OPC) based encapsulation matrices to treat historic legacy wastes within the UK's Intermediate Level Waste (ILW) inventory. Currently these wastes are encapsulated in composite OPC cement systems based on high replacement with blast furnace slag of pulverised fuel ash. However, the high alkalinity of these cements can lead to high corrosion rates with reactive metals found in some wastes releasing hydrogen and forming expansive corrosion products. This paper therefore details preliminary results from studies on two commercial products, calcium sulfo-aluminate (CSA) andmore » magnesium phosphate (MP) cement which react with a different hydration chemistry, and which may allow wastes containing these metals to be encapsulated with lower reactivity. The results indicate that grouts can be formulated from both cements over a range of water contents and reactant ratios that have significantly improved fluidity in comparison to typical OPC cements. All designed mixes set in 24 hours with zero bleed and the pH values in the plastic state were in the range 10-11 for CSA and 5-7 for MP cements. In addition, a marked reduction in aluminium corrosion rate has been observed in both types of cements compared to a composite OPC system. These results therefore provide encouragement that both cement types can provide a possible alternative to OPC in the immobilisation of reactive wastes, however further investigation is needed. (authors)« less

Magnetic Tomography - Assessing Tie Bar and Dowel Bar Placement Accuracy

DOT National Transportation Integrated Search

2017-12-01

The Kansas Department of Transportation (KDOT) constructs portland cement concrete pavements (PCCP) for new highway expansions and/or for replacement of existing highway pavement using slip-form paving operations. Typical concrete pavement constructi...

Alkali-aggregate reaction under the influence of deicing salts in the Hokuriku district, Japan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katayama, Tetsuya; Tagami, Masahiko; Sarai, Yoshinori

2004-11-15

Concrete cores taken from highway bridges and culverts undergoing alkali-silica reaction (ASR) were investigated petrographically by means of core scanning, point counting, polarizing microscopy, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), electron-probe microanalysis with energy-dispersive spectrometry, in conjunction with wet chemical analyses and expansion tests. Field damage was roughly proportional to the content of andesite in the gravel aggregates due to the presence of highly reactive cristobalite and tridymite. Electron-probe microanalyzer analysis of unhydrated cement phases in the concrete revealed that the cement used had contained at least 0.5% to 1.0% alkali (Na{sub 2}Oeq) and that both the aggregatesmore » and the deicing salts had supplied part of the water-soluble alkali to concrete toward the threshold of producing ASR (Na{sub 2}O{sub eq} 3.0 kg/m{sup 3}). An accelerated concrete core expansion test (1 M NaOH, 80 deg. C) of the damaged structures mostly gave core expansions of >0.10% at 21 days (or >0.05% at 14 days), nearly comparable to those of a slow expansion test with saturated NaCl solution (50 deg. C, 91 days) which produced Cl-containing ASR gel.« less

Mechanical Expansion of Steel Tubing as a Solution to Leaky Wellbores

PubMed Central

Radonjic, Mileva; Kupresan, Darko

2014-01-01

Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe (casing), and protects metal components from corrosive fluids. These are essential for uncompromised wellbore integrity. Cements can undergo multiple forms of failure, such as debonding at the cement/rock and cement/metal interfaces, fracturing, and defects within the cement matrix. Failures and defects within the cement will ultimately lead to fluid migration, resulting in inter-zonal fluid migration and premature well abandonment. Currently, there are over 1.8 million operating wells worldwide and over one third of these wells have leak related problems defined as Sustained Casing Pressure (SCP)1. The focus of this research was to develop an experimental setup at bench-scale to explore the effect of mechanical manipulation of wellbore casing-cement composite samples as a potential technology for the remediation of gas leaks. The experimental methodology utilized in this study enabled formation of an impermeable seal at the pipe/cement interface in a simulated wellbore system. Successful nitrogen gas flow-through measurements demonstrated that an existing microannulus was sealed at laboratory experimental conditions and fluid flow prevented by mechanical manipulation of the metal/cement composite sample. Furthermore, this methodology can be applied not only for the remediation of leaky wellbores, but also in plugging and abandonment procedures as well as wellbore completions technology, and potentially preventing negative impacts of wellbores on subsurface and surface environments. PMID:25490436

Mechanical expansion of steel tubing as a solution to leaky wellbores.

PubMed

Radonjic, Mileva; Kupresan, Darko

2014-11-20

Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe (casing), and protects metal components from corrosive fluids. These are essential for uncompromised wellbore integrity. Cements can undergo multiple forms of failure, such as debonding at the cement/rock and cement/metal interfaces, fracturing, and defects within the cement matrix. Failures and defects within the cement will ultimately lead to fluid migration, resulting in inter-zonal fluid migration and premature well abandonment. Currently, there are over 1.8 million operating wells worldwide and over one third of these wells have leak related problems defined as Sustained Casing Pressure (SCP). The focus of this research was to develop an experimental setup at bench-scale to explore the effect of mechanical manipulation of wellbore casing-cement composite samples as a potential technology for the remediation of gas leaks. The experimental methodology utilized in this study enabled formation of an impermeable seal at the pipe/cement interface in a simulated wellbore system. Successful nitrogen gas flow-through measurements demonstrated that an existing microannulus was sealed at laboratory experimental conditions and fluid flow prevented by mechanical manipulation of the metal/cement composite sample. Furthermore, this methodology can be applied not only for the remediation of leaky wellbores, but also in plugging and abandonment procedures as well as wellbore completions technology, and potentially preventing negative impacts of wellbores on subsurface and surface environments.

An Experimental Investigation on the Effect of Addition of Ternary Blend on the Mix Design Characteristics of High Strength Concrete using Steel Fibre

NASA Astrophysics Data System (ADS)

Sinha, Deepa A., Dr; Verma, A. K., Dr

2017-08-01

This paper presents the results of M60 grade of concrete. M60 grade of concrete is achieved by maximum density technique. Concrete is brittle and weak in tension and develops cracks during curing and due to thermal expansion / contraction over a period ot time. Thus the effect of addition of 1% steel fibre is studied. For ages, concrete has been one of the widely used materials for construction. When cement is manufactured, every one ton of cement produces around one ton of carbon dioxide leading to global warming and also as natural resources are finishing, so use of supplementary cementitious material like alccofine and flyash is used as partial replacement of cement is considered. The effect of binary and ternary blend on the strength characteristics is studied. The results indicate that the concrete made with alccofine and flyash generally show excellent fresh and hardened properties. The ternary system that is Portland cement-fly ash-Alccofine concrete was found to increase the strength of concrete when compared to concrete made with Portland cement or even from Portland cement and fly ash.

Evaluation of shrinkage and cracking in concrete of ring test by acoustic emission method

NASA Astrophysics Data System (ADS)

Watanabe, Takeshi; Hashimoto, Chikanori

2015-03-01

Drying shrinkage of concrete is one of the typical problems related to reduce durability and defilation of concrete structures. Lime stone, expansive additive and low-heat Portland cement are used to reduce drying shrinkage in Japan. Drying shrinkage is commonly evaluated by methods of measurement for length change of mortar and concrete. In these methods, there is detected strain due to drying shrinkage of free body, although visible cracking does not occur. In this study, the ring test was employed to detect strain and age cracking of concrete. The acoustic emission (AE) method was adopted to detect micro cracking due to shrinkage. It was recognized that in concrete using lime stone, expansive additive and low-heat Portland cement are effective to decrease drying shrinkage and visible cracking. Micro cracking due to shrinkage of this concrete was detected and evaluated by the AE method.

Observations on dedolomitization of carbonate concrete aggregates, implications for ACR and expansion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prinčič, Tina, E-mail: Tina.Princic@uni-lj.si; Štukovnik, Petra; Pejovnik, Stane

2013-12-15

Some carbonate aggregates used in concrete are unstable in a high alkaline solution, which is present also in pore solution of cement binder. This paper investigates the process of dedolomitization of carbonate aggregate rocks and mortar bars. Selected aggregates, limestone and dolostone are of high purity without reactive silica involvement confirmed by the XRD and the XRF. For the process of dedolomitization the effect of various temperatures, solutions and time was examined. In this investigation, measurements of expansion, optical and scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction were used. Te results indicate that the process ofmore » dedolomitization occurred not only in the NaOH solution but also in the water on the mortar bar with virgin dolostone aggregate. Elevated temperature, 60 °C, increased the rate of reaction. Furthermore, the rate of reaction significantly correlates with time, which has also been confirmed through the Rietveld analysis. -- Highlights: •The dedolomitization caused no expansion. •It occurs in the dolostone aggregate without reactive silica involvement. •It has taken place already with the presence of the cement binder. •A significant alteration occurred: formation of rims, new pores and phases.« less

Multi-criteria analysis of the mechanism of degradation of Portland cement based mortars exposed to external sulphate attack

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Hachem, R.; Roziere, E.; Grondin, F.

2012-10-15

This work aims to contribute to the design of durable concrete structures exposed to external sulphate attacks (ESA). Following a preliminary study aimed at designing a representative test, the present paper suggests a study on the effect of the water-to-cement (w/c) ratio and the cement composition in order to understand the degradation mechanisms. Length and mass measurements were registered continuously, leached calcium and hydroxide ions were also quantified. In parallel, scanning electron microscopy observations as well as X-ray microtomography were realised at different times to identify the formed products and the crack morphology. Test results provide information on the basicmore » aspects of the degradation mechanism, such as the main role of leaching and diffusion in the sulphate attack process. The mortar composition with a low w/c ratio leads to a better resistance to sulphate attack because the microstructure is less permeable. Reducing the C{sub 3}A content results in a macro-cracking decrease but it does not prevent expansion, which suggests the contribution of other expansive products, such as gypsum, in damage due to ESA. The observation of the cracks network in the microstructure helps to understand the micro-mechanisms of the degradation process.« less

Evaluation of Metakaolin and Slag for GDOT Concrete Specifications and Mass Concrete Provision - Phase I

DOT National Transportation Integrated Search

2017-11-01

This report documents the evaluation of cement replacement with mekaolin and slag materials supplied by multiple vendors by measuring compressive strength, tensile strength, modulus of rupture, modulus of elasticity, sulfate expansion, alkali-silica ...

Monitoring of hardening and hygroscopic induced strains in a calcium phosphate bone cement using FBG sensor.

PubMed

Bimis, A; Karalekas, D; Bouropoulos, N; Mouzakis, D; Zaoutsos, S

2016-07-01

This study initially deals with the investigation of the induced strains during hardening stage of a self-setting calcium phosphate bone cement using fiber-Bragg grating (FBG) optical sensors. A complementary Scanning Electron Microscopy (SEM) investigation was also conducted at different time intervals of the hardening period and its findings were related to the FBG recordings. From the obtained results, it is demonstrated that the FBG response is affected by the microstructural changes taking place when the bone cement is immersed into the hardening liquid media. Subsequently, the FBG sensor was used to monitor the absorption process and hygroscopic response of the hardened and dried biocement when exposed to a liquid/humid environment. From the FBG-based calculated hygric strains as a function of moisture concentration, the coefficient of moisture expansion (CME) of the examined bone cement was obtained, exhibiting two distinct linear regions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Use of fly ash, slag, or silica fume to inhibit alkali-silica reactivity.

DOT National Transportation Integrated Search

1995-01-01

This study had two objectives: (1) to evaluate the effectiveness of particular mineral admixtures when combined with portland cements of varying alkali content in preventing expansion due to alkali-silica reactivity (ASR), and (2) to determine if set...

In-situ Mechanical Manipulation of Wellbore Cements as a Solution to Leaky Wells

NASA Astrophysics Data System (ADS)

Kupresan, D.; Radonjic, M.; Heathman, J.

2013-12-01

Wellbore cement provides casing support, zonal isolation, and casing protection from corrosive fluids, which are essential for wellbore integrity. Cements can undergo one or more forms of failure such as debonding at cement/formation and cement/casing interface, fracturing and defects within cement matrix. Failures and defects within cement will ultimately lead to fluids migration, resulting in inter-zonal fluid migration and premature well abandonment. There are over 27,000 abandoned oil and gas wells only in The Gulf of Mexico (some of them dating from the late 1940s) with no gas leakage monitoring. Cement degradation linked with carbon sequestration can potentially lead to contamination of fresh water aquifers with CO2. Gas leaks can particularly be observed in deviated wells used for hydraulic fracking (60% leakage rate as they age) as high pressure fracturing increases the potential for migration pathways. Experimental method utilized in this study enables formation of impermeable seals at interfaces present in a wellbore by mechanically manipulating wellbore cement. Preliminary measurements obtained in bench scale experiments demonstrate that an impermeable cement/formation and cement/casing interface can be obtained. In post-modified cement, nitrogen gas flow-through experiments showed complete zonal isolation and no permeability in samples with pre-engineered microannulus. Material characterization experiments of modified cement revealed altered microstructural properties of cement as well as changes in mineralogical composition. Calcium-silicate-hydrate (CSH), the dominant mineral in hydrated cement which provides low permeability of cement, was modified as a result of cement pore water displacement, resulting in more dense structures. Calcium hydroxide (CH), which is associated with low resistance of cement to acidic fluids and therefore detrimental in most wellbore cements, was almost completely displaced and/or integrated in CSH as a result of mechanical manipulation (shear stress). The main advantage of this methodology is that mechanical manipulation of cement can induce healing of existing fractures, channels and microannulus seal in a wellbore without introducing new materials (e.g. cement squeeze jobs). Furthermore, this methodology is less sensitive to the influence of downhole conditions such as pressure, temperature and formation fluids, since it uses cement pore water as a medium to alter cement sheath. Based on lab experiments observation, it is possible to perceive that once tested at the industrial scale and if successful, the implementation of this method in the field can potentially mitigate leaky wells in CO2 sequestration projects, wellbores completed for hydraulic-fracturing and other conventional oil and gas producing wells. Key words: Wellbore cement integrity; Leaky wells; Cement microstructures; Casing expansion effect on cement mineralogy alterations.

Developing a More Rapid Test to Assess Sulfate Resistance of Hydraulic Cements

PubMed Central

Ferraris, Chiara; Stutzman, Paul; Peltz, Max; Winpigler, John

2005-01-01

External sulfate attack of concrete is a major problem that can appear in regions where concrete is exposed to soil or water containing sulfates, leading to softening and cracking of the concrete. Therefore, it is important that materials selection and proportioning of concrete in susceptible regions be carefully considered to resist sulfate attack. American Society for Testing Materials (ASTM) limits the tricalcium aluminate phase in cements when sulfate exposure is of concern. The hydration products of tricalcium aluminate react with the sulfates resulting in expansion and cracking. While ASTM standard tests are available to determine the susceptibility of cements to sulfate attack, these tests require at least 6 months and often up to a year to perform; a delay that hinders development of new cements. This paper presents a new method for testing cement resistance to sulfate attack that is three to five times faster than the current ASTM tests. Development of the procedure was based upon insights on the degradation process by petrographic examination of sulfate-exposed specimens over time. Also key to the development was the use of smaller samples and tighter environmental control. PMID:27308177

Effects of portland cement particle size on heat of hydration : [summary].

DOT National Transportation Integrated Search

2013-12-01

Generally, when materials are heated (or cooled), : they expand (or contract) to a greater or lesser : extent. Even a material as rock-like as concrete : is susceptible to thermal effects, and expansion : joints are used for this reason: to allow con...

Thermal stress control using waste steel fibers in massive concretes

NASA Astrophysics Data System (ADS)

Sarabi, Sahar; Bakhshi, Hossein; Sarkardeh, Hamed; Nikoo, Hamed Safaye

2017-11-01

One of the important subjects in massive concrete structures is the control of the generated heat of hydration and consequently the potential of cracking due to the thermal stress expansion. In the present study, using the waste turnery steel fibers in the massive concretes, the amount of used cement was reduced without changing the compressive strength. By substituting a part of the cement with waste steel fibers, the costs and the generated hydration heat were reduced and the tensile strength was increased. The results showed that by using 0.5% turnery waste steel fibers and consequently, reducing to 32% the cement content, the hydration heat reduced to 23.4% without changing the compressive strength. Moreover, the maximum heat gradient reduced from 18.5% in the plain concrete sample to 12% in the fiber-reinforced concrete sample.

Effect of 3 cements on white spot lesion formation after full-coverage rapid maxillary expander: A comparative in-vivo study.

PubMed

Yagci, Ahmet; Korkmaz, Yasemin Nur; Yagci, Filiz; Atilla, Aykan Onur; Buyuk, Suleyman Kutalmiş

2016-12-01

The aim of this study was to assess the effects of 3 luting agents (glass ionomer cement, compomer, and polycarboxylate cement) on white spot lesion formation in patients with full-coverage bonded acrylic splint expanders. White spot lesion formation was assessed with quantitative light-induced fluorescence. Full-coverage rapid maxillary expanders were cemented with glass ionomer cement, compomer, and polycarboxylate cement in groups 1, 2, and 3, respectively. A control group comprised patients who never had orthodontic treatment. Quantitative light-induced fluorescence images taken before and after rapid maxillary expansion treatment were analyzed for these parameters: the percentages of fluorescence loss with respect to the fluorescence of sound tooth tissue (ΔF) and maximum loss of fluorescence intensity in the whole lesion; lesion area with ΔF equal to less than a -5% threshold; and the percentage of fluorescence loss with respect to the fluorescence of sound tissue times the area that indicated lesion volume. All 3 groups showed statistically significantly greater demineralization than the control group. The 3 experimental groups differed from each other in half of the parameters calculated. Teeth in the polycarboxylate group developed the most white spot lesions. With the highest rate of white spot lesion formation, polycarboxylate cements should not be used for full-coverage bonded acrylic splint expanders. Compomers may be preferred over glass ionomer cements, based on the findings of this study. Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Properties of Portland cement--stabilised MSWI fly ashes.

PubMed

Polettini, A; Pomi, R; Sirini, P; Testa, F

2001-11-16

In the present paper, the properties of Portland cement mixtures containing fly ashes (FA) collected at four different Italian municipal solid waste incineration (MSWI) plants were investigated. In particular, physical/mechanical characteristics (setting time, unconfined compressive strength (UCS) and shrinkage/expansion), as well as the acid neutralisation behaviour of the solidified products were considered. The FA composition, revealing enrichment in heavy metals, chlorides and sulphates, significantly altered the hydration behaviour of Portland cement. Consequently, for some of the investigated FA the maximum allowable content for the mixtures to achieve appreciable mechanical strength was 20 wt.%. Even at low FA dosages setting of cement was strongly delayed. In order to improve the properties of FA/cement mixtures, the use of additives was tested.Moreover, the acid neutralisation capacity (ANC) of the solidified products was evaluated in order to assess the ability of the matrix to resist acidification, and also to provide information on hydration progression, as well as on heavy metal release under different pH conditions. Comparison of the results from the present work with previous studies carried out on spiked mixtures lead to the conclusion that the mechanical properties of the stabilised FA could not be predicted based on the effect exerted by heavy metals and anions only, even when the dilution effect exerted on cement was taken into account. It was likely that a major role was also played by alkalis, which were present in the FA at much higher concentrations than in cement.

Novel method for titanium crown casting using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded investment.

PubMed

Zhang, Zutai; Tamaki, Yukimichi; Hotta, Yasuhiro; Miyazaki, Takashi

2006-07-01

For titanium casting, most commercial investments for titanium recommend casting at a low mold temperature to reduce oxidation. However, the thermal expansion values of the molds at low casting temperatures may be insufficient. The purpose of the current study was to investigate the possibility of obtaining accurate titanium crown casts using wax pattern fabricated by a CAD/CAM system with a non-expanded mold. Three types of experimental magnesia-based investments (A, B and C) were made and their properties were evaluated for dental use. Two kinds of wax patterns for full-coverage coping crowns (S-0: cement space of 0 microm; S-20: cement space of 20 microm) were fabricated using a commercial CAD/CAM system. A traditional method (TM) using inlay wax was performed for comparison. The investment for titanium casting was decided from the fundamental data of experimental investments. Titanium crowns were replaced on the stone die and the thickness of the cement layer was evaluated. There were no significant differences for the setting time and setting expansion among the experimental investments, but the aluminous cement content played a role in hardening and contracting the mold. The fit of the titanium crowns differed significantly between the TM and the CAD/CAM system. The ranges of thickness obtained from the TM, S-0 and S-20 were 20.78-357.88 microm, 25.12-107.46 microm and 17.84-58.92 microm, respectively. High quality titanium crown casting was obtained using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded MgO-based investment.

Meso-scale modeling of irradiated concrete in test reactor

DOE PAGES

Giorla, Alain B.; Vaitová, M.; Le Pape, Yann; ...

2015-10-18

In this paper, we detail a numerical model accounting for the effects of neutron irradiation on concrete at the mesoscale. Irradiation experiments in test reactor (Elleuch et al.,1972), i.e., in accelerated conditions, are simulated. Concrete is considered as a two-phase material made of elastic inclusions (aggregate) subjected to thermal and irradiation-induced swelling and embedded in a cementitious matrix subjected to shrinkage and thermal expansion. The role of the hardened cement paste in the post-peak regime (brittle-ductile transition with decreasing loading rate), and creep effects are investigated. Radiation-induced volumetric expansion (RIVE) of the aggregate cause the development and propagation of damagemore » around the aggregate which further develops in bridging cracks across the hardened cement paste between the individual aggregate particles. The development of damage is aggravated when shrinkage occurs simultaneously with RIVE during the irradiation experiment. The post-irradiation expansion derived from the simulation is well correlated with the experimental data and, the obtained damage levels are fully consistent with previous estimations based on a micromechanical interpretation of the experimental post-irradiation elastic properties (Le Pape et al.,2015). In conclusion, the proposed modeling opens new perspectives for the interpretation of test reactor experiments in regards to the actual operation of light water reactors.« less

Polymer-Cement Composites Containing Waste Perlite Powder

PubMed Central

Łukowski, Paweł

2016-01-01

Polymer-cement composites (PCCs) are materials in which the polymer and mineral binder create an interpenetrating network and co-operate, significantly improving the performance of the material. On the other hand, the need for the utilization of waste materials is a demand of sustainable construction. Various mineral powders, such as fly ash or blast-furnace slag, are successfully used for the production of cement and concrete. This paper deals with the use of perlite powder, which is a burdensome waste from the process of thermal expansion of the raw perlite, as a component of PCCs. The results of the testing of the mechanical properties of the composite and some microscopic observations are presented, indicating that there is a possibility to rationally and efficiently utilize waste perlite powder as a component of the PCC. This would lead to creating a new type of building material that successfully meets the requirements of sustainable construction. PMID:28773961

Preparation of in situ hardening composite microcarriers: Calcium phosphate cement combined with alginate for bone regeneration

PubMed Central

Park, Jung-Hui; Lee, Eun-Jung; Knowles, Jonathan C

2014-01-01

Novel microcarriers consisting of calcium phosphate cement and alginate were prepared for use as three-dimensional scaffolds for the culture and expansion of cells that are effective for bone tissue engineering. The calcium phosphate cement-alginate composite microcarriers were produced by an emulsification of the composite aqueous solutions mixed at varying ratios (calcium phosphate cement powder/alginate solution = 0.8–1.2) in an oil bath and the subsequent in situ hardening of the compositions during spherodization. Moreover, a porous structure could be easily created in the solid microcarriers by soaking the produced microcarriers in water and a subsequent freeze-drying process. Bone mineral-like apatite nanocrystallites were shown to rapidly develop on the calcium phosphate cement–alginate microcarriers under moist conditions due to the conversion of the α-tricalcium phosphate phase in the calcium phosphate cement into a carbonate–hydroxyapatite. Osteoblastic cells cultured on the microspherical scaffolds were proven to be viable, with an active proliferative potential during 14 days of culture, and their osteogenic differentiation was confirmed by the determination of alkaline phosphatase activity. The in situ hardening calcium phosphate cement–alginate microcarriers developed herein may be used as potential three-dimensional scaffolds for cell delivery and tissue engineering of bone. PMID:23836845

Examination of the jarosite-alunite precipitate addition in the raw meal for the production of sulfoaluminate cement clinker.

PubMed

Katsioti, M; Tsakiridis, P E; Leonardou-Agatzini, S; Oustadakis, P

2006-04-17

The aim of the present research work was to investigate the possibility of adding a jarosite-alunite chemical precipitate, a waste product of a new hydrometallurgical process developed to treat economically low-grade nickel oxides ores, in the raw meal for the production of sulfoaluminate cement clinker. For that reason, two samples of raw meals were prepared, one contained 20% gypsum, as a reference sample ((SAC)Ref) and another with 11.31% jarosite-alunite precipitate ((SAC)J/A). Both raw meals were sintered at 1300 degrees C. The results of chemical and mineralogical analyses as well as the microscopic examination showed that the use of the jarosite-alunite precipitate did not affect the mineralogical characteristics of the so produced sulfoaluminate cement clinker and there was confirmed the formation of the sulfoaluminate phase (C4A3S), the most typical phase of this cement type. Furthermore, both clinkers were tested by determining the grindability, setting time, compressive strength and expansibility. The hydration products were examined by XRD analysis at 2, 7, 28 and 90 days. The results of the physico-mechanical tests showed that the addition of jarosite-alunite precipitate did not negatively affect the quality of the produced cement.

Biodeterioration of the Cement Composites

NASA Astrophysics Data System (ADS)

Luptáková, Alena; Eštoková, Adriana; Mačingová, Eva; Kovalčíková, Martina; Jenčárová, Jana

2016-10-01

The destruction of natural and synthetic materials is the spontaneous and irreversible process of the elements cycling in nature. It can by accelerated or decelerated by physical, chemical and biological influences. Biological influences are represented by the influence of the vegetation and microorganisms (MO). The destruction of cement composites by different MO through the diverse mechanisms is entitled as the concrete biodeterioration. Several sulphur compounds and species of MO are involved in this complex process. Heterotrophic and chemolithotrophic bacteria together with fungi have all been found in samples of corroding cement composites. The MO involved in the process metabolise the presented sulphur compounds (hydrogen sulphide, elemental sulphur etc.) to sulphuric acid reacting with concrete. When sulphuric acid reacts with a concrete matrix, the first step involves a reaction between the acid and the calcium hydroxide forming calcium sulphate. This is subsequently hydrated to form gypsum, the appearance of which on the surface of concrete pipes takes the form of a white, mushy substance which has no cohesive properties. In the continuing attack, the gypsum would react with the calcium aluminate hydrate to form ettringite, an expansive product. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to biodeterioration. The aim of this work was the study of the cement composites biodeterioration by the bacteria Acidithiobacillus thiooxidans. Experimental works were focused on the comparison of special cement composites and its resistance affected by the activities of used sulphur-oxidising

Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

NASA Astrophysics Data System (ADS)

Qureshi, T. S.; Al-Tabbaa, A.

2016-08-01

Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high ‘N50’and moderately high ‘92-200’) of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92-200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 μm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).

Effect of PCM on the Hydration Process of Cement-Based Mixtures: A Novel Thermo-Mechanical Investigation.

PubMed

Fabiani, Claudia; Pisello, Anna Laura; D'Alessandro, Antonella; Ubertini, Filippo; Cabeza, Luisa F; Cotana, Franco

2018-05-23

The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to their melting temperature and operation boundaries. Further to that, the present paper aims at investigating an innovative use of PCM for absorbing heat released by cement during its curing process, which typically contributes to micro-cracking of massive concrete elements, therefore compromising their mechanical performance during their service life. The experiments carried out in this work showed how PCM, even in small quantities (i.e., up to 1% in weight of cement) plays a non-negligible benefit in reducing differential thermal increases between core and surface and therefore mechanical stresses originating from differential thermal expansion, as demonstrated by thermal monitoring of cement-based cubes. Both PCM types analyzed in the study (with melting temperatures at 18 and 25 ∘ C) were properly dispersed in the mix and were shown to be able to reduce the internal temperature of the cement paste by several degrees, i.e., around 5 ∘ C. Additionally, such small amount of PCM produced a reduction of the final density of the composite and an increase of the characteristic compressive strength with respect to the plain recipe.

Enhancement of thermal neutron shielding of cement mortar by using borosilicate glass powder.

PubMed

Jang, Bo-Kil; Lee, Jun-Cheol; Kim, Ji-Hyun; Chung, Chul-Woo

2017-05-01

Concrete has been used as a traditional biological shielding material. High hydrogen content in concrete also effectively attenuates high-energy fast neutrons. However, concrete does not have strong protection against thermal neutrons because of the lack of boron compound. In this research, boron was added in the form of borosilicate glass powder to increase the neutron shielding property of cement mortar. Borosilicate glass powder was chosen in order to have beneficial pozzolanic activity and to avoid deleterious expansion caused by an alkali-silica reaction. According to the experimental results, borosilicate glass powder with an average particle size of 13µm showed pozzolanic activity. The replacement of borosilicate glass powder with cement caused a slight increase in the 28-day compressive strength. However, the incorporation of borosilicate glass powder resulted in higher thermal neutron shielding capability. Thus, borosilicate glass powder can be used as a good mineral additive for various radiation shielding purposes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microstructural and Microanalytical Study on Concrete Exposed to the Sulfate Environment

NASA Astrophysics Data System (ADS)

Qing, Fang; Beixing, Li; Jiangang, Yin; Xiaolu, Yuan

2017-11-01

Microstructural properties have been examined to investigate the effect of mineral admixtures on the sulfate resistance of concrete. Concrete and cement paste specimens made with ordinary Portland cement (OPC) or ordinary Portland cement incorporating 20% fly ash (FA) or 30% ground blast furnace slag (GBFS), were made and exposed to 250 cycles of the cyclic sulfate environment. Microstructural and Microanalytical study was conducted by means of x-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Results indicate that the pore structure of concrete after sulfate exposure possesses the fractal feature. The OPC concrete presents more complex pore internal surface, higher porosity and less micro-pores than the concrete incorporating fly ash and GBFS. Portlandite in OPC concrete and OPC-FA concrete is mainly converted to gypsum; while for OPC-GBFS concrete, both gypsum and ettringite are formed. In the cyclic sulfate environment, repeated hydration and dehydration of sulfates produce the expansive stress in pores, aggravating the demolishment of concrete structure.

An alternative clinical approach to achieve greater anterior than posterior maxillary expansion in cleft lip and palate patients.

PubMed

Oliveira, Dauro Douglas; Bartolomeo, Flávia Uchôa Costa; Cardinal, Lucas; Figueiredo, Daniel Santos Fonseca; Palomo, Juan Martin; Andrade, Ildeu

2014-11-01

Cleft lip and palate patients commonly present maxillary constriction, particularly in the anterior region. The aim of this case report was to describe an alternative clinical approach that used a smaller Hyrax screw unconventionally positioned to achieve greater anterior than posterior expansion in patients with complete unilateral cleft lip and palate. The idea presented here is to take advantage of a reduced dimension screw to position it anteriorly. When only anterior expansion was needed (patient 1), the appliance was soldered to the first premolar bands and associated to a transpalatal arch cemented to the first molars. However, when overall expansion was required (patient 2), the screw was positioned anteriorly, but soldered to the first molar bands. Intercanine, premolar, and first molar widths were measured on dental casts with a digital caliper. Pre-expansion and postexpansion radiographs and tomographies were also evaluated. A significant anterior expansion and no intermolar width increase were registered in the first patient. Although patient 2 also presented a greater anterior than posterior expansion, a noteworthy expansion occurred at the molar region. The alternative approach to expand the maxilla in cleft patients reported here caused greater anterior than posterior expansion when the Mini-Hyrax was associated to a transpalatal arch, and its reduced dimension also minimized discomfort and facilitated hygiene.

Influence of the Ca/Si ratio of the C–S–H phase on the interaction with sulfate ions and its impact on the ettringite crystallization pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunther, Wolfgang; Lothenbach, Barbara; Skibsted, Jørgen, E-mail: jskib@chem.au.dk

2015-03-15

The effect of the Ca/Si ratio of the calcium–silicate–hydrate (C–S–H) phase on the interaction with sulfate ions is investigated for C–S–H phases (Ca/Si = 0.83, 1.25, 1.50) and mortar samples of blended Portland cements. It is shown that leaching of calcium from C–S–H and portlandite affects the composition of the pore solution and contributes to the developing crystallization pressure of ettringite. Sulfate profiles show that sulfate binding before cracking is similar for different Ca/Si ratios whereas the highest expansion rates are observed for the mortars with the highest Ca/Si ratios. After leaching in sulfate solutions, the C–S–H samples have beenmore » characterized by {sup 29}Si MAS NMR, thermogravimetric analysis, and elemental solution analysis. Generally, the exposure to sulfate solutions results in decalcification of the C–S–H, which increases with decreasing Ca/Si ratio. The data are in good agreement with thermodynamic modeling, indicating that equilibrium is almost achieved in the leached systems. Finally, the expansion of mortar samples exposed to sulfate solutions was much less at lower Ca/Si ratios of the cement blends. This reduced expansion can be related to the decrease of the supersaturation of the pore solution with respect to ettringite at lower Ca/Si ratios of the C–S–H and in the absence of portlandite.« less

Mesos-scale modeling of irradiation in pressurized water reactor concrete biological shields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Pape, Yann; Huang, Hai

Neutron irradiation exposure causes aggregate expansion, namely radiation-induced volumetric expansion (RIVE). The structural significance of RIVE on a portion of a prototypical pressurized water reactor (PWR) concrete biological shield (CBS) is investigated by using a meso- scale nonlinear concrete model with inputs from an irradiation transport code and a coupled moisture transport-heat transfer code. RIVE-induced severe cracking onset appears to be triggered by the ini- tial shrinkage-induced cracking and propagates to a depth of > 10 cm at extended operation of 80 years. Relaxation of the cement paste stresses results in delaying the crack propagation by about 10 years.

Red mud addition in the raw meal for the production of Portland cement clinker.

PubMed

Tsakiridis, P E; Agatzini-Leonardou, S; Oustadakis, P

2004-12-10

The aim of the present research work was to investigate the possibility of adding red mud, an alkaline leaching waste, which is obtained from bauxite during the Bayer process for alumina production, in the raw meal for the production of Portland cement clinker. For that reason, two samples of raw meals were prepared: one with ordinary raw materials, as a reference sample ((PC)Ref), and another with 3.5% red mud ((PC)R/M). The effect on the reactivity of the raw mix was evaluated on the basis of the unreacted lime content in samples sintered at 1350, 1400 and 1450 degrees C. Subsequently, the clinkers were produced by sintering the two raw meals at 1450 degrees C. The results of chemical and mineralogical analyses as well as the microscopic examination showed that the use of the red mud did not affect the mineralogical characteristics of the so produced Portland cement clinker. Furthermore, both clinkers were tested by determining the grindability, setting time, compressive strength and expansibility. The hydration products were examined by XRD analysis at 2, 7, 28 and 90 days. The results of the physico-mechanical tests showed that the addition of the red mud did not negatively affect the quality of the produced cement.

Application of Cement Science to Improved Wellbore Infrastructures Mileva Radonjic and Darko Kupresan Craft & Hawkins Department of Petroleum Engineering, Louisiana State University, USA Corresponding author: mileva@lsu.edu Key words: micro-annular gas flow, nano-properties of wellbore cements, micro-porosity

NASA Astrophysics Data System (ADS)

Radonjic, M.

2015-12-01

Recent focus on carbon emission from cement industry inspired researchers to improve CSH properties by reducing Ca/Si ratio at the nanoscale, and lower porosity (permeability) of hydrated cement at micro scale. If implemented in wellbore cement technology, both of these efforts could provide advanced properties for wellbore infrastructure. These advancements would further reduce the issue of leaky wellbores in fluid injections, hydraulic fracturing and subsurface storage for existing operating wells. Numerous inadequately abandoned wells, however, pose more complex engineering problems, primarily due to the difficulty in locating fluid flow pathways along the wellbore structure. In order to appreciate the difficulty of this problem, we need to remind ourselves that: a typical 30,000-ft. wellbore with an average production casing of 8 inches in diameter can be presented in scale by a 6-m long human hair of 150 μm these structures are placed in the subsurface, often not just vertical in geometry but deviated close to 90° tangent where monitoring and remediation becomes demanding and if we consider that wellbore cement is not continuously placed along the wellbore and it is approximately 1/10 of a wellbore diameter, we can see that the properties of these materials demand application of nano-science and a different scale phenomena than perhaps previously acknowledged. The key concept behind Ca/Si reduction associated with improved mechanical properties is traditionally achieved chemically, by addition of supplemental cementitious materials. In our study we have tried to evaluate CSH alterations due to mechanically induced phase transformation. The data suggest that confined compression-extrusion of hydrated wellbore cement and the consequent propagation of pore water can change cement composition by dissolving and removing Ca, therefore reducing Ca/Si of cement phases. The advantage of this approach is that the process is less impacted by pressure/temperature oscillations found in subsurface conditions. In addition, we have proved experimentally, that even cement samples stored in corrosive environment for two years can successfully be treated and healed by confined compression of tubular expansion for purpose of microannular gas flow remediation.

Effect of pulverized fuel ash and CO{sub 2} curing on the water resistance of magnesium oxychloride cement (MOC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Pingping; Poon, Chi Sun, E-mail: cecspoon@polyu.edu.hk; Tsang, Daniel C.W.

This paper presents a study on the use of pulverized fuel ash (PFA) to improve the water resistance of magnesium oxychloride cement (MOC). Strength retention coefficients and volume stability were tested to evaluate the water resistance of MOC, in which the addition of PFA resulted in a remarkable improvement. The characterization of hydration products before and after water immersion was carried out using quantitative X-ray diffraction (QXRD), thermogravimetric (TG), Fourier-transformed infrared spectroscopy (FTIR) and scanning electron microscope (SEM). With the Q-XRD analysis, it was shown that the addition of PFA could result in the great increase of the amount ofmore » amorphous phase during air curing. This amorphous gel was identified as a mixture of magnesium-chloride-silicate-hydrate gel (M-Cl-S-H gel) and magnesium-chloride-hydrate gel (M-Cl-H gel) by elemental mapping scanning. It suggested that PFA could not only react with MOC to form M-Cl-S-H gel, but also change the morphology of magnesium oxychloride. The generation of insoluble M-Cl-S-H gel and M-Cl-H gel and densification of the microstructure contributed to the improvement of the water resistance of MOC. The MOC mortar expanded during air curing due to the hydration of excess MgO. Water immersion led to more expansion of MOC mortar as a result of the continuously hydration of excess MgO and the formation of Mg(OH){sub 2}. Adding PFA could increase the expansion of MOC mortar during air curing, which may because the amorphous gel could remain more water and benefit to the hydration of MgO. While, the addition of PFA could decrease the expansion of cement mortar during water immersion perhaps due to the reduction of the content of excess MgO and the insoluble amorphous-gel-layer that protect the MgO from hydration. Moreover, CO{sub 2} curing could further improve the performance of the PFA-blended MOC due to the formation of a higher content of amorphous gel.« less

Advanced Numerical Model for Irradiated Concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giorla, Alain B.

In this report, we establish a numerical model for concrete exposed to irradiation to address these three critical points. The model accounts for creep in the cement paste and its coupling with damage, temperature and relative humidity. The shift in failure mode with the loading rate is also properly represented. The numerical model for creep has been validated and calibrated against different experiments in the literature [Wittmann, 1970, Le Roy, 1995]. Results from a simplified model are shown to showcase the ability of numerical homogenization to simulate irradiation effects in concrete. In future works, the complete model will be appliedmore » to the analysis of the irradiation experiments of Elleuch et al. [1972] and Kelly et al. [1969]. This requires a careful examination of the experimental environmental conditions as in both cases certain critical information are missing, including the relative humidity history. A sensitivity analysis will be conducted to provide lower and upper bounds of the concrete expansion under irradiation, and check if the scatter in the simulated results matches the one found in experiments. The numerical and experimental results will be compared in terms of expansion and loss of mechanical stiffness and strength. Both effects should be captured accordingly by the model to validate it. Once the model has been validated on these two experiments, it can be applied to simulate concrete from nuclear power plants. To do so, the materials used in these concrete must be as well characterized as possible. The main parameters required are the mechanical properties of each constituent in the concrete (aggregates, cement paste), namely the elastic modulus, the creep properties, the tensile and compressive strength, the thermal expansion coefficient, and the drying shrinkage. These can be either measured experimentally, estimated from the initial composition in the case of cement paste, or back-calculated from mechanical tests on concrete. If some are unknown, a sensitivity analysis must be carried out to provide lower and upper bounds of the material behaviour. Finally, the model can be used as a basis to formulate a macroscopic material model for concrete subject to irradiation, which later can be used in structural analyses to estimate the structural impact of irradiation on nuclear power plants.« less

Biomass fly ash incorporation in cement based materials =

NASA Astrophysics Data System (ADS)

Rajamma, Rejini

In recent years, pressures on global environment and energy security have led to an increasing demand on renewable energy sources, and diversification of Europe's energy supply. Among these resources the biomass could exert an important role, since it is considered a renewable and CO2 neutral energy resource once the consumption rate is lower than the growth rate, and can potentially provide energy for heat, power and transports from the same installation. Currently, most of the biomass ash produced in industrial plants is either disposed of in landfill or recycled on agricultural fields or forest, and most times this goes on without any form of control. However, considering that the disposal cost of biomass ashes are raising, and that biomass ash volumes are increasing worldwide, a sustainable ash management has to be established. The main objective of the present study is the effect of biomass fly ashes in cement mortars and concretes in order to be used as a supplementary cementitious material. The wastes analyzed in the study were collected from the fluidized bed boilers and grate boilers available in the thermal power plants and paper pulp plants situated in Portugal. The physical as well as chemical characterisations of the biomass fly ashes were investigated. The cement was replaced by the biomass fly ashes in 10, 20 and 30% (weight %) in order to investigate the fresh properties as well as the hardened properties of biomass fly ash incorporated cement mortar and concrete formulations. Expansion reactions such as alkali silica reaction (ASR), sulphate attack (external and internal) were conducted in order to check the durability of the biomass fly ash incorporated cement mortars and concretes. Alternative applications such as incorporation in lime mortars and alkali activation of the biomass fly ashes were also attempted. The biomass fly ash particles were irregular in shape and fine in nature. The chemical characterization revealed that the biomass fly ashes were similar to a class C fly ash. The mortar results showed a good scope for biomass fly ashes as supplementary cementitious materials in lower dosages (<20%). The poor workability, concerns about the organic content, alkalis, chlorides and sulphates stand as the reasons for preventing the use of biomass fly ash in high content in the cement mortars. The results obtained from the durability tests have shown a clear reduction in expansion for the biomass fly ash mortars/concretes and the binder blend made with biomass fly ash (20%) and metakaolin (10%) inhibited the ASR reaction effectively. The biomass fly ash incorporation in lime mortars did not improve the mortar properties significantly though the carbonation was enhanced in the 15-20% incorporation. The biomass fly ash metakaolin blend worked well in the alkali activated complex binder application also. Portland cement free binders (with 30-40 MPa compressive strength) were obtained on the alkali activation of biomass fly ashes (60-80%) blended with metakaolin (20-40%).

Effects of the restoration mortar on chalk stone buildings

NASA Astrophysics Data System (ADS)

Ion, R. M.; Teodorescu, S.; Ştirbescu, R. M.; Dulamă, I. D.; Şuică-Bunghez, I. R.; Bucurică, I. A.; Fierăscu, R. C.; Fierscu, I.; Ion, M. L.

2016-06-01

The monument buildings as components of cultural heritage are exposed to degradation of surfaces and chemical and mechanical degradation, often associated to soiling and irreversible deterioration of the building. In many conservative and restorative works, a cement-based mortar was used without knowing all the adverse effects of this material on the building. This paper deals with the study of the effects of natural cement used in restorative works in the particular case of the Basarabi-Murfatlar Churches Ensemble. Cement-based materials exposed to sulfate present in the chalk stone - gypsum (CaSO4.2H2O), can induce signs of deterioration, due to ettringite ([Ca3Al (OH)612H2O]2(SO4)32H2O) or thaumasite (Ca3[Si(OH)612H2O](CO3)SO4) formation. These phases contribute to strain within the material, inducing expansion, strength loss, spalling and severe degradation. Several combined techniques (XRD, EDXRF, ICP-AES, SEM, EDS, sulphates content, FT-IR and Raman analysis were carried out to put into evidence the effects of them on the building walls.

Resistance of class C fly ash belite cement to simulated sodium sulphate radioactive liquid waste attack.

PubMed

Guerrero, A; Goñi, S; Allegro, V R

2009-01-30

The resistance of class C fly ash belite cement (FABC-2-W) to concentrated sodium sulphate salts associated with low level wastes (LLW) and medium level wastes (MLW) is discussed. This study was carried out according to the Koch and Steinegger methodology by testing the flexural strength of mortars immersed in simulated radioactive liquid waste rich in sulphate (48,000 ppm) and demineralised water (used as a reference), at 20 degrees C and 40 degrees C over a period of 180 days. The reaction mechanisms of sulphate ion with the mortar was carried out through a microstructure study, which included the use of Scanning electron microscopy (SEM), porosity and pore-size distribution and X-ray diffraction (XRD). The results showed that the FABC mortar was stable against simulated sulphate radioactive liquid waste (SSRLW) attack at the two chosen temperatures. The enhancement of mechanical properties was a result of the formation of non-expansive ettringite inside the pores and an alkaline activation of the hydraulic activity of cement promoted by the ingress of sulphate. Accordingly, the microstructure was strongly refined.

Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

NASA Astrophysics Data System (ADS)

Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.; Medina, A. N.; Baesso, M. L.; Astrath, N. G. C.; Astrath, F. B. G.; Santos, A. D.; Moraes, J. C. S.; Bento, A. C.

2013-11-01

The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (˜7 min) and with similar thermal expansion (˜12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its application in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10-3 cm2/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s0.5/cm2 K and volume heat capacity (5.2 ± 0.7) J/cm3 K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water).

Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.

The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (∼7 min) and with similar thermal expansion (∼12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its applicationmore » in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10{sup −3} cm{sup 2}/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s{sup 0.5}/cm{sup 2} K and volume heat capacity (5.2 ± 0.7) J/cm{sup 3} K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water)« less

Effect of temperature on the durability of class C fly ash belite cement in simulated radioactive liquid waste: synergy of chloride and sulphate ions.

PubMed

Guerrero, A; Goñi, S; Allegro, V R

2009-06-15

The durability of class C fly ash belite cement (FABC-2-W) in simulated radioactive liquid waste (SRLW) rich in a mixed sodium chloride and sulphate solution is presented here. The effect of the temperature and potential synergic effect of chloride and sulfate ions are discussed. This study has been carried out according to the Koch-Steinegger test, at the temperature of 20 degrees C and 40 degrees C during a period of 180 days. The durability has been evaluated by the changes of the flexural strength of mortar, fabricated with this cement, immersed in a simulated radioactive liquid waste rich in sulfate (0.5M), chloride (0.5M) and sodium (1.5M) ions--catalogued like severely aggressive for the traditional Portland cement--and demineralised water, which was used as reference. The reaction mechanism of sulphate, chloride and sodium ions with the mortar was evaluated by scanning electron microscopy (SEM), porosity and pore-size distribution, and X-ray diffraction (XRD). The results showed that the chloride binding and formation of Friedel's salt was inhibited by the presence of sulphate. Sulphate ion reacts preferentially with the calcium aluminate hydrates forming non-expansive ettringite which precipitated inside the pores; the microstructure was refined and the mechanical properties enhanced. This process was faster and more marked at 40 degrees C.

Utilization of recycled glass derived from cathode ray tube glass as fine aggregate in cement mortar.

PubMed

Ling, Tung-Chai; Poon, Chi-Sun

2011-08-30

Rapid advances in the electronic industry led to an excessive amount of early disposal of older electronic devices such as computer monitors and old televisions (TV) before the end of their useful life. The management of cathode ray tubes (CRT), which have been a key component in computer monitors and TV sets, has become a major environmental problem worldwide. Therefore, there is a pressing need to develop sustainable alternative methods to manage hazardous CRT glass waste. This study assesses the feasibility of utilizing CRT glass as a substitute for natural aggregates in cement mortar. The CRT glass investigated was an acid-washed funnel glass of dismantled CRT from computer monitors and old TV sets. The mechanical properties of mortar mixes containing 0%, 25%, 50%, 75% and 100% of CRT glass were investigated. The potential of the alkali-silica reaction (ASR) and leachability of lead were also evaluated. The results confirmed that the properties of the mortar mixes prepared with CRT glass was similar to that of the control mortar using sand as fine aggregate, and displayed innocuous behaviour in the ASR expansion test. Incorporating CRT glass in cement mortar successfully prevented the leaching of lead. We conclude that it is feasible to utilize CRT glass in cement mortar production. Copyright © 2011 Elsevier B.V. All rights reserved.

New cementitious system: The case of glass frit

NASA Astrophysics Data System (ADS)

Fares, Galal

Canada ranks as the world's third largest aluminium producer, and more than 80% of its aluminum industry is concentrated in Quebec. However, the spent pot-liner waste produced by the aluminium smelters accumulates with time into a considerable amount threatening the Canadian environment, especially that of Quebec. A new-engineered material, known as glass fit (GF) has been developed through the chemical treatment of such waste. GF shows potential hydraulic and pozzolanic properties. GF has been studied as a binder itself and as a supplementary cementitious material (SCM). The activation of industrial by-products into clinkerless binders is a novel trend that has attracted the attention of many researchers. The activation of GF into binder to produce paste, mortar and concrete was the first aim of this study. Potential activation of GF using different types and combinations of inorganic activators and temperatures of activation was successfully achieved and high strength concretes were obtained. Moreover, mortars with high compressive strength were obtained with well-formulated activators at ambient temperature. On the other hand, the utilization of industrial by-products as a partial replacement for cement in concrete is a widespread practice. As GF contains a high concentration of sodium in its structure, there is a concern as to the effect of sodium content on the development of alkali-silica reaction (ASR) expansion of concrete. Therefore, this study also aimed to investigate the effect of GF sodium content in the enhancement of ASR expansion and to find new synergistic mixtures that can effectively mitigate ASR expansion in the long term. We observed that ASR expansion decreases with the replacement level of GF. Different synergistic diagrams containing known SCM (silica fume, fly ash, and slag) were achieved from which different effective mixtures can effectively alleviate ASR expansion. In conclusion, the use of GF in the manufacture of concrete has great benefits. Economically, it could save millions of Canadian dollars needed for the treatment and landfilling of spent pot-liner waste. Ecologically, it could reduce GHG emissions associated with the production of cement clinkers. In this study, most of the well-known by-products are used according to the sustainability theory.

Experimental Study on Comprehensive Performance of Full Tailings Paste Filling in Jiaojia Gold Mine.

NASA Astrophysics Data System (ADS)

Zhang, Z. H.; Zou, Q. B.; Wang, P. Z.

2017-11-01

Filling mining method is the main method of modern underground mining. High concentration cementation is carried out using coarse tailing of +37 μm, and the mine has maturely used classified tailings paste filling technology. The gold mine studied on the performance of full tailings paste filling in order to maximize the use of tailings, reduce -37 μm fine tailings discharged into the tailing pond, reduce mining cost and eliminate security risks. The results show that: comprehensive index of full tailings paste filling is higher than that of classified tailings high concentration cementation filling, and the full tailings paste filling of 76% mass concentration has the best comprehensive index of slump, expansibility, yield stress and viscosity to meet the mining method requirements, which can effectively reduce the mining loss rate and dilution rate.

THERMAL PROPERTIES AND HEATING AND COOLING DURABILITY OF REACTOR SHIELDING CONCRETE (in Japanese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosoi, J.; Chujo, K.; Saji, K.

1959-01-01

A study was made of the thermal properties of various concretes made of domestic raw materials for radiation shields of a power reactor and of a high- flux research reactor. The results of measurements of thermal expansion coefficient, specific heat, thermal diffusivity, thermal conductivity, cyclical heating, and cooling durability are described. Relationships between thermal properties and durability are discussed and several photographs of the concretes are given. It is shown that the heating and cooling durability of such a concrete which has a large thermal expansion coefficient or a considerable difference between the thermal expansion of coarse aggregate and themore » one of cement mortar part or aggregates of lower strength is very poor. The decreasing rates of bending strength and dynamical modulus of elasticity and the residual elongation of the concrete tested show interesting relations with the modified thermal stress resistance factor containing a ratio of bending strength and thermal expansion coefficient. The thermal stress resistance factor seems to depend on the conditions of heat transfer on the surface and on heat release in the concrete. (auth)« less

On the relevance of volume increase for the length changes of mortar bars in sulfate solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunther, Wolfgang, E-mail: wkunther@googlemail.com; Lothenbach, Barbara; Scrivener, Karen L.

2013-04-01

The ingress of sulfate ions into cementitious materials leads to the formation of ettringite, gypsum and other phases. The increase in solid volume through the formation of these phases is often assumed to be the only reason for expansion. In this paper we systematically compare the volume increase predicted by thermodynamic modeling to macroscopic expansion for mortars made with CEM I in different sulfate solutions and for mortars made with a range of blended cements in sodium sulfate solution. It is shown that the length changes cannot be explained by simple volume increase alone. A more plausible explanation of expansionmore » lies in the theory of crystallization pressure, in which crystals forming from a supersaturated solution may exert pressure on their surroundings. It is observed that expansion occurs in systems where thermodynamic modeling predicts the co-existence of ettringite with gypsum. In such a case, if monosulfate and gypsum are both present locally, the solution can be highly supersaturated with respect to ettringite, whose formation in confined conditions (such as within C–S–H) can then exert expansive forces.« less

Stable and rugged etalon for the Dynamics Explorer Fabry-Perot interferometer. 1: Design and construction.

PubMed

Rees, D; Fuller-Rowell, T J; Lyons, A; Killeen, T L; Hays, P B

1982-11-01

This is one of two papers which describe the development and performance of a very stable and rugged etalon designed for use in the Fabry-Perot interferometer, one of the instruments of the NASA Dynamics Explorer satellite mission, and which will obtain global measurements of the thermospheric and mesospheric wind and temperature with an accuracy of aporoximately 10 m/sec. The etalon consists of two flat plates of fused silica, with spacers constructed of Zerodur (a polycrystalline glass ceramic of extremely low expansion coefficient) which are cemented together using cyanoacrylic adhesives. This provides adequate mechanical integrity and stability for any space flight application and has a thermal expansion coefficient of the etalon cavity of <10(-7)/ degrees C.

Experimental collaboration for thick concrete structures with alkali-silica reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ezell, N Dianne Bull; Hayes, Nolan W.; Lenarduzzi, Roberto

Alkali-Silica Reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, non-crystalline silica in aggregates. An expansive gel is formed within the aggregates which results in micro-cracks in aggregates and adjacent cement paste. The reaction requires the presence of water and has been predominantly detected in groundwater-impacted portions of below grade structures, with limited impact to exterior surfaces in above grade structures. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, shear strength, and tensile strength. Since ASR degradation often takes significant amounts of time, developingmore » ASR detection techniques is important to the sustainability and extended operation lifetimes of nuclear power plants (NPPs). The University of Tennessee, Knoxville (UTK) in collaboration with Oak Ridge National Laboratory (ORNL) designed and built an experiment representative of typical NPP structures to study ASR in thick concrete structures.« less

Experimental collaboration for thick concrete structures with alkali-silica reaction

NASA Astrophysics Data System (ADS)

Ezell, N. Dianne Bull; Hayes, Nolan; Lenarduzzi, Roberto; Clayton, Dwight; Ma, Z. John; Le Pape, Sihem; Le Pape, Yann

2018-04-01

Alkali-Silica Reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, non-crystalline silica in aggregates. An expansive gel is formed within the aggregates which results in micro-cracks in aggregates and adjacent cement paste. The reaction requires the presence of water and has been predominantly detected in groundwater-impacted portions of below grade structures, with limited impact to exterior surfaces in above grade structures. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, shear strength, and tensile strength. Since ASR degradation often takes significant amounts of time, developing ASR detection techniques is important to the sustainability and extended operation lifetimes of nuclear power plants (NPPs). The University of Tennessee, Knoxville (UTK) in collaboration with Oak Ridge National Laboratory (ORNL) designed and built an experiment representative of typical NPP structures to study ASR in thick concrete structures.

Influence of bicarbonate ions on the deterioration of mortar bars in sulfate solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunther, W., E-mail: Wolfgang.Kunther@empa.ch; Lothenbach, B.; Scrivener, K.

2013-02-15

This work investigates the influence of bicarbonate ions on the deterioration of cementitious material exposed to sulfate ions. Mortars based on a CEM I and on a CEM III/B cement were investigated. Experimental investigations were compared to thermodynamic modeling and phase characterization to understand the differences in deterioration. The presence of bicarbonate ions significantly reduced the expansion of the CEM I mortars. Thermodynamic modeling showed that at high concentrations of bicarbonate ettringite and gypsum become unstable. Microstructural characterization combined with information from thermodynamic modeling suggests that conditions of high supersaturation with respect to ettringite are unlikely in the samples exposedmore » in solutions containing bicarbonate. Consequently, expansive forces are not generated by the crystallization pressure of ettringite. There was little expansion of the CEM III/B sample even in the sodium sulfate solution. In the bicarbonate solution this mortar showed a highly leached zone at the surface in which calcite was observed.« less

Development of leachate test for delayed ettringite formation potential in cementitious materials

NASA Astrophysics Data System (ADS)

France-Mensah, Jojo

Delayed Ettringite Formation (DEF) has been known to be the cause of expansion and cracking at latter ages in concrete that has been heat cured at temperatures around 70 degree Celsius or above. Currently, the only method available for measuring DEF-related physical expansion in concrete can sometimes take over a year to yield relevant results. A leachate method was proposed as a means of taking advantage of the release and solubility of the adsorbed ions (e.g., calcium, sulfates and aluminates) and alkali ions (e.g., sodium and potassium) in the pore solution after heat curing of the cement paste matrix. These ions, known to contribute to DEF, were leached out of concrete into the leaching solution. The results of the leachate test were correlated to physical expansion data of similar samples from an earlier study. The aim of this research is to apply this knowledge to develop an accelerated leachate test method for identifying the potential for DEF in cementitious materials in a shorter time than the existing method. The objectives of this research are: (1) to identify the ion(s) through leaching that is/are the controlling factors in predicting the rate of expansion and overall expansion of mortar; (2) to identify the ion(s) that is/are responsible for the lag time or age of deleterious expansion through DEF; and (3) to investigate the effect of heat curing on the overall, rate of, and age (time) of expansion.

The Use of Natural Pozzolan in Concrete as an Additive or Substitute for Cement

DTIC Science & Technology

2011-12-01

identified opal and chert as the common forms of reactive silica. ERDC/CERL TR-11-46 4 For cracking and expansion to result from the ASR, the following combi...chemical composition of three natural pozzolanic samples was deter- mined through XRD analysis. In addition to these analyses, several addi- tional tests...reflected angle, which results in an inaccurate plot. The correct angle is required to deter- mine the correct composition. A very finely ground sample

Erosion of water-based cements evaluated by volumetric and gravimetric methods.

PubMed

Nomoto, Rie; Uchida, Keiko; Momoi, Yasuko; McCabe, John F

2003-05-01

To compare the erosion of glass ionomer, zinc phosphate and polycarboxylate cements using volumetric and gravimetric methods. For the volumetric method, the eroded depth of cement placed in a cylindrical cavity in PMMA was measured using a dial gauge after immersion in an eroding solution. For the gravimetric method, the weight of the residue of a solution in which a cylindrical specimen had been immersed was measured. 0.02 M lactic acid solution (0.02 M acid) and 0.1 M lactic acid/sodium lactate buffer solution (0.1 M buffer) were used as eroding solutions. The pH of both solutions was 2.74 and the test period was 24 h. Ranking of eroded depth and weight of residue was polycarboxylate>zinc phosphate>glass ionomers. Differences in erosion were more clearly defined by differences in eroded depth than differences in weight of residue. In 0.02 M acid, the erosion of glass ionomer using the volumetric method was effected by the hygroscopic expansion. In 0.1 M buffer, the erosion for polycarboxylate and zinc phosphate using the volumetric method was much greater than that using the gravimetric method. This is explained by cryo-SEM images which show many holes in the surface of specimens after erosion. It appears that zinc oxide is dissolved leaving a spongy matrix which easily collapses under the force applied to the dial gauge during measurement. The volumetric method that employs eroded depth of cement using a 0.1 M buffer solution is able to quantify erosion and to make material comparisons.

Physicochemical and mechanical properties of zirconium oxide and niobium oxide modified Portland cement-based experimental endodontic sealers.

PubMed

Viapiana, R; Flumignan, D L; Guerreiro-Tanomaru, J M; Camilleri, J; Tanomaru-Filho, M

2014-05-01

To evaluate the physicochemical and mechanical properties of Portland cement-based experimental sealers (ES) with different radiopacifying agents (zirconium oxide and niobium oxide micro- and nanoparticles) in comparison with the following conventional sealers: AH Plus, MTA Fillapex and Sealapex. The materials were tested for setting time, compressive strength, flow, film thickness, radiopacity, solubility, dimensional stability and formaldehyde release. Data were subjected to anova and Tukey tests (P < 0.05). MTA Fillapex had the shortest setting time and lowest compressive strength values (P < 0.05) compared with the other materials. The ES had flow values similar to the conventional materials, but higher film thickness (P < 0.05) and lower radiopacity (P < 0.05). Similarly to AH Plus, the ES were associated with dimensional expansion (P > 0.05) and lower solubility when compared with MTA Fillapex and Sealapex (P < 0.05). None of the endodontic sealers evaluated released formaldehyde after mixing. With the exception of radiopacity, the Portland cement-based experimental endodontic sealers presented physicochemical properties according to the specifications no 57 ANSI/ADA (ADA Professional Product Review, 2008) and ISO 6876 (Dentistry - Root Canal Sealing Materials, 2012, British Standards Institution, London, UK). The sealers had setting times and flow ability that was adequate for clinical use, satisfactory compressive strength and low solubility. Additional studies should be carried out with the purpose of decreasing the film thickness and to determine the ideal ratio of radiopacifying agents in Portland cement-based root canal sealers. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Importance of microscopy in durability studies of solidified and stabilized contaminated soils

USGS Publications Warehouse

Klich, I.; Wilding, L.P.; Drees, L.R.; Landa, E.R.

1999-01-01

Solidification/stabilization (S/S) is recognized by the U.S. EPA as a best demonstrated available technology for the containment of contaminated soils and other hazardous wastes that cannot be destroyed by chemical, thermal, or biological means. Despite the increased use of S/S technologies, little research has been conducted on the weathering and degradation of solidified and stabilized wastes once the treated materials have been buried. Published data to verify the performance and durability of landfilled treated wastes over time are rare. In this preliminary study, optical and electron microscopy (scanning electron microscopy [SEM], transmission electron microscopy [TEM] and electron probe microanalyses [EPMA]) were used to evaluate weathering features associated with metal-bearing contaminated soil that had been solidified and stabilized with Portland cement and subsequently buried on site, stored outdoors aboveground, or achieved in a laboratory warehouse for up to 6 yr. Physical and chemical alteration processes identified include: freeze-thaw cracking, cracking caused by the formation of expansive minerals such as ettringite, carbonation, and the movement of metals from waste aggregates into the cement micromass. Although the extent of degradation after 6 yr is considered slight to moderate, results of this study show that the same environmental concerns that affect the durability of concrete must be considered when evaluating the durability and permanence of the solidification and stabilization of contaminated soils with cement. In addition, such evaluations cannot be based on leaching and chemical analyses alone. The use of all levels of microscopic analyses must be incorporated into studies of the long-term performance of S/S technologies.Solidification/stabilization (S/S) is recognized by the U.S. EPA as a best demonstrated available technology for the containment of contaminated soils and other hazardous wastes that cannot be destroyed by chemical, thermal, or biological means. Despite the increased use of S/S technologies, little research has been conducted on the weathering and degradation of solidified and stabilized wastes once the treated materials have been buried. Published data to verify the performance and durability of landfilled treated wastes over time are rare. In this preliminary study, optical and electron microscopy (scanning electron microscopy [SEM], transmission electron microscopy [TEM] and electron probe microanalyses [EPMA]) were used to evaluate weathering features associated with metal-bearing contaminated soil that had been solidified and stabilized with Portland cement and subsequently buried on site, stored outdoors aboveground, or archived in a laboratory, warehouse for up to 6 yr. Physical and chemical alteration processes identified include: freeze-thaw cracking, cracking caused by the formation of expansive minerals such as ettringite, carbonation, and the movement of metals from waste aggregates into the cement micromass. Although the extent of degradation after 6 yr is considered slight to moderate, results of this study show that the same environmental concerns that affect the durability of concrete must be considered when evaluating the durability and permanence of the solidification and stabilization of contaminated soils with cement. In addition, such evaluations cannot be based on leaching and chemical analyses alone. The use of all levels of microscopic analyses must be incorporated into studies of the long-term performance of S/S technologies.

Detecting alkali-silica reaction in thick concrete structures using linear array ultrasound

NASA Astrophysics Data System (ADS)

Bull Ezell, N. Dianne; Albright, Austin; Clayton, Dwight; Santos-Villalobos, Hector

2018-03-01

Commercial nuclear power plants (NPPs) depend heavily on concrete structures, making the long-term performance of these structures crucial for safe operation, especially with license period extensions to 60 years and possibly beyond. Alkali-silica reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, noncrystalline silica (aggregates). In the presence of water, an expansive gel is formed within the aggregates, which results in microcracks in aggregates and adjacent cement paste. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, flexural stiffness, shear strength, and tensile strength. Currently, no nondestructive evaluation methods have proven effective in identifying ASR before surface cracks form. ASR is identified visibly or by petrographic analysis. Although ASR definitely impacts concrete material properties, the performance of concrete structures exhibiting ASR depends on whether or not the concrete is unconfined or confined with reinforcing bars. Confinement by reinforcing bars restrainsthe expansion of ASR-affected concrete, similar to prestressing, thus improving the performance of a structure. Additionally, there is no direct correlation between the mechanical properties of concrete sample cores and the in-situ properties of the concrete. The University of Tennessee-Knoxville, Oak Ridge National Laboratory, and a consortium of universities have developed an accelerated ASR experiment. Three large concrete specimens, representative of NPP infrastructure, were constructed containing both embedded and surface instruments. This paper presents preliminary analysis of these specimens using a frequency-banded synthetic aperture focusing technique.

Influence of Titanium Dioxide Nanoparticles on the Sulfate Attack upon Ordinary Portland Cement and Slag-Blended Mortars

PubMed Central

Atta-ur-Rehman; Qudoos, Abdul; Kim, Hong Gi

2018-01-01

In this study, the effects of titanium dioxide (TiO2) nanoparticles on the sulfate attack resistance of ordinary Portland cement (OPC) and slag-blended mortars were investigated. OPC and slag-blended mortars (OPC:Slag = 50:50) were made with water to binder ratio of 0.4 and a binder to sand ratio of 1:3. TiO2 was added as an admixture as 0%, 3%, 6%, 9% and 12% of the binder weight. Mortar specimens were exposed to an accelerated sulfate attack environment. Expansion, changes in mass and surface microhardness were measured. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Thermogravimetry Analysis (TGA) and Differential Scanning Calorimetry (DSC) tests were conducted. The formation of ettringite and gypsum crystals after the sulfate attack were detected. Both these products had caused crystallization pressure in the microstructure of mortars and deteriorated the mortars. Our results show that the addition of nano-TiO2 accelerated expansion, variation in mass, loss of surface microhardness and widened cracks in OPC and slag-blended mortars. Nano-TiO2 containing slag-blended mortars were more resistant to sulfate attack than nano-TiO2 containing OPC mortars. Because nano-TiO2 reduced the size of coarse pores, so it increased crystallization pressure due to the formation of ettringite and gypsum thus led to more damage under sulfate attack. PMID:29495616

Face and neck dermatitis from a stainless steel orthodontic appliance.

PubMed

Ehrnrooth, Minna; Kerosuo, Heidi

2009-11-01

Although nickel is the most common cause of contact allergy, nickel-containing orthodontic appliances seldom cause adverse reactions that result in discontinuation of treatment. We report on an eruption of dermatitis in the face and neck of an adult female patient after placement of a rapid maxillary expansion appliance (RME). Because the patient suspected nickel allergy, her tolerance to the appliance material was tested intraorally before treatment by cementing bands on four teeth for a week. No visible adverse reactions were seen during the test. One week after cementation of the RME appliance, the patient reported strong itching of the face and a red rash. Clinical examination showed itchy papular erythema on the face and neck. No intraoral reactions or symptoms were present. The RME appliance was removed, and symptoms disappeared in 4 to 5 days. The patient was referred for a nickel patch test, which gave a strong positive result. Adverse patient reactions of potential allergic origin should be diagnosed carefully, and their possible impact on further treatment should be evaluated accordingly.

The Assessment of Cement Mortars after Thermal Degradation by Acoustic Non-destructive Methods

NASA Astrophysics Data System (ADS)

Topolář, L.; Štefková, D.; Hoduláková, M.

2017-10-01

Thanks, the terrorist attacks on the worldwide interest in the design of structures for fire greatly increased. One of the advantages of concrete over other building materials is its inherent fire-resistive properties. The concrete structural components still must be able to withstand dead and live loads without collapse even though the rise in temperature causes a decrease in the strength and modulus of elasticity for concrete and steel reinforcement. In addition, fully developed fires cause expansion of structural components and the resulting stresses and strains must be resisted. This paper reports the results of measurements by Impact-echo method and measurement by ultrasound. Both methods are based on the acoustic properties of the material which are dependent on its condition. These acoustic methods allow identifying defects and are thus suitable for monitoring the building structure condition. The results are obtained in the laboratory during the degradation of composite materials based on cement by high-temperature.

Alkali Silica Reaction In The Presence Of Metakaolin - The Significant Role of Calcium Hydroxide

NASA Astrophysics Data System (ADS)

Zapała-Sławeta, Justyna

2017-10-01

Reducing the internal corrosion, which is the result of reactions between alkalis and reactive aggregates is especially important in ensuring durability properties of concrete. One of the methods of inhibiting the reaction is using some mineral additives which have pozzolanic properties. This paper presents the efficacy of high-reactivity metakaolin in reducing expansion due to alkali-silica reaction. It was demonstrated that metakaolin in the amount from 5% to 20% by mass of Portland cement reduce linear expansion of mortar bars with opal aggregate. Nevertheless, the safe expansion level in the specimens, classified as non-destructive to concrete, was recorded for the mortars prepared with 20% addition of metakaolin. Depletion of free calcium hydroxide content was considered as one of the most beneficial effects of metakaolin in controlling alkali silica reaction. Based on thermogravimetric analysis (TGA) performed on mortar bars with and without metakaolin the differences in portlandite content were determined. Microstructural observation of the specimens containing metakaolin indicated the presence of a reaction products but fewer in number than those forming in the mortars without mineral additives.

Salt Attack on Rocks and Expansion of Soils on Mars

NASA Astrophysics Data System (ADS)

Vaniman, D. T.; Bish, D. L.; Chipera, S. J.; Carey, J. W.

2004-12-01

Salt-rich sediments observed by the MER rover Opportunity at Meridiani Planum show that brines have been present on Mars in the past, but a role for groundwater in widespread rock weathering and soil formation is uncertain. Experiments by several groups suggest instead the action of acid fog over long time spans, with episodic input of volcanic gases, as a more significant agent of Mars weathering. Salt minerals formed in these acid weathering experiments consistently include gypsum and alunogen, with epsomite or hexahydrite forming where olivine provides a source of Mg. Analogous to the martian acid fog scenario are terrestrial acid rain or acid fog attacks on building and monument stone by chemical action and mechanical wedging through growth of gypsum, anhydrite, epsomite, hexahydrite, kieserite, and other sulfate minerals. Physical effects can be aggressive, operating by both primary salt growth and hydration of anhydrous or less-hydrous primary salts. In contrast, soils evolve to states where chemical attack is lessened and salt mineral growth leads to expansion with cementation; in this situation the process becomes constructive rather than destructive. We have made synthetic salt-cemented soils (duricrusts) from clays, zeolites, palagonites and other media mixed with ultrapure Mg-sulfate solutions. Although near-neutral in pH, these solutions still exchange or leach Ca from the solids to form cements containing gypsum as well as hexahydrite. At low total P (1 torr) and low RH (<1%) hexahydrite becomes amorphous but gypsum does not. If allowed to rehydrate from vapor at higher RH, the Mg-sulfate component of the duricrust expands by formation of a complex mixture of Mg-sulfate phases with various hydration states. The expanded form is retained even if the duricrust is again dehydrated, suggesting that soil porosity thus formed is difficult to destroy. These processes can be considered in the context of Viking, Pathfinder, and MER evidence for differing salt components in the weathered surfaces of rocks versus duricrust-like materials in soils. The divergent chemical trends indicate that soil formation on Mars is not merely a result of enhanced weathering of locally comminuted rock but requires an eolian component. The resulting soils thus appear to be a three-component mixture of local detritus, a regional or global eolian component, and acid fog additions. In the absence of rainfall or groundwater action, expanded and salt-cemented soil horizons are likely to persist as a regolith component in soil-atmosphere interactions over long time spans.

MTA and F-doped MTA cements used as sealers with warm gutta-percha. Long-term study of sealing ability.

PubMed

Gandolfi, M G; Prati, C

2010-10-01

To evaluate the long-term sealing ability (up to 6 months) of two experimental calcium silicate MTA cements used as root canal sealers in association with warm gutta-percha. Calcium silicate (MTA) and calcium-fluoro-silicate powders were prepared. Sodium fluoride was included in FMTA (Fluoride-doped Mineral Trioxide Aggregate) as an expansive and retardant agent. Single-rooted teeth were instrumented with NiTi rotary instruments, filled with warm gutta-percha in association with one of the experimental sealers or with AH Plus as a control (n = 20 for each sealer) and stored at 37 °C. Sealing was assessed at 24, 48 h, 1, 2 weeks and 1, 3, 6 months by a fluid filtration method. Scanning electron microscopy with energy dispersive analysis (SEM/EDX) was used to study the dentine/sealer interface of roots stored for 6 months and the surface of cement disks stored for 24 h. All sealers revealed a statistically significant reduction (P < 0.05) in fluid filtration after the first 2 weeks. No statistically significant differences were observed between FMTA and AH Plus at all analysis times. At short times (24, 48-h), no statistically significant differences were found between the experimental cements and AH Plus. At long-term evaluations (1, 3, 6 months), FMTA and AH Plus sealed significantly better (P < 0.05) than MTA. FMTA was associated with lower fluid filtration rates, and the seal was stable from 48 h to 6 months, thus proving the most effective material. Scanning electron microscopy with energy dispersive analysis of root sections filled with calcium silicate sealers revealed the formation of a blend layer of gutta-percha and cement consequent to the warm gutta-percha condensation technique. Scanning electron microscopy with energy dispersive analysis of 24-h-stored disks identified a Ca-rich coating on the outer surface consisting of globular particles (calcium hydroxide and calcium carbonate), and a deeper internal Ca- and Si-rich region consisting of needle-like ettringite crystals and round formations of calcium silicate hydrate gel. Fluoride-doped MTA demonstrated stable sealing during a period of up to 6 months and significantly better than conventional calcium silicate MTA cements and comparable to AH Plus. The study supports the suitability of calcium silicate MTA cements as sealers in association with warm gutta-percha for root filling. © 2010 International Endodontic Journal.

Skeletal and dental changes following surgically assisted rapid palatal expansion.

PubMed

Byloff, Friedrich K; Mossaz, Claude F

2004-08-01

The purpose of this study was to analyse the changes produced by surgically assisted rapid palatal expansion (SARPE) longitudinally on 14 patients aged between 18 and 41 years. A pre-fabricated Hyrax appliance was cemented prior to the surgical intervention, which consisted of a maxillary buccal corticotomy with pterygoid separation. Models and postero-anterior (PA) headfilms were taken before expansion (T1), at the end of expansion (T2), at the end of retention (T3) and at least 1 year post-surgery (T4). Overall expansion and relapse were measured directly on the casts. Transverse distances increased more at the first molars (8.7 mm) and premolars (8.1 and 8.3 mm) than in the canine (5.2 mm) and second molar (5.5 mm) region. Minimal relapse occurred during the retention phase. The arch width decreased more during the post-retention period, with more pronounced reduction at the teeth used as anchorage during the expansion procedure (-2.0 mm for the first premolars and -2.6 mm for the first molars). The mean total dental relapse was 28 per cent. PA radiographic analysis for angular changes showed 9.6 degrees of lateral tipping per side during expansion. One-third of this movement relapsed during the retention period (-3.3 degrees) and this trend (-6.0 degrees) continued during the post-retention phase to reach practically the original value at T1. Skeletal changes monitored on the PA headfilms were minimal with great individual variation. The mean expansion measured in the proximity of the osteotomy site was only 1.3 mm. From this amount, 0.4 mm was lost during the retention and post-retention periods. Based on these findings, it appears that maxillary skeletal expansion by SARPE is mainly a lateral rotation of the two maxillary halves with only minimal horizontal translation.

The central tower of the cathedral of Schleswig - New investigations to understand the alcali-silica reaction of historical mortars

NASA Astrophysics Data System (ADS)

Wedekind, Wanja; Protz, Andreas

2016-04-01

The damaging alcali-silica reaction leads to crack-formation and structural destruction at noumerous, constructed with cement mortar, buildings worldwide. The ASR-reaction causes the expansion of altered aggregates by the formation of a swelling gel. This gel consists of calcium silicate hydrate (C-S-H) that increases in volume with water, which exerts an expansive pressure inside the material. The cathedral of Schleswig is one of the oldest in northern Germany. The first church was built in 985-965. The Romanesque building part was erected around 1180 and the Gothic nave at the end of the 13th century. The central tower was constructed between 1888 and 1894 with brick and cement mortar. With 112 meters, the tower is the second-largest church spire of the country of Schleswig-Holstein in northern Germany. Due to the formation of cracks and damages from 1953 to 1956 first restoration works took place. Further developments of cracks are making restoration necessary again today. For developing a suitable conservation strategy, different investigations were done. The investigation included the determination of the pore space properties, the hygric and thermal dilatation and mercury porosimetry measurements. Furthermore, the application of cathodoluminescence microscopy may give information about the alteration process and microstructures present and reveal the differences between unaltered and altered mortars. An obvious relation between the porosity and the swelling intensity could be detected. Furthermore it becomes apparent, that a clear zonation of the mortar took place. The mortar near the surface is denser with a lower porosity and has a significantly lower swelling or dilatation.

Evaluation of DSS-14 pedestal-review of top surface repair procedures

NASA Technical Reports Server (NTRS)

Oesterle, R. G.; Musser, D. W.; Salse, E. A. B.

1983-01-01

Proposed repair procedures for the top surface of the pedestal supporting the hydrostatic bearing runner for the 64m Antenna are presented. These procedures included: (1) removal of existing grout and concrete to approximately 8 in. below original concrete surface using a presplitting technique with expansive cement followed by secondary breaking; (2) preparation of exposed concrete surface including an epoxy bonding agent; and (3) replacement of material removed with 8 in. of new concrete surface including an epoxy bonding agent; and (4) replacement of material removed with 8 in. of new concrete and 4 in. of new grout.

Crack closure on rehydration of glass-ionomer materials.

PubMed

Sidhu, Sharanbir K; Pilecki, Peter; Sherriff, Martyn; Watson, Timothy F

2004-10-01

Moisture-sensitivity of immature glass-ionomer cements suggests that hydration-induced volumetric expansion might close and potentially heal established cracks. Crack closure in glass-ionomer cements (GICs) was observed following rehydration. Circular cavities were prepared in 15 teeth: 10 were restored with resin-modified GICs (5 with Fuji II LC and 5 with Photac-Fil) and 5 were restored with a conventional GIC (Fuji IX); all were dehydrated for 1 min with air and imaged immediately by confocal microscopy. Crack formation in each was located, after which water was placed on the surface and observed for 15 min via a CCD camera. Dehydration caused cracks with measurable gaps, while rehydration resulted in varying degrees of closure: closure was limited in the conventional GIC, and complete or near complete along part/s of the crack in the resin-modified GICs. In all, closure movement became imperceptible after the first 10 min. Statistical analysis indicated no significant difference between the closure behavior of all materials. However, the resin-modified GICs appeared to show a greater potential for closure of established cracks than the conventional GIC upon rehydration.

Reuse of ground waste glass as aggregate for mortars.

PubMed

Corinaldesi, V; Gnappi, G; Moriconi, G; Montenero, A

2005-01-01

This work was aimed at studying the possibility of reusing waste glass from crushed containers and building demolition as aggregate for preparing mortars and concrete. At present, this kind of reuse is still not common due to the risk of alkali-silica reaction between the alkalis of cement and silica of the waste glass. This expansive reaction can cause great problems of cracking and, consequently, it can be extremely deleterious for the durability of mortar and concrete. However, data reported in the literature show that if the waste glass is finely ground, under 75mum, this effect does not occur and mortar durability is guaranteed. Therefore, in this work the possible reactivity of waste glass with the cement paste in mortars was verified, by varying the particle size of the finely ground waste glass. No reaction has been detected with particle size up to 100mum thus indicating the feasibility of the waste glass reuse as fine aggregate in mortars and concrete. In addition, waste glass seems to positively contribute to the mortar micro-structural properties resulting in an evident improvement of its mechanical performance.

The analysis of thermoplastic characteristics of special polymer sulfur composite

NASA Astrophysics Data System (ADS)

Książek, Mariusz

2017-01-01

Specific chemical environments step out in the industry objects. Portland cement composites (concrete and mortar) were impregnated by using the special polymerized sulfur and technical soot as a filler (polymer sulfur composite). Sulfur and technical soot was applied as the industrial waste. Portland cement composites were made of the same aggregate, cement and water. The process of special polymer sulfur composite applied as the industrial waste is a thermal treatment process in the temperature of about 150-155°C. The result of such treatment is special polymer sulfur composite in a liquid state. This paper presents the plastic constants and coefficients of thermal expansion of special polymer sulfur composites, with isotropic porous matrix, reinforced by disoriented ellipsoidal inclusions with orthotropic symmetry of the thermoplastic properties. The investigations are based on the stochastic differential equations of solid mechanics. A model and algorithm for calculating the effective characteristics of special polymer sulfur composites are suggested. The effective thermoplastic characteristics of special polymer sulfur composites, with disoriented ellipsoidal inclusions, are calculated in two stages: First, the properties of materials with oriented inclusions are determined, and then effective constants of a composite with disoriented inclusions are determined on the basis of the Voigt or Rice scheme. A brief summary of new products related to special polymer sulfur composites is given as follows: Impregnation, repair, overlays and precast polymer concrete will be presented. Special polymer sulfur as polymer coating impregnation, which has received little attention in recent years, currently has some very interesting applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beaver, J.L. Jr.

Suniland field is located in the west Texas Permian basin. Production is primarily from peritidal shelf dolomites of the Permian (Guadalupian) San Andres Formation. San Andres deposition was highly cyclical, with at least two upward-shoaling megacycles comprising the lower 600 ft (183 m) of the formation; many smaller cycles occur within the megacycles. The field consists of an elongate, low-relief, east-west-trending anticline formed from draping over a pre-San Andres structural high. Hydrocarbon trapping is controlled primarily by structural closure and discontinuity of San Andres reservoir facies. Anhydrite cement precipitation also may cause an updip (northerly) permeability loss. Reservoirs occur inmore » thin, permeable oolitic grainstone intervals possessing primary intergranular porosity in combination with vugular and moldic pore systems. These grainstones interfinger with porous but generally impermeable oolitic packstones. Adjacent wackestones and mudstones are generally nonporous and impermeable. Porosity occlusion is primarily from precipitation of late dolomite cements. Anhydrite cements do not occlude porosity to a high degree. Oil production from the San Andres Formation at Suniland field is from nine separate reservoirs comprising two major pay categories, designated Sand Andres and lower San Andres. Pay depths range from 3,755 to 4,211 ft (1,144 to 1,283 m). Cumulative oil production to January 1986 is 7.35 million bbl from 69 wells. Permian (Leonardian) Glorieta production accounts for about 16% of total production. Reservoirs produce from solution gas expansion at low gas-to-oil ratios and high water cuts. Effective porosity in pay zones averages 14%; permeability averages 17 md.« less

The effect of a nanofilled resin-based coating on water absorption by teeth restored with glass ionomer.

PubMed

Hankins, Amanda D; Hatch, Robert H; Benson, Jarred H; Blen, Bernard J; Tantbirojn, Daranee; Versluis, Antheunis

2014-04-01

A nanofilled, resin-based light-cured coating (G-Coat Plus, GC America, Alsip, Ill.) may reduce water absorption by glass ionomers. The authors investigated this possibility by measuring cuspal flexure caused by swelling of glass ionomer-restored teeth. The authors cut large mesio-occlusodistal slots (4-millimeter wide, 4-mm deep) in 12 extracted premolars and restored them with a glass ionomer cement (Fuji IX GP Extra, GC America). Six teeth were coated, and the other six were uncoated controls. The authors digitized the teeth in three dimensions by using an optical scanner after preparation and restoration and during an eight-week storage in water. They calculated cuspal flexure and analyzed the results by using an analysis of variance and Student-Newman-Keuls post hoc tests (significance level .05). They used dye penetration along the interface to verify bonding. Inward cuspal flexure indicated restoration shrinkage. Coated restorations had significantly higher flexure (mean [standard deviation], -11.9 [3.5] micrometers) than did restorations without coating (-7.3 [1.5] μm). Flexure in both groups decreased significantly (P < .05) during water storage and, after eight weeks, it changed to expansion for uncoated control restorations. Dye penetration along the interfaces was not significant, which ruled out debonding as the cause of cuspal relaxation. Teeth restored with glass ionomer cement exhibited shrinkage, as seen by inward cuspal flexure. The effect of the protective coating on water absorption was evident in the slower shrinkage compensation. The study results show that teeth restored with glass ionomers exhibited setting shrinkage that deformed tooth cusps. Water absorption compensated for the shrinkage. Although the coating may be beneficial for reducing water absorption, it also slows the shrinkage compensation rate (that is, the rate that hygroscopic expansion compensates for cuspal flexure from shrinkage).

In-vitro Study on Temperature Changes in the Pulp Chamber Due to Thermo-Cure Glass Ionomer Cements

PubMed Central

van Duinen, Raimond NB; Shahid, Saroash; Hill, Robert

2016-01-01

The application of the Glass Ionomer Cements in clinical dentistry is recommended due to properties such as fluoride release, chemical adhesion to tooth, negligible setting shrinkage, and coefficient of thermal expansion close to tooth, low creep, and good color stability. However, the cement is vulnerable to early exposure to moisture due to slow setting characteristics. The uses of external energy such as ultrasound and radiant heat (Thermo-curing) have been reported to provide acceleration of the setting chemistry and enhance physical properties. Aim: The aim of this in vitro study was to analyze temperature changes in the pulpal chamber when using radiant heat to accelerate the setting of GICs. Material and Methods:The encapsulated GIC Equia Forte was used for this study. The temperature changes in the pulp were measured using thermocouple in the cavities which were 2,6 and 4,7mm deep with and without filling. Results:The results showed that a temperature rise (ΔT) in the pulp chamber was 3,7°C. ΔT for the 2.6mm and 4.7mm deep cavity and without placing any restoration the temperature was 4,2°C and 2,6°C respectively. After the restoration has been placed, the ΔT range in the pulp chamber was lower ranging from 1.9°C to 2.4°C. Conclusion: It could be concluded that Thermo-curing of the GIC during the setting is safe for the pulp and can be recommended in clinical practice. PMID:28275275

Combined Effects of Temperature and Irradiation on Concrete Damage

DOE PAGES

Le Pape, Yann; Giorla, Alain; Sanahuja, Julien

2016-01-01

Aggregate radiation-induced volumetric expansion (RIVE) is a predominant mechanism in the formation of mechanical damage in the hardened cement paste (hcp) of irradiated concrete under fast-neutron flux (Giorla et al. 2015). Among the operating conditions difference between test reactors and light water reactors (LWRs), the difference of irradiation flux and temperature is significant. While a temperature increase is quite generally associated with a direct, or indirect (e.g., by dehydration) loss of mechanical properties (Maruyama et al. 2014), we found that it causes a partial annealing of irradiation amorphization of α-quartz, hence, reducing RIVE rate. Based on data collected by Bykovmore » et al. (1981), an incremental RIVE model coupling neutron fluence and temperature is developed. The elastic properties and coefficient of thermal expansion (CTE) of irradiated polycrystalline quartz are interpreted through analytical homogenization of experimental data on irradiated α-quartz published by Mayer and Lecomte (1960). Moreover, the proposed model, implemented in the meso-scale simulation code AMIE, is compared to experimental data obtained on ordinary concrete made of quartz/quartzite aggregate (Dubrovskii et al. 1967). Substantial discrepancy, in terms of damage and volumetric expansion developments, is found when comparing irradiation scenarios assuming constant flux and temperature, as opposed to more realistic test reactor operation conditions.« less

N-vinylpyrrolidone modified glass-ionomer resins for improved dental restoratives

NASA Astrophysics Data System (ADS)

Xie, Dong

The studies described in this dissertation focus on improvement of mechanical properties of current glass-ionomer cements. Thermal properties and microstructures of the cements were correlated with their mechanical strengths. The first study evaluated mechanical properties of selected commercial glass-ionomer cements and examined their microstructures. The results showed that resin-modified glass-ionomer cements (RM GICs) exhibited much higher flexural (FS) and diametral tensile strengths (DTS), compared to conventional GICs (C GICs). In addition, they exhibited comparable compressive strength (CS), relatively low microhardness and less wear resistance than C GICs. The C GICs exhibited brittle behavior, whereas the RM GICs underwent substantial plastic deformation in compression. The mechanical properties of the GICs were closely related to their microstructures. Factors such as the density of the microstructure, the integrity of the interface between the glass particles and polymer matrix, particle size and the number and size of voids have important roles in determining the mechanical properties. The second study evaluated thermal properties of these GICs. The results showed that the RM GICs exhibited higher thermal transition temperatures than those of the C GICs, thermal expansion coefficients of these cements were close to those of human teeth, and the indentation creep of the RM GICs were higher than the C GICs. The third study explored and evaluated the effect of a water-soluble monomer, N-vinylpyrrolidone (NVP), on the performance of current C GICs, indicating a significant improvement in both mechanical and working properties. The fourth study demonstrated the process of determining the optimal molar ratio of the NVP-containing copolymers, using design of experiment. The results showed that the optimal molar ratio for these copolymers was 7:1:3 for poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone), based on the FS test. The molar ratio of 8:2:1 (AA:IA:NVP) was considered as the best molar ratio for these copolymers, based on the DTS and CS tests. The fifth study formulated the NVP-containing RM GICs using a statistical design of experiment. The results indicated that the best graft ratio for 2-isocyanatoethyl methacrylate (IEM) in this system was 15% of the terpolymer by a molar ratio. The optimal formulation was found to be at the weight ratio of 55:15:30 (RM NVP-containing terpolymer: 2-hydroxyethyl methacrylate (HEMA): Hsb2O). Stress-strain curves showed that a relatively high amount of water in the formulation led to higher elastic modulus and proportional limit and lower malleability, whereas a relatively high amount of HEMA gave the opposite results. The sixth study evaluated the NVP modified GICs (NVPM GICs) with the best molar ratios and optimal formulations in the mechanical, thermal and working properties. The results showed that the effect of molecular weight on mechanical properties of the NVPM GICs were evident. Different glass powders exhibited different effects on properties of the NVPM GICs, due to different compositions, size and affinity. Powder/liquid ratios had significant effects on the mechanical properties of NVPM GICs, especially on FS. P/W ratios are only beneficial to the NVPM GICs mixed with the Fuji II glass powders. The NVPM GICs showed a higher WT than the models, due to water retention of the NVP ring. Thermal expansion coefficients for the NVPM GICs were close to those for the natural tooth. Mismatch between the glass powders used and the polymer matrix was a big concern in this study and should be solved in the future.

Effects of a hinged expansion screw for median mandibular distraction treatment on the lower first molars regarding tooth inclination and intermolar transverse distance.

PubMed

Muchitsch, Alfred Peter; Winsauer, Heinz; Wendl, Brigitte; Pichelmayer, Margit; Kuljuh, Elma; Navysany, Marie Therese; Muchitsch, Markus

2014-01-01

The goal of this study was to assess the extent to which median mandibular distraction via a cemented and screw-retained full-coverage splint appliance employing a hinged expansion screw causes inclination changes in the lower first molars and widens the dental arch. Our study included 17 patients (12 females and 5 males; average age 16 years and 3 months) who presented with transverse space deficits and pronounced dental crowding. Baseline and final mandibular casts reflecting the situations before and after 6 weeks of median distraction therapy were created, scanned, and matched via their coordinate systems. Perpendiculars were drawn at the geometric centers between the cusp tips of teeth 36 and 46 and projected against the frontal plane. The intersection angles yielded single-tooth and total inclination values for both molars, and the difference between the intermolar distances measured at the geometric centers of both teeth provided the amount of transverse expansion. An intraclass correlation coefficient (ICC) of >0.99 was obtained in a series of three measurements. After distraction treatment, the total inclination values between teeth 36 and 46 changed by +2.93 ± 9.14°. The corresponding single-tooth inclinations changed by +0.68 ± 6.32° and -2.25 ± 4.33°, respectively. Both molars underwent similar degrees of buccal or lingual tipping. Compared to a mean expansion of +6.9 ± 1.83 mm at the distraction screw, a distance increase of only +3.77 ± 1.27 mm along the transversal connecting teeth 36 and 46 was recorded. Pearson's correlation coefficient was 0.336 between total tipping and intermolar expansion (p=0.187) and -0.426 between total tipping and patient age (p=0.088). Expansion amounts were approximately twice as long at the expansion screw as between the first molars. This V-shaped expansion pattern was due to the hinged connections between each expansion screw and the full-coverage splints. The buccal and lingual tipping of molars measured may be due to varying heights of the posterior alveolar ridge during mixed dentition or to anatomy-related differences in the expansion-screw position. In all cases we observed a mainly parallel opening of the distraction gap on the vertical plane.

Properties of experimental titanium cast investment mixing with water reducing agent solution.

PubMed

Zhang, Zutai; Ding, Ning; Tamaki, Yukimichi; Hotta, Yasuhiro; Han-Cheol, Cho; Miyazaki, Takashi

2012-01-01

This study aimed to develop a dental investment for titanium casting. ZrO(2) and Al(2)O(3) were selected as refractory materials to prepare three investments (Codes: A-C) according to the quantity of Zr. Al(2)O(3) cement was used as a binder at a ratio of 15%, they were mixed with special mixing liquid. B1 was used as a control mixed with water. Fundamental examinations were statistically evaluated. A casting test was performed with investment B. Fluidities, setting times, and green strengths showed no remarkable differences; however, they were significantly different from those of B1. Expansion values for A, B, C, and B1 at 850°C were 1.03%±0.08%, 1.96%±0.17%, 4.35%±0.23%, and 1.50%±0.28%, respectively. Castings were covered by only small amounts of mold materials. The hardness test showed no significant differences between castings from B and the ones from commercial investments. The experimental special mixing liquid effectively reduced the water/powder ratio and improved the strength and thermal expansion.

Thermodynamics, kinetics, and mechanics of cesium sorption in cement paste: A multiscale assessment

NASA Astrophysics Data System (ADS)

Arayro, Jack; Dufresne, Alice; Zhou, Tingtao; Ioannidou, Katerina; Ulm, Josef-Franz; Pellenq, Roland; Béland, Laurent Karim

2018-05-01

Cesium-137 is a common radioactive byproduct found in nuclear spent fuel. Given its 30 year half life, its interactions with potential storage materials—such as cement paste—is of crucial importance. In this paper, simulations are used to establish the interaction of calcium silicate hydrates (C-S-H)—the main binding phase of cement paste—with Cs at the nano- and mesoscale. Different C-S-H compositions are explored, including a range of Ca/Si ratios from 1.0 to 2.0. These calculations are based on a set of 150 atomistic models, which qualitatively and quantitatively reproduce a number of experimentally measured features of C-S-H—within limits intrinsic to the approximations imposed by classical molecular dynamics and the steps followed when building the models. A procedure where hydrated Ca2 + ions are swapped for Cs1 + ions shows that Cs adsorption in the C-S-H interlayer is preferred to Cs adsorption at the nanopore surface when Cs concentrations are lower than 0.19 Mol/kg. Interlayer sorption decreases as the Ca/Si ratio increases. The activation relaxation technique nouveau is used to access timescales out of the reach of traditional molecular dynamics (MD). It indicates that characteristic diffusion time for Cs1 + in the C-S-H interlayer is on the order of a few hours. Cs uptake in the interlayer has little impact on the elastic response of C-S-H. It leads to swelling of the C-S-H grains, but mesoscale calculations that access length scales out of the range of MD indicate that this leads to practically negligible expansive pressures for Cs concentrations relevant to nuclear waste repositories.

A practical method for estimating maximum shear modulus of cemented sands using unconfined compressive strength

NASA Astrophysics Data System (ADS)

Choo, Hyunwook; Nam, Hongyeop; Lee, Woojin

2017-12-01

The composition of naturally cemented deposits is very complicated; thus, estimating the maximum shear modulus (Gmax, or shear modulus at very small strains) of cemented sands using the previous empirical formulas is very difficult. The purpose of this experimental investigation is to evaluate the effects of particle size and cement type on the Gmax and unconfined compressive strength (qucs) of cemented sands, with the ultimate goal of estimating Gmax of cemented sands using qucs. Two sands were artificially cemented using Portland cement or gypsum under varying cement contents (2%-9%) and relative densities (30%-80%). Unconfined compression tests and bender element tests were performed, and the results from previous studies of two cemented sands were incorporated in this study. The results of this study demonstrate that the effect of particle size on the qucs and Gmax of four cemented sands is insignificant, and the variation of qucs and Gmax can be captured by the ratio between volume of void and volume of cement. qucs and Gmax of sand cemented with Portland cement are greater than those of sand cemented with gypsum. However, the relationship between qucs and Gmax of the cemented sand is not affected by the void ratio, cement type and cement content, revealing that Gmax of the complex naturally cemented soils with unknown in-situ void ratio, cement type and cement content can be estimated using qucs.

Steam Cured Self-Consolidating Concrete and the Effects of Limestone Filler

NASA Astrophysics Data System (ADS)

Aqel, Mohammad A.

The purpose of this thesis is to determine the effect and the mechanisms associated with replacing 15% of the cement by limestone filler on the mechanical properties and durability performance of self-consolidating concrete designed and cured for precast/prestressed applications. This study investigates the role of limestone filler on the hydration kinetics, mechanical properties (12 hours to 300 days), microstructural and durability performance (rapid chloride permeability, linear shrinkage, sulfate resistance, freeze-thaw resistance and salt scaling resistance) of various self-consolidating concrete mix designs containing 5% silica fume and steam cured at a maximum holding temperature of 55°C. This research also examines the resistance to delayed ettringite formation when the concrete is steam cured at 70°C and 82°C and its secondary consequences on the freeze-thaw resistance. The effect of several experimental variables related to the concrete mix design and also the curing conditions are examined, namely: limestone filler fineness, limestone filler content, cement type, steam curing duration and steam curing temperature. In general, the results reveal that self-consolidating concrete containing 15% limestone filler, steam cured at 55°C, 70°C and 82°C, exhibited similar or superior mechanical and transport properties as well as long term durability performance compared to similar concrete without limestone filler. When the concrete is steam cured at 55°C, the chemical reactivity of limestone filler has an important role in enhancing the mechanical properties at 16 hours (compared to the concrete without limestone filler) and compensating for the dilution effect at 28 days. Although, at 300 days, the expansion of all concrete mixes are below 0.05%, the corresponding freeze-thaw durability factors vary widely and are controlled by the steam curing temperature and the chemical composition of the cement. Overall, the material properties indicate that the use of 15% limestone filler as cement replacement is a viable option for the precast/prestressed concrete applications, and in addition, would also have economic and environmental benefits.

A modified PMMA cement (Sub-cement) for accelerated fatigue testing of cemented implant constructs using cadaveric bone.

PubMed

Race, Amos; Miller, Mark A; Mann, Kenneth A

2008-10-20

Pre-clinical screening of cemented implant systems could be improved by modeling the longer-term response of the implant/cement/bone construct to cyclic loading. We formulated bone cement with degraded fatigue fracture properties (Sub-cement) such that long-term fatigue could be simulated in short-term cadaver tests. Sub-cement was made by adding a chain-transfer agent to standard polymethylmethacrylate (PMMA) cement. This reduced the molecular weight of the inter-bead matrix without changing reaction-rate or handling characteristics. Static mechanical properties were approximately equivalent to normal cement. Over a physiologically reasonable range of stress-intensity factor, fatigue crack propagation rates for Sub-cement were higher by a factor of 25+/-19. When tested in a simplified 2 1/2-D physical model of a stem-cement-bone system, crack growth from the stem was accelerated by a factor of 100. Sub-cement accelerated both crack initiation and growth rate. Sub-cement is now being evaluated in full stem/cement/femur models.

Mineral resource of the month: hydraulic cement

USGS Publications Warehouse

van Oss, Hendrik G.

2012-01-01

Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

Evaluation of the amount of excess cement around the margins of cement-retained dental implant restorations: the effect of the cement application method.

PubMed

Chee, Winston W L; Duncan, Jesse; Afshar, Manijeh; Moshaverinia, Alireza

2013-04-01

Complete removal of excess cement from subgingival margins after cementation of implant-supported restorations has been shown to be unpredictable. Remaining cement has been shown to be associated with periimplant inflammation and bleeding. The purpose of this study was to investigate and compare the amount of excess cement after cementation with 4 different methods of cement application for cement-retained implant-supported restorations. Ten implant replicas/abutments (3i) were embedded in acrylic resin blocks. Forty complete veneer crowns (CVCs) were fabricated by waxing onto the corresponding plastic waxing sleeves. The wax patterns were cast and the crowns were cemented to the implant replicas with either an interim (Temp Bond) or a definitive luting agent (FujiCEM). Four methods of cement application were used for cementation: Group IM-Cement applied on the internal marginal area of the crown only; Group AH-Cement applied on the apical half of the axial walls of the crown; Group AA-Cement applied to all axial walls of the interior surface of the crown, excluding the occlusal surface; and Group PI-Crown filled with cement then seated on a putty index formed to the internal configuration of the restoration (cementation device) (n=10). Cement on the external surfaces was removed before seating the restoration. Cement layers were applied on each crown, after which the crown was seated under constant load (80 N) for 10 minutes. The excess cement from each specimen was collected and measured. One operator performed all the procedures. Results for the groups were compared, with 1 and 2-way ANOVA and the Tukey multiple range test (α=.05). No significant difference in the amount of excess/used cement was observed between the 2 different types of cements (P=.1). Group PI showed the least amount of excess cement in comparison to other test groups (P=.031). No significant difference was found in the amount of excess cement among groups MI, AH, and AA. Group AA showed the highest amount of excess cement. The volume of cement used for group PI specimens was significantly higher than for those in the other groups (P=.001). With respect to the volume of cement loaded into the test crowns no statistically significant difference was observed among other test groups (groups IM, AH, and AA). Group MI used the least amount of cement, followed by group AH and AA. No correlation between the amount of used cement and the amount of excess cement was found in any of the tested groups. Within the limitations of this in vitro study, the least amount of excess cement was present when a cementation device was used to displace the excess cement before seating the crown on the abutment (Group PI). With this technique a uniform layer of the luting agent is distributed over the internal surface of the crown leaving minimal excess cement when the restoration is seated. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Effects of a cementing technique in addition to luting agent on the uniaxial retention force of a single-tooth implant-supported restoration: an in vitro study.

PubMed

Santosa, Robert E; Martin, William; Morton, Dean

2010-01-01

Excess residual cement around the implant margin has been shown to be detrimental to the peri-implant tissue. This in vitro study examines the retentive strengths of two different cementing techniques and two different luting agents on a machined titanium abutment and solid screw implants. The amount of reduction of excess cement weight between the two cementation techniques was assessed. Forty gold castings were fabricated for 4.1 mm in diameter and 10 mm in length solid-screw dental implants paired with 5.5-mm machined titanium abutments. Twenty implants received a provisional cement, and 20 implants received a definitive cement. Each group was further divided into two groups. In the control group, cement was applied and the castings seated over the implant-abutment assembly. The excess cement was then removed. In the study group, a "practice abutment" was used to express excess cement prior to cementation. The weight of the implant-casting assembly was measured and the residual weight of cement was calculated. The samples were then stored for 24 hours at 100% humidity prior to tensile strength testing. Statistical analysis revealed significant differences in tensile strength across the groups. Further Tukey tests showed no significant difference in tensile strength between the practice abutment technique and the conventional technique for both definitive and provisional cements. There was a significant reduction in residual cement weight, irrespective of the type of cement, when the practice abutment was used prior to cementation. Cementation of implant restorations on a machined abutment using the practice abutment technique and definitive cement may provide similar uniaxial retention force and significantly reduced residual cement weight compared to the conventional technique of cement removal.

Influence of cement film thickness on the retention of implant-retained crowns.

PubMed

Mehl, Christian; Harder, Sönke; Steiner, Martin; Vollrath, Oliver; Kern, Matthias

2013-12-01

The main goal of this study was to establish a new, high precision procedure to evaluate the influence of cement film thickness on the retention of cemented implant-retained crowns. Ninety-six tapered titanium abutments (6° taper, 4.3 mm diameter, Camlog) were shortened to 4 mm. Computer-aided design was used to design the crowns, and selective laser sintering, using a cobalt-chromium alloy, was used to produce the crowns. This method used a focused high-energy laser beam to fuse a localized region of metal powder to build up the crowns gradually. Before cementing, preset cement film thicknesses of 15, 50, 80, or 110 μm were established. Glass ionomer, polycarboxylate, or resin cements were used for cementation. After 3 days storage in demineralized water, the retention of the crowns was measured in tension using a universal testing machine. The cement film thicknesses could be achieved with a high level of precision. Interactions between the factors cement and cement film thickness could be found (p ≤ 0.001). For all cements, crown retention decreased significantly between a cement film thickness of 15 and 50 μm (p ≤ 0.001). At 15 μm cement film thickness, the resin cement was the most retentive cement, followed by the polycarboxylate and then the glass ionomer cement (p ≤ 0.05). The results suggest that cement film thickness has an influence on the retentive strength of cemented implant-retained crowns. © 2013 by the American College of Prosthodontists.

The mechanical effect of the existing cement mantle on the in-cement femoral revision.

PubMed

Keeling, Parnell; Lennon, Alexander B; Kenny, Patrick J; O'Reilly, Peter; Prendergast, Patrick J

2012-08-01

Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct. Primary cement mantles were formed by cementing a polished stem into sections of tubular steel. If in the test group, the mantle underwent conditioning in saline to simulate ageing and was subject to a fatigue of 1 million cycles. If in the control group no such conditioning or fatigue was carried out. The cement-in-cement procedure was then undertaken. Both groups underwent a fatigue of 1 million cycles subsequent to the revision procedure. Application of a Mann-Whitney test on the recorded subsidence (means: 0.51, 0.46, n=10+10, P=0.496) and inducible displacement (means: 0.38, 0.36, P=0.96) revealed that there was no statistical difference between the groups. This study represents further biomechanical investigation of the mechanical behaviour of cement-in-cement revision constructs. Results suggest that pre-revision fatigue and ageing of the cement may not be deleterious to the mechanical performance of the revision construct. Thus, this study provides biomechanical evidence to back-up recent successes with this useful revision technique. Copyright © 2012 Elsevier Ltd. All rights reserved.

The effect of using a cement gun with a narrow nozzle on cement penetration for total elbow arthroplasty: a cadaveric study.

PubMed

Smith, Geoffrey C S; McCann, Phillip S; Simpson, Danielle; Blewitt, Neil; Amirfeyz, Rouin

2015-02-01

To compare the cement mantle characteristics associated with use of a narrow nozzle cement gun versus the use of a 60-mL catheter tip syringe. Twelve cadaveric distal humeri were cemented with either a cement gun or a syringe without canal occlusion. The humeri were sectioned and photographed. The corticocancellous junction and the outer margin of the cement mantle were analyzed digitally. The corticocancellous junction defined the available area for cement penetration. The outline of the cement mantle defined the actual area of penetration. The ratio of penetration to the available area was recorded for each slice. The mean ratio for each humerus was multiplied by the number of slices in that sample containing cement to calculate a cement index. The cement penetration ratios observed in cross-sections at the same level and the cement index were significantly greater with the use of the cement gun than with the use of the syringe. There was no difference in the number of slices that contained cement. The use of a cement gun with a narrow nozzle improved cement mantle characteristics compared with the use of a syringe when measured in a cadaveric model in the absence of canal occlusion. Improving cement mantle characteristics may decrease the incidence of aseptic loosening after total elbow arythroplasty. Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Effect of temporary cements on the shear bond strength of luting cements

PubMed Central

FIORI-JÚNIOR, Marco; MATSUMOTO, Wilson; SILVA, Raquel Assed Bezerra; PORTO-NETO, Sizenando Toledo; SILVA, Jaciara Miranda Gomes

2010-01-01

Objective The purpose of this study was to evaluate, by shear bond strength (SBS) testing, the influence of different types of temporary cements on the final cementation using conventional and self-etching resin-based luting cements. Material and Methods Forty human teeth divided in two halves were assigned to 8 groups (n=10): I and V (no temporary cementation); II and VI: Ca(OH)2-based cement; III and VII: zinc oxide (ZO)based cement; IV and VIII: ZO-eugenol (ZOE)-based cement. Final cementation was done with RelyX ARC cement (groups I to IV) and RelyX Unicem cement (groups V to VIII). Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. Results Means were (MPa): I - 3.80 (±1.481); II - 5.24 (±2.297); III - 6.98 (±1.885); IV - 6.54 (±1.459); V - 5.22 (±2.465); VI - 4.48 (±1.705); VII - 6.29 (±2.280); VIII - 2.47 (±2.076). Comparison of the groups that had the same temporary cementation (Groups II and VI; III and VII; IV and VIII) showed statistically significant difference (p<0.001) only between Groups IV and VIII, in which ZOE-based cements were used. The use of either Ca(OH)2 based (Groups II and VI) or ZO-based (Groups III and VII) cements showed no statistically significant difference (p>0.05) for the different luting cements (RelyXTM ARC and RelyXTM Unicem). The groups that had no temporary cementation (Groups I and V) did not differ significantly from each other either (p>0.05). Conclusion When temporary cementation was done with ZO- or ZOE-based cements and final cementation was done with RelyX ARC, there was an increase in the SBS compared to the control. In the groups cemented with RelyX Unicem, however, the use of a ZOE-based temporary cement affected negatively the SBS of the luting agent used for final cementation. PMID:20379679

Meteoric calcite cementation: diagenetic response to relative fall in sea-level and effect on porosity and permeability, Las Negras area, southeastern Spain

NASA Astrophysics Data System (ADS)

Li, Zhaoqi; Goldstein, Robert H.; Franseen, Evan K.

2017-03-01

A dolomitized Upper Miocene carbonate system in southeast Spain contains extensive upper and lower zones of calcite cementation that cut across the stratigraphy. Cement textures including isopachous and circumgranular, which are consistent with phreatic-zone cementation. Cements in the upper cemented zone are non-luminescent, whereas those in the lower cemented zone exhibit multiple bands of luminescent and non-luminescent cements. In the upper cemented zone, isotopic data show two meteoric calcite lines (MCL) with mean δ18O at - 5.1‰ and - 5.8‰ VPDB, whereas no clear MCL is defined in the lower cemented zone where mean δ18O for calcite cement is at - 6.7‰ VPDB. δ13C values in both cement zones are predominantly negative, ranging from - 10 to + 2‰ VPDB, suggestive of carbon from soil gas or decayed organics. Measurements of Tm ice in primary fluid inclusions yield a mode of 0.0 °C in both zones, indicating calcite cementation from fresh water. These two zones define the positions of two different paleo-water tables that formed during a relative sea-level fall and erosional downcutting during the Plio-Pleistocene. The upper cemented zone pre-dated the lower cemented zone on the basis of known relative sea-level history. Meteoric calcite cementation reduced porosity and permeability, but measured values are inconsistent with simple filling of open pore space. Each texture, boundstone, grainstone, packstone, wackestone, produces a different relationship between percent calcite cement and porosity/permeability. Distribution of cements may be predictable on the basis of known sea-level history, and the effect of the cementation can be incorporated into subsurface geomodels by defining surfaces of rock boundaries that separate cemented zones from uncemented zones, and applying texture-specific relationships among cementation, porosity and permeability.

Traction test of temporary dental cements.

PubMed

Román-Rodríguez, Juan-Luis; Millan-Martínez, Diego; Fons-Font, Antonio; Agustín-Panadero, Rubén; Fernández-Estevan, Lucía

2017-04-01

Classic self-curing temporary cements obstruct the translucence of provisional restorations. New dual-cure esthetic temporary cements need investigation and comparison with classic cements to ensure that they are equally retentive and provide adequate translucence. The objective is to analyze by means of traction testing in a in vitro study the retention of five temporary cements. Ten molars were prepared and ten provisional resin restorations were fabricated using CAD-CAM technology (n=10). Five temporary cements were selected: self-curing temporary cements, Dycal (D), Temp Bond (TB), Temp Bond Non Eugenol (TBNE); dual-curing esthetic cements Temp Bond Clear (TBC) and Telio CS link (TE). Each sample underwent traction testing, both with thermocycling (190 cycles at 5-55º) and without thermocycling. TE and TBC obtained the highest traction resistance values. Thermocycling reduced the resistance of all cements except TBC. The dual-cure esthetic cements tested provided optimum outcomes for bonding provisional restorations. Key words: Temporary dental cements, cements resistance.

High Early-Age Strength Concrete for Rapid Repair

NASA Astrophysics Data System (ADS)

Maler, Matthew O.

The aim of this research was to identify High Early-Age Strength (HES) concrete batch designs, and evaluate their suitability for use in the rapid repair of highways and bridge decks. To this end, two criteria needed to be met; a minimum compressive strength of 20.68 MPa (3000 psi) in no later than 12 hours, and a drying shrinkage of less than 0.06 % at 28 days after curing. The evaluations included both air-entrained, and non-air-entrained concretes. The cement types chosen for this study included Type III and Type V Portland cement and "Rapid Set"--a Calcium Sulfoaluminate (CSA) cement. In addition, two blended concretes containing different ratios of Type V Portland cement and CSA cement were investigated. The evaluation of the studied concretes included mechanical properties and transport properties. Additionally, dimensional stability and durability were investigated. Evaluations were conducted based on cement type and common cement factor. Fresh property tests showed that in order to provide a comparable workability, and still remain within manufactures guideline for plasticizer, the water-to-cement ratio was adjusted for each type of cement utilized. This resulted in the need to increase the water-to-cement ratio as the Blaine Fineness of the cement type increased (0.275 for Type V Portland cement, 0.35 for Type III Portland cement, and 0.4 for Rapid Set cement). It was also observed that negligible changes in setting time occurred with increasing cement content, whereas changes in cement type produced notable differences. The addition of air-entrainment had beneficial effect on workability for the lower cement factors. Increasing trends for peak hydration heat were seen with increases in cement factor, cement Blaine Fineness, and accelerator dosage. Evaluation of hardened properties revealed opening times as low as 5 hours for Type V Portland cement with 2.0 % accelerator per cement weight and further reduction in opening time by an hour when accelerator dosage was increased to 2.8 % by cement weight. When Type III Portland cement and Rapid Set cement were used, the opening time reduced to as low as 4.5 hours and 1 hour, respectively. The results for Type V Portland cement concretes showed that as cement factor increased so did mechanical properties until the cement factor exceeded 504 kg/m3 (850 lb/yd3), at which point the peak heat of hydration exceeded 46.1 °C (115 °F) and the mechanical properties decreased. Other evaluations on the studied High Early-Age Strength Type V Portland cement concretes revealed increases in absorption, rapid chloride penetration, water permeability, drying shrinkage, corrosion resistance, and resistance to wear with increases in cement content. The addition of air-entrainment had adverse effects on compressive strength, absorption, and rapid chloride migration; while showing lower values for rapid chloride penetration. Curing had positive effects on all hardened properties of the studied HES concretes containing Type V cement. When examining the studied Type III Portland cement concretes, it was seen that an increase in cement content led to decreases in mechanical properties. It is noted that the peak heat of hydration for these concrete exceeded the threshold of 46.1 °C (115 °F). In addition, increases in cement factor also resulted in decreases in rapid chloride migration, frost resistance and resistance to wear. Increases in cement content resulted in increases in absorption, rapid chloride penetration, water permeability, drying shrinkage, and corrosion resistance. The use of air-entrainment imparted decreases in compressive strength and rapid chloride penetration, increases in absorption, and negligible effects on rapid chloride migration. Extending curing period resulted in beneficial effects on all properties of the studied Type III cement concretes. The studied CSA cement concretes had slightly decreasing strength trends as cement content was increased. Concretes containing CSA cement produced the lowest opening time (one hour) and the highest peak hydration heats of all concretes studied. While its corrosion and frost resistance reduced as cement content increased, the absorption and rapid chloride penetration increased with increasing cement content. For drying shrinkage, opening time curing showed more volume change with increasing cement content, whereas extending curing to 24 hours and 28 days resulted in reduction of drying shrinkage. Increasing cement factor had minimal effects on water permeability and abrasion resistance. Air-entrainments reduced compressive strength, but increased absorption and rapid chloride penetration. Rapid chloride migration was found to be incompatible with CSA cements concretes. All hardened properties of the studied CSA cement concretes improved once curing age was extended to 24 hours and 28 days. (Abstract shortened by ProQuest.).

Synthesis of Portland cement and calcium sulfoaluminate-belite cement for sustainable development and performance

NASA Astrophysics Data System (ADS)

Chen, Irvin Allen

Portland cement concrete, the most widely used manufactured material in the world, is made primarily from water, mineral aggregates, and portland cement. The production of portland cement is energy intensive, accounting for 2% of primary energy consumption and 5% of industrial energy consumption globally. Moreover, portland cement manufacturing contributes significantly to greenhouse gases and accounts for 5% of the global CO2 emissions resulting from human activity. The primary objective of this research was to explore methods of reducing the environmental impact of cement production while maintaining or improving current performance standards. Two approaches were taken, (1) incorporation of waste materials in portland cement synthesis, and (2) optimization of an alternative environmental friendly binder, calcium sulfoaluminate-belite cement. These approaches can lead to less energy consumption, less emission of CO2, and more reuse of industrial waste materials for cement manufacturing. In the portland cement part of the research, portland cement clinkers conforming to the compositional specifications in ASTM C 150 for Type I cement were successfully synthesized from reagent-grade chemicals with 0% to 40% fly ash and 0% to 60% slag incorporation (with 10% intervals), 72.5% limestone with 27.5% fly ash, and 65% limestone with 35% slag. The synthesized portland cements had similar early-age hydration behavior to commercial portland cement. However, waste materials significantly affected cement phase formation. The C3S--C2S ratio decreased with increasing amounts of waste materials incorporated. These differences could have implications on proportioning of raw materials for cement production when using waste materials. In the calcium sulfoaluminate-belite cement part of the research, three calcium sulfoaluminate-belite cement clinkers with a range of phase compositions were successfully synthesized from reagent-grade chemicals. The synthesized calcium sulfoaluminate-belite cement that contained medium C4A3 S¯ and C2S contents showed good dimensional stability, sulfate resistance, and compressive strength development and was considered the optimum phase composition for calcium sulfoaluminate-belite cement in terms of comparable performance characteristics to portland cement. Furthermore, two calcium sulfoaluminate-belite cement clinkers were successfully synthesized from natural and waste materials such as limestone, bauxite, flue gas desulfurization sludge, Class C fly ash, and fluidized bed ash proportioned to the optimum calcium sulfoaluminate-belite cement synthesized from reagent-grade chemicals. Waste materials composed 30% and 41% of the raw ingredients. The two calcium sulfoaluminate-belite cements synthesized from natural and waste materials showed good dimensional stability, sulfate resistance, and compressive strength development, comparable to commercial portland cement.

Improving the geotechnical properties of expansive soils by mixture with olive mill wastewater

NASA Astrophysics Data System (ADS)

Ureña, C.; Azañón, J. M.; Corpas, F.; Nieto, F.; León-Buendía, C.

2012-04-01

In Southern Spain, Olive grove is an artificial forest which has a surface of 18.000 km2, representing more than 25% of olive oil world production. During the manufacturing process of this oil, different types of residues are generated. The most important is a biomass called olive mill wastewater. It is a dark colored liquid which can not be directly poured onto natural watercourses. On the one hand, part of this biomass is burnt to produce electrical energy or treated to make a bio-diesel. On the other hand, we propose the use of olive mill wastewater as a stabilization agent for expansive clayey soils. Using raw biomass as a stabilization agent two objectives are achieved: adding value to biomass and reducing the problems of expansive soils. Moreover, an important reduction of economic costs can take place. A pure bentonite clay was chosen as a sample of original expansive soil. It is abundant in Southern Spain and its main component is Na-Montmorillonite. Bentonite is very susceptible to changes in the environmental available moisture and very unsuitable for its use in civil engineering due to its low bearing capacity, high plasticity and volume changes. Several dosages (5%, 10%, 15%) of olive mill wastewater were added to the original sample of bentonite. To study eventual improvements in the mechanical properties of soil, Proctor, Atterberg Limits, California Bearing Ratio, Swelling Pressure and X-Ray Diffraction tests were carried out, following Spanish standards UNE by AENOR. Both geotechnical and mineralogical characterizations were developed at two different curing times: 15 and 30 days. The Plasticity Index (PI) of the original bentonite soil was 251 (High Plasticity). The addition of 15% of olive mill wastewater yielded reductions of PI similar to those produced by the addition of 5% of Portland cement. The California Bearing Ratio (CBR) values increased slightly after the treatment with biomass leading to very similar values to those obtained after the conventional treatment with coal fly ash. One of the most important parameters to evaluate the swelling potential, swelling pressure, dramatically decreased in samples treated with olive mill wastewater, from 220kPa in the original sample of bentonite to values under 60kPa after 30 days. Regarding the mineralogy of the treated soil, X-ray Diffraction tests suggested a noticeable reduction in the amount of smectite within the crystalline structure of treated soils. Moreover, the smectite 001 peak shifted to right indicating a smaller d-spacing and hence a more stable mineral structure. To sum up, the improvements achieved by adding olive mill wastewater were, to some extent, similar to those produced by lower dosages of conventional additives (Portland cement or coal fly ash). The first results obtained in this work therefore indicate promising properties of biomass for its use in stabilization of expansive soils. A further research is still necessary. Finally, it must be pointed out that the use of raw biomass proceeding from olive grove might considerably improve the waste management in olive oil industry while offering new opportunities to civil works.

Comparative study on strength properties of cement mortar by partial replacement of cement with ceramic powder and silica fume

NASA Astrophysics Data System (ADS)

Himabindu, Ch.; Geethasri, Ch.; Hari, N.

2018-05-01

Cement mortar is a mixture of cement and sand. Usage of high amount of cement increases the consumption of natural resources and electric power. To overcome this problem we need to replace cement with some other material. Cement is replaced with many other materials like ceramic powder, silica fume, fly ash, granulated blast furnace slag, metakaolin etc.. In this research cement is replaced with ceramic powder and silica fume. Different combinations of ceramic powder and silica fume in cement were replaced. Cement mortar cubes of 1:3 grade were prepared. These cubes were cured under normal water for 7 days, 14days and 28 days. Compressive strength test was conducted for all mixes of cement mortar cubes.

Effect of dental cements on peri-implant microbial community: comparison of the microbial communities inhabiting the peri-implant tissue when using different luting cements.

PubMed

Korsch, Michael; Marten, Silke-Mareike; Dötsch, Andreas; Jáuregui, Ruy; Pieper, Dietmar H; Obst, Ursula

2016-12-01

Cementing dental restorations on implants poses the risk of undetected excess cement. Such cement remnants may favor the development of inflammation in the peri-implant tissue. The effect of excess cement on the bacterial community is not yet known. The aim of this study was to analyze the effect of two different dental cements on the composition of the microbial peri-implant community. In a cohort of 38 patients, samples of the peri-implant tissue were taken with paper points from one implant per patient. In 15 patients, the suprastructure had been cemented with a zinc oxide-eugenol cement (Temp Bond, TB) and in 23 patients with a methacrylate cement (Premier Implant Cement, PIC). The excess cement found as well as suppuration was documented. Subgingival samples of all patients were analyzed for taxonomic composition by means of 16S amplicon sequencing. None of the TB-cemented implants had excess cement or suppuration. In 14 (61%) of the PIC, excess cement was found. Suppuration was detected in 33% of the PIC implants without excess cement and in 100% of the PIC implants with excess cement. The taxonomic analysis of the microbial samples revealed an accumulation of oral pathogens in the PIC patients independent of the presence of excess cement. Significantly fewer oral pathogens occurred in patients with TB compared to patients with PIC. Compared with TB, PIC favors the development of suppuration and the growth of periodontal pathogens. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez-Buendia, A.M.; Climent, V.; Verdu, P.

The reactivity of carbonate rock with the alkali content of cement, commonly called alkali-carbonate reaction (ACR), has been investigated. Alkali-silica reaction (ASR) can also contribute in the alkali-aggregate reaction (AAR) in carbonate rock, mainly due to micro- and crypto-crystalline quartz or clay content in carbonate aggregate. Both ACR and ASR can occur in the same system, as has been also evidenced on this paper. Carbonate aggregate samples were selected using lithological reactivity criteria, taking into account the presence of dedolomitization, partial dolomitization, micro- and crypto-crystalline quartz. Selected rocks include calcitic dolostone with chert (CDX), calcitic dolostone with dedolomitization (CDD), limestonemore » with chert (LX), marly calcitic dolostone with partial dolomitization (CD), high-porosity ferric dolostone with clays (FD). To evaluate the reactivity, aggregates were studied using expansion tests following RILEM AAR-2, AAR-5, a modification using LiOH AAR-5Li was also tested. A complementary study was done using petrographic monitoring with polarised light microscopy on aggregates immersed in NaOH and LiOH solutions after different ages. SEM-EDAX has been used to identify the presence of brucite as a product of dedolomitization. An ACR reaction showed shrinkage of the mortar bars in alkaline solutions explained by induced dedolomitization, while an ASR process typically displayed expansion. Neither shrinkage nor expansion was observed when mortar bars were immersed in solutions of lithium hydroxide. Carbonate aggregate classification with AAR pathology risk has been elaborated based on mechanical behaviours by expansion and shrinkage. It is proposed to be used as a petrographic method for AAR diagnosis to complement the RILEM AAR1 specifically for carbonate aggregate. Aggregate materials can be classified as I (non-reactive), II (potentially reactive), and III (probably reactive), considering induced dedolomitization ACR (dedolomitization degree) and ASR.« less

Comparison of the Solubility of Conventional Luting Cements with that of the Polyacid Modified Composite Luting Cement and Resin-modified Glass lonomer Cement.

PubMed

Karkera, Reshma; Raj, A P Nirmal; Isaac, Lijo; Mustafa, Mohammed; Reddy, R Naveen; Thomas, Mathew

2016-12-01

This study was planned to find the solubility of the conventional luting cements in comparison with that of the polyacid-modified composite luting cement and recently introduced resin-modified glass ionomer cement (RMGIC) with exposure to water at early stages of mixing. An in vitro study of the solubility of the following five commercially available luting cements, viz., glass ionomer cement (GIC) (Fuji I, GC), zinc phosphate (Elite 100, GC), polyacid-modified resin cement (PMCR) (Principle, Dentsply), polycarboxylate cement (PC) (Poly - F, Dentsply), RMGIC (Vitremer, 3M), was conducted. For each of these groups of cements, three resin holders were prepared containing two circular cavities of 5 mm diameter and 2 mm depth. All the cements to be studied were mixed in 30 seconds and then placed in the prepared cavities in the resin cement holder for 30 seconds. From all of the observed luting cements, PMCR cement had shown the lowest mean loss of substance at all immersion times and RMGIC showed the highest mean loss of substanceat all immersion times in water from 2 to 8 minutes. The solubility of cements decreased by 38% for GIC, 33% for ZnPO 4 , 50% for PMCR, 29% for PC, and 17% for RMGIC. The PMCR cement (Principle-Dentsply) had shown lowest solubility to water at the given time intervals of immersion. This was followed by PC, zinc phosphate, and GIC to various time intervals of immersion.

Development of high-performance blended cements

NASA Astrophysics Data System (ADS)

Wu, Zichao

2000-10-01

This thesis presents the development of high-performance blended cements from industrial by-products. To overcome the low-early strength of blended cements, several chemicals were studied as the activators for cement hydration. Sodium sulfate was discovered as the best activator. The blending proportions were optimized by Taguchi experimental design. The optimized blended cements containing up to 80% fly ash performed better than Type I cement in strength development and durability. Maintaining a constant cement content, concrete produced from the optimized blended cements had equal or higher strength and higher durability than that produced from Type I cement alone. The key for the activation mechanism was the reaction between added SO4 2- and Ca2+ dissolved from cement hydration products.

Calcium phosphate compatible bone cement: Characterization, bonding properties and tissue response

NASA Astrophysics Data System (ADS)

Roemhildt, Maria Lynn

A novel, inorganic, bone cement, containing calcium phosphate, developed for implant fixation was evaluated. Setting properties were determined over a range of temperatures. The flow of the cement was greatly increased by application of vibration. Changes in the cement during hydration and aging were evaluated. Compressive strength of the cement over time was studied under simulated physiological conditions from 1 hour to 1 year after setting. After 1 day, this cement had equivalent compressive strength to commercially used PMMA cement. The strength was found to increase over 1 month and high strength was maintained up to 1 year. The shear strength of the cement-metal interface was studied in vitro using a pull-out test. Prepared specimens were stored under physiological conditions and tested at 4 hours, 24 hours, and 60 days. Comparable interfacial shear strength values were found at 4 hours, 24 hours and 60 days for the experimental cement and were not significantly different from values obtained for PMMA cement. In vivo tissue response was evaluated after cement implantation in the femoral medullary canal in canines. Tissue response and bonding at the cement-bone interface were evaluated at 2, 6, and 12 weeks. Cortical bone was found in direct contact with the OC-cement and was healthy. The strength of the cement-bone interface, measured using a push-out test, was significantly higher for the experimental cement than for commercial PMMA bone cement.

Peri-Implantitis Associated with Type of Cement: A Retrospective Analysis of Different Types of Cement and Their Clinical Correlation to the Peri-Implant Tissue.

PubMed

Korsch, Michael; Walther, Winfried

2015-10-01

The cementation of fixed implant-supported dental restorations involves the risk of leaving excess cement in the mouth which can promote biofilm formation in the peri-implant sulcus. As a result, an inflammation may develop. The aim of the present study was to investigate the clinical effect of two different luting cements on the peri-implant tissue. Within the scope of a retrospective clinical follow-up study, the prosthetic structures of 22 patients with 45 implants were revised. In all cases, a methacrylate cement (Premier Implant Cement [PIC], Premier® Dental Products Company, Plymouth Meeting, PA, USA) had been used for cementation. In 16 additional patients with 28 implants, the suprastructures were retained with a zinc oxide-eugenol cement (Temp Bond [TB], Kerr Sybron Dental Specialities, Glendora, CA, USA). These patients were evaluated in the course of routine treatment. In both populations, the retention time of the suprastructures was similar (TB 3.77 years, PIC 4.07 years). In the PIC cases, 62% of all implants had excess cement. In the TB cases, excess cement was not detectable on any of the implants. Bleeding on probing was significantly more frequent on implants cemented with PIC (100% with and 94% without excess cement) than on implants cemented with TB (46%). Pocket suppuration was observed on 89% of the PIC-cemented implants with excess cement (PIC without excess cement 24%), whereas implants with TB were not affected by it at all. The peri-implant bone loss was significantly greater in the PIC patients (with excess cement 1.37 mm, without excess cement 0.41 mm) than it was in the TB patients (0.07 mm). The frequency of undetected excess cement depends essentially on the type of cement used. Cements that tend to leave more undetected excess have a higher prevalence for peri-implant inflammation and cause a more severe peri-implant bone loss. © 2014 Wiley Periodicals, Inc.

In vitro bond strength and fatigue stress test evaluation of different adhesive cements used for fixed space maintainer cementation

PubMed Central

Cantekin, Kenan; Delikan, Ebru; Cetin, Secil

2014-01-01

Objective: The purposes of this research were to (1) compare the shear-peel bond strength (SPBS) of a band of a fixed space maintainer (SM) cemented with five different adhesive cements; and (2) compare the survival time of bands of SM with each cement type after simulating mechanical fatigue stress. Materials and Methods: Seventy-five teeth were used to assess retentive strength and another 50 teeth were used to assess the fatigue survival time. SPBS was determined with a universal testing machine. Fatigue testing was conducted in a ball mill device. Results: The mean survival time of bands cemented with R & D series Nova Glass-LC (6.2 h), Transbond Plus (6.7 h), and R & D series Nova Resin (6.8 h) was significantly longer than for bands cemented with Ketac-Cem (5.4 h) and GC Equia (5.2 h) (P < 0.05). Conclusion: Although traditional glass ionomer cement (GIC) cement presented higher retentive strength than resin-based cements (resin, resin modified GIC, and compomer cement), resin based cements, especially dual cure resin cement (nova resin cement) and compomer (Transbond Plus), can be expected to have lower failure rates for band cementation than GIC (Ketac-Cem) in the light of the results of the ball mill test. PMID:25202209

Design and development of advanced castable refractory materials

NASA Astrophysics Data System (ADS)

Davis, Robert Bruce

New formulations of castable refractory composite materials were studied. This technology is used to produce low cost composite concrete structures designed for high temperature stability, superior wear resistance and improved strength. An in situ fired, castable cement installation is a heterogeneous structure divided into three zones according to the temperature history and microstructure. The properties of each zone depend on the predominant bonding mode between constituents. Each zone has a characteristic microstructure that influences the integrity of the monolith. The hot side may have a highly dense and developed network of ceramic bonds between constituent particles while the cold side may never reach temperatures sufficient to drive off free water. The thermal, structural and tribological properties depend on the microstructure and the type of bonding that holds the monolith together. The phase distributions are defined by sets of metastable phase conditions driven by the local hydrated chemistry, nearest neighbor oxide compounds, impurities and sintering temperature. Equilibrium phase diagrams were used to select optimum compositions based on higher melting point phases. The phase diagrams were also used to target high temperature phase fields that are stable over wide temperature and stoichiometric ranges. Materials selection of candidate hydraulic clinkers, high temperature oxides, and reinforcement phases were based on requirements for high temperature stability. The calcium aluminate (CaO-Al2O3) and calcium dialuminate (CaO-(Al2O3)2) are common refractory clinkers used in castable refractory cements. The thermodynamics and kinetics of cement hydrate formation are well studied and suited to become the building block of a design for a superior refractory castable cement. The inert oxides mixed with the calcium aluminate clinkers are magnesia (MgO), alumina (Al 2O3), spinel (MgAl2O4) and chromic (Cr2O3). The bulk of the experiments concentrated in the Al2O3--MgO--CaO ternary system. Materials selection criteria for reinforcement materials was based on improved high temperature stability, increased strength, reduced thermal expansion mismatch, low thermal conductivity and increasing wear resistance. The reinforcement phases selected for this investigation are zircon (ZrSiO4), zirconia (ZrO2), spinel (MgAl2O4) and dead burnt magnesia (MgO). Batches of the formulations were tested for thermal conductivity, wear resistance and mechanical strength. Relative rankings of the formulations against commercial products indicate improved or similar performance with increased maximum temperature limits and improved thermal insulating power. The new cement formulations proved to exhibit superior high temperature stability with an increasing volume fraction of high temperature oxides. The addition of reinforcement aggregates and powder sizing to offset the loss of strength. The room temperature compression strength and wear resistance of the optimized formulations exceeded the properties of conventional refractory, brick and castable cement tested concurrently.

Influence of temporary cement contamination on the surface free energy and dentine bond strength of self-adhesive cements.

PubMed

Takimoto, Masayuki; Ishii, Ryo; Iino, Masayoshi; Shimizu, Yusuke; Tsujimoto, Akimasa; Takamizawa, Toshiki; Ando, Susumu; Miyazaki, Masashi

2012-02-01

The surface free energy and dentine bond strength of self-adhesive cements were examined after the removal of temporary cements. The labial dentine surfaces of bovine mandibular incisors were wet ground with #600-grit SiC paper. Acrylic resin blocks were luted to the prepared dentine surfaces using HY Bond Temporary Cement Hard (HY), IP Temp Cement (IP), Fuji TEMP (FT) or Freegenol Temporary Cement (TC), and stored for 1 week. After removal of the temporary cements with an ultrasonic tip, the contact angle values of five specimens per test group were determined for the three test liquids, and the surface-energy parameters of the dentine surfaces were calculated. The dentine bond strengths of the self-adhesive cements were measured after removal of the temporary cements in a shear mode at a crosshead speed of 1.0mm/min. The data were subjected to one-way analysis of variance (ANOVA) followed by Tukey's HSD test. For all surfaces, the value of the estimated surface tension component γ(S)(d) (dispersion) was relatively constant at 41.7-43.3 mJm(-2). After removal of the temporary cements, the value of the γ(S)(h) (hydrogen-bonding) component decreased, particularly with FT and TC. The dentine bond strength of the self-adhesive cements was significantly higher for those without temporary cement contamination (8.2-10.6 MPa) than for those with temporary cement contamination (4.3-7.1 MPa). The γ(S) values decreased due to the decrease of γ(S)(h) values for the temporary cement-contaminated dentine. Contamination with temporary cements led to lower dentine bond strength. The presence of temporary cement interferes with the bonding performance of self-adhesive cements to dentine. Care should be taken in the methods of removal of temporary cement when using self-adhesive cements. Copyright © 2011 Elsevier Ltd. All rights reserved.

Monitoring the integrity of the cement-metal interface of total joint components in vitro using acoustic emission and ultrasound.

PubMed

Davies, J P; Tse, M K; Harris, W H

1996-08-01

Debonding of the cement-metal interface of cemented femoral components of total hip arthroplasty has been shown from clinical and autopsy material to be a common occurrence. Experimentally, debonding has been shown to increase markedly the strains in the adjacent cement mantle. Studies of autopsy-retrieved specimens demonstrate that debonding of the cement-metal interface is a key initiating event in loosening of cemented femoral components of total hip arthroplasty. However, both the radiographic and autopsy evidence of cement-metal interfacial debonding exist after the fact, that is, after debonding has occurred. The lack of prospective data showing that debonding does indeed occur under physiologic loading and occurs prior to other forms of failure of fixation leaves uncertain the issue of debonding and its role in initiating loosening of cemented femoral components. Knowing when, where, and to what extent the cement-metal interface debonds is critical information in understanding the process of loosening of cemented femoral components. Such information would contribute to improving the durability of stems and improving cementing techniques. In this study, the two nondestructive techniques of acoustic emission and ultrasonic evaluation of the cement-metal interface of cemented femoral stems of total hip arthroplasty were combined to investigate when, where, and to what extent cement-metal debonding occurred in vitro in simulated femurs loaded physiologically in fatigue in simulated single-leg stance. Debonding of the cement-metal interface of a cemented femoral component in this model was both an initiating event and a major mechanism of compromise of the cement-metal interface. Additional acoustic emission signals arose from cracks that developed in the cement.

Micro-mechanical damage of trabecular bone-cement interface under selected loading conditions: a finite element study.

PubMed

Zhang, Qing-Hang; Tozzi, Gianluca; Tong, Jie

2014-01-01

In this study, two micro finite element models of trabecular bone-cement interface developed from high resolution computed tomography (CT) images were loaded under compression and validated using the in situ experimental data. The models were then used under tension and shear to examine the load transfer between the bone and cement and the micro damage development at the bone-cement interface. In addition, one models was further modified to investigate the effect of cement penetration on the bone-cement interfacial behaviour. The simulated results show that the load transfer at the bone-cement interface occurred mainly in the bone cement partially interdigitated region, while the fully interdigitated region seemed to contribute little to the mechanical response. Consequently, cement penetration beyond a certain value would seem to be ineffective in improving the mechanical strength of trabecular bone-cement interface. Under tension and shear loading conditions, more cement failures were found in denser bones, while the cement damage is generally low under compression.

Traction test of temporary dental cements

PubMed Central

Millan-Martínez, Diego; Fons-Font, Antonio; Agustín-Panadero, Rubén; Fernández-Estevan, Lucía

2017-01-01

Background Classic self-curing temporary cements obstruct the translucence of provisional restorations. New dual-cure esthetic temporary cements need investigation and comparison with classic cements to ensure that they are equally retentive and provide adequate translucence. The objective is to analyze by means of traction testing in a in vitro study the retention of five temporary cements. Material and Methods Ten molars were prepared and ten provisional resin restorations were fabricated using CAD-CAM technology (n=10). Five temporary cements were selected: self-curing temporary cements, Dycal (D), Temp Bond (TB), Temp Bond Non Eugenol (TBNE); dual-curing esthetic cements Temp Bond Clear (TBC) and Telio CS link (TE). Each sample underwent traction testing, both with thermocycling (190 cycles at 5-55º) and without thermocycling. Results TE and TBC obtained the highest traction resistance values. Thermocycling reduced the resistance of all cements except TBC. Conclusions The dual-cure esthetic cements tested provided optimum outcomes for bonding provisional restorations. Key words:Temporary dental cements, cements resistance. PMID:28469824

Creep and fatigue behavior of a novel 2-component paste-like formulation of acrylic bone cements.

PubMed

Köster, Ulrike; Jaeger, Raimund; Bardts, Mareike; Wahnes, Christian; Büchner, Hubert; Kühn, Klaus-Dieter; Vogt, Sebastian

2013-06-01

The fatigue and creep performance of two novel acrylic bone cement formulations (one bone cement without antibiotics, one with antibiotics) was compared to the performance of clinically used bone cements (Osteopal V, Palacos R, Simplex P, SmartSet GHV, Palacos R+G and CMW1 with Gentamicin). The preparation of the novel bone cement formulations involves the mixing of two paste-like substances in a static mixer integrated into the cartridge which is used to apply the bone cement. The fatigue performance of the two novel bone cement formulations is comparable to the performance of the reference bone cements. The creep compliance of the bone cements is significantly influenced by the effects of physical ageing. The model parameters of Struik's creep law are used to compare the creep behavior of different bone cements. The novel 2-component paste-like bone cement formulations are in the group of bone cements which exhibit a higher creep resistance.

Increased Antibiotic Release from a Bone Cement Containing Bacterial Cellulose

PubMed Central

Nakai, Takahisa; Enomoto, Koichi; Uchio, Yuji; Yoshino, Katsumi

2010-01-01

Background Major disadvantages of antibiotic bone cements include limited drug release and reduced strength resulting from the addition of high doses of antibiotics. Bacterial cellulose, a three-dimensional hydrophilic mesh, may retain antibiotics and release them gradually. We hypothesized that the addition of cellulose to antibiotic bone cement would improve mechanical strength and antibiotic release. Questions/purposes We therefore examined the mechanical strength and antibiotic release of cellulose antibiotic cement. Methods A high dose of antibiotics (5 g per 40 g cement powder) was incorporated into bacterial cellulose and then mixed with bone cement. We compared the compression strength, fracture toughness, fatigue life, and elution kinetics of this formulation with those of plain cement and a traditional antibiotic cement. Results The average values for compression strength, fracture toughness, and fatigue life of the cellulose antibiotic cement were 97%, 97%, and 78% of the values obtained for plain cement, respectively. The corresponding values for the traditional antibiotic cement were 79%, 82%, and 17%, respectively. The cumulative elution over 35 days was 129% greater from the cellulose antibiotic cement than from the traditional antibiotic cement. Conclusions With a high dose of antibiotics, incorporating cellulose into the bone cement prevented compression and fracture fragility, improved fatigue life, and increased antibiotic elution. Clinical Relevance Antibiotic cements containing cellulose may have applications in clinical situations that require high levels of antibiotic release and preservation of the mechanical properties of the cement. PMID:20945120

Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jihoon; Moridis, George

2014-11-01

We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, lowmore » cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.« less

Imaging Wellbore Cement Degradation by Carbon Dioxide under Geologic Sequestration Conditions Using X-ray Computed Microtomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Hun Bok; Jansik, Danielle; Um, Wooyong

2013-01-02

ABSTRACT: X-ray microtomography (XMT), a nondestructive three-dimensional imaging technique, was applied to demonstrate its capability to visualize the mineralogical alteration and microstructure changes in hydrated Portland cement exposed to carbon dioxide under geologic sequestration conditions. Steel coupons and basalt fragments were added to the cement paste in order to simulate cement-steel and cement-rock interfaces. XMT image analysis showed the changes of material density and porosity in the degradation front (density: 1.98 g/cm3, porosity: 40%) and the carbonated zone (density: 2.27 g/cm3, porosity: 23%) after reaction with CO2- saturated water for 5 months compared to unaltered cement (density: 2.15 g/cm3, porosity:more » 30%). Three-dimensional XMT imaging was capable of displaying spatially heterogeneous alteration in cement pores, calcium carbonate precipitation in cement cracks, and preferential cement alteration along the cement-steel and cement-rock interfaces. This result also indicates that the interface between cement and host rock or steel casing is likely more vulnerable to a CO2 attack than the cement matrix in a wellbore environment. It is shown here that XMT imaging can potentially provide a new insight into the physical and chemical degradation of wellbore cement by CO2 leakage.« less

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development,more » and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.« less

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

PubMed

Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

2016-12-28

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

DOE PAGES

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel; ...

2016-12-06

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development,more » and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.« less

The Influence of Cement Morphology Parameters on the Strength of the Cement-Bone Interface in Tibial Tray Fixation.

PubMed

Nagel, Katrin; Bishop, Nicholas E; Schlegel, Ulf J; Püschel, Klaus; Morlock, Michael M

2017-02-01

The strength of the cement-bone interface in tibial component fixation depends on the morphology of the cement mantle. The purpose of this study was to identify thresholds of cement morphology parameters to maximize fixation strength using a minimum amount of cement. Twenty-three cadaveric tibiae were analyzed that had been implanted with tibial trays in previous studies and for which the pull-out strength of the tray had been measured. Specimens were separated into a group failing at the cement-bone interface (INTERFACE) and one failing in the bulk bone (BULK). Maximum pull-out strength corresponds to the ultimate strength of the bulk bone if the cement-bone interface is sufficiently strong. 3D models of the cement mantle in situ were reconstructed from computed tomography scans. The influences of bone mineral density and 6 cement morphology parameters (reflecting cement penetration, bone-cement interface, cement volume) on pull-out strength of the BULK group were determined using multiple regression analysis. The threshold of each parameter for classification of the specimens into either group was determined using receiver operating characteristic analysis. Cement penetration exceeding a mean of 1.1 mm or with a maximum of 5.6 mm exclusively categorized all BULK bone failure specimens. Failure strength of BULK failure specimens increased with bone mineral density (R 2  = 0.67, P < .001) but was independent of the cement morphology parameters. To maximize fixation strength, a mean cement penetration depth of at least 1.1 mm should be achieved during tibial tray cementing. Copyright © 2016 Elsevier Inc. All rights reserved.

Comparison of microleakage of three acid-base luting cements versus one resin-bonded cement for Class V direct composite inlays.

PubMed

Piemjai, Morakot; Miyasaka, Kumiko; Iwasaki, Yasuhiko; Nakabayashi, Nobuo

2002-12-01

Demineralized dentin beneath set cement may adversely affect microleakage under fixed restorations. Microleakage of direct composite inlays cemented with acid-base cements and a methyl methacrylate resin cement were evaluated to determine their effect on the integrity of the underlying hybridized dentin. Sixty Class V box preparations (3 mm x 3 mm x 1.5 mm) were precisely prepared in previously frozen bovine teeth with one margin in enamel and another margin in dentin. Direct composite inlays (EPIC-TMPT) for each preparation were divided into 4 groups of 15 specimens each and cemented with 3 acid-base cements (control group): Elite, Ketac-Cem, Hy-Bond Carbo-Cem, and 1 adhesive resin cement: C&B Metabond. All specimens were stored in distilled water for 24 hours at 37 degrees C before immersion in 0.5% basic fuchsin for 24 hours. The dye penetration was measured on the sectioned specimens at the tooth-cement interface of enamel and cementum margins and recorded with graded criteria under light microscopy (Olympus Vanox-T) at original magnification x 50, 100, and 200. A Kruskal-Wallis and the Mann-Whitney test at P<.05 were used to analyze leakage score. All cementum margins of the 3 acid-base cements tested demonstrated significantly higher leakage scores than cementum margins for inlays cemented with the resin cement tested(P<.01). No leakage along the tooth-cement interface was found for inlays retained with the adhesive resin cement. Within the limitations of this study, the 3 acid-base cements tested exhibited greater microleakage at the cementum margins than did the adhesive resin cement that was tested.

Retention of cast crown copings cemented to implant abutments.

PubMed

Dudley, J E; Richards, L C; Abbott, J R

2008-12-01

The cementation of crowns to dental implant abutments is an accepted form of crown retention that requires consideration of the properties of available cements within the applied clinical context. Dental luting agents are exposed to a number of stressors that may reduce crown retention in vivo, not the least of which is occlusal loading. This study investigated the influence of compressive cyclic loading on the physical retention of cast crown copings cemented to implant abutments. Cast crown copings were cemented to Straumann synOcta titanium implant abutments with three different readily used and available cements. Specimens were placed in a humidifier, thermocycled and subjected to one of four quantities of compressive cyclic loading. The uniaxial tensile force required to remove the cast crown copings was then recorded. The mean retention values for crown copings cemented with Panavia-F cement were statistically significantly greater than both KetacCem and TempBond non-eugenol cements at each compressive cyclic loading quantity. KetacCem and TempBond non-eugenol cements produced relatively low mean retention values that were not statistically significantly different at each quantity of compressive cyclic loading. Compressive cyclic loading had a statistically significant effect on Panavia-F specimens alone, but increased loading quantities produced no further statistically significant difference in mean retention. Within the limitations of the current in vitro conditions employed in this study, the retention of cast crown copings cemented to Straumann synOcta implant abutments with a resin, glass ionomer and temporary cement was significantly affected by cement type but not compressive cyclic loading. Resin cement is the cement of choice for the definitive non-retrievable cementation of cast crown copings to Straumann synOcta implant abutments out of the three cements tested.

Hydration products and thermokinetic properties of cement-bentonite and cement-chalk mortars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klyusov, A.A.

1988-08-20

Bentonite and chalk are the most popular auxiliary additives to portland cement for borehole cementation. The authors studied by physicochemical analysis methods (x-ray phase, derivatographic, and scanning and electron microscopy in combination with microdiffraction) the newly formed solid-phase composition of cement-bentonite and cement-chalk mortars (binder-additive ratio 9:1) prepared from portland cement for cold boreholes and 8% calcium chloride solution at a water-mixing ratio of 0.9. The mechanism of the influence of Ca-bentonite and chalk additives on the portland cement hydration rate was ascertained from the heat evolution rate curves. It was found that the phase compositions of the hydration productsmore » are represented in the studied systems by newly formed substances typical for portland cement. It has been noted that Ca-bentonite interacts with the calcium hydroxide of hydrated cement with the formation of hexagonal and cubic calcium hydroaluminates. Unlike Ca-bentonite, chalk does not react with portland cement at normal and reduced temperatures, does not block hydrated cement particles, which, in turn, ensures all other conditions remaining equal, a higher initial rate of hydration of cement-chalk mortar.« less

Influence of Cements Containing Calcareous Fly Ash as a Main Component Properties of Fresh Cement Mixtures

NASA Astrophysics Data System (ADS)

Gołaszewski, Jacek; Kostrzanowska-Siedlarz, Aleksandra; Ponikiewski, Tomasz; Miera, Patrycja

2017-10-01

The main goal of presented research was to examine usability of cements containing calcareous fly ash (W) from technological point of view. In the paper the results of tests concerning the influence of CEM II and CEM IV cements containing fly ash (W) on rheological properties, air content, setting times and plastic shrinkage of mortars are presented and discussed. Moreover, compatibility of plasticizers with cements containing fly ash (W) was also studied. Additionally, setting time and hydration heat of cements containing calcareous fly ash (W) were determined. In a broader aspect, the research contributes to promulgation of the possibility of using calcareous fly ash (W) in cement and concrete technology, what greatly benefits the environment protection (utilization of waste fly ash). Calcareous fly ash can be used successfully as the main component of cement. Cements produced by blending with processed fly ash or cements produced by interginding are characterized by acceptable technological properties. In respect to CEM I cements, cements containing calcareous fly ash worsen workability, decrease air content, delay setting time of mixtures. Cements with calcareous fly ash show good compatibility with plasticizers.

76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-08

... and Cement Clinker From Japan Determination On the basis of the record \\1\\ developed in the subject... duty order on gray Portland cement and cement clinker from Japan would be likely to lead to... and Cement Clinker from Japan: Investigation No. 731- TA-461 (Third Review). By order of the...

The extent of slits at the interfaces between luting cements and enamel, dentin and alloy.

PubMed

Oilo, G

1978-01-01

Four different cements were used to assess the presence of slits at the cement/tooth or the cement/alloy interfaces using a tooth-crown model. The model consisted of ground sections of teeth and plane plates of silver/palladium alloy. The plates were fixed with bolts between two brass plates and with three different dimensions of the cement film between tooth and alloy, i.e. 50 micrometer, 100 micrometer and 200 micrometer. The tooth-alloy specimens were sectioned and the adaption of cements was studied with an indirect technique (replica) in a scanning electron microscope. The extent of slits was expressed as the length of all slits relative to the total length of the interface in each specimen. The results showed that the zinc phosphate cement and polycarboxylate cement exhibited a slight to moderate tendency to formation of slits at the interfaces. The EBA cement had a small extent of slits adjacent to thin cement films, but more slits were observed with increasing film thickness. The composite resin cement had a marked tendency to slit formation independent of the cement film thickness.

In vitro tensile strength of luting cements on metallic substrate.

PubMed

Orsi, Iara A; Varoli, Fernando K; Pieroni, Carlos H P; Ferreira, Marly C C G; Borie, Eduardo

2014-01-01

The aim of this study was to determine the tensile strength of crowns cemented on metallic substrate with four different types of luting agents. Twenty human maxillary molars with similar diameters were selected and prepared to receive metallic core castings (Cu-Al). After cementation and preparation the cores were measured and the area of crown's portion was calculated. The teeth were divided into four groups based on the luting agent used to cement the crowns: zinc phosphate cement; glass ionomer cement; resin cement Rely X; and resin cement Panavia F. The teeth with the crowns cemented were subjected to thermocycling and later to the tensile strength test using universal testing machine with a load cell of 200 kgf and a crosshead speed of 0.5 mm/min. The load required to dislodge the crowns was recorded and converted to MPa/mm(2). Data were subjected to Kruskal-Wallis analysis with a significance level of 1%. Panavia F showed significantly higher retention in core casts (3.067 MPa/mm(2)), when compared with the other cements. Rely X showed a mean retention value of 1.877 MPa/mm(2) and the zinc phosphate cement with 1.155 MPa/mm(2). Glass ionomer cement (0.884 MPa/mm(2)) exhibited the lowest tensile strength value. Crowns cemented with Panavia F on cast metallic posts and cores presented higher tensile strength. The glass ionomer cement showed the lowest tensile strength among all the cements studied.

Apatite formation on bioactive calcium-silicate cements for dentistry affects surface topography and human marrow stromal cells proliferation.

PubMed

Gandolfi, Maria Giovanna; Ciapetti, Gabriela; Taddei, Paola; Perut, Francesca; Tinti, Anna; Cardoso, Marcio Vivan; Van Meerbeek, Bart; Prati, Carlo

2010-10-01

The effect of ageing in phosphate-containing solution of bioactive calcium-silicate cements on the chemistry, morphology and topography of the surface, as well as on in vitro human marrow stromal cells viability and proliferation was investigated. A calcium-silicate cement (wTC) mainly based on dicalcium-silicate and tricalcium-silicate was prepared. Alpha-TCP was added to wTC to obtain wTC-TCP. Bismuth oxide was inserted in wTC to prepare a radiopaque cement (wTC-Bi). A commercial calcium-silicate cement (ProRoot MTA) was tested as control. Cement disks were aged in DPBS for 5 h ('fresh samples'), 14 and 28 days, and analyzed by ESEM/EDX, SEM/EDX, ATR-FTIR, micro-Raman techniques and scanning white-light interferometry. Proliferation, LDH release, ALP activity and collagen production of human marrow stromal cells (MSC) seeded for 1-28 days on the cements were evaluated. Fresh samples exposed a surface mainly composed of calcium-silicate hydrates CSH (from the hydration of belite and alite), calcium hydroxide, calcium carbonate, and ettringite. Apatite nano-spherulites rapidly precipitated on cement surfaces within 5 h. On wTC-TCP the Ca-P deposits appeared thicker than on the other cements. Aged cements showed an irregular porous calcium-phosphate (Ca-P) coating, formed by aggregated apatite spherulites with interspersed calcite crystals. All the experimental cements exerted no acute toxicity in the cell assay system and allowed cell growth. Using biochemical results, the scores were: fresh cements>aged cements for cell proliferation and ALP activity (except for wTC-Bi), whereas fresh cements

Cemented fixation with PMMA or Bis-GMA resin hydroxyapatite cement: effect of implant surface roughness.

PubMed

Walsh, W R; Svehla, M J; Russell, J; Saito, M; Nakashima, T; Gillies, R M; Bruce, W; Hori, R

2004-09-01

Implant surface roughness is an important parameter governing the overall mechanical properties at the implant-cement interface. This study investigated the influence of surface roughness using polymethylmethcrylate (PMMA) and a Bisphenol-a-glycidylmethacyrlate resin-hydroxyapatite cement (CAP). Mechanical fixation at the implant-cement interface was evaluated in vitro using static shear and fatigue loading with cobalt chrome alloy (CoCr) dowels with different surface roughness preparations. Increasing surface roughness improved the mechanical properties at the implant-cement interface for both types of cement. CAP cement fixation was superior to PMMA under static and dynamic loading.

Longevity of metal-ceramic crowns cemented with self-adhesive resin cement: a prospective clinical study

PubMed

Brondani, Lucas Pradebon; Pereira-Cenci, Tatiana; Wandsher, Vinicius Felipe; Pereira, Gabriel Kalil; Valandro, Luis Felipe; Bergoli, César Dalmolin

2017-04-10

Resin cements are often used for single crown cementation due to their physical properties. Self-adhesive resin cements gained widespread due to their simplified technique compared to regular resin cement. However, there is lacking clinical evidence about the long-term behavior of this material. The aim of this prospective clinical trial was to assess the survival rates of metal-ceramic crowns cemented with self-adhesive resin cement up to six years. One hundred and twenty-nine subjects received 152 metal-ceramic crowns. The cementation procedures were standardized and performed by previously trained operators. The crowns were assessed as to primary outcome (debonding) and FDI criteria. Statistical analysis was performed using Kaplan-Meier statistics and descriptive analysis. Three failures occurred (debonding), resulting in a 97.6% survival rate. FDI criteria assessment resulted in scores 1 and 2 (acceptable clinical evaluation) for all surviving crowns. The use of self-adhesive resin cement is a feasible alternative for metal-ceramic crowns cementation, achieving high and adequate survival rates.

Influence of the temperature on the cement disintegration in cement-retained implant restorations.

PubMed

Linkevicius, Tomas; Vindasiute, Egle; Puisys, Algirdas; Linkeviciene, Laura; Svediene, Olga

2012-01-01

The aim of this study was to estimate the average disintegration temperature of three dental cements used for the cementation of the implant-supported prostheses. One hundred and twenty metal frameworks were fabricated and cemented on the prosthetic abutments with different dental cements. After heat treatment in the dental furnace, the samples were set for the separation to test the integration of the cement. Results have shown that resin-modified glass-ionomer cement (RGIC) exhibited the lowest disintegration temperature (p<0.05), but there was no difference between zinc phosphate cement (ZPC) and dual cure resin cement (RC) (p>0.05). Average separation temperatures: RGIC - 306 ± 23 °C, RC - 363 ± 71 °C, it could not be calculated for the ZPC due to the eight unseparated specimens. Within the limitations of the study, it could be concluded that RGIC cement disintegrates at the lowest temperature and ZPC is not prone to break down after exposure to temperature.

Retrieval of Cement Embolus from Inferior Vena Cava After Percutaneous Vertebroplasty

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athreya, S., E-mail: sathreya@stjoes.c; Mathias, N.; Rogers, P.

Percutaneous vertebroplasty is an accepted treatment for painful vertebral compression fractures caused by osteoporosis and malignant disease. Venous leakage of cement and pulmonary cement embolism have been reported complications. We describe a paravertebral venous cement leak resulting in the deposition of a cement cast in the inferior vena cava and successful retrieval of the cement embolus.

76 FR 54206 - Gray Portland Cement and Clinker From Japan: Final Results of the Expedited Third Sunset Review...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-31

... manufacturing cement, has no use other than grinding into finished cement. Microfine cement was specifically... DEPARTMENT OF COMMERCE International Trade Administration [A-588-815] Gray Portland Cement and... portland cement and clinker from Japan. As a result of this third sunset review, the Department finds that...

Effects of abutment diameter, luting agent type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments.

PubMed

Safari, Sina; Hosseini Ghavam, Fereshteh; Amini, Parviz; Yaghmaei, Kaveh

2018-02-01

The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (α=.05). The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly ( P =.006). The difference in retention between the cemented and recemented copings was not statistically significant ( P =.40). Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement.

Development of an Improved Cement for Geothermal Wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trabits, George

2015-04-20

After an oil, gas, or geothermal production well has been drilled, the well must be stabilized with a casing (sections of steel pipe that are joined together) in order to prevent the walls of the well from collapsing. The gap between the casing and the walls of the well is filled with cement, which locks the casing into place. The casing and cementing of geothermal wells is complicated by the harsh conditions of high temperature, high pressure, and a chemical environment (brines with high concentrations of carbon dioxide and sulfuric acid) that degrades conventional Portland cement. During the 1990s andmore » early 2000s, the U.S. Department of Energy’s Geothermal Technologies Office (GTO) provided support for the development of fly-ash-modified calcium aluminate phosphate (CaP) cement, which offers improved resistance to degradation compared with conventional cement. However, the use of CaP cements involves some operational constraints that can increase the cost and complexity of well cementing. In some cases, CaP cements are incompatible with chemical additives that are commonly used to adjust cement setting time. Care must also be taken to ensure that CaP cements do not become contaminated with leftover conventional cement in pumping equipment used in conventional well cementing. With assistance from GTO, Trabits Group, LLC has developed a zeolite-containing cement that performs well in harsh geothermal conditions (thermal stability at temperatures of up to 300°C and resistance to carbonation) and is easy to use (can be easily adjusted with additives and eliminates the need to “sterilize” pumping equipment as with CaP cements). This combination of properties reduces the complexity/cost of well cementing, which will help enable the widespread development of geothermal energy in the United States.« less

Fracture Resistance of Lithium Disilicate Ceramics Bonded to Enamel or Dentin Using Different Resin Cement Types and Film Thicknesses.

PubMed

Rojpaibool, Thitithorn; Leevailoj, Chalermpol

2017-02-01

To investigate the influence of cement film thickness, cement type, and substrate (enamel or dentin) on ceramic fracture resistance. One hundred extracted human third molars were polished to obtain 50 enamel and 50 dentin specimens. The specimens were cemented to 1-mm-thick lithium disilicate ceramic plates with different cement film thicknesses (100 and 300 μm) using metal strips as spacers. The cements used were etch-and-rinse (RelyX Ultimate) and self-adhesive (RelyX U200) resin cements. Compressive load was applied on the ceramic plates using a universal testing machine, and fracture loads were recorded in Newtons (N). Statistical analysis was performed by multiple regression (p < 0.05). Representative specimens were evaluated by scanning electron microscopy to control the cement film thickness. The RelyX Ultimate group with a cement thickness of 100 μm cemented to enamel showed the highest mean fracture load (MFL; 1591 ± 172.59 N). The RelyX Ultimate groups MFLs were significantly higher than the corresponding RelyX U200 groups (p < 0.05), and thinner film cement demonstrated a higher MFL than thicker films (p < 0.05). Bonding to dentin resulted in lower MFL than with enamel (p < 0.001). Higher fracture loads were related to thinner cement film thickness and RelyX Ultimate resin cement. Bonding to dentin resulted in lower fracture loads than bonding to enamel. Reduced resin film thickness could reduce lithium disilicate restoration fracture. Etch-and-rinse resin cements are recommended for cementing on either enamel or dentin, compared with self-adhesive resin cement, for improved fracture resistance. © 2015 by the American College of Prosthodontists.

Effects of abutment diameter, luting agent type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments

PubMed Central

Safari, Sina; Amini, Parviz; Yaghmaei, Kaveh

2018-01-01

PURPOSE The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. MATERIALS AND METHODS Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (α=.05). RESULTS The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly (P=.006). The difference in retention between the cemented and recemented copings was not statistically significant (P=.40). CONCLUSION Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement. PMID:29503708

Evaluation of stainless steel crowns cemented with glass-ionomer and resin-modified glass-ionomer luting cements.

PubMed

Yilmaz, Yucel; Simsek, Sera; Dalmis, Anya; Gurbuz, Taskin; Kocogullari, M Elcin

2006-04-01

To evaluate in vitro and in vivo conditions of stainless steel crowns (SSC) cemented using one luting glass-ionomer cement (Aqua Meron) and one luting resin-modified glass-ionomer cement (Vitremer). In the in vitro part of this study, retentive properties of SSCs cemented using Aqua Meron and Vitremer on extracted primary first molars were tested. In addition, two specimens of each group were used to evaluate the tooth hard tissue-cement, within the cement itself, cement-SSC, and tooth hard tissue-cement-SSC under scanning electron microscope (SEM). In the in vivo part of this study, 152 SSCs were placed on the first or second primary molars of 86 children, and cemented using either Aqua Meron or Vitremer. The crowns were examined for retention. In addition, the clinical views of the crowns were recorded with an intraoral camera. No significant difference was found between the mean retentive forces of Aqua Meron and Vitremer (P> 0.05). SSCs cemented with Aqua Meron and Vitremer had an average lifespan of 26.44 and 24.07 months respectively. Only one (0.66%) of 152 SSCs was lost from the Aqua Meron group during post-cementation periods. Nineteen of the 152 SSCs (12.5%) had dents or perforations.

Microleakage of adhesive and nonadhesive luting cements for stainless steel crowns.

PubMed

Memarpour, Mahtab; Mesbahi, Maryam; Rezvani, Gita; Rahimi, Mehran

2011-01-01

This study's purpose was to compare the ability of 5 luting cements to reduce microleakage at stainless steel crown (SSC) margins on primary molar teeth. Standard preparations were performed on 100 extracted primary molar teeth for SSC restoration. After fitting SSCs, samples were randomly divided into 5 groups of 20 teeth each, which were cemented with nonadhesive cement consisting of polycarboxylate (PC) or zinc phosphate (ZP), or with adhesive cement consisting of glass ionomer (GIC), resin-modified glass ionomer cement (RMGIC), or RMGIC with a bonding agent (RMGIC+DBA). After aging and thermocycling, the specimens were placed in 1% methylene blue, sectioned, and evaluated under a digital microscope. The data were compared between groups with the t test, analysis of variance, and the least significant difference test. Microleakage with adhesive cements was significantly lower than with nonadhesive cements (P<.05). Differences between cements were statistically significant at P<.001. RMGIC+DBA showed the lowest microleakage, followed in increasing order by RMGIC, GIC, and ZP. The PC cement showed the greatest microleakage. Adhesive cements were more effective in reducing microleakage in stainless steel crowns than nonadhesive cements. Use of a bonding agent with a resin-modified glass ionomer cement yielded better results than using the latter alone.

Effect of temporary cements on the microtensile bond strength of self-etching and self-adhesive resin cement.

PubMed

Carvalho, Edilausson Moreno; Carvalho, Ceci Nunes; Loguercio, Alessandro Dourado; Lima, Darlon Martins; Bauer, José

2014-11-01

The aim of this study was to evaluate the microtensile bond strength (µTBS) of self-etching and self-adhesive resin cement systems to dentin affected by the presence of remnants of either eugenol-containing or eugenol-free temporary cements. Thirty extracted teeth were obtained and a flat dentin surface was exposed on each tooth. Acrylic blocks were fabricated and cemented either with one of two temporary cements, one zinc oxide eugenol (ZOE) and one eugenol free (ZOE-free), or without cement (control). After cementation, specimens were stored in water at 37°C for 1 week. The restorations and remnants of temporary cements were removed and dentin surfaces were cleaned with pumice. Resin composite blocks were cemented to the bonded dentin surfaces with one of two resin cements, either self-etching (Panavia F 2.0) or self-adhesive (RelyX U-100). After 24 h, the specimens were sectioned to obtain beams for submission to µTBS. The fracture mode was evaluated under a stereoscopic loupe and a scanning electron microscope (SEM). Data from µTBS were submitted to two-way repeated-measure ANOVA and the Tukey test (alpha = 0.05). The cross-product interaction was statistically significant (p < 0.0003). The presence of temporary cements reduced the bond strength to Panavia self-etching resin cements only (p < 0.05). Fracture occurred predominantly at the dentin-adhesive interface. The presence of eugenol-containing temporary cements did not interfere in the bond strength to dentin of self-adhesive resin cements.

Evaluation of selected properties of a new root repair cement containing surface pre-reacted glass ionomer fillers.

PubMed

Yassen, Ghaeth H; Huang, Ruijie; Al-Zain, Afnan; Yoshida, Takamitsu; Gregory, Richard L; Platt, Jeffrey A

2016-11-01

This study evaluated selected properties of a prototype root repair cement containing surface pre-reacted glass ionomer fillers (S-PRG) in comparison to mineral trioxide aggregate (MTA) and intermediate restorative material (IRM). The antibacterial effect of S-PRG, MTA, and IRM cements was tested against Porphyromonas gingivalis and Enterococcus faecalis after 1 and 3 days of aging of the cements. The set cements were immersed in distilled water for 4 h to 28 days, and ion-releasing ability was evaluated. Initial and final setting times of all cements were evaluated using Gilmore needles. The push-out bond strength between radicular dentin and all cements was tested at different levels of the roots. S-PRG and IRM cements, but not MTA cement, demonstrated significant antibacterial effect against P. gingivalis. All types of cements exhibited significant antibacterial effect against E. faecalis without being able to eliminate the bacterium. S-PRG cement provided continuous release of fluoride, strontium, boron, sodium, aluminum, and zinc throughout all tested time points. Both initial and final setting times were significantly shorter for S-PRG and IRM cements in comparison to MTA. The push-out bond strength was significantly lower for S-PRG cement in comparison to MTA and IRM at coronal and middle levels of the roots. S-PRG cement demonstrated significant antibacterial effects against endodontic pathogens, multiple ion-releasing ability, relatively short setting time, and low bonding strength. S-PRG cement can be used as a one-visit root repair material with promising antibacterial properties and ion-releasing capacity.

Effect of wet curing duration on durability parameters of hydraulic cement concretes.

DOT National Transportation Integrated Search

2010-01-01

Hydraulic cement concrete slabs were cast and stored outdoors in Charlottesville, Virginia, to study the impact of wet curing duration on durability parameters. Concrete mixtures were produced using portland cement, portland cement with slag cement, ...

[Experimental rationale for carcinogenic risk of asbestos cement industry and its products].

PubMed

Pylev, D N; Smirnova, O V; Vasil'eva, L A; Khrustalev, S A; Vezentsev, A I; Gudkova, E A; Naumova, L N

2010-01-01

During intraperitoneal administration of dispersiveness-comparable chrysotile or asbestos cement fibers to rats (20 mg thrice), mesotheliomas were found in 45.1 and 7.7% of cases respectively. Asbestos cement dust induced tumors in 2.5% of cases, which is of biological importance. Cement or freeze asbestos destruction cement dust failed to cause tumors. The latter were not detected in a control group receiving physiological saline. Asbestos cement fibers and fascicles are covered by a cement matrix. Fiber amorphization gradually occurs. In lung tissue, there may be destruction of the cement coat of fascicles and release of native chrysotile fibers that are carcinogenic.

In Vitro Evaluation of Planktonic Growth on Experimental Cement-Retained Titanium Surfaces.

PubMed

Balci, Nur; Cakan, Umut; Aksu, Burak; Akgul, Oncu; Ulger, Nurver

2016-04-08

BACKGROUND The purpose of this study was to compare the effects of selected cements, or their combination with titanium, on the growth of two periodontopathic bacteria: Prevotella intermedia (Pi) and Fusobacterium nucleatum (Fn). MATERIAL AND METHODS This study was comprised of several experimental groups: 1) Dental luting cements (glass ionomer cement, methacrylate-based resin cement, zinc-oxide eugenol cement, eugenol-free zinc oxide cement; 2) titanium discs; and 3) titanium combination cement discs. The disks were submerged in bacterial suspensions of either Fn or Pi. Planktonic bacterial growth within the test media was measured by determining the optical density of the cultures (OD600). Mean and standard deviations were calculated for planktonic growth from three separate experiments. RESULTS Intergroup comparison of all experimental groups revealed increased growth of Pi associated with cement-titanium specimens in comparison with cement specimens. Regarding the comparison of all groups for Fn, there was an increased amount of bacterial growth in cement-titanium specimens although the increase was not statistically significant. CONCLUSIONS The combination of cement with titanium may exacerbate the bacterial growth capacity of Pi and Fn in contrast to their sole effect.

In Vitro Evaluation of Planktonic Growth on Experimental Cement-Retained Titanium Surfaces

PubMed Central

Balci, Nur; Cakan, Umut; Aksu, Burak; Akgul, Oncu; Ulger, Nurver

2016-01-01

Background The purpose of this study was to compare the effects of selected cements, or their combination with titanium, on the growth of two periodontopathic bacteria: Prevotella intermedia (Pi) and Fusobacterium nucleatum (Fn). Material/Methods This study was comprised of several experimental groups: 1) Dental luting cements (glass ionomer cement, methacrylate-based resin cement, zinc-oxide eugenol cement, eugenol-free zinc oxide cement; 2) titanium discs; and 3) titanium combination cement discs. The disks were submerged in bacterial suspensions of either Fn or Pi. Planktonic bacterial growth within the test media was measured by determining the optical density of the cultures (OD600). Mean and standard deviations were calculated for planktonic growth from three separate experiments. Results Intergroup comparison of all experimental groups revealed increased growth of Pi associated with cement-titanium specimens in comparison with cement specimens. Regarding the comparison of all groups for Fn, there was an increased amount of bacterial growth in cement-titanium specimens although the increase was not statistically significant. Conclusions The combination of cement with titanium may exacerbate the bacterial growth capacity of Pi and Fn in contrast to their sole effect. PMID:27058704

Comparison of retention and demineralization inhibition potential of adhesive banding cements in primary teeth.

PubMed

Prabhakar, A R; Mahantesh, T; Ahuja, Vipin

2010-01-01

The purpose of this study was to evaluate the efficacy of banding cements in terms of retentive capability and demineralization inhibition potential. We included 48 non-carious primary mandibular second molar teeth. Preformed stainless steel bands were adapted onto the teeth. All teeth were randomly assigned to four groups: Group I (Adaptation of bands without cementation), Group II (Cementation of bands using conventional Glass Ionomer Cement), Group III (Cementation of bands using Resin-modified Glass Ionomer Cement), Group IV (Cementation of bands using Resin cement), and placed in artificial saliva. Each day, specimens were taken from artificial saliva and suspended in an artificial caries solution for 35 minutes, every 8 hours. At the end of 3 months, retention of bands was estimated using an Instron Universal Testing Machine. The mode of failure was recorded and specimens were sectioned and examined under polarized microscope for demineralized lesions. The mean retention value was highest with resin cement, followed by RMGIC, GIC, and Control group respectively. The RMGIC group showed more favorable modes of failures. All the experimental groups showed significant demineralization inhibition potential. RMGIC is the preferable banding cement and can be used effectively to cement bands in primary dentition.

Cement selection for implant-supported crowns fabricated with different luting space settings.

PubMed

Gultekin, Pinar; Gultekin, B Alper; Aydin, Murat; Yalcin, Serdar

2013-02-01

To measure and compare the retentive strength of cements specifically formulated for luting restorations onto implant abutments and to investigate the effect of varying cement gap on retention strength of implant-supported crowns. Standard titanium abutments were scanned by means of a 3D digital laser scanner. One hundred and sixty standard metal copings were designed by a Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) system with two cement gap values (20 and 40 μm). The copings were cemented to the abutments using the following eight cements with one being the control, zinc oxide temporary cement, while the other seven were specifically formulated implant cements (n = 10): Premier Implant Cement, ImProv, Multilink Implant, EsTemp Implant, Cem-Implant, ImplaTemp, MIS Crown Set, and TempBond NE. The specimens were placed in 100% humidity for 24 hours, and subjected to a pull-out test using a universal testing machine at a 0.5 mm/min crosshead speed. The test results were analyzed with two-way ANOVA, one-way ANOVA, post hoc Tamhane' s T2, and student's t-tests at a significance level of 0.05. Statistical analysis revealed significant differences in retention strength across the cement groups (p < 0.01). Resin-based cements showed significantly higher decementation loads than a noneugenol zinc oxide provisional cement (TempBond NE) (p < 0.01), with the highest tensile resistance seen with Multilink Implant, followed by Cem-Implant, MIS Crown Set, ImProv, Premier Implant Cement, EsTemp Implant, and ImplaTemp. Increasing the cement gap from 20 to 40 μm improved retention significantly for the higher strength cements: Multilink Implant, Premier Implant Cement, ImProv, Cem-Implant, and MIS Crown Set (p < 0.01), while it had no significant effect on retention for the lower strength cements: EsTemp Implant, ImplaTemp, and TempBond NE (p > 0.05). Resin cements specifically formulated for implant-supported restorations demonstrated significant differences in retention strength. The ranking of cements presented in the study is meant to be an arbitrary guide for the clinician in deciding the appropriate cement selection for CAD/CAM-fabricated metal copings onto implant abutments with different luting space settings. © 2012 by the American College of Prosthodontists.

The cysteine-rich domain regulates ADAM protease function in vivo.

PubMed

Smith, Katherine M; Gaultier, Alban; Cousin, Helene; Alfandari, Dominique; White, Judith M; DeSimone, Douglas W

2002-12-09

ADAMs are membrane-anchored proteases that regulate cell behavior by proteolytically modifying the cell surface and ECM. Like other membrane-anchored proteases, ADAMs contain candidate "adhesive" domains downstream of their metalloprotease domains. The mechanism by which membrane-anchored cell surface proteases utilize these putative adhesive domains to regulate protease function in vivo is not well understood. We address this important question by analyzing the relative contributions of downstream extracellular domains (disintegrin, cysteine rich, and EGF-like repeat) of the ADAM13 metalloprotease during Xenopus laevis development. When expressed in embryos, ADAM13 induces hyperplasia of the cement gland, whereas ADAM10 does not. Using chimeric constructs, we find that the metalloprotease domain of ADAM10 can substitute for that of ADAM13, but that specificity for cement gland expansion requires a downstream extracellular domain of ADAM13. Analysis of finer resolution chimeras indicates an essential role for the cysteine-rich domain and a supporting role for the disintegrin domain. These and other results reveal that the cysteine-rich domain of ADAM13 cooperates intramolecularly with the ADAM13 metalloprotease domain to regulate its function in vivo. Our findings thus provide the first evidence that a downstream extracellular adhesive domain plays an active role in regulating ADAM protease function in vivo. These findings are likely relevant to other membrane-anchored cell surface proteases.

The exploration study of fire damage to concrete specimen using x-ray computed tomography

NASA Astrophysics Data System (ADS)

Su, Yu-Min; Lee, Min-Gin; Chen, Guan-Ying

2015-04-01

Portland Cement Concrete (PCC) loses the evaporable water at about 100 °C, decomposes C-S-H at about 200 °C, and dehydrates CH at about 500 °C, and deconstruct C-S-H at about 900°C. The concrete degradation or cracks are caused by several possible parameters, such as vapor pressure in pores, thermal gradient, and varied expansion rates of cement pastes and aggregates. The objective of the exploration study was to assess the porosity before and after conditioning of high temperature in the laboratory with the medical X-ray computed tomography. The experimental program was determined to identify the mineral properties of the aggregates used and determine the consensus properties of compressive, splitting tensile, and flexural strengths. Concrete cylinders were subject with one temperature conditioning, namely 400°C, but two different heat conditioning time namely four and eight hours. The X-ray CT, before and after high temperature conditioning, was administrated on the concrete cylinders to inspect the depth of the damage zone, which shall consist of more porosity than undamaged one. The damage zone will be examined and identified through the changes in porosity of concrete paste and aggregates within a concrete cylinder. The significance of the exploration study was to provide an in-depth insight to define the damaged zone for a better understanding of the following repairing and reinforced work.

Microleakage of Glass Ionomer-based Provisional Cement in CAD/CAM-Fabricated Interim Crowns: An in vitro Study.

PubMed

Farah, Ra'fat I; Al-Harethi, Naji

2016-10-01

The aim of this study was to compare in vitro the marginal microleakage of glass ionomer-based provisional cement with resin-based provisional cement and zinc oxide non-eugenol (ZONE) provisional cement in computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated interim restorations. Fifteen intact human premolars were prepared in a standardized manner for complete coverage of crown restorations. Interim crowns for the prepared teeth were then fabricated using CAD/CAM, and the specimens were randomized into three groups of provisional cementing agents (n = 5 each): Glass ionomer-based provisional cement (GC Fuji TEMP LT™), bisphenol-A-glycidyldimethacrylate (Bis-GMA)/ triethylene glycol dimethacrylate (TEGDMA) resin-based cement (UltraTemp® REZ), and ZONE cement (TempBond NE). After 24 hours of storage in distilled water at 37°C, the specimens were thermocycled and then stored again for 24 hours in distilled water at room temperature. Next, the specimens were placed in freshly prepared 2% aqueous methylene blue dye for 24 hours and then embedded in autopolymerizing acrylic resin blocks and sectioned in buccolingual and mesiodistal directions to assess dye penetration using a stereomicroscope. The results were statistically analyzed using a nonparametric Kruskal-Wallis test. Dunn's post hoc test with a Bonferroni correction test was used to compute multiple pairwise comparisons that identified differences among groups; the level of significance was set at p < 0.05. All groups exhibited marginal microleakage; the Bis-GMA/TEGDMA resin-based provisional cement demonstrated the lowest microleakage scores, which were statistically different from those of the glass ionomer-based provisional cement and the ZONE cement. The provisional cementing agents exhibited different sealing abilities. The Bis-GMA/TEGDMA resin-based provisional cement exhibited the most effective favorable sealing properties against dye penetration compared with the glass ionomer-based provisional cement and conventional ZONE cement. Newly introduced glass ionomer-based provisional cement proved to be inferior to resin-based provisional cement as far as marginal microleakage is concerned.

[Significance of bone mineral density and modern cementing technique for in vitro cement penetration in total shoulder arthroplasty].

PubMed

Pape, G; Raiss, P; Kleinschmidt, K; Schuld, C; Mohr, G; Loew, M; Rickert, M

2010-12-01

Loosening of the glenoid component is one of the major causes of failure in total shoulder arthroplasty. Possible risk factors for loosening of cemented components include an eccentric loading, poor bone quality, inadequate cementing technique and insufficient cement penetration. The application of a modern cementing technique has become an established procedure in total hip arthroplasty. The goal of modern cementing techniques in general is to improve the cement-penetration into the cancellous bone. Modern cementing techniques include the cement vacuum-mixing technique, retrograde filling of the cement under pressurisation and the use of a pulsatile lavage system. The main purpose of this study was to analyse cement penetration into the glenoid bone by using modern cement techniques and to investigate the relationship between the bone mineral density (BMD) and the cement penetration. Furthermore we measured the temperature at the glenoid surface before and after jet-lavage of different patients during total shoulder arthroplasty. It is known that the surrounding temperature of the bone has an effect on the polymerisation of the cement. Data from this experiment provide the temperature setting for the in-vitro study. The glenoid surface temperature was measured in 10 patients with a hand-held non-contact temperature measurement device. The bone mineral density was measured by DEXA. Eight paired cadaver scapulae were allocated (n = 16). Each pair comprised two scapulae from one donor (matched-pair design). Two different glenoid components were used, one with pegs and the other with a keel. The glenoids for the in-vitro study were prepared with the bone compaction technique by the same surgeon in all cases. Pulsatile lavage was used to clean the glenoid of blood and bone fragments. Low viscosity bone cement was applied retrogradely into the glenoid by using a syringe. A constant pressure was applied with a modified force sensor impactor. Micro-computed tomography scans were applied to analyse the cement penetration into the cancellous bone. The mean temperature during the in-vivo arthroplasty of the glenoid was 29.4 °C (27.2-31 °C) before and 26.2 °C (25-27.5 °C) after jet-lavage. The overall peak BMD was 0.59 (range 0.33-0.99) g/cm (2). Mean cement penetration was 107.9 (range 67.6-142.3) mm (2) in the peg group and 128.3 (range 102.6-170.8) mm (2) in the keel group. The thickness of the cement layer varied from 0 to 2.1 mm in the pegged group and from 0 to 2.4 mm in the keeled group. A strong negative correlation between BMD and mean cement penetration was found for the peg group (r (2) = -0.834; p < 0.01) and for the keel group (r (2) = -0.727; p < 0.041). Micro-CT shows an inhomogenous dispersion of the cement into the cancellous bone. Data from the in-vivo temperature measurement indicate that the temperature at the glenohumeral surface under operation differs from the body core temperature and should be considered in further in-vitro studies with human specimens. Bone mineral density is negatively correlated to cement penetration in the glenoid. The application of a modern cementing technique in the glenoid provides sufficient cementing penetration although there is an inhomogenous dispersion of the cement. The findings of this study should be considered in further discussions about cementing technique and cement penetration into the cancellous bone of the glenoid. © Georg Thieme Verlag KG Stuttgart · New York.

Effect of surface treatment and type of cement on push-out bond strength of zirconium oxide posts.

PubMed

Almufleh, Balqees S; Aleisa, Khalil I; Morgano, Steven M

2014-10-01

The effect of the surface treatment of zirconium oxide posts on their push-out bond strength is controversial. The purpose of this study was to compare the effects of 2 surface treatments on the bond strength of zirconium oxide posts cemented with different cements and to assess the failure mode. Seventy extracted human teeth were divided into 7 groups (n=10). Custom zirconium oxide posts (Cercon; Degudent) were fabricated for 6 groups. Posts in 3 groups were airborne-particle abraded (A). Posts in the other 3 groups were tribochemical silica coated (T). Three cements were used. Zinc phosphate cement was used to cement the zirconium oxide posts in groups AZ and TZ, RelyX ARC cement was used in groups ARA and TRA, and RelyX Unicem cement was used in groups ARU and TRU. Group C contained custom metal posts cemented with zinc phosphate cement. Specimens were horizontally sectioned into 3 sections and subjected to a push-out test. A mixed model analysis of variance, 1-way ANOVA, and the Tukey multiple comparison tests were used for statistical analysis. The highest push-out bond strength was recorded for Group ARU (21.03 MPa), and the lowest was recorded for Group ARA (7.57 MPa). No significant difference in push-out bond strength was found among the different surface treatments and root regions (P>.05). The type of cement had a significant effect on the push-out bond strength of zirconium oxide posts (P=.049). RelyX Unicem cement recorded (19.57 ±8.83 MPa) significantly higher push-out bond strength compared with zinc phosphate (9.95 ±6.31 MPa) and RelyX ARC cements (9.39 ±5.45 MPa). Adhesive failure at the post-cement interface was recorded for 75% of the posts cemented with zinc phosphate and RelyX ARC cements, while mixed failure was recorded for 75% of the posts cemented with RelyX Unicem cement. The type of cement used resulted in a statistically significant difference in the push-out bond strength of zirconium oxide posts, while both the surface treatment and root region resulted in no statistically significant effect after artificial aging. RelyX Unicem cement had significantly higher push-out bond strength than did zinc phosphate and RelyX ARC cements. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Development of monetite-nanosilica bone cement: a preliminary study.

PubMed

Zhou, Huan; Luchini, Timothy J F; Agarwal, Anand K; Goel, Vijay K; Bhaduri, Sarit B

2014-11-01

In this paper, we reported the results of our efforts in developing DCPA/nanosilica composite orthopedic cement. It is motivated by the significances of DCPA and silicon in bone physiological activities. More specifically, this paper examined the effects of various experimental parameters on the properties of such composite cements. In this work, DCPA cement powders were synthesized using a microwave synthesis technique. Mixing colloidal nanosilica directly with synthesized DCPA cement powders can significantly reduce the washout resistance of DCPA cement. In contrast, a DCPA-nanosilica cement powder prepared by reacting Ca(OH)2 , H3 PO4 and nanosilica together showed good washout resistance. The incorporation of nanosilica in DCPA can improve compressive strength, accelerate cement solidification, and intensify surface bioactivity. In addition, it was observed that by controlling the content of NaHCO3 during cement preparation, the resulting composite cement properties could be modified. Allowing for the development of different setting times, mechanical performance and crystal features. It is suggested that DCPA-nanosilica composite cement can be a potential candidate for bone healing applications. © 2014 Wiley Periodicals, Inc.

[Augmentation with PMMA cement].

PubMed

Kühn, K-D; Höntzsch, D

2015-09-01

Cements based on polymethyl methacrylate (PMMA) can be used without any problem in a variety of clinical augmentations. Cement-related complications in surgical procedures involving PMMA cements, such as embolism, thermal necrosis, toxicity and hypersensitivity, are often due to other causes. Knowledge about the properties of the cement helps the user to safely employ PMMA cements in augmentations. High radio-opacity is required in vertebral body augmentations and this is provided in particular by zirconium dioxide. In vertebral body augmentations, a low benzoyl peroxide (BPO) content can considerably prolong the liquid dough phase. In augmentations with cement fillings in the region of a tumor, a high BPO content can specifically increase the peak temperature of the PMMA cement. In osteosynthetic augmentations with PMMA, necrosis is rare because heat development in the presence of metallic implants is low due to heat conduction via the implant. Larger cement fillings where there is no heat conduction via metal implants can exhibit substantially higher peak temperatures. The flow properties of PMMA cements are of particular importance for the user to allow optimum handling of PMMA cements. In patients with hypersensitivity to antibiotics, there is no need to avoid the use of PMMA as there are sufficient PMMA-based alternatives. The PMMA cements are local drug delivery systems and antibiotics, antiseptics, antimycotics and also cytostatics can be mixed with the cement. Attention must be paid to antagonistic and synergistic effects.

Effect of cement washout on loosening of abutment screws and vice versa in screw- and cement- retained implant-supported dental prosthesis

PubMed Central

Kim, Seok-Gyu; Son, Mee-Kyoung

2015-01-01

PURPOSE The purpose of this study was to examine the abutment screw stability of screw- and cement-retained implant-supported dental prosthesis (SCP) after simulated cement washout as well as the stability of SCP cements after complete loosening of abutment screws. MATERIALS AND METHODS Thirty-six titanium CAD/CAM-made implant prostheses were fabricated on two implants placed in the resin models. Each prosthesis is a two-unit SCP: one screw-retained and the other cemented. After evaluating the passive fit of each prosthesis, all implant prostheses were randomly divided into 3 groups: screwed and cemented SCP (Control), screwed and noncemented SCP (Group 1), unscrewed and cemented SCP (Group 2). Each prosthesis in Control and Group 1 was screwed and/or cemented, and the preloading reverse torque value (RTV) was evaluated. SCP in Group 2 was screwed and cemented, and then unscrewed (RTV=0) after the cement was set. After cyclic loading was applied, the postloading RTV was measured. RTV loss and decementation ratios were calculated for statistical analysis. RESULTS There was no significant difference in RTV loss ratio between Control and Group 1 (P=.16). No decemented prosthesis was found among Control and Group 2. CONCLUSION Within the limits of this in vitro study, the stabilities of SCP abutment screws and cement were not significantly changed after simulated cement washout or screw loosening. PMID:26140172

Biomechanical three-dimensional finite element analysis of monolithic zirconia crown with different cement type

PubMed Central

2015-01-01

PURPOSE The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns. PMID:26816578

Properties of Cement Mortar Produced from Mixed Waste Materials with Pozzolanic Characteristics.

PubMed

Yen, Chi-Liang; Tseng, Dyi-Hwa; Wu, Yue-Ze

2012-07-01

Waste materials with pozzolanic characteristics, such as sewage sludge ash (SSA), coal combustion fly ash (FA), and granulated blast furnace slag (GBS), were reused as partial cement replacements for making cement mortar in this study. Experimental results revealed that with dual replacement of cement by SSA and GBS and triple replacement by SSA, FA, and GBS at 50% of total cement replacement, the compressive strength (Sc) of the blended cement mortars at 56 days was 93.7% and 92.9% of the control cement mortar, respectively. GBS had the highest strength activity index value and could produce large amounts of CaO to enhance the pozzolanic activity of SSA/FA and form calcium silicate hydrate gels to fill the capillary pores of the cement mortar. Consequently, the Sc development of cement mortar with GBS replacement was better than that without GBS, and the total pore volume of blended cement mortars with GBS/SSA replacement was less than that with FA/SSA replacement. In the cement mortar with modified SSA and GBS at 70% of total cement replacement, the Sc at 56 days was 92.4% of the control mortar. Modifying the content of calcium in SSA also increased its pozzolanic reaction. CaCl(2) accelerated the pozzolanic activity of SSA better than lime did. Moreover, blending cement mortars with GBS/SSA replacement could generate more monosulfoaluminate to fill capillary pores.

Properties of Cement Mortar Produced from Mixed Waste Materials with Pozzolanic Characteristics

PubMed Central

Yen, Chi-Liang; Tseng, Dyi-Hwa; Wu, Yue-Ze

2012-01-01

Abstract Waste materials with pozzolanic characteristics, such as sewage sludge ash (SSA), coal combustion fly ash (FA), and granulated blast furnace slag (GBS), were reused as partial cement replacements for making cement mortar in this study. Experimental results revealed that with dual replacement of cement by SSA and GBS and triple replacement by SSA, FA, and GBS at 50% of total cement replacement, the compressive strength (Sc) of the blended cement mortars at 56 days was 93.7% and 92.9% of the control cement mortar, respectively. GBS had the highest strength activity index value and could produce large amounts of CaO to enhance the pozzolanic activity of SSA/FA and form calcium silicate hydrate gels to fill the capillary pores of the cement mortar. Consequently, the Sc development of cement mortar with GBS replacement was better than that without GBS, and the total pore volume of blended cement mortars with GBS/SSA replacement was less than that with FA/SSA replacement. In the cement mortar with modified SSA and GBS at 70% of total cement replacement, the Sc at 56 days was 92.4% of the control mortar. Modifying the content of calcium in SSA also increased its pozzolanic reaction. CaCl2 accelerated the pozzolanic activity of SSA better than lime did. Moreover, blending cement mortars with GBS/SSA replacement could generate more monosulfoaluminate to fill capillary pores. PMID:22783062

N-acetyl cysteine (NAC)-mediated detoxification and functionalization of poly(methyl methacrylate) bone cement.

PubMed

Tsukimura, Naoki; Yamada, Masahiro; Aita, Hideki; Hori, Norio; Yoshino, Fumihiko; Chang-Il Lee, Masaichi; Kimoto, Katsuhiko; Jewett, Anahid; Ogawa, Takahiro

2009-07-01

Currently used poly(methyl methacrylate) (PMMA)-based bone cement lacks osteoconductivity and induces osteolysis and implant loosening due to its cellular and tissue-toxicity. A high percentage of revision surgery following the use of bone cement has become a significant universal problem. This study determined whether incorporation of the amino acid derivative N-acetyl cysteine (NAC) in bone cement reduces its cytotoxicity and adds osteoconductivity to the material. Biocompatibility and bioactivity of PMMA-based bone cement with or without 25mm NAC incorporation was examined using rat bone marrow-derived osteoblastic cells. Osteoconductive potential of NAC-incorporated bone cement was determined by microCT bone morphometry and implant biomechanical test in the rat model. Generation of free radicals within the polymerizing bone cement was examined using electron spin resonance spectroscopy. Severely compromised viability and completely suppressed phenotypes of osteoblasts on untreated bone cement were restored to the normal level by NAC incorporation. Bone volume formed around 25mm NAC-incorporated bone cement was threefold greater than that around control bone cement. The strength of bone-bone cement integration was 2.2 times greater for NAC-incorporated bone cement. For NAC-incorporated bone cement, the spike of free radical generation ended within 12h, whereas for control bone cement, a peak level lasted for 6 days and a level greater than half the level of the peak was sustained for 20 days. NAC also increased the level of antioxidant glutathione in osteoblasts. These results suggest that incorporation of NAC in PMMA bone cement detoxifies the material by immediate and effective in situ scavenging of free radicals and increasing intracellular antioxidant reserves, and consequently adds osteoconductivity to the material.

Effects of Cement, Abutment Surface Pretreatment, and Artificial Aging on the Force Required to Detach Cantilever Fixed Dental Prostheses from Dental Implants.

PubMed

Kappel, Stefanie; Chepura, Taras; Schmitter, Marc; Rammelsberg, Peter; Rues, Stefan

To examine the in vitro effects of different cements, abutment surface preconditioning, and artificial aging on the maximum tensile force needed to detach cantilever fixed dental prostheses (FDPs) from dental implants with titanium abutments. A total of 32 tissue-level implants were combined with standardized titanium abutments. For each test group, eight cantilever FDPs were fabricated using selective laser melting (cobalt-chromium [CoCr] alloy). The inner surfaces of the cantilever FDPs and half of the abutments were sandblasted and then joined by use of four different cements (two permanent and two semi-permanent) in two different amounts per cement. Subgroups were tested after either artificial aging (thermocycling and chewing simulation) or 3 days of water storage. Finally, axial pull off-tests were performed for each abutment separately. Cement type and surface pretreatment significantly affected decementation behavior. The highest retention forces (approximately 1,200 N) were associated with sandblasted abutments and permanent cements. With unconditioned abutments, temporary cements (Fu < 100 N), as well as glass-ionomer cement (Fu ≈ 100 N), resulted in rather low retention forces. Zinc phosphate cement guaranteed high retention forces. After aging, retention was sufficient only for cementation with zinc phosphate cement and for the combination of sandblasted abutments and glass-ionomer cement. When glass-ionomer cement is used to fix cantilever FDPs on implants, sandblasting of standard titanium abutments may help prevent loss of retention. Retention forces were still high for FDPs fixed with zinc phosphate cement, even when the abutments were not pretreated. Use of permanent cements only, however, is recommended to prevent unwanted loosening of cantilever FDPs.

Micro-mechanical modeling of the cement-bone interface: the effect of friction, morphology and material properties on the micromechanical response.

PubMed

Janssen, Dennis; Mann, Kenneth A; Verdonschot, Nico

2008-11-14

In order to gain insight into the micro-mechanical behavior of the cement-bone interface, the effect of parametric variations of frictional, morphological and material properties on the mechanical response of the cement-bone interface were analyzed using a finite element approach. Finite element models of a cement-bone interface specimen were created from micro-computed tomography data of a physical specimen that was sectioned from an in vitro cemented total hip arthroplasty. In five models the friction coefficient was varied (mu=0.0; 0.3; 0.7; 1.0 and 3.0), while in one model an ideally bonded interface was assumed. In two models cement interface gaps and an optimal cement penetration were simulated. Finally, the effect of bone cement stiffness variations was simulated (2.0 and 2.5 GPa, relative to the default 3.0 GPa). All models were loaded for a cycle of fully reversible tension-compression. From the simulated stress-displacement curves the interface deformation, stiffness and hysteresis were calculated. The results indicate that in the current model the mechanical properties of the cement-bone interface were caused by frictional phenomena at the shape-closed interlock rather than by adhesive properties of the cement. Our findings furthermore show that in our model maximizing cement penetration improved the micromechanical response of the cement-bone interface stiffness, while interface gaps had a detrimental effect. Relative to the frictional and morphological variations, variations in the cement stiffness had only a modest effect on the micro-mechanical behavior of the cement-bone interface. The current study provides information that may help to better understand the load-transfer mechanisms taking place at the cement-bone interface.

Comparative study on the tensile bond strength and marginal fit of complete veneer cast metal crowns using various luting agents: An in vitro study

PubMed Central

Parameswari, B. Devi; Rajakumar, M.; Lambodaran, G.; Sundar, Shyam

2016-01-01

Introduction: Several commercially available luting agents are used to cement the dental restorations such as intra-coronal, extra-coronal, and fixed partial dentures. Tensile bond strength (TBS) and accurate marginal fit are the essential factors to determine the good clinical results in fixed prosthesis. The retentivity of the luting cements is assessed by their adhesive capacity over the tooth surface and metal surface. Generally, the adhesive ability has been evaluated with in vitro testing, with tensile bond tests. The failure of fixed prosthesis may be happened as a result of incomplete seating during cementation. Most research on cementation of crowns relates seating failure to the thickness of the cement film. Materials and Methods: The study is divided into four groups with 10 samples for each of the luting cement taken up for testing TBS and four groups with 5 samples for each luting agent chosen for assessing marginal fit. The results were tabulated and statistically analyzed. Results: In this in vitro study, the TBS of luting cements, and marginal fit in relation to luting cements were tested by using appropriate testing devices. The TBS of cement is measured using universal testing machine, and the results are tabulated. The marginal gap that exists between the margin of the cast metal crown, and the finish line is measured using travelling microscope before and after cementation. The difference between these two values gives the discrepancy that is due to the film thickness of cement used for luting the restoration. Summary and Conclusion: The TBS value of zinc phosphate cement and glass ionomer cement were found to be almost same. The chemical adhesiveness of the glass ionomer with calcium ions of enamel and dentin may be the attributed reason (ionic bonding). In this study, the polycarboxylate is the one that showed low TBS, and it may be attributed to the weakness of the cement due to reduced film thickness, though this cement has a chemical bonding nature. The observation of results of marginal fit in this study is the increased gap found in zinc phosphate cement followed by resin cement, zinc polycarboxylate, and glass ionomer cement. It is agreeable to estimate the marginal fit of the restoration, which could be affected by the film thickness of the luting cement along with other factors. PMID:27829765

Comparative study on the tensile bond strength and marginal fit of complete veneer cast metal crowns using various luting agents: An in vitro study.

PubMed

Parameswari, B Devi; Rajakumar, M; Lambodaran, G; Sundar, Shyam

2016-10-01

Several commercially available luting agents are used to cement the dental restorations such as intra-coronal, extra-coronal, and fixed partial dentures. Tensile bond strength (TBS) and accurate marginal fit are the essential factors to determine the good clinical results in fixed prosthesis. The retentivity of the luting cements is assessed by their adhesive capacity over the tooth surface and metal surface. Generally, the adhesive ability has been evaluated with in vitro testing, with tensile bond tests. The failure of fixed prosthesis may be happened as a result of incomplete seating during cementation. Most research on cementation of crowns relates seating failure to the thickness of the cement film. The study is divided into four groups with 10 samples for each of the luting cement taken up for testing TBS and four groups with 5 samples for each luting agent chosen for assessing marginal fit. The results were tabulated and statistically analyzed. In this in vitro study, the TBS of luting cements, and marginal fit in relation to luting cements were tested by using appropriate testing devices. The TBS of cement is measured using universal testing machine, and the results are tabulated. The marginal gap that exists between the margin of the cast metal crown, and the finish line is measured using travelling microscope before and after cementation. The difference between these two values gives the discrepancy that is due to the film thickness of cement used for luting the restoration. The TBS value of zinc phosphate cement and glass ionomer cement were found to be almost same. The chemical adhesiveness of the glass ionomer with calcium ions of enamel and dentin may be the attributed reason (ionic bonding). In this study, the polycarboxylate is the one that showed low TBS, and it may be attributed to the weakness of the cement due to reduced film thickness, though this cement has a chemical bonding nature. The observation of results of marginal fit in this study is the increased gap found in zinc phosphate cement followed by resin cement, zinc polycarboxylate, and glass ionomer cement. It is agreeable to estimate the marginal fit of the restoration, which could be affected by the film thickness of the luting cement along with other factors.

Use of Incineration Solid Waste Bottom Ash as Cement Mixture in Cement Production

NASA Astrophysics Data System (ADS)

Jun, N. H.; Abdullah, M. M. A. B.; Jin, T. S.; Kadir, A. A.; Tugui, C. A.; Sandu, A. V.

2017-06-01

Incineration solid waste bottom ash was use to examine the suitability as a substitution in cement production. This study enveloped an innovative technology option for designing new equivalent cement that contains incineration solid waste bottom ash. The compressive strength of the samples was determined at 7, 14, 28 and 90 days. The result was compared to control cement with cement mixture containing incineration waste bottom ash where the result proved that bottom ash cement mixture able achieve its equivalent performance compared to control cement which meeting the requirement of the standards according to EN 196-1. The pozzolanic activity index of bottom ash cement mixture reached 0.92 at 28 days and 0.95 at 90 and this values can be concluded as a pozzolanic material with positive pozzolanic activity. Calcium hydroxide in Portland cement decreasing with the increasing replacement of bottom ash where the reaction occur between Ca(OH)2 and active SiO2.

Study on Cr(VI) Leaching from Cement and Cement Composites

PubMed Central

Palascakova, Lenka; Kanuchova, Maria

2018-01-01

This paper reports an experimental study on hexavalent chromium leaching from cement samples and cement composites containing silica fume and zeolite additions that were subjected to various leaching agents. The water-soluble Cr(VI) concentrations in cements ranged from 0.2 to 3.2 mg/kg and represented only 1.8% of the total chromium content. The presence of chromium compounds with both chromium oxidation states of III and VI was detected in the cement samples by X-ray photoelectron spectroscopy (XPS). Leaching tests were performed in a Britton-Robinson buffer to simulate natural conditions and showed increased dissolution of Cr(VI) up to 6 mg/kg. The highest amount of leached hexavalent chromium was detected after leaching in HCl. The findings revealed that the leaching of chromium from cements was higher by 55–80% than that from the cement composites. A minimum concentration was observed for all cement samples when studying the relationship between the soluble Cr(VI) and the cement storage time. PMID:29690550

Study on Cr(VI) Leaching from Cement and Cement Composites.

PubMed

Estokova, Adriana; Palascakova, Lenka; Kanuchova, Maria

2018-04-22

This paper reports an experimental study on hexavalent chromium leaching from cement samples and cement composites containing silica fume and zeolite additions that were subjected to various leaching agents. The water-soluble Cr(VI) concentrations in cements ranged from 0.2 to 3.2 mg/kg and represented only 1.8% of the total chromium content. The presence of chromium compounds with both chromium oxidation states of III and VI was detected in the cement samples by X-ray photoelectron spectroscopy (XPS). Leaching tests were performed in a Britton-Robinson buffer to simulate natural conditions and showed increased dissolution of Cr(VI) up to 6 mg/kg. The highest amount of leached hexavalent chromium was detected after leaching in HCl. The findings revealed that the leaching of chromium from cements was higher by 55⁻80% than that from the cement composites. A minimum concentration was observed for all cement samples when studying the relationship between the soluble Cr(VI) and the cement storage time.

Effects of Coal Gangue on Cement Grouting Material Properties

NASA Astrophysics Data System (ADS)

Liu, J. Y.; Chen, H. X.

2018-05-01

The coal gangue is one of the most abundant industrial solid wastes and pollute source of air and water. The use of coal gangue in the production of cement grouting material comforms to the basic state policy of environment protection and the circular using of natural resources. Through coal gangue processing experiment, coal gangue cement grouting materials making test, properties detection of properties and theoretical analysis, the paper studied the effects of coal gangue on the properties of cement grouting materials. It is found that at the range of 600 to 700 °C, the fluidity and the compressive and flexural strengths of the cement grouting materials increase with the rising up of the calcination temperatures of coal gangue. The optimum calcination temperature is around 700 °C. The part substitution of cement by the calcined coal gangue in the cement grouting material will improve the mechanical properties of the cement grouting material, even thought it will decrease its fluidity. The best substitution amount of cement by coal gangue is about 30%. The fluidity and the long term strength of the ordinary silicate cement grouting material is obviously higher than that of the sulphoaluminate cement one as well as that of the silicate-sulphoaluminate complex cement one.

Enhanced osteointegration of poly(methylmethacrylate) bone cements by incorporating strontium-containing borate bioactive glass

PubMed Central

Huang, Chengcheng; Zhang, Meng; Ruan, Changshun; Peng, Songlin; Li, Li; Liu, Wenlong; Wang, Ting; Li, Bing; Huang, Wenhai; Rahaman, Mohamed N.; Lu, William W.; Pan, Haobo

2017-01-01

Although poly(methylmethacrylate) (PMMA) cements are widely used in orthopaedics, they have numerous drawbacks. This study aimed to improve their bioactivity and osseointegration by incorporating strontium-containing borate bioactive glass (SrBG) as the reinforcement phase and bioactive filler of PMMA cement. The prepared SrBG/PMMA composite cements showed significantly decreased polymerization temperature when compared with PMMA and retained properties of appropriate setting time and high mechanical strength. The bioactivity of SrBG/PMMA composite cements was confirmed in vitro, evidenced by ion release (Ca, P, B and Sr) from SrBG particles. The cellular responses of MC3T3-E1 cells in vitro demonstrated that SrBG incorporation could promote adhesion, migration, proliferation and collagen secretion of cells. Furthermore, our in vivo investigation revealed that SrBG/PMMA composite cements presented better osseointegration than PMMA bone cement. SrBG in the composite cement could stimulate new-bone formation around the interface between the composite cement and host bone at eight and 12 weeks post-implantation, whereas PMMA bone cement only stimulated development of an intervening connective tissue layer. Consequently, the SrBG/PMMA composite cement may be a better alternative to PMMA cement in clinical applications and has promising orthopaedic applications by minimal invasive surgery. PMID:28615491

Characterization of PCC Cement by Addition of Napa Soil from Subdistrict Sarilamak 50 Kota District as Alternative Additional Material for Semen Padang

NASA Astrophysics Data System (ADS)

Mawardi, M.; Deyundha, D.; Zainul, R.; Zalmi P, R.

2018-04-01

The study has been conducted to determine characteristics of the portland composite cement by the addition of napa soil from Sarilamak subdistrict, 50 Kota District as an alternative additional material at PT. Semen Padang. Napa soil is a natural material highly containing silica and alumina minerals so that it can be one of material in producing cement. This study aims to determine the effect of napa soil on the quality of portland composite cement. Napa soil used in the variation compositions 0%, 4%, 8%, 12% and 16%, for control of cement used 8 % of pozzolan and 0 % of napa soil. Determination of cement quality by testing cement characteristics include blaine test, sieving, lost of ignition or LOI, insoluble residue, normal consistency, setting time and compressive strength. Cement was characterized using XRF. Fineness of cement decreases with the addition of napa soil. Lost of Ignition of cement decreased, while the insoluble residue increased with the addition of napa soil. Normal consistency of cement increasing, so does initial setting time and final setting time of cement. While the resultant compressive strength decreases with the addition of napa soil on 28 days, 342, 325, 307, 306, and 300 kg / cm2.

Enhanced osteointegration of poly(methylmethacrylate) bone cements by incorporating strontium-containing borate bioactive glass.

PubMed

Cui, Xu; Huang, Chengcheng; Zhang, Meng; Ruan, Changshun; Peng, Songlin; Li, Li; Liu, Wenlong; Wang, Ting; Li, Bing; Huang, Wenhai; Rahaman, Mohamed N; Lu, William W; Pan, Haobo

2017-06-01

Although poly(methylmethacrylate) (PMMA) cements are widely used in orthopaedics, they have numerous drawbacks. This study aimed to improve their bioactivity and osseointegration by incorporating strontium-containing borate bioactive glass (SrBG) as the reinforcement phase and bioactive filler of PMMA cement. The prepared SrBG/PMMA composite cements showed significantly decreased polymerization temperature when compared with PMMA and retained properties of appropriate setting time and high mechanical strength. The bioactivity of SrBG/PMMA composite cements was confirmed in vitro , evidenced by ion release (Ca, P, B and Sr) from SrBG particles. The cellular responses of MC3T3-E1 cells in vitro demonstrated that SrBG incorporation could promote adhesion, migration, proliferation and collagen secretion of cells. Furthermore, our in vivo investigation revealed that SrBG/PMMA composite cements presented better osseointegration than PMMA bone cement. SrBG in the composite cement could stimulate new-bone formation around the interface between the composite cement and host bone at eight and 12 weeks post-implantation, whereas PMMA bone cement only stimulated development of an intervening connective tissue layer. Consequently, the SrBG/PMMA composite cement may be a better alternative to PMMA cement in clinical applications and has promising orthopaedic applications by minimal invasive surgery. © 2017 The Author(s).

[Atmospheric emission of PCDD/Fs from modern dry processing cement kilns with preheating in the southwest area, China].

PubMed

Zhang, Xiao-Ling; Lu, Yi; Jian, Chuan; Guo, Zhi-Shun; Zhu, Ming-Ji; Deng, Li; Sun, Jing; Zhang, Qin

2014-01-01

Six cement kilns were measured for emissions of PCDD/Fs in the Southwest Area, China. The results indicated that the emission levels of PCDD/Fs were 0.0029-0.0062 ng-m(-3) (Average, 0.0043 ng X m(-3)) from cement kilns which did not burn solid waste, and 0.028 ng X m(-3) from co-processing sewage sludge in cement kiln. The levels of PCDD/Fs emissions from cement manufacturing in the Southwest Area were significantly below the national emissions standard (0.1 ng x m(-3)). Emission factors of PCDD/Fs from the six cement kilns varied between 0.0089 and 0.084 microg x t(-1) cement, which were near or below the lowest emission factor reported by UNEP in 2005. Moreover, the emission factor of PCDD/Fs from co-processing sewage sludge in cement kiln was 7.6 times of the average factors from the other five cement kilns. Moreover,congener distribution of PCDD/F in stack gas from the two types of cement kilns was very different. The results showed that modern dry process cement kilns with preheating have lower emissions of PCDD/Fs. This suggested that the product of co-processing solid waste in cement kilns should be largely enhanced in China in future.

Optimisation of a two-liquid component pre-filled acrylic bone cement system: a design of experiments approach to optimise cement final properties.

PubMed

Clements, James; Walker, Gavin; Pentlavalli, Sreekanth; Dunne, Nicholas

2014-10-01

The initial composition of acrylic bone cement along with the mixing and delivery technique used can influence its final properties and therefore its clinical success in vivo. The polymerisation of acrylic bone cement is complex with a number of processes happening simultaneously. Acrylic bone cement mixing and delivery systems have undergone several design changes in their advancement, although the cement constituents themselves have remained unchanged since they were first used. This study was conducted to determine the factors that had the greatest effect on the final properties of acrylic bone cement using a pre-filled bone cement mixing and delivery system. A design of experiments (DoE) approach was used to determine the impact of the factors associated with this mixing and delivery method on the final properties of the cement produced. The DoE illustrated that all factors present within this study had a significant impact on the final properties of the cement. An optimum cement composition was hypothesised and tested. This optimum recipe produced cement with final mechanical and thermal properties within the clinical guidelines and stated by ISO 5833 (International Standard Organisation (ISO), International standard 5833: implants for surgery-acrylic resin cements, 2002), however the low setting times observed would not be clinically viable and could result in complications during the surgical technique. As a result further development would be required to improve the setting time of the cement in order for it to be deemed suitable for use in total joint replacement surgery.

A comparison of retentive strength of implant cement depending on various methods of removing provisional cement from implant abutment

PubMed Central

Keum, Eun-Cheol

2013-01-01

PURPOSE This study evaluated the effectiveness of various methods for removing provisional cement from implant abutments, and what effect these methods have on the retention of prosthesis during the definitive cementation. MATERIALS AND METHODS Forty implant fixture analogues and abutments were embedded in resin blocks. Forty cast crowns were fabricated and divided into 4 groups each containing 10 implants. Group A was cemented directly with the definitive cement (Cem-Implant). The remainder were cemented with provisional cement (Temp-Bond NE), and classified according to the method for cleaning the abutments. Group B used a plastic curette and wet gauze, Group C used a rubber cup and pumice, and Group D used an airborne particle abrasion technique. The abutments were observed using a stereomicroscope after removing the provisional cement. The tensile bond strength was measured after the definitive cementation. Statistical analysis was performed using one-way analysis of variance test (α=.05). RESULTS Group B clearly showed provisional cement remaining, whereas the other groups showed almost no cement. Groups A and B showed a relatively smooth surface. More roughness was observed in Group C, and apparent roughness was noted in Group D. The tensile bond strength tests revealed Group D to have significantly the highest tensile bond strength followed in order by Groups C, A and B. CONCLUSION A plastic curette and wet gauze alone cannot effectively remove the residual provisional cement on the abutment. The definitive retention increased when the abutments were treated with rubber cup/pumice or airborne particle abraded to remove the provisional cement. PMID:24049563

In vitro evaluation of microleakage of various types of dental cements.

PubMed

Medić, Vesna; Obradović-Djuricić, Kosovka; Dodić, Slobodan; Petrović, Renata

2010-01-01

Microleakage is defined as the clinically undetectable seepage of oral fluids containing bacteria and debris between cement layer and tooth restoration. This in vitro study investigated the effect of different dental cements (zinc-phosphate, polycarboxylate, glass-ionomer and resin cement) on microleakage in different ceramic crown systems (metal ceramic crown, metal ceramic crown with a porcelain margin, Empress 2 and in Ceram all-ceramic crowns) fixed on extracted human teeth. One hundred and sixty intact human premolars were randomized to four groups of forty teeth each, according to the different ceramic crown systems. They were prepared in a standardized manner for metal-ceramic and all-ceramic crowns. Crowns were made following a standard laboratory technique, and each group of crowns were divided into four groups according to the different cement agents and cemented on their respective abutments. The specimens were subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco-oral and meso-distal direction. The microleakage in the area of tooth-cement interface was defined as linear penetration of methylene blue and was determined with a microscope to assign microleakage scores using a five-point scale. A significant association was found between a cement type and degree of microleakage (p = 0.001). No statistically significant differences were found among the different ceramic crown systems luted with the same dental cement. The smallest degree of microleakage was observed in specimens luted with resin cement (X = 1.73), followed by glass-ionomer cement (X=2.45) and polycarboxylate cement (X = 3.20). The greatest degree of microleakage was detected in the crowns fixed with zincphosphate cement (X = 3.33). The investigated dental cements revealed different sealing abilities. The use of resin cement resulted in the percentage of 0 microleakage scores. Due to this feature, the resin cement is to be recommended in everyday clinical practice.

In-vitro study of resin-modified glass ionomer cements for cementation of orthodontic bands. Isolation, surplus removal and humidity as factors influencing the bond strength between enamel, cement and metal.

PubMed

Liebmann, S M; Jost-Brinkmann, P G

1999-01-01

The aim of this in vitro study was to investigate different light-cured and chemically cured resin-modified glass ionomer cements used for the cementation of orthodontic bands and to analyze various factors influencing the adhesive strength between enamel, cement and stainless steel. Four resin-modified glass ionomers (Fuji Ortho LC/GC, Fuji Duet/GC, Unitek Multi-Cure Glass Ionomer Orthodontic Band Cement/3M Unitek, Vitremer/3M) and 1 compomer (Band-Lok/Reliance) were examined. Flattened and polished bovine teeth embedded in polyurethane resin were used as enamel specimens. Before cementation, 50% of the specimens were moistened with the aerosol of an inhalation device, while the rest were dried with compressed air. Stainless steel cylinders (CrNi 18 10) were perpendicularly bonded onto the polished enamel using a custom-made cementation device and immediately topped with a pressure of 0.25 MPa. The cement was isolated with either Ketac Glaze/ESPE, Fuji Coat/GC, Cacao Butter/GC, Dryfoil/Jalenko or Final Varnish/VOCO, or was left uncoated. Eight minutes after the beginning of mixing, either the surplus cement was removed with a scalpel or surplus removal was simulated with ultrasound. After 24 hours storage in a water bath at 37 degrees C and 1,000 thermocycles the shear bond strength was determined. Significant differences with respect to the shear bond strength were found among the following cements, ranking from highest to lowest: Fuji Duet, Unitek cement > Fuji Ortho LC > Vitremer > Band-Lok. The application of a barrier coating significantly increased the shear bond strength of all cements except Fuji Ortho LC. The light-cured resin Ketac Glaze proved to be the most effective barrier coating. A dry enamel surface increased the bond strength of all investigated cements except Unitek cement. The use of ultrasound led to no significant reduction in shear bond strength in comparison with surplus removal with a scalpel.

Criteria for Remote Sensing Detection of Sulfate Cemented Soils on Mars

NASA Technical Reports Server (NTRS)

Cooper, Christopher D.; Mustard, John F.

2000-01-01

Spectral measurements of loose and cemented mixtures of palagonitic soil and sulfates were made to determine whether cemented soils could be identified on Mars. Cemented MgSO4 mixtures exhibit an enhanced 9 micron sulfate fundamental compared to gypsum mixtures due to more diffuse and pervasive cementing.

21 CFR 888.4200 - Cement dispenser.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

21 CFR 888.4200 - Cement dispenser.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

21 CFR 888.4200 - Cement dispenser.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

21 CFR 888.4200 - Cement dispenser.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

40 CFR 146.86 - Injection well construction requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... stages. (4) Circulation of cement may be accomplished by staging. The Director may approve an alternative... injection tubing and long string casing. (b) Casing and cementing of Class VI wells. (1) Casing and cement... confining zone(s); (viii) Type or grade of cement and cement additives; and (ix) Quantity, chemical...

21 CFR 888.4200 - Cement dispenser.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

75 FR 7305 - Drake Switching Company, LLC-Operation Exemption- Drake Cement, LLC

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-18

... Switching Company, LLC--Operation Exemption-- Drake Cement, LLC Drake Switching Company, LLC (DSC), a... and operated by Drake Cement, LLC.\\1\\ \\1\\ Drake Cement, LLC filed a verified notice of exemption to acquire these track in STB Finance Docket No. 35350, Drake Cement, LLC--Acquisition Exemption--Clarkdale...

Retardation effect of different alcohols on the cement coagulation in polycarboxylate- and naphthalene-based cement admixtures

NASA Astrophysics Data System (ADS)

Huang, S. M.; Zhou, F. L.

2017-12-01

Alcohol has great potential to delay the coagulation of cement. The effects of alcohol on paste fluidity and normal consistency coagulation time have been studied for polycarboxylate superplasticizer and naphthene cement admixture. Seven alcohols were combined with polycarboxylate superplasticizer and naphthene at a concentration of 0.01-0.09%, respectively, including n-propanol, methanol, sorbitol, ethylene glycol, glycerol, ethanol, and mannitol. The fluidity and normal consistency coagulation time of each cement admixture were measured. The performance of both polycarboxylate superplasticizer and naphthene cement admixtures were compared to develop cement admixture with delayed coagulation.

Thermally conductive cementitious grout for geothermal heat pump systems

DOEpatents

Allan, Marita

2001-01-01

A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.

Vibrational investigation of calcium-silicate cements for endodontics in simulated body fluids

NASA Astrophysics Data System (ADS)

Taddei, Paola; Modena, Enrico; Tinti, Anna; Siboni, Francesco; Prati, Carlo; Gandolfi, Maria Giovanna

2011-05-01

Calcium-silicate MTA (Mineral Trioxide Aggregate) cements have been recently developed for oral and endodontic surgery. This study was aimed at investigating commercial (White ProRoot MTA, White and Grey MTA-Angelus) and experimental (wTC-Bi) accelerated calcium-silicate cements with regards to composition, hydration products and bioactivity upon incubation for 1-28 days at 37 °C, in Dulbecco's Phosphate Buffered Saline (DPBS). Deposits on the surface of the cements and the composition changes during incubation were investigated by micro-Raman and ATR/FT-IR spectroscopy, and pH measurements. Vibrational techniques disclosed significant differences in composition among the unhydrated cements, which significantly affected the bioactivity as well as pH, and hydration products of the cements. After one day in DPBS, all the cements were covered by a more or less homogeneous layer of B-type carbonated apatite. The experimental cement maintained a high bioactivity, only slightly lower than the other cements and appears a valid alternative to commercial cements, in view of its adequate setting time properties. The bioactivity represents an essential property to favour bone healing and makes the calcium-silicate cements the gold standard materials for root-apical endodontic surgery.

Influence of Blended Cements with Calcareous Fly Ash on Chloride Ion Migration and Carbonation Resistance of Concrete for Durable Structures.

PubMed

Glinicki, Michał A; Jóźwiak-Niedźwiedzka, Daria; Gibas, Karolina; Dąbrowski, Mariusz

2016-01-02

The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement-ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash.

The contemporary cement cycle of the United States

USGS Publications Warehouse

Kapur, A.; Van Oss, H. G.; Keoleian, G.; Kesler, S.E.; Kendall, A.

2009-01-01

A country-level stock and flow model for cement, an important construction material, was developed based on a material flow analysis framework. Using this model, the contemporary cement cycle of the United States was constructed by analyzing production, import, and export data for different stages of the cement cycle. The United States currently supplies approximately 80% of its cement consumption through domestic production and the rest is imported. The average annual net addition of in-use new cement stock over the period 2000-2004 was approximately 83 million metric tons and amounts to 2.3 tons per capita of concrete. Nonfuel carbon dioxide emissions (42 million metric tons per year) from the calcination phase of cement manufacture account for 62% of the total 68 million tons per year of cement production residues. The end-of-life cement discards are estimated to be 33 million metric tons per year, of which between 30% and 80% is recycled. A significant portion of the infrastructure in the United States is reaching the end of its useful life and will need to be replaced or rehabilitated; this could require far more cement than might be expected from economic forecasts of demand for cement. ?? 2009 Springer Japan.

Effect of cements on fracture resistance of monolithic zirconia crowns

PubMed Central

Nakamura, Keisuke; Mouhat, Mathieu; Nergård, John Magnus; Lægreid, Solveig Jenssen; Kanno, Taro; Milleding, Percy; Örtengren, Ulf

2016-01-01

Abstract Objectives The present study investigated the effect of cements on fracture resistance of monolithic zirconia crowns in relation to their compressive strength. Materials and methods Four different cements were tested: zinc phosphate cement (ZPC), glass-ionomer cement (GIC), self-adhesive resin-based cement (SRC) and resin-based cement (RC). RC was used in both dual cure mode (RC-D) and chemical cure mode (RC-C). First, the compressive strength of each cement was tested according to a standard (ISO 9917-1:2004). Second, load-to-failure test was performed to analyze the crown fracture resistance. CAD/CAM-produced monolithic zirconia crowns with a minimal thickness of 0.5 mm were prepared and cemented to dies with each cement. The crown–die samples were loaded until fracture. Results The compressive strength of SRC, RC-D and RC-C was significantly higher than those of ZPC and GIC (p < 0.05). However, there was no significant difference in the fracture load of the crown between the groups. Conclusion The values achieved in the load-to-failure test suggest that monolithic zirconia crowns with a minimal thickness of 0.5 mm may have good resistance against fracture regardless of types of cements. PMID:27335900

Influence of Photoinitiator on Accelerated Artificial Aging and Bond Strength of Experimental Resin Cements.

PubMed

Righi, Helouise; Costa, Ana Rosa; Oliveira, Dayane Carvalho Ramos Salles de; Abuna, Gabriel Flores; Sinhoreti, Mario Alexandre Coelho; Naufel, Fabiana Scarparo

2018-01-01

The goal of this study was to evaluate in vitro the effect of the photoinitiator phenylpropanedione (PPD), alone or combined with camphorquinone (CQ), on color stability of photoactivated resin cements and their bond strength to ceramics using a micro-shear test. Four resin cements were used: a commercial brand cement (RelyX Veneer®) and 3 experimental cements with different types and concentration of photoinitiators. For color analysis, ceramic discs were cemented on bovine dentin specimens to simulate indirect restorations (n=8) and were exposed to UV for 120 h and tested for color alteration using a reflectance spectrophotometer and the CIEL*a*b* system. Data were analyzed by Anova and Tukey's test at 5% significance level. The color test results did not present statistically significant difference for the ∆E for all the studied cements, neither for ∆L, ∆a and ∆b. For the bond strength, all the studied cements showed statistically significant differences to each other, with the highest result for the RelyX Veneer® (29.07 MPa) cement, followed by the cement with CQ (21.74 MPa) and CQ+PPD (19.09 MPa) cement; the lowest result was obtained by the cement using only PPD as a photoinitiator (13.99 MPa). So, based on the studied parameters, PPD was not advantageous as photoinitiator of resin cements, because it showed a low value of bond strength to the ceramics and no superior color stability.

Incidence of undetected cement on CAD/CAM monolithic zirconia crowns and customized CAD/CAM implant abutments. A prospective case series.

PubMed

Wasiluk, Grzegorz; Chomik, Ewa; Gehrke, Peter; Pietruska, Małgorzata; Skurska, Anna; Pietruski, Jan

2017-07-01

The aim of this study was to assess the frequency of cement residues after cementation of CAD/CAM monolithic zirconia crowns on customized CAD/CAM titanium abutments. Sixty premolars and molars were restored on Astra Tech Osseospeed TX ™ implants using single monolithic zirconia crowns fixed on two types of custom-made abutments: Atlantis ™ titanium or Atlantis ™ Gold Hue. Occlusal openings providing access to the abutment screws were designed for retrievability of the crown/abutment connection. After fixation with glass ionomer cement, the crown/abutment units were unscrewed to evaluate the presence of residual cement. Dichotomous assessment of the presence or absence of cement at the crown/abutment unit and peri-implant tissues was performed. Clinically undetected cement excess was visible on 44 of 60 restorations (73.3%). There was no interdependency between residual cement presence and implant location or diameter. However, a dependency between the presence of residual cement and the aspect of the abutment/crown connection could be noted. The majority of the residues were observed on the distal (17.9%) and mesial (15%) aspects. While on the palatal/lingual aspect, the cement was visible in 8.8%; only 3.4% of all surfaces displayed cement residues. Within the limitations of the study, it can be concluded that the use of customized CAD/CAM abutments do not guarantee avoidance of subgingival cement residues after crown cementation. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Influence of technique and manipulation on self-adhesive resin cements used to cement intraradicular posts.

PubMed

Shiratori, Fábio Kenji; Valle, Accácio Lins do; Pegoraro, Thiago Amadei; Carvalho, Ricardo Marins; Pereira, Jefferson Ricardo

2013-07-01

Resin cements are widely used to cement intraradicular posts, but bond strength is significantly influenced by the technique and material used for cementation. The purpose of this study was to evaluate the bond strength of 3 self-adhesive cements used to cement intraradicular glass fiber posts. The cements all required different application and handling techniques. Forty-five human maxillary canines were selected and randomly divided into 3 groups n= 15 by drawing lots: Group BIS - Biscem, Group BRE - Breeze, and Group MAX - Maxcem. Each group was divided into 3 subgroups according to application and handling techniques: Sub-group A - Automix/Point tip applicator, Sub-group L - Handmix/Lentulo, and Sub-group C - Handmix/Centrix. Cementation of the posts was performed according to the manufacturers' instructions. The push-out test was performed with a crosshead speed of 0.5 mm/min, and bond strength was expressed in megapascals. The results were evaluated by 2-way ANOVA and the all pairwise multiple comparison procedures (Tukey test) (α=.05). Breeze cement showed the highest average for the subgroups A, L, and C when compared to the Biscem cement and Maxcem Elite (P<.05). Statistically significant differences among the subgroups were only observed for Biscem. This study shows that application and handling techniques may influence the bond strength of different self-adhesive cements when used for intraradicular post cementation. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Comparative evaluation of marginal leakage of provisional crowns cemented with different temporary luting cements: In vitro study.

PubMed

Arora, Sheen Juneja; Arora, Aman; Upadhyaya, Viram; Jain, Shilpi

2016-01-01

As, the longevity of provisional restorations is related to, a perfect adaptation and a strong, long-term union between restoration and teeth structures, therefore, evaluation of marginal leakage of provisional restorative materials luted with cements using the standardized procedures is essential. To compare the marginal leakage of the provisional crowns fabricated from Autopolymerizing acrylic resin crowns and bisphenol A-glycidyl dimethacrylate (BIS-GMA) resin crowns. To compare the marginal leakage of the provisional crowns fabricated from autopolymerizing acrylic resin crowns and BIS-GMA resin crowns cemented with different temporary luting cements. To compare the marginal leakage of the provisional crowns fabricated from autopolymerizing acrylic resin (SC-10) crowns cemented with different temporary luting cements. To compare the marginal leakage of the provisional crowns fabricated from BIS-GMA resin crowns (Protemp 4) cemented with different temporary luting cements. Freshly extracted 60 maxillary premolars of approximately similar dimensions were mounted in dental plaster. Tooth reduction with shoulder margin was planned to use a customized handpiece-holding jig. Provisional crowns were prepared using the wax pattern fabricated from computer aided designing/computer aided manufacturing milling machine following the tooth preparation. Sixty provisional crowns were made, thirty each of SC-10 and Protemp 4 and were then cemented with three different luting cements. Specimens were thermocycled, submerged in a 2% methylene blue solution, then sectioned and observed under a stereomicroscope for the evaluation of marginal microleakage. A five-level scale was used to score dye penetration in the tooth/cement interface and the results of this study was analyzed using the Chi-square test, Mann-Whitney U-test, Kruskal-Wallis H-test and the results were statistically significant P < 0.05 the power of study - 80%. Marginal leakage was significant in both provisional crowns cemented with three different luting cements along the axial walls of teeth (P < 0.05) confidence interval - 95%. The temporary cements with eugenol showed more microleakage than those without eugenol. SC-10 crowns showed more microleakage compared to Protemp 4 crowns. SC-10 crowns cemented with Kalzinol showed maximum microleakage and Protemp 4 crowns cemented with HY bond showed least microleakage.

Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Um, Wooyong; Jung, Hun Bok; Martin, Paul F.

2011-11-01

Portland cement, a common sealing material for wellbores for geological carbon sequestration was reacted with CO{sub 2} in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate cement-CO{sub 2} reaction along the wellbore from carbon injection depth to the near-surface. Hydrated Portland cement columns (14 mm diameter x 90 mm length; water-to-cement ratio = 0.33) including additives such as steel coupons and Wallula basalt fragments were reacted with CO{sub 2} in the wet supercritical (the top half) and dissolved (the bottom half) phases under carbon sequestration condition with high pressure (10 MPa) and temperature (50 C)more » for 5 months, while small-sized hydrated Portland cement columns (7 mm diameter x 20 mm length; water-to-cement ratio = 0.38) were reacted with CO{sub 2} in dissolved phase at high pressure (10 MPa) and temperature (50 C) for 1 month or with wet CO{sub 2} in gaseous phase at low pressure (0.2 MPa) and temperature (20 C) for 3 months. XMT images reveal that the cement reacted with CO{sub 2} saturated groundwater had degradation depth of {approx}1 mm for 1 month and {approx}3.5 mm for 5 month, whereas the degradation was minor with cement exposure to supercritical CO{sub 2}. SEM-EDS analysis showed that the carbonated cement was comprised of three distinct zones; the innermost less degraded zone with Ca atom % > C atom %, the inner degraded zone with Ca atom % {approx} C atom % due to precipitation of calcite, the outer degraded zone with C atom % > Ca atom % due to dissolution of calcite and C-S-H, as well as adsorption of carbon to cement matrix. The outer degraded zone of carbonated cement was porous and fractured because of dissolution-dominated reaction by carbonic acid exposure, which resulted in the increase in BJH pore volume and BET surface area. In contrast, cement-wet CO{sub 2}(g) reaction at low P (0.2 MPa)-T (20 C) conditions for 1 to 3 months was dominated by precipitation of micron-sized calcite on the outside surface of cement, which resulted in the decrease in BJH pore volume and BET surface area. Cement carbonation and pore structure change are significantly dependent on pressure and temperature conditions as well as the phase of CO{sub 2}, which controls the balance between precipitation and dissolution in cement matrix. Geochemical modeling result suggests that ratio of solid (cement)-to-solution (carbonated water) has a significant effect on cement carbonation, thus the cement-CO{sub 2} reaction experiment needs to be conducted under realistic conditions representing the in-situ wellbore environment of carbon sequestration field site. Total porosity and air permeability for a duplicate cement column with water-to-cement ratio of 0.38 measured after oven-drying by Core Laboratories using Boyle's Law technique and steady-state method were 31% and 0.576 mD. A novel method to measure the effective liquid permeability of a cement column using X-ray micro-tomography images after injection of pressurized KI (potassium iodide) is under development by PNNL. Preliminary results indicate the permeability of a cement column with water-to-cement ratio of 0.38 is 4-8 mD. PNNL will apply the method to understand the effective permeability change of Portland cement by CO{sub 2}(g) reaction under a variety of pressure and temperature conditions to develop a more reliable well-bore leakage risk model.« less

Correlation of pull-out strength of cement-augmented pedicle screws with CT-volumetric measurement of cement.

PubMed

Fölsch, Christian; Goost, Hans; Figiel, Jens; Paletta, Jürgen R J; Schultz, Wolfgang; Lakemeier, Stefan

2012-12-01

Cement augmentation of pedicle screws increases fixation strength in an osteoporotic spine. This study was designed to determine the cement distribution and the correlation between the pull-out strength of the augmented screw and the cement volume within polyurethane (PU) foam. Twenty-eight cannulated pedicle screws (6×45 mm) (Peter Brehm, Erlangen, Germany) with four holes at the distal end of the screw were augmented with the acrylic Stabilit ER Bone Cement Vertebral Augmentation System (DFine Inc., San Jose, CA, USA) and implanted into open-cell rigid PU foam (Pacific Research Laboratories, Vashon Island, WA, USA) with a density of 0.12 g/cm3, resembling severe osteoporosis. Volumetric measurement of the cement with consideration of the distribution around the screws was done with multislice computed tomography scan (Somatom Definition, Siemens, Erlangen, Germany). Pull-out strength was tested with a servohydraulic system (MTS System Corporation, Eden Prairie, MN, USA), and nonaugmented screws served as control. Pearson's correlation coefficient with significance level α=0.05 and one-way analysis of variance test were used. We found a high (r=0.88) and significant (p<0.01) correlation between the cement volume and the pull-out strength, which increased by more than 5-fold with a volume of 3 ml. The correlation appeared linear at least up to 4 ml cement volume and failure always occurred at the cement-bone interface. The cement distribution was symmetric and circular around the most proximal hole, with a distance of 14 mm from the tip, and nearly 90% of the cement was found 6 mm distal and cranial to it. The 95% confidence interval for the relative amount of cement was 37%-41% within 2 mm of the most proximal hole. Compared with the control, a cement volume between 2.0 and 3.0 ml increased the pull-out strength significantly and is relevant for clinical purposes, whereas a volume of 0.5 ml did not. A cement volume beyond 3.0 ml should further increase the pull-out strength because the correlation was linear at least up to 4.0 ml, but the possibility of in vivo cement leakage with increasing volume has to be considered. Pressure-controlled cement application might be a tool to avoid this complication. The cement almost completely penetrated the most proximal perforation.

In vitro shear bond strength of cementing agents to fixed prosthodontic restorative materials.

PubMed

Piwowarczyk, Andree; Lauer, Hans-Christoph; Sorensen, John A

2004-09-01

Durable bonding to fixed prosthodontic restorations is desirable; however, little information is available on the strength of the bond between different cements and fixed prosthodontic restorative materials. This study determined the shear-bond strength of cementing agents to high-gold-content alloy castings and different dental ceramics: high-strength aluminum oxide (Procera AllCeram), leucite-reinforced (IPS Empress), and lithium disilicate glass-ceramic (IPS Empress 2). Prepolymerized resin composite cylinders (5.5 mm internal diameter, n=20) were bonded to the pretreated surfaces of prosthodontic materials. High-gold-content alloy and high-strength aluminum oxide surfaces were airborne-particle-abraded, and pressable ceramics were hydrofluoric acid-etched and silanized prior to cementing. The cementing agents tested were a zinc-phosphate cement (Fleck's zinc cement), glass ionomer cements (Fuji I, Ketac-Cem), resin-modified glass ionomer cements (Fuji Plus, Fuji Cem, RelyX Luting), resin cements (RelyX ARC, Panavia F, Variolink II, Compolute), and a self-adhesive universal resin cement (RelyX Unicem). Half the specimens (n=10) were tested after 30 minutes; the other half (n=10) were stored in distilled water at 37 degrees C for 14 days and then thermal cycled 1000 times between 5 degrees C and 55 degrees C prior to testing. Shear-bond strength tests were performed using a universal testing machine at a constant crosshead speed of 0.5 mm/min. Statistical analysis was performed by multifactorial analysis of variance taking interactions between effects into account. For multiple paired comparisons, the Tukey method was used (alpha=.05). In a 3-way ANOVA model, the main factors substrate, cement, time, and all corresponding interactions were statistically significant (all P <.0001). In subsequent separate 1-way or 2-way ANOVA models for each substrate type, significant differences between cement types and polymerizing modes were found (all P <.001). None of the cement types provided the highest bonding values with all substrate types. After 14 days of water storage followed by thermal cycling, only the self-adhesive universal resin cement (RelyX Unicem) and 2 of the resin cements (Panavia F and Compolute) exhibited strong bond strengths to specific prosthodontic materials. In contrast, zinc-phosphate, glass ionomer, and resin-modified glass ionomer cements showed the lowest values of all tested cementing agents after 14 days of water storage followed by thermal cycling.

Marginal Adaptation and Quality of Interfaces in Lithium Disilicate Crowns - Influence of Manufacturing and Cementation Techniques.

PubMed

Melo Freire, C A; Borges, G A; Caldas, Dbm; Santos, R S; Ignácio, S A; Mazur, R F

To evaluate the cement line thickness and the interface quality in milled or injected lithium disilicate ceramic restorations and their influence on marginal adaptation using different cement types and different adhesive cementation techniques. Sixty-four bovine teeth were prepared for full crown restoration (7.0±0.5 mm in height, 8.0 mm in cervical diameter, and 4.2 mm in incisal diameter) and were divided into two groups: CAD/CAM automation technology, IPS e.max CAD (CAD), and isostatic injection by heat technology, IPS e.max Press (PRESS). RelyX ARC (ARC) and RelyX U200 resin cements were used as luting agents in two activation methods: initial self-activation and light pre-activation for one second (tack-cure). Next, the specimens were stored in distilled water at 23°C ± 2°C for 72 hours. The cement line thickness was measured in micrometers, and the interface quality received scores according to the characteristics and sealing aspects. The evaluations were performed with an optical microscope, and scanning electron microscope images were presented to demonstrate the various features found in the cement line. For the cement line thickness, data were analyzed with three-way analysis of variance (ANOVA) and the Games-Howell test (α=0.05). For the variable interface quality, the data were analyzed with the Mann-Whitney U-test, the Kruskal-Wallis test, and multiple comparisons nonparametric Dunn test (α=0.05). The ANOVA presented statistical differences among the ceramic restoration manufacturing methods as well as a significant interaction between the manufacturing methods and types of cement (p<0.05). The U200 presented lower cement line thickness values when compared to the ARC with both cementation techniques (p<0.05). With regard to the interface quality, the Mann-Whitney U-test and the Kruskal-Wallis test demonstrated statistical differences between the ceramic restoration manufacturing methods and cementation techniques. The PRESS ceramics obtained lower scores than did the CAD ceramics when using ARC cement (p<0.05). Milled restorations cemented with self-adhesive resin cement resulted in a thinner cement line that is statistically different from that of CAD or pressed ceramics cemented with resin cement with adhesive application. No difference between one-second tack-cure and self-activation was noted.

Integrity of Pre-existing Wellbores in Geological Sequestration of CO 2 – Assessment Using a Coupled Geomechanics-fluid Flow Model

DOE PAGES

Kelkar, Sharad; Carey, J. William; Dempsey, David; ...

2014-12-31

Assessment of potential CO 2 and brine leakage from wellbores is central to any consideration of the viability of geological CO 2 sequestration. Depleted oil and gas reservoirs are some of the potential candidates for consideration as sequestration sites. The sequestration sites are expected to cover laterally extensive areas to be of practical interest. Hence there is a high likelihood that such sites will contain many pre-existing abandoned wells. Most existing work on wellbore integrity has focused on field and laboratory studies of chemical reactivity. Very little work has been done on the impacts of mechanical stresses on wellbore performance.more » This study focuses on the potential enhancement of fluid flow pathways in the near-wellbore environment due to modifications in the geomechanical stress field resulting from the CO 2 injection operations. The majority of the operational scenarios for CO 2 sequestration lead to significant rise in the formation pore pressure. This is expected to lead to an expansion of the reservoir rock and build-up of shear stresses near wellbores where the existence of cement and casing are expected to constrain the expansion. If the stress buildup is large enough, this can lead to failure with attendant permeability enhancement that can potentially provide leakage pathways to shallower aquifers and the surface. In this study, we use a numerical model to simulate key features of a wellbore (casing, annulus and cement) embedded in a system that includes the upper aquifer, caprock, and storage aquifer. We present the sensitivity of damage initiation and propagation to various operational and formation parameters. We consider Mohr-Coulomb shear-failure models; tensile failure is also likely to occur but will require higher stress changes and will be preceded by shear failure. The modeling is performed using the numerical simulator FEHM developed at LANL that models coupled THM processes during multi-phase fluid flow and deformation in fractured porous media. FEHM has been developed extensively under projects on conventional/unconventional energy extraction (geothermal, oil, and gas), radionuclide and contaminant transport, watershed management, and CO 2 sequestration.« less

Environmental engineering interventions to control the expansion of salty lakes and marshes in siwa oasis.

PubMed

El-Naggar, Hesham M

2010-01-01

The main activity in Siwa Oasis society is the agriculture, it depends on the groundwater. The agricultural drainage water and the unused saline water of naturally flowing springs are poured into four main salty lakes. This leads to an increase in the surface area of the saltwater lakes, marshes and rise in water table levels. to investigate some environmental engineering interventions to control the expansion of saltwater surface area in Siwa Oasis. Field visits, observation sheets and questionnaire survey with farmers were carried out to find out the main environmental problems in the Oasis. Environmental survey was carried out to collect different rocks and stones samples as natural construction materials from the desert that surrounds Siwa Oasis. Physical analyses, chemical composition and principal mechanical parameters were conducted on the collected samples. After the analysis, the safa rocks were the best natural construction materials in the Siwa Oasis. So, it could be used to build a construction wall around the salty lakes and marshes. Walls could convert the lakes into basins. The water will be evaporated at high rate during summer season by solar energy. After evaporation, the remaining salty rock named "karshef" can be easily collected from the lakes to be used as a low cost construction material for traditional building houses in Siwa Oasis. Therefore, the water level of lakes will be reduced to dryness and land could be reused as agricultural land. Among different rocks, safa rocks proved to be the best natural construction materials to construct a defense wall around the lakes and marshes. They will save about 80% of the concrete cost. The formed karshef rocks from the lakes will be used in the construction of the traditional building houses which will save about 90% of the concrete buildings. This intervention will save energy as it exchanges fuel consuming man-made material such as cement with naturally made material. This can reduce the green house gases generated from the cement industry. Economical feasibility study should be carried out to estimate the capital cost for the retaining wall.

Phase distribution and microstructural changes of self-compacting cement paste at elevated temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, G.; Liu, X.; De Schutter, G.

2007-06-15

Self-compacting concrete, as a new smart building material with various advanced properties, has been used for a wide range of structures and infrastructures. However little investigation have been reported on the properties of Self-compacting when it is exposed to elevated temperatures. Previous experiments on fire test have shown the differences between high performance concrete and traditional concrete at elevated temperature. This difference is largely depending on the microstructural properties of concrete matrix, i.e. the cement paste, especially on the porosity, pore size distribution and the connectivity of pores in cement pastes. In this contribution, the investigations are focused on themore » cement paste. The phase distribution and microstructural changes of self-compacting cement paste at elevated temperatures are examined by mercury intrusion porosimetry and scanning electron microscopy. The chemical decomposition of self-compacting cement paste at different temperatures is determined by thermogravimetric analysis. The experimental results of self-compacting cement paste are compared with those of high performance cement paste and traditional cement paste. It was found that self-compacting cement paste shows a higher change of the total porosity in comparison with high performance cement paste. When the temperature is higher than 700 deg. C, a dramatic loss of mass was observed in the self-compacting cement paste samples with addition of limestone filler. This implies that the SCC made by this type of self-compacting cement paste will probably show larger damage once exposed to fire. Investigation has shown that 0.5 kg/m{sup 3} of Polypropylene fibers in the self-compacting cement paste can avoid the damage efficiently.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Um, Wooyong; Rod, Kenton A.; Jung, Hun Bok

Cement samples were reacted with CO 2-saturated groundwater, with or without added H2S (1 wt.%), at 50°C and 10 MPa for up to 13 months (CO 2 only) or for up to 3.5 months (CO 2 + H 2S) under static conditions. After the reaction, X-ray computed tomography images revealed that calcium carbonate precipitation (CaCO 3) occurred extensively within the fractures in the cement matrix, but only partially along fractures at the cement-basalt interface. Exposure of a fractured cement sample to CO2-saturated groundwater (50°C and 10 MPa) over a period of 13 months demonstrated progressive healing of cement fractures bymore » CaCO 3(s) precipitation. After reaction with CO 2 + H 2S-saturated groundwater, CaCO 3 (s) precipitation also occurred more extensively within the cement fracture than along the cement-basalt caprock interfaces. X-ray diffraction analysis showed that major cement carbonation products of the CO 2 + H 2S-saturated groundwater were calcite, aragonite, and vaterite, all consistent with cement carbonation by CO 2-saturated groundwater. While pyrite is thermodynamically favored to form, due to the low H 2S concentration it was not identified by XRD in this study. The cement alteration rate into neat Portland cement columns by CO 2-saturated groundwater was similar at ~0.02 mm/d, regardless of the cement-curing pressure and temperature (P-T) conditions, or the presence of H 2S in the brine. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO 2- or CO 2 + H 2S-saturated groundwater, whereas fractures along the cement-caprock interface are likely to remain open and vulnerable to the leakage of CO 2.« less

A Novel Injectable Borate Bioactive Glass Cement as an Antibiotic Delivery Vehicle for Treating Osteomyelitis

PubMed Central

Cui, Xu; Gu, Yi-Fei; Jia, Wei-Tao; Rahaman, Mohamed N.; Wang, Yang; Huang, Wen-Hai; Zhang, Chang-Qing

2014-01-01

Background A novel injectable cement composed of chitosan-bonded borate bioactive glass (BG) particles was evaluated as a carrier for local delivery of vancomycin in the treatment of osteomyelitis in a rabbit tibial model. Materials and Methods The setting time, injectability, and compressive strength of the borate BG cement, and the release profile of vancomycin from the cement were measured in vitro. The capacity of the vancomycin-loaded BG cement to eradicate methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis in rabbit tibiae in vivo was evaluated and compared with that for a vancomycin-loaded calcium sulfate (CS) cement and for intravenous injection of vancomycin. Results The BG cement had an injectability of >90% during the first 3 minutes after mixing, hardened within 30 minutes and, after hardening, had a compressive strength of 18±2 MPa. Vancomycin was released from the BG cement into phosphate-buffered saline for up to 36 days, and the cumulative amount of vancomycin released was 86% of the amount initially loaded into the cement. In comparison, vancomycin was released from the CS cement for up 28 days and the cumulative amount released was 89%. Two months post-surgery, radiography and microbiological tests showed that the BG and CS cements had a better ability to eradicate osteomyelitis when compared to intravenous injection of vancomycin, but there was no significant difference between the BG and CS cements in eradicating the infection. Histological examination showed that the BG cement was biocompatible and had a good capacity for regenerating bone in the tibial defects. Conclusions These results indicate that borate BG cement is a promising material both as an injectable carrier for vancomycin in the eradication of osteomyelitis and as an osteoconductive matrix to regenerate bone after the infection is cured. PMID:24427311

The fatigue behavior of an amorphous brittle composite material

NASA Astrophysics Data System (ADS)

Kumar, Brijesh

The use of poly methyl methacrylate (PMMA) based bone cement as a grouting agent for the in-vivo fixation of orthopaedic implants has been in practice for nearly fifty years. Fatigue failure of the bone cement has been identified as the primary cause of cement failure. Implant loosening due to the failure of the cement is one of the major reasons necessitating revision surgery. The need for a more fatigue resistant bone cement is well documented in the literature. One method of producing a more fatigue resistant bone cement is to reinforce it with short fibers. The fundamental purpose of this work was to investigate the possible improvement of the fatigue characteristics of bone cement provided by the following two types of fiber reinforcements: short flexible Polyethylene Terephalate (PET) fibers and stiff milled carbon fibers. It has been shown that the reinforcement of the bone cement with fibers provides substantial improvement of the fracture toughness of the bone cement. In this investigation the impact of fiber reinforcement on the fatigue properties of the bone cement was studied. The effects of the fiber reinforcement on the fatigue life of bone cement has been determined experimentally. Since fatigue characteristics are known to have considerable scatter, a methodology was developed to analyze the experimental data in a statistically rigorous manner. The effect of the fiber reinforcement on bone cement was also analyzed using a theoretical approach and by conducting extensive Scanning Electron Microscopy (SEM) of the fractured surfaces. The results of this study indicate that fiber reinforcement improves the fatigue life of bone cement at a very high level of reliability. This could potentially lead to a more fatigue tolerant bone cement, which would delay the need for revision surgery due to implant loosening.

Influence of the spatial distribution of cementation on the permeability and mechanical attributes of sedimentary and fault rocks

NASA Astrophysics Data System (ADS)

Mozley, P.; Yoon, H.; Williams, R. T.; Goodwin, L. B.

2015-12-01

The spatial distribution of pore-filling authigenic minerals (cements) is highly variable and controlled in large part by the mineralogy of the cements and host sediment grains. Two end-member distributions of cements that commonly occur in sedimentary material are: (1) concretionary, in which precipitation occurred in specific zones throughout the sediment, with intervening areas largely uncemented; and (2) grain-rimming, in which precipitation occurred on grain-surfaces relatively uniformly throughout the rock. Concretions form in rocks in which sediment grains have a different composition from the cement, whereas rim cements form in those that have the same composition. Both the mechanical attributes and permeability of a given volume of rock are affected to a much greater extent by grain rimming cements, which have a significant impact on properties at even low abundances. Concretionary cements have little impact on bulk properties until relatively large volumes have precipitated (~80% cemented) and concretions begin to link up. Precipitation of cement in fault zones also impacts both mechanical and hydrologic properties. Cementation will stiffen and strengthen unlithified sediment, thereby controlling the locus of fracturing in protolith or damage zones. Where fracture networks form in fault damage zones, they are initially high permeability elements. However, progressive cementation greatly diminishes fracture permeability, resulting in cyclical permeability variation linked to fault slip. To quantitatively describe the interactions of groundwater flow, permeability, and patterns and abundance of cements, we use pore-scale modeling of coupled fluid flow, reactive transport, and heterogeneous mineral-surface reactions. By exploring the effects of varying distributions of porosity and mineralogy, which impact patterns of cementation, we provide mechanistic explanations of the interactions of coupled processes under various flow and chemistry conditions.

A novel injectable borate bioactive glass cement as an antibiotic delivery vehicle for treating osteomyelitis.

PubMed

Ding, Hao; Zhao, Cun-Ju; Cui, Xu; Gu, Yi-Fei; Jia, Wei-Tao; Rahaman, Mohamed N; Wang, Yang; Huang, Wen-Hai; Zhang, Chang-Qing

2014-01-01

A novel injectable cement composed of chitosan-bonded borate bioactive glass (BG) particles was evaluated as a carrier for local delivery of vancomycin in the treatment of osteomyelitis in a rabbit tibial model. The setting time, injectability, and compressive strength of the borate BG cement, and the release profile of vancomycin from the cement were measured in vitro. The capacity of the vancomycin-loaded BG cement to eradicate methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis in rabbit tibiae in vivo was evaluated and compared with that for a vancomycin-loaded calcium sulfate (CS) cement and for intravenous injection of vancomycin. The BG cement had an injectability of >90% during the first 3 minutes after mixing, hardened within 30 minutes and, after hardening, had a compressive strength of 18 ± 2 MPa. Vancomycin was released from the BG cement into phosphate-buffered saline for up to 36 days, and the cumulative amount of vancomycin released was 86% of the amount initially loaded into the cement. In comparison, vancomycin was released from the CS cement for up 28 days and the cumulative amount released was 89%. Two months post-surgery, radiography and microbiological tests showed that the BG and CS cements had a better ability to eradicate osteomyelitis when compared to intravenous injection of vancomycin, but there was no significant difference between the BG and CS cements in eradicating the infection. Histological examination showed that the BG cement was biocompatible and had a good capacity for regenerating bone in the tibial defects. These results indicate that borate BG cement is a promising material both as an injectable carrier for vancomycin in the eradication of osteomyelitis and as an osteoconductive matrix to regenerate bone after the infection is cured.

Influence of carbonation on the acid neutralization capacity of cements and cement-solidified/stabilized electroplating sludge.

PubMed

Chen, Quanyuan; Zhang, Lina; Ke, Yujuan; Hills, Colin; Kang, Yanming

2009-02-01

Portland cement (PC) and blended cements containing pulverized fuel ash (PFA) or granulated blast-furnace slag (GGBS) were used to solidify/stabilize an electroplating sludge in this work. The acid neutralization capacity (ANC) of the hydrated pastes increased in the order of PC > PC/GGBS > PC/PFA. The GGBS or PFA replacement (80 wt%) reduced the ANC of the hydrated pastes by 30-50%. The ANC of the blended cement-solidified electroplating sludge (cement/sludge 1:2) was 20-30% higher than that of the hydrated blended cement pastes. Upon carbonation, there was little difference in the ANC of the three cement pastes, but the presence of electroplating sludge (cement/sludge 1:2) increased the ANC by 20%. Blended cements were more effective binders for immobilization of Ni, Cr and Cu, compared with PC, whereas Zn was encapsulated more effectively in the latter. Accelerated carbonation improved the immobilization of Cr, Cu and Zn, but not Ni. The geochemical code PHREEQC, with the edited database from EQ3/6 and HATCHES, was used to calculate the saturation index and solubility of likely heavy metal precipitates in cement-based solidification/stabilization systems. The release of heavy metals could be related to the disruption of cement matrices and the remarkable variation of solubility of heavy metal precipitates at different pH values.

Peri-implant stress correlates with bone and cement morphology: Micro-FE modeling of implanted cadaveric glenoids.

PubMed

Wee, Hwabok; Armstrong, April D; Flint, Wesley W; Kunselman, Allen R; Lewis, Gregory S

2015-11-01

Aseptic loosening of cemented joint replacements is a complex biological and mechanical process, and remains a clinical concern especially in patients with poor bone quality. Utilizing high resolution finite element analysis of a series of implanted cadaver glenoids, the objective of this study was to quantify relationships between construct morphology and resulting mechanical stresses in cement and trabeculae. Eight glenoid cadavers were implanted with a cemented central peg implant. Specimens were imaged by micro-CT, and subject-specific finite element models were developed. Bone volume fraction, glenoid width, implant-cortex distance, cement volume, cement-cortex contact, and cement-bone interface area were measured. Axial loading was applied to the implant of each model and stress distributions were characterized. Correlation analysis was completed across all specimens for pairs of morphological and mechanical variables. The amount of trabecular bone with high stress was strongly negatively correlated with both cement volume and contact between the cement and cortex (r = -0.85 and -0.84, p < 0.05). Bone with high stress was also correlated with both glenoid width and implant-cortex distance. Contact between the cement and underlying cortex may dramatically reduce trabecular bone stresses surrounding the cement, and this contact depends on bone shape, cement amount, and implant positioning. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Cement-in-cement acetabular revision with a constrained tripolar component.

PubMed

Leonidou, Andreas; Pagkalos, Joseph; Luscombe, Jonathan

2012-02-17

Dislocation of a total hip replacement (THR) is common following total hip arthroplasty (THA). When nonoperative management fails to maintain reduction, revision surgery is considered. The use of constrained acetabular liners has been extensively described. Complete removal of the old cement mantle during revision THA can be challenging and is associated with significant complications. Cement-in-cement revision is an established technique. However, the available clinical and experimental studies focus on femoral stem revision. The purpose of this study was to present a case of cement-in-cement acetabular revision with a constrained component for recurrent dislocations and to investigate the current best evidence for this technique. This article describes the case of a 74-year-old woman who underwent revision of a Charnley THR for recurrent low-energy dislocations. A tripolar constrained acetabular component was cemented over the primary cement mantle following removal of the original liner by reaming, roughening the surface, and thoroughly irrigating and drying the primary cement. Clinical and radiological results were good, with the Oxford Hip Score improving from 11 preoperatively to 24 at 6 months postoperatively. The good short-term results of this case and the current clinical and biomechanical data encourage the use of the cement-in-cement technique for acetabular revision. Careful irrigation, drying, and roughening of the primary surface are necessary. Copyright 2012, SLACK Incorporated.

Morphological and chemical characterization of the dentin/resin cement interface produced with a self-etching primer.

PubMed

Walker, Mary P; Wang, Yong; Spencer, Paulette

2002-01-01

The purpose of this study was to analyze a resin cement/dentin interface by comparing the diffusion of a resin cement into dentin surfaces pretreated with a self-etching primer with or without pretreatment by conventional acid etching. Dentin surfaces of 8 unerupted human third molars were treated with a self-etch primer (Panavia 21) with or without conventional phosphoric acid pretreatment. Panavia 21 resin cement was applied according to manufacturer's instructions. Dentin/resin cement interface sections from each tooth were examined with scanning electron microscopy and micro-Raman spectroscopy. When the self-etch primer was used following conventional acid pretreatment, the resin cement did not penetrate to the depth of the zone of demineralized dentin, leaving a substantial area of exposed dentin matrix at the dentin/cement interface. In contrast, there was substantial resin cement diffusion throughout the demineralized dentin when the self-etch primer was used without acid etching pretreatment. The in vitro evaluation of resin cement penetration throughout the zone of demineralized dentin is an important step in identifying sites of exposed dentin matrix that may promote postoperative sensitivity and may leave the dentin/resin cement interface vulnerable to premature degradation under clinical conditions. In this study, the self-etch primer used alone produced substantial resin cement penetration and left no exposed dentin matrix at the dentin/resin cement interface.

The long-term in vivo behavior of polymethyl methacrylate bone cement in total hip arthroplasty.

PubMed

Oonishi, Hiroyuki; Akiyama, Haruhiko; Takemoto, Mitsuru; Kawai, Toshiyuki; Yamamoto, Koji; Yamamuro, Takao; Oonishi, Hironobu; Nakamura, Takashi

2011-10-01

The long-term success of cemented total hip arthroplasty (THA) has been well established. Improved outcomes, both radiographically and clinically, have resulted mainly from advances in stem design and improvements in operating techniques. However, there is concern about the durability of bone cement in vivo. We evaluated the physical and chemical properties of CMW1 bone cements retrieved from patients undergoing revision THA. CMW1 cements were retrieved from 14 patients who underwent acetabular revision because of aseptic loosening. The time in vivo before revision was 7-30 years. The bending properties of the retrieved bone cement were assessed using the three-point bending method. The molecular weight and chemical structure were analyzed by gel permeation chromatography and Fourier-transform infrared spectroscopy. The porosity of the bone cements was evaluated by 3-D microcomputer tomography. The bending strength decreased with increasing time in vivo and depended on the density of the bone cement, which we assume to be determined by the porosity. There was no correlation between molecular weight and time in vivo. The infrared spectra were similar in the retrieved cements and in the control CMW1 cements. Our results indicate that polymer chain scission and significant hydrolysis do not occur in CMW1 cement after implantation in vivo, even in the long term. CMW1 cement was stable through long-term implantation and functional loading.

Post retention: the effect of sequence of post-space preparation, cementation time, and different sealers.

PubMed

Boone, K J; Murchison, D F; Schindler, W G; Walker, W A

2001-12-01

Many endodontic sealers contain constituents that have been shown to inhibit the polymerization of resin cements. This may be important when prefabricated posts are cemented at the same appointment as root canal obturation. This study evaluated the effects of cementing posts with a resin cement immediately or at a delayed time period after obturation using Roth's 801 Elite Grade or AH26 sealer cements. The contribution of mechanical post-space preparation was also assessed as a critical variable. One hundred twenty extracted canines were randomly divided into eight experimental groups. The variables evaluated were the order of post preparation (either before or after obturation), the type of sealer used, and the time of post cementation. All teeth received a stainless steel #6 Parapost XP cemented with a resin cement, Panavia 21. Each experimental group underwent tensile testing for retention using an Instron universal testing machine. For both sealers posts cemented in teeth in which the canal was obturated before post-space preparation and thus had sealer-contaminated dentin removed by the space preparation procedure had significantly higher retentive values than those obturated after post-space preparation in which contaminated dentin might remain. Sealer used and time of cementation had no specific effect on retention. Achieving a clean, "freshened" dentinal surface during mechanical post-space preparation seems to be a critical variable for post retention when a resin cement is used.

A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation.

PubMed

Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen

2016-12-15

To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation.

Cermet cements.

PubMed

McLean, J W

1990-01-01

Cermet ionomer cements are sintered metal/glass powders, which can be made to react with poly(acids). These new cements are significantly more resistant to abrasion than regular glass ionomer cements and are widely accepted as core build-up materials and lining cements. They can strengthen teeth and provide the clinician with an opportunity to treat early dental caries.

Evaluation of a Glass Ionomer Restoration to Treat Hypersensitive Cervical Anatomic Deficiencies.

DTIC Science & Technology

1983-03-01

glass ionomer cement to existing dental cements such as...that the milder pulp reaction to a glass ionomer cement as opposed to a phosphoric acid cement may be explained by the weaker acid makeup of the ASPA...7 Sensitivity Evaluation ........................... 9 Treatment of Dentinal Sensitivity................. 12 Glass Ionomer Cements

40 CFR 146.12 - Construction requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

...; and (B) A cement bond, temperature, or density log after the casing is set and cemented. (ii) For... cement bond, temperature, or density log after the casing is set and cemented. (e) At a minimum, the... water. The casing and cement used in the construction of each newly drilled well shall be designed for...

40 CFR 60.541 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... facility (parts per million by volume) Dc=density of cement or spray material (grams per liter (lb per... which the tire is mounted. Bead cementing operation means the system that is used to apply cement to the... consists of a cement application station, such as a dip tank, spray booth and nozzles, cement trough and...

77 FR 46371 - National Emission Standards for Hazardous Air Pollutants for the Portland Cement Manufacturing...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-03

...-AQ93 National Emission Standards for Hazardous Air Pollutants for the Portland Cement Manufacturing... Portland Cement Manufacturing Industry and Standards of Performance for Portland Cement Plants,'' which was... Manufacturing Industry and Standards of Performance for Portland Cement Plants'' under Docket ID No. EPA-HQ-OAR...

Waiting time for coronal preparation and the influence of different cements on tensile strength of metal posts.

PubMed

Oliveira, Ilione Kruschewsky Costa Sousa; Arsati, Ynara Bosco de Oliveira Lima; Basting, Roberta Tarkany; França, Fabiana Mantovani Gomes

2012-01-01

This study aimed to assess the effect of post-cementation waiting time for core preparation of cemented cast posts and cores had on retention in the root canal, using two different luting materials. Sixty extracted human canines were sectioned 16 mm from the root apex. After cast nickel-chromium metal posts and cores were fabricated and luted with zinc phosphate (ZP) cement or resin cement (RC), the specimens were divided into 3 groups (n = 10) according to the waiting time for core preparation: no preparation (control), 15 minutes, or 1 week after the core cementation. At the appropriate time, the specimens were subjected to a tensile load test (0.5 mm/min) until failure. Two-way ANOVA (time versus cement) and the Tukey tests (P < 0.05) showed significantly higher (P < 0.05) tensile strength values for the ZP cement groups than for the RC groups. Core preparation and post-cementation waiting time for core recontouring did not influence the retention strength. ZP was the best material for intraradicular metal post cementation.

Experimental Investigation of Multi-mode Fiber Laser Cutting of Cement Mortar.

PubMed

Lee, Dongkyoung; Pyo, Sukhoon

2018-02-10

This study successfully applied multi-mode laser cutting with the variation of the laser cutting speed to cement mortar for the first time. The effects of the amount of silica sand in the cement mortar on laser cutting are tested and analyzed. The kerf width and penetration depth of the specimens after laser cutting are investigated. As the laser cutting speed increases, the penetration depth decreases for both cement paste and cement mortar, whereas the kerf width becomes saturated and increases, respectively, for cement paste and cement mortar. Cross sections of the specimens are compared with illustrations. Top-view images of the cement mortar with indicators of the physical characteristics, such as re-solidification, burning, and cracks are examined, and the possible causes of these characteristics are explained. The optical absorption rates of cement-based materials are quantified at wide ranges of wavelength to compare the absorption rates in accordance with the materials compositions. The chemical composition variation before and after laser cutting is also compared by EDX (Energy Dispersive X-Ray) analysis. In addition to these observations, material removal mechanisms for cement mortar are proposed.

Experimental Investigation of Multi-mode Fiber Laser Cutting of Cement Mortar

PubMed Central

2018-01-01

This study successfully applied multi-mode laser cutting with the variation of the laser cutting speed to cement mortar for the first time. The effects of the amount of silica sand in the cement mortar on laser cutting are tested and analyzed. The kerf width and penetration depth of the specimens after laser cutting are investigated. As the laser cutting speed increases, the penetration depth decreases for both cement paste and cement mortar, whereas the kerf width becomes saturated and increases, respectively, for cement paste and cement mortar. Cross sections of the specimens are compared with illustrations. Top-view images of the cement mortar with indicators of the physical characteristics, such as re-solidification, burning, and cracks are examined, and the possible causes of these characteristics are explained. The optical absorption rates of cement-based materials are quantified at wide ranges of wavelength to compare the absorption rates in accordance with the materials compositions. The chemical composition variation before and after laser cutting is also compared by EDX (Energy Dispersive X-Ray) analysis. In addition to these observations, material removal mechanisms for cement mortar are proposed. PMID:29439431

Evaluation of four biodegradable, injectable bone cements in an experimental drill hole model in sheep.

PubMed

von Rechenberg, Brigitte; Génot, Oliver R; Nuss, Katja; Galuppo, Larry; Fulmer, Mark; Jacobson, Evan; Kronen, Peter; Zlinszky, Kati; Auer, Jörg A

2013-09-01

Four cement applications were tested in this investigation. Two dicalcium phosphate dihydrate (DCPD-brushite) hydraulic cements, an apatite hydraulic fiber loaded cement, and a calcium sulfate cement (Plaster of Paris) were implanted in epiphyseal and metaphyseal cylindrical bone defects in sheep. The in vivo study was performed to assess the biocompatibility and bone remodeling of four cement formulations. After time periods of 2, 4, and 6 months, the cement samples were clinically and histologically evaluated. Histomorphometrically, the amount of new bone formation, fibrous tissue, and bone marrow and the area of remaining cement were measured. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. Cements differed mainly in their resorption time. Calcium sulfate was already completely resorbed at 2 months and showed a variable amount of new bone formation and/or fibrous tissue in the original drill hole over all time periods. The two DCPD cements in contrast were degraded to a large amount at 6 months, whereas the apatite was almost unchanged over all time periods. Copyright © 2013. Published by Elsevier B.V.

Modified femoral pressuriser generates a longer lasting high pressure during cement pressurisation

PubMed Central

2011-01-01

Background The strength of the cement-bone interface in hip arthroplasty is strongly related to cement penetration into the bone. A modified femoral pressuriser has been investigated, designed for closer fitting into the femoral opening to generate higher and more constant cement pressure compared to a commercial (conventional) design. Methods Femoral cementation was performed in 10 Sawbones® models, five using the modified pressuriser and five using a current commercial pressuriser as a control. Pressure during the cementation was recorded at the proximal and distal regions of the femoral implant. The peak pressure and the pressure-time curves were analysed by student's t-test and Two way ANOVA. Results The modified pressuriser showed significantly and substantially longer durations at higher cementation pressures and slightly, although not statistically, higher peak pressures compared to the conventional pressuriser. The modified pressuriser also produced more controlled cement leakage. Conclusion The modified pressuriser generates longer higher pressure durations in the femoral model. This design modification may enhance cement penetration into cancellous bone and could improve femoral cementation. PMID:22004662

Wide-scale utilization of MSWI fly ashes in cement production and its impact on average heavy metal contents in cements: The case of Austria.

PubMed

Lederer, Jakob; Trinkel, Verena; Fellner, Johann

2017-02-01

A number of studies present the utilization of fly ashes from municipal solid waste incineration (MSWI) in cement production as a recycling alternative to landfilling. While there is a lot of research on the impact of MSWI fly ashes utilization in cement production on the quality of concrete or the leaching of heavy metals, only a few studies have determined the resulting heavy metal content in cements caused by this MSWI fly ashes utilization. Making use of the case of Austria, this study (1) determines the total content of selected heavy metals in cements currently produced in the country, (2) designs a scenario and calculates the resulting heavy metal contents in cements assuming that all MSWI fly ashes from Austrian grate incinerators were used as secondary raw materials for Portland cement clinker production and (3) evaluates the legal recyclability of demolished concretes produced from MSWI fly ash amended cements based on their total heavy metal contents. To do so, data from literature and statistics are combined in a material flow analysis model to calculate the average total contents of heavy metals in cements and in the resulting concretes according to the above scenario. The resulting heavy metal contents are then compared (i) to their respective limit values for cements as defined in a new technical guideline in Austria (BMLFUW, 2016), and (ii) to their respective limit values for recycling materials from demolished concrete. Results show that MSWI fly ashes utilization increases the raw material input in cement production by only +0.9%, but the total contents of Cd by +310%, and Hg, Pb, and Zn by +70% to +170%. However these and other heavy metal contents are still below their respective limit values for Austrian cements. The same legal conformity counts for recycling material derived from concretes produced from the MSWI fly ash cements. However, if the MSWI fly ash ratio in all raw materials used for cement production were increased from 0.9% to 22%, which is suggested by some studies, the limit values for cements as defined by the BMLFUW (2016) will be exceeded. Furthermore, the concrete produced from this cement will not be recyclable anymore due to its high total heavy metal contents. This and the comparatively high contribution of MSWI fly ashes to total heavy metal contents in cements indicate their relatively low resource potential if compared to other secondary raw materials in the cement industry. Copyright © 2016 Elsevier Ltd. All rights reserved.

Experimental study of potential wellbore cement carbonation by various phases of carbon dioxide during geologic carbon sequestration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Hun Bok; Um, Wooyong

2013-08-16

Hydrated Portland cement was reacted with carbon dioxide (CO2) in supercritical, gaseous, and aqueous phases to understand the potential cement alteration processes along the length of a wellbore, extending from deep CO2 storage reservoir to the shallow subsurface during geologic carbon sequestration. The 3-D X-ray microtomography (XMT) images displayed that the cement alteration was significantly more extensive by CO2-saturated synthetic groundwater than dry or wet supercritical CO2 at high P (10 MPa)-T (50°C) conditions. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) analysis also exhibited a systematic Ca depletion and C enrichment in cement matrix exposed to CO2-saturated groundwater. Integratedmore » XMT, XRD, and SEM-EDS analyses identified the formation of extensive carbonated zone filled with CaCO3(s), as well as the porous degradation front and the outermost silica-rich zone in cement after exposure to CO2-saturated groundwater. The cement alteration by CO2-saturated groundwater for 2-8 months overall decreased the porosity from 31% to 22% and the permeability by an order of magnitude. Cement alteration by dry or wet supercritical CO2 was slow and minor compared to CO2-saturated groundwater. A thin single carbonation zone was formed in cement after exposure to wet supercritical CO2 for 8 months or dry supercritical CO2 for 15 months. Extensive calcite coating was formed on the outside surface of a cement sample after exposure to wet gaseous CO2 for 1-3 months. The chemical-physical characterization of hydrated Portland cement after exposure to various phases of carbon dioxide indicates that the extent of cement carbonation can be significantly heterogeneous depending on CO2 phase present in the wellbore environment. Both experimental and geochemical modeling results suggest that wellbore cement exposure to supercritical, gaseous, and aqueous phases of CO2 during geologic carbon sequestration is unlikely to damage the wellbore integrity because cement alteration by all phases of CO2 is dominated by carbonation reaction. This is consistent with previous field studies of wellbore cement with extensive carbonation after exposure to CO2 for 3 decades. However, XMT imaging indicates that preferential cement alteration by supercritical CO2 or CO2-saturated groundwater can occur along the cement-steel or cement-rock interfaces. This highlights the importance of further investigation of cement degradation along the interfaces of wellbore materials to ensure permanent geologic carbon storage.« less

Study of deformation of resin cements used in fixing of root posts through fiber Bragg grating sensors

NASA Astrophysics Data System (ADS)

Pulido, C. A.; Franco, A. P. G. O.; Karam, L. Z.; Kalinowski, H. J.; Gomes, O. M. M.

2014-05-01

The aim of the study was to evaluate the polymerization shrinkage "in situ" in resin cements inside the root canal during the fixation of glass fiber posts. For cementation teeth were randomly divided into 2 groups according to the resin cement used: Group1 - resin cement dual Relyx ARC (3M/ESPE), and Group 2 - resin cement dual Relyx U200 (3M/ESPE). Before inserting the resin cement into the root canal, two Bragg grating sensors were recorded and pasted in the region without contact with the canal, one at the apical and other at the coronal thirds of the post. The sensors measured the deformation of the resin cements in coronal and apical root thirds to obtain the values in micro-strain (μɛ).

In vivo response of bioactive PMMA-based bone cement modified with alkoxysilane and calcium acetate.

PubMed

Sugino, Atsushi; Ohtsuki, Chikara; Miyazaki, Toshiki

2008-11-01

The use of polymethylmethacrylate (PMMA)-based bone cement is popular in orthopedics for the fixation of artificial joints with bone. However, it has a major problem with prostheses loosening because of coverage by fibrous tissue after long-term implantation. Recently, a bioactive bone cement has been developed that shows direct bonding to living bone through modification of PMMA resin with gamma-methacryloxypropyltrimethoxysilane (MPS) and calcium acetate. The cement is designed to exhibit bioactivity, through incorporation of silanol groups and calcium ions. Thus, it has the potential to form a layer of bone-like hydroxyapatite, which is essential for achieving direct bonding to living bone. This type of modification allows the cement to show spontaneous hydroxyapatite formation on its surface in a simulated body fluid after one day, and there is evidence of osteoconduction of the cement in rabbit tibia for periods of more than three weeks. However, the influence of the dissolved ions from the modified cement has not yet been clarified. Thus, the authors focused on the dissolution of the modified PMMA-based bone cement and its tissue response in muscle and bone by comparison with the behavior of non-modified PMMA-based bone cement. One week after implantation in the latissimus dorsi of a rabbit, the modified PMMA-based bone cement showed more inflammatory width than the commercial cement. However, four weeks after implantation, the inflammatory width of both cements was essentially the same. The osteoconductivity around the modified cement was higher than that for the conventional cement after four weeks implantation. These results indicate that the initial dissolution of calcium acetate from the modified cement to form the hydroxyapatite induced the acute inflammation around tissue, but also developed the osteoconductivity. It is suggested that the initial inflammation can be effective for inducing osteoconduction through a bone healing reaction when the material provides an environment that promotes bone formation.

Influence of Temporary Cements on the Bond Strength of Self-Adhesive Cement to the Metal Coronal Substrate.

PubMed

Peixoto, Raniel Fernandes; De Aguiar, Caio Rocha; Jacob, Eduardo Santana; Macedo, Ana Paula; De Mattos, Maria da Gloria Chiarello; Antunes, Rossana Pereira de Almeida

2015-01-01

This research evaluated the influence of temporary cements (eugenol-containing [EC] or eugenol-free [EF]) on the tensile strength of Ni-Cr copings fixed with self-adhesive resin cement to the metal coronal substrate. Thirty-six temporary crowns were divided into 4 groups (n=9) according to the temporary cements: Provy, Dentsply (eugenol-containing), Temp Cem, Vigodent (eugenol-containing), RelyX Temp NE, 3M ESPE (eugenol-free) and Temp Bond NE, Kerr Corp (eugenol-free). After 24 h of temporary cementation, tensile strength tests were performed in a universal testing machine at a crosshead speed of 0.5 mm/min and 1 kN (100 kgf) load cell. Afterwards, the cast metal cores were cleaned by scraping with curettes and air jet. Thirty-six Ni-Cr copings were cemented to the cast metal cores with self-adhesive resin cement (RelyX U200, 3M ESPE). Tensile strength tests were performed again. In the temporary cementation, Temp Bond NE (12.91 ± 2.54) and Temp Cem (12.22 ± 2.96) presented the highest values of tensile strength and were statistically similar to each other (p>0.05). Statistically significant difference (p<0.05) was observed only between Provy (164.44 ± 31.23) and Temp Bond NE (88.48 ± 21.83) after cementation of Ni-Cr copings with self-adhesive resin cement. In addition, Temp Cem (120.68 ± 48.27) and RelyX Temp NE (103.04 ± 26.09) showed intermediate tensile strength values. In conclusion, the Provy eugenol-containing temporary cement was associated with the highest bond strength among the resin cements when Ni-Cr copings were cemented to cast metal cores. However, the eugenol cannot be considered a determining factor in increased bond strength, since the other tested cements (1 eugenol-containing and 2 eugenol-free) were similar.

Cementing a wellbore using cementing material encapsulated in a shell

DOEpatents

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

2016-08-16

A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugama, Toshifumi; Pyatina, Tatiana

The study aims at evaluating the bond durability of a carbon microfiber (CMF)-reinforced alkali-activating calcium aluminate cement (CAC)/fly ash F (FAF) blend cementitious material adhering to carbon steel (CS) under stresses induced by a 350°C heat-25°Cwater cooling cycle. This cementitious material/CS joint sample was originally prepared in an autoclave at 300°C under a pressure of 8.3 MPa. For comparison, two reference geothermal well cements, Class G modified with silica (G) and calciumaluminum phosphate (CaP), were employed as well reinforced with CMF. In the CAC/FAF blending cement systems, the CAC-derived cementitious reaction products preferentially adhered to CS surfaces, rather than thatmore » of FAF-related reaction products. CMF played a pivotal role in creating tough interfacial bond structure of cement layer adhering to CS. The bond toughness also was supported by the crystalline cementitious reaction products including sodalite, brownmillerite, and hedenbergite as major phases, and aragonite, boehmite, and garronite as minor ones. The brownmillerite as an interfacial reaction product between cement and CS promoted the chemical bonding of the cement to CS, while the other phases served in providing the attractive bonding of the cement to CS. The post-stress-test joint samples revealed the formation of additional brown-millerite, aragonite, and garronite, in particular brownmillerite as the major one. The combination of chemical bonding and self-advancing adherence behavior of the cement was essential for creating a better interfacial bond structure. A similar interfacial bond structure was observed with CaP. The crystalline phase composition of the autoclaved cement revealed apatite, zeolite, and ferrowyllieite as major reaction products, and aragonite and al-katoite as the minor ones. Ferrowyllieite was identified as cement/CS interfacial reaction product contributing to the chemical bond of cement, while the other phases aided in providing the attractive bond of cement. After a stress test, two phases, ferrowyllieite and aragonite, promoted the self-advancing adherence of cement to CS. However, the effectiveness of these phases in improving adherence performance of cement was less than that of CAC/FAF blend cement, reflecting the fact that the bond durability of CAC/FAF blend cement was far better than that of the CaP. In contrast, the autoclaved silica-modified G cement consisting of xonotlite, and 0.9 nm-to-bermorite and riversideite, with calcite as the crystalline reaction products, had no significant effect on improving the shear bond strength and the bond’s toughness. No interaction product with CS was found in the cement adhering to CS. After a stress test, the calcite phase acted only to promote the self-advancing adherence of cement, but its extent was minimal compared with that of the other cements, thereby resulting in poor bond durability.« less

Biomechanical evaluation of bone screw fixation with a novel bone cement.

PubMed

Juvonen, Tiina; Nuutinen, Juha-Pekka; Koistinen, Arto P; Kröger, Heikki; Lappalainen, Reijo

2015-07-30

Bone cement augmentation is commonly used to improve the fixation stability of orthopaedic implants in osteoporotic bone. The aim of this study was to evaluate the effect of novel bone cements on the stability of bone screw fixation by biomechanical testing and to compare them with a conventional Simplex(®)P bone cement and requirements of the standards. Basic biomechanical properties were compared with standard tests. Adhesion of bone cements were tested with polished, glass blasted and corundum blasted stainless steel surfaces. Screw pullout testing with/without cement was carried out using a synthetic bone model and cancellous and cortical bone screws. All the tested bone cements fulfilled the requirements of the standard for biomechanical properties and improved the screw fixation stability. Even a threefold increase in shear and tensile strength was achieved with increasing surface roughness. The augmentation improved the screw pullout force compared to fixation without augmentation, 1.2-5.7 times depending on the cement and the screw type. The good biomechanical properties of novel bone cement for osteoporotic bone were confirmed by experimental testing. Medium viscosity of the bone cements allowed easy handling and well-controlled penetration of bone cement into osteoporotic bone. By proper parameters and procedures it is possible to achieve biomechanically stable fixation in osteoporotic bone. Based on this study, novel biostable bone cements are very potential biomaterials to enhance bone screw fixation in osteoporotic bone. Novel bone cement is easy to use without hand mixing using a dual syringe and thus makes it possibility to use it as required during the operation.

Incorporation of chlorhexidine diacetate in provisional cements: antimicrobial activity against Streptococcus mutans and the effect on tensile strength in vitro.

PubMed

Lewinstein, I; Zenziper, E; Block, J; Kfir, A

2012-11-01

To test the antibacterial capacities and tensile strengths of three commercially available provisional cements to which chlorhexidine diacetate was added and compare them to the same unmodified cements. Sixty cylindrical samples were prepared from either three noneugenol provisional cements or the same cements modified by the addition of chlorhexidine diacetate at 7.5% w/w, with a total of 360 samples. The cements tested included Tempbond NE, Rely X Temp NE and Freegenol. Forty-eight samples from each cement were aged in saline that was replaced twice a week for up to 96 days. Twelve of these samples were removed at either 1, 15, 30 or 96 days and assessed for antibacterial properties against Streptococcus mutans with an agar diffusion test. Twelve samples of each cement, with and without chlorhexidine diacetate, were also tested 7 days after the initial setting for their tensile strength using a diametrical tensile strength test applied with an Instron machine. The results were analysed using either one-way or three-way anova. The addition of chlorhexidine diacetate resulted in provisional cements with antibacterial properties that persisted through ageing in saline for up to 96 days. The addition of chlorhexidine did not reduce the diametrical strength of the cements. The addition of chlorhexidine diacetate to provisional cements rendered all three cements antibacterial against S. mutans and this activity was maintained even after prolonged ageing of the cements, without compromising their tensile strength at 7 days. © 2012 International Endodontic Journal.

Study of the Peak Shear Strength of a Cement-Filled Hard Rock Joint

NASA Astrophysics Data System (ADS)

She, Cheng-Xue; Sun, Fu-Ting

2018-03-01

The peak shear strength of a cement-filled hard rock joint is studied by theoretical analysis and laboratory testing. Based on the concept of the shear resistance angle, by combining the statistical method and fractal theory, three new parameters are proposed to characterize the three-dimensional joint morphology, reflecting the effects of the average roughness, multi-scale asperities and the dispersion degree of the roughness distribution. These factors are independent of the measurement scale, and they reflect the anisotropy of the joint roughness. Compressive shear tests are conducted on cement-filled joints. Because joints without cement can be considered special cement-filled joints in which the filling degree of cement is zero, they are also tested. The cement-filled granite joint fails primarily along the granite-cement interfaces. The filling degree of cement controls the joint failure and affects its mechanical behaviour. With a decrease in the filling degree of cement, the joint cohesion decreases; however, the dilatancy angle and the basic friction angle of the interface increase. As the filling degree approaches zero, the cohesion approaches zero, while the dilatancy angle and the basic friction angle increase to those of the joint without cement. A set of formulas is proposed to evaluate the peak shear strength of the joints with and without cement. The formulas are shown to be reasonable by comparison with the tested peak shear strength, and they reflect the anisotropy of the strength. This research deepens the understanding of cement-filled joints and provides a method to evaluate their peak shear strength.

Effect of eugenol-based endodontic sealer on the adhesion of intraradicular posts cemented after different periods.

PubMed

Dias, Larissa Lustosa Lima; Giovani, Alessandro Rogério; Silva Sousa, Yara Teresinha Corrêa; Vansan, Luiz Pascoal; Alfredo, Edson; Sousa-Neto, Manoel Damião; Paulino, Silvana Maria

2009-01-01

This study evaluated in vitro the influence of an eugenol-based sealer (EndoFill) on the retention of stainless steel prefabricated posts cemented with zinc phosphate and resin-based (Panavia F) cements after different periods of root canal obturation, using the pull-out test. Sixty upper canines were decoronated and the roots were embedded in resin blocks. The specimens were distributed into 3 groups, according to the period elapsed between canal obturation and post cementation: Group I - immediately; Group II - 72 h and Group III - 4 months. The groups were subdivided according to the type of cement used for post cementation: A - zinc phosphate and B - Panavia F. Following the experimental periods, specimens were subjected to pullout test in an Instron machine with application of tensile force at a crosshead speed of 0.5 mm/min until post dislodgement. The maximum forces required for post removal were recorded (kN) and means were subjected to statistical analysis by 2-way ANOVA and Tukey-Kramer test (alpha=0.001) There were statistically significant differences (p<0.01) between the posts cemented with zinc phosphate cement (0.2112 kN) and Panavia F (0.0501 kN). However, no statistically significant differences (p>0.05) were found between the three post cementation periods, regardless of the cement. It was concluded that the eugenol-based sealer influenced the tensile strength of the posts cemented with the resin cement, but had no influence on the time waited between root canal obturation and post space preparation/post cementation.

EFFECT OF EUGENOL-BASED ENDODONTIC SEALER ON THE ADHESION OF INTRARADICULAR POSTS CEMENTED AFTER DIFFERENT PERIODS

PubMed Central

Dias, Larissa Lustosa Lima; Giovani, Alessandro Rogério; Sousa, Yara Teresinha Corrêa Silva; Vansan, Luiz Pascoal; Alfredo, Edson; Sousa-Neto, Manoel Damião; Paulino, Silvana Maria

2009-01-01

Objective: This study evaluated in vitro the influence of an eugenol-based sealer (EndoFill) on the retention of stainless steel prefabricated posts cemented with zinc phosphate and resin-based (Panavia F) cements after different periods of root canal obturation, using the pull-out test. Material and methods: Sixty upper canines were decoronated and the roots were embedded in resin blocks. The specimens were distributed into 3 groups, according to the period elapsed between canal obturation and post cementation: Group I - immediately; Group II - 72 h and Group III - 4 months. The groups were subdivided according to the type of cement used for post cementation: A - zinc phosphate and B - Panavia F. Following the experimental periods, specimens were subjected to pull- out test in an Instron machine with application of tensile force at a crosshead speed of 0.5 mm/min until post dislodgement. The maximum forces required for post removal were recorded (kN) and means were subjected to statistical analysis by 2-way ANOVA and Tukey-Kramer test (α=0.001) Results: There were statistically significant differences (p<0.01) between the posts cemented with zinc phosphate cement (0.2112 kN) and Panavia F (0.0501 kN). However, no statistically significant differences (p>0.05) were found between the three post cementation periods, regardless of the cement. Conclusions: It was concluded that the eugenol-based sealer influenced the tensile strength of the posts cemented with the resin cement, but had no influence on the time waited between root canal obturation and post space preparation/post cementation. PMID:20027430

Considerations for proper selection of dental cements.

PubMed

Simon, James F; Darnell, Laura A

2012-01-01

Selecting the proper cement for sufficient bond strength has become progressively complicated as the number of different materials for indirect restorations has increased. The success of any restoration is highly dependent on the proper cement being chosen and used. The function of the cement is not only to seal the restoration on the tooth but also, in some cases, to support the retention of the restoration. This ability to strengthen retention varies by the cement chosen by the clinician; therefore, careful consideration must precede cement selection.

Development of fluorapatite cement for dental enamel defects repair.

PubMed

Wei, Jie; Wang, Jiecheng; Shan, Wenpeng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

2011-06-01

In order to restore the badly carious lesion of human dental enamel, a crystalline paste of fluoride substituted apatite cement was synthesized by using the mixture of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and ammonium fluoride. The apatite cement paste could be directly filled into the enamel defects (cavities) to repair damaged dental enamel. The results indicated that the hardened cement was fluorapatite [Ca(10)(PO(4))(6)F(2), FA] with calcium to phosphorus atom molar ratio (Ca/P) of 1.67 and Ca/F ratio of 5. The solubility of FA cement in Tris-HCl solution (pH = 5) was slightly lower than the natural enamel, indicating the FA cement was much insensitive to the weakly acidic solutions. The FA cement was tightly combined with the enamel surface, and there was no obvious difference of the hardness between the FA cement and natural enamel. The extracts of FA cement caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. In addition, the results showed that the FA cement had good mechanical strength, hydrophilicity, and anti-bacterial adhesion properties. The study suggested that using FA cement was simple and promising approach to effectively and conveniently restore enamel defects.

Cemental tear: To know what we have neglected in dental practice.

PubMed

Jeng, Po-Yuan; Luzi, Arlinda Luzi; Pitarch, Rocio Marco; Chang, Mei-Chi; Wu, Yu-Hsueh; Jeng, Jiiang-Huei

2018-04-01

Cemental tear is a special kind of root surface fracture, contributing to periodontal and periapical breakdown. However, it is a challenge for doctors to diagnose, resulting in delayed or improper treatment. We reviewed the predisposing factors, location, radiographic/clinical characteristics, diagnosis and treatments of cemental tears. From the literature, patients with cemental tear were mainly males, over 60 year-old. Possible predisposing factors include gender, age, tooth type, traumatic occlusal force and vital teeth. Cemental tears were common in upper and lower anterior teeth, single or multiple, and can be present in cervical, middle and apical third of roots. Morphology of cemental tears can be either piece-shaped or U-shaped. Clinically, cemental tear shows a unitary periodontal pocket and signs/symptoms mimicking localized periodontitis, apical periodontitis and vertical root fractures. Treatment of cemental tears include scaling, root planning, root canal treatment, periodontal/periapical surgery, guided tissue regeneration, bone grafting, and intentional replantation. Recurrence of cemental tear is possible especially when the fracture involves root apex. Extraction is recommended for teeth with poor prognosis. In conclusion, cemental tears can involve both periodontal and periapical area. Dentists should understand the predisposing factors and clinical features of cemental tears for early diagnosis/treatment to prevent bone loss/tooth extraction. Copyright © 2017. Published by Elsevier B.V.

Sculpting with Cement.

ERIC Educational Resources Information Center

Olson, Lynn

1983-01-01

Cement offers many creative possibilities for school art programs. Instructions are given for sculpting with fiber-cement and sand-cement, as well as for finishing processes and the addition of color. Safety is stressed. (IS)

Evaluation of ternary blended cements for use in transportation concrete structures

NASA Astrophysics Data System (ADS)

Gilliland, Amanda Louise

This thesis investigates the use of ternary blended cement concrete mixtures for transportation structures. The study documents technical properties of three concrete mixtures used in federally funded transportation projects in Utah, Kansas, and Michigan that used ternary blended cement concrete mixtures. Data were also collected from laboratory trial batches of ternary blended cement concrete mixtures with mixture designs similar to those of the field projects. The study presents the technical, economic, and environmental advantages of ternary blended cement mixtures. Different barriers of implementation for using ternary blended cement concrete mixtures in transportation projects are addressed. It was concluded that there are no technical, economic, or environmental barriers that exist when using most ternary blended cement concrete mixtures. The technical performance of the ternary blended concrete mixtures that were studied was always better than ordinary portland cement concrete mixtures. The ternary blended cements showed increased durability against chloride ion penetration, alkali silica reaction, and reaction to sulfates. These blends also had less linear shrinkage than ordinary portland cement concrete and met all strength requirements. The increased durability would likely reduce life cycle costs associated with concrete pavement and concrete bridge decks. The initial cost of ternary mixtures can be higher or lower than ordinary portland cement, depending on the supplementary cementitious materials used. Ternary blended cement concrete mixtures produce less carbon dioxide emissions than ordinary portland cement mixtures. This reduces the carbon footprint of construction projects. The barriers associated with implementing ternary blended cement concrete for transportation projects are not significant. Supplying fly ash returns any investment costs for the ready mix plant, including silos and other associated equipment. State specifications can make designing ternary blended cements more acceptable by eliminating arbitrary limitations for supplementary cementitious materials (SCMs) use and changing to performance-based standards. Performance-based standards require trial batching of concrete mixture designs, which can be used to optimize ternary combinations of portland cement and SCMs. States should be aware of various SCMs that are appropriate for the project type and its environment.

Bond Durability of Carbon-Microfiber-Reinforced Alkali-Activated High-Temperature Cement Adhering to Carbon Steel

DOE PAGES

Sugama, Toshifumi; Pyatina, Tatiana

2017-02-01

The study aims at evaluating the bond durability of a carbon microfiber (CMF)-reinforced alkali-activating calcium aluminate cement (CAC)/fly ash F (FAF) blend cementitious material adhering to carbon steel (CS) under stresses induced by a 350°C heat-25°Cwater cooling cycle. This cementitious material/CS joint sample was originally prepared in an autoclave at 300°C under a pressure of 8.3 MPa. For comparison, two reference geothermal well cements, Class G modified with silica (G) and calciumaluminum phosphate (CaP), were employed as well reinforced with CMF. In the CAC/FAF blending cement systems, the CAC-derived cementitious reaction products preferentially adhered to CS surfaces, rather than thatmore » of FAF-related reaction products. CMF played a pivotal role in creating tough interfacial bond structure of cement layer adhering to CS. The bond toughness also was supported by the crystalline cementitious reaction products including sodalite, brownmillerite, and hedenbergite as major phases, and aragonite, boehmite, and garronite as minor ones. The brownmillerite as an interfacial reaction product between cement and CS promoted the chemical bonding of the cement to CS, while the other phases served in providing the attractive bonding of the cement to CS. The post-stress-test joint samples revealed the formation of additional brown-millerite, aragonite, and garronite, in particular brownmillerite as the major one. The combination of chemical bonding and self-advancing adherence behavior of the cement was essential for creating a better interfacial bond structure. A similar interfacial bond structure was observed with CaP. The crystalline phase composition of the autoclaved cement revealed apatite, zeolite, and ferrowyllieite as major reaction products, and aragonite and al-katoite as the minor ones. Ferrowyllieite was identified as cement/CS interfacial reaction product contributing to the chemical bond of cement, while the other phases aided in providing the attractive bond of cement. After a stress test, two phases, ferrowyllieite and aragonite, promoted the self-advancing adherence of cement to CS. However, the effectiveness of these phases in improving adherence performance of cement was less than that of CAC/FAF blend cement, reflecting the fact that the bond durability of CAC/FAF blend cement was far better than that of the CaP. In contrast, the autoclaved silica-modified G cement consisting of xonotlite, and 0.9 nm-to-bermorite and riversideite, with calcite as the crystalline reaction products, had no significant effect on improving the shear bond strength and the bond’s toughness. No interaction product with CS was found in the cement adhering to CS. After a stress test, the calcite phase acted only to promote the self-advancing adherence of cement, but its extent was minimal compared with that of the other cements, thereby resulting in poor bond durability.« less

Utilization of CO2 in High Performance Building and Infrastructure Products

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeCristofaro, Nicholas

The overall objective of DE-FE0004222 was to demonstrate that calcium silicate phases, in the form of either naturally-occuring minerals or synthetic compounds, could replace Portland cement in concrete manufacturing. The calcium silicate phases would be reacted with gaseous CO2 to create a carbonated concrete end-product. If successful, the project would offer a pathway to a significant reduction in the carbon footprint associated with the manufacture of cement and its use in concrete (approximately 816 kg of CO2 is emitted in the production of one tonne of Portland cement). In the initial phases of the Technical Evaluation, Rutgers University teamed withmore » Solidia Technologies to demonstrate that natural wollastonite (CaSiO3), milled to a particle size distribution consistent with that of Portland cement, could indeed fit this bill. The use of mineral wollastonite as a cementitious material would potentially eliminate the CO2 emitted during cement production altogether, and store an additional 250 kg of CO2 during concrete curing. However, it was recognized that mineral wollastonite was not available in volumes that could meaningfully impact the carbon footprint associated with the cement and concrete industries. At this crucial juncture, DE-FE0004222 was redirected to use a synthetic version of wollastonite, hereafter referred to as Solidia Cement™, which could be manufactured in conventional cement making facilities. This approach enables the new cementitious material to be made using existing cement industry raw material supply chains, capital equipment, and distribution channels. It would also offer faster and more complete access to the concrete marketplace. The latter phases of the Technical Evaluation, conducted with Solidia Cement made in research rotary kilns, would demonstrate that industrially viable CO2-curing practices were possible. Prototypes of full-scale precast concrete products such as pavers, concrete masonry units, railroad ties, hollow-core slabs, and aerated concrete were produced to verify the utility of the CO2-curing process. These products exhibited a range of part dimensions and densities that were representative of the precast concrete industry. In the subsequent Demonstration of Commercial Development phase, the characteristics and performance of Solidia Cement made at a LafargeHolcim cement plant were established. This Solidia Cement was then used to demonstrate the CO2-curing process within operating concrete plants. Pavers, concrete masonry units and roofing tiles were produced according to ASTM and manufacturer specifications. A number of attractive manufacturing economies were recognized when Solidia Cement-based concrete parts were compared to their Portland cement based counterparts. These include reduced raw materials waste, reduced dependence on admixtures to control efflorescence, shorter curing time to full concrete strength, faster equipment clean-up, reduced equipment maintenance, and improved inventory management. These economies make the adoption of the Solidia Cement / CO2-curing process attractive even in the absence of environmental incentives. The culminating activity of the Demonstration of Commercial Development phase was the conversion of 10% of the manufacturing capacity at a concrete paver and block company from Portland cement-based products to Solidia Cement-based products. The successful completion of the Demonstration of Commercial Development phase clearly illustrated the environmental benefits associated with Solidia Cement and Solidia Concrete technologies. The industrial production of Solidia Cement, as a low-lime alternative to traditional Portland cement, reduces CO2 emissions at the cement kiln from 816 kg of CO2 per tonne of Portland cement clinker to 570 kg per tonne of Solidia Cement clinker. Industrial scale CO2-curing of Solidia Concrete sequestered a net of 183 kg of CO2 per tonne of Solidia Cement used in concrete pavers. Taken together, these two effects reduced the CO2 footprint associated with the production and use of cement in concrete products by over 50% (a reduction of 430 kg of CO2 per tonne of cement). Applied at the first commercial Solidia Concrete manufacturing site, the two effects will combine to reduce the CO2 footprint associated with the production and use of cement by over 10,000 tonnes per year. When applied across the precast concrete industry in the U.S., it is estimated that the CO2 footprint will be reduced by 8.6 million tonnes per year (20 million tonnes of cement used in precast concrete x 430 kg of CO2 per tonne of cement). Applied across the entire concrete industry in the U.S., it is expected that 43 million tonnes of CO2 will be avoided per year (100 million tonnes of cement used in all concrete x 430 kg of CO2 per tonne of cement).« less

76 FR 50252 - Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-12

... and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review Concerning the Antidumping Duty Order on Gray Portland Cement and Cement Clinker From Japan AGENCY: United States International... clinker from Japan would be likely to lead to continuation or recurrence of material injury within a...

Preparation and Mechanical Properties of Graphene Oxide: Cement Nanocomposites

PubMed Central

Babak, Fakhim; Abolfazl, Hassani; Alimorad, Rashidi; Parviz, Ghodousi

2014-01-01

We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1–2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar. PMID:24574878

Acoustic response of cemented granular sedimentary rocks: molecular dynamics modeling.

PubMed

García, Xavier; Medina, Ernesto

2007-06-01

The effect of cementation processes on the acoustical properties of sands is studied via molecular dynamics simulation methods. We propose numerical methods where the initial uncemented sand is built by simulating the settling process of sediments. Uncemented samples of different porosity are considered by emulating natural mechanical compaction of sediments due to overburden. Cementation is considered through a particle-based model that captures the underlying physics behind the process. In our simulations, we consider samples with different degrees of compaction and cementing materials with distinct elastic properties. The microstructure of cemented sands is taken into account while adding cement at specific locations within the pores, such as grain-to-grain contacts. Results show that the acoustical properties of cemented sands are strongly dependent on the amount of cement, its stiffness relative to the hosting medium, and its location within the pores. Simulation results are in good correspondence with available experimental data and compare favorably with some theoretical predictions for the sound velocity within a range of cement saturation, porosity, and confining pressure.

An investigation of thermal changes of various permanent dental cements.

PubMed

Duymus, Zeynep Yesil; Yilmaz, Baykal; Karaalioglu, F Osman

2009-05-01

The aim of this study was to investigate and compare the temperature rises which occurred during the setting reactions of different permanent cements used to lute fixed partial prosthodontics. In this study, four cements were used. They were mixed in three different proportions: according to manufacturers' recommendations, at doubled powder ratio, and at doubled liquid ratio. With a thermocouple, the temperature rises which occurred during the setting reactions were measured. For each proportion, the measurement was repeated five times such that a total of 60 measurements were done for the four different cements. Data were analyzed using analysis of variance (ANOVA). ANOVA results showed that cement type and the interaction between cement type and the powder-liquid ratio were statistically significant factors (p<0.001). Similarly, the powder-liquid ratio was a statistically significant (p<0.01) factor. Among the dental cements tested, zinc phosphate cement showed the highest temperature rise during setting reaction, whereas glass ionomer cement showed the lowest.

Cytotoxicity Comparison of Harvard Zinc Phosphate Cement Versus Panavia F2 and Rely X Plus Resin Cements on Rat L929-fibroblasts.

PubMed

Mahasti, Sahabi; Sattari, Mandana; Romoozi, Elham; Akbar-Zadeh Baghban, Alireza

2011-01-01

Resin cements, regardless of their biocompatibility, have been widely used in restorative dentistry during the recent years. These cements contain hydroxy ethyl methacrylate (HEMA) molecules which are claimed to penetrate into dentinal tubules and may affect dental pulp. Since tooth preparation for metal ceramic restorations involves a large surface of the tooth, cytotoxicity of these cements would be more important in fixed prosthodontic treatments. The purpose of this study was to compare the cytotoxicity of two resin cements (Panavia F2 and Rely X Plus) versus zinc phosphate cement (Harvard) using rat L929-fibroblasts in vitro. In this experimental study, ninety hollow glass cylinders (internal diameter 5-mm, height 2-mm) were made and divided into three groups. Each group was filled with one of three experimental cements; Harvard Zinc Phosphate cement, Panavia F2 resin cement and Rely X Plus resin cement. L929- Fibroblast were passaged and subsequently cultured in 6-well plates of 5×10(5) cells each. The culture medium was RPMI_ 1640. All samples were incubated in CO2. Using enzyme-linked immune-sorbent assay (ELISA) and (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) (MTT) assay, the cytotoxicity of the cements was investigated at 1 hour, 24 hours and one week post exposure. Statistical analyses were performed via two-way ANOVA and honestly significant difference (HSD) Tukey tests. This study revealed significant differences between the three cements at the different time intervals. Harvard cement displayed the greatest cytotoxicity at all three intervals. After 1 hour Panavia F2 showed the next greatest cytotoxicity, but after 24-hours and oneweek intervals Rely X Plus showed the next greatest cytotoxicity. The results further showed that cytotoxicity decreased significantly in the Panavia F2 group with time (p<0.005), cytotoxicity increased significantly in the Rely X Plus group with time (p<0.001), and the Harvard cement group failed to showed no noticeable change in cytotoxicity with time. Although this study has limitations, it provides evidence that Harvard zinc phosphate cement is the most cytotoxic product and Panavia F2 appears to be the least cytotoxic cement over time.

Comparative evaluation of marginal leakage of provisional crowns cemented with different temporary luting cements: In vitro study

PubMed Central

Arora, Sheen Juneja; Arora, Aman; Upadhyaya, Viram; Jain, Shilpi

2016-01-01

Background or Statement of Problem: As, the longevity of provisional restorations is related to, a perfect adaptation and a strong, long-term union between restoration and teeth structures, therefore, evaluation of marginal leakage of provisional restorative materials luted with cements using the standardized procedures is essential. Aims and Objectives: To compare the marginal leakage of the provisional crowns fabricated from Autopolymerizing acrylic resin crowns and bisphenol A-glycidyl dimethacrylate (BIS-GMA) resin crowns. To compare the marginal leakage of the provisional crowns fabricated from autopolymerizing acrylic resin crowns and BIS-GMA resin crowns cemented with different temporary luting cements. To compare the marginal leakage of the provisional crowns fabricated from autopolymerizing acrylic resin (SC-10) crowns cemented with different temporary luting cements. To compare the marginal leakage of the provisional crowns fabricated from BIS-GMA resin crowns (Protemp 4) cemented with different temporary luting cements. Methodology: Freshly extracted 60 maxillary premolars of approximately similar dimensions were mounted in dental plaster. Tooth reduction with shoulder margin was planned to use a customized handpiece-holding jig. Provisional crowns were prepared using the wax pattern fabricated from computer aided designing/computer aided manufacturing milling machine following the tooth preparation. Sixty provisional crowns were made, thirty each of SC-10 and Protemp 4 and were then cemented with three different luting cements. Specimens were thermocycled, submerged in a 2% methylene blue solution, then sectioned and observed under a stereomicroscope for the evaluation of marginal microleakage. A five-level scale was used to score dye penetration in the tooth/cement interface and the results of this study was analyzed using the Chi-square test, Mann–Whitney U-test, Kruskal–Wallis H-test and the results were statistically significant P < 0.05 the power of study - 80%. Results: Marginal leakage was significant in both provisional crowns cemented with three different luting cements along the axial walls of teeth (P < 0.05) confidence interval - 95%. Conclusion: The temporary cements with eugenol showed more microleakage than those without eugenol. SC-10 crowns showed more microleakage compared to Protemp 4 crowns. SC-10 crowns cemented with Kalzinol showed maximum microleakage and Protemp 4 crowns cemented with HY bond showed least microleakage. PMID:27134427

Injectable biomaterials for minimally invasive orthopedic treatments.

PubMed

Jayabalan, M; Shalumon, K T; Mitha, M K

2009-06-01

Biodegradable and injectable hydroxy terminated-poly propylene fumarate (HT-PPF) bone cement was developed. The injectable formulation consisting HT-PPF and comonomer, n-vinyl pyrrolidone, calcium phosphate filler, free radical catalyst, accelerator and radiopaque agent sets rapidly to hard mass with low exothermic temperature. The candidate bone cement attains mechanical strength more than the required compressive strength of 5 MPa and compressive modulus 50 MPa. The candidate bone cement resin elicits cell adhesion and cytoplasmic spreading of osteoblast cells. The cured bone cement does not induce intracutaneous irritation and skin sensitization. The candidate bone cement is tissue compatible without eliciting any adverse tissue reactions. The candidate bone cement is osteoconductive and inductive and allow osteointegration and bone remodeling. HT-PPF bone cement is candidate bone cement for minimally invasive radiological procedures for the treatment of bone diseases and spinal compression fractures.

The long-term in vivo behavior of polymethyl methacrylate bone cement in total hip arthroplasty

PubMed Central

2011-01-01

Background and purpose The long-term success of cemented total hip arthroplasty (THA) has been well established. Improved outcomes, both radiographically and clinically, have resulted mainly from advances in stem design and improvements in operating techniques. However, there is concern about the durability of bone cement in vivo. We evaluated the physical and chemical properties of CMW1 bone cements retrieved from patients undergoing revision THA. Methods CMW1 cements were retrieved from 14 patients who underwent acetabular revision because of aseptic loosening. The time in vivo before revision was 7–30 years. The bending properties of the retrieved bone cement were assessed using the three-point bending method. The molecular weight and chemical structure were analyzed by gel permeation chromatography and Fourier-transform infrared spectroscopy. The porosity of the bone cements was evaluated by 3-D microcomputer tomography. Results The bending strength decreased with increasing time in vivo and depended on the density of the bone cement, which we assume to be determined by the porosity. There was no correlation between molecular weight and time in vivo. The infrared spectra were similar in the retrieved cements and in the control CMW1 cements. Interpretation Our results indicate that polymer chain scission and significant hydrolysis do not occur in CMW1 cement after implantation in vivo, even in the long term. CMW1 cement was stable through long-term implantation and functional loading. PMID:22103279

Compressive, diametral tensile and biaxial flexural strength of cutting-edge calcium phosphate cements.

PubMed

Luo, Jun; Ajaxon, Ingrid; Ginebra, Maria Pau; Engqvist, Håkan; Persson, Cecilia

2016-07-01

Calcium phosphate cements (CPCs) are widely used in bone repair. Currently there are two main types of CPCs, brushite and apatite. The aim of this project was to evaluate the mechanical properties of particularly promising experimental brushite and apatite formulations in comparison to commercially available brushite- and apatite-based cements (chronOS(™) Inject and Norian(®) SRS(®), respectively), and in particular evaluate the diametral tensile strength and biaxial flexural strength of these cements in both wet and dry conditions for the first time. The cements׳ porosity and their compressive, diametral tensile and biaxial flexural strength were tested in wet (or moist) and dry conditions. The surface morphology was characterized by scanning electron microscopy. Phase composition was assessed with X-ray diffraction. It was found that the novel experimental cements showed better mechanical properties than the commercially available cements, in all loading scenarios. The highest compressive strength (57.2±6.5MPa before drying and 69.5±6.0MPa after drying) was found for the experimental brushite cement. This cement also showed the highest wet diametral tensile strength (10.0±0.8MPa) and wet biaxial flexural strength (30.7±1.8MPa). It was also the cement that presented the lowest porosity (approx. 12%). The influence of water content was found to depend on cement type, with some cements showing higher mechanical properties after drying and some no difference after drying. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Cement-in-cement stem revision for Vancouver type B periprosthetic femoral fractures after total hip arthroplasty. A 3-year follow-up of 23 cases.

PubMed

Briant-Evans, Toby W; Veeramootoo, Darmaraja; Tsiridis, Eleftherios; Hubble, Matthew J

2009-10-01

Revision surgery for periprosthetic femoral fractures around an unstable cemented femoral stem traditionally requires removal of existing cement. We propose a new technique whereby a well-fixed cement mantle can be retained in cases with simple fractures that can be reduced anatomically when a cemented revision is planned. This technique is well established in femoral stem revision, but not in association with a fracture. We treated 23 Vancouver type B periprosthetic femoral fractures by reducing the fracture and cementing a revision stem into the pre-existing cement mantle, with or without supplementary fixation. 3 patients died in the first 6 months for reasons unrelated to surgery. In addition, 1 was too frail to attend follow-up and was therefore excluded from the study, and 1 patient underwent revision surgery for a nonunion. The remaining 18 cases all healed with radiographic union after an average time of 4.4 (2-11) months. There was no sign of loosening or subsidence of the revision stems within the old cement mantle in any of these cases at the most recent follow-up after an average of 3 (0.3-9) years. Our results support the use of the cement-in-cement revision in anatomically reducible periprosthetic fractures with a well-preserved pre-existing cement mantle. This technique is particularly useful for the elderly patient and for those who are not fit for prolonged surgical procedures.

Porosity of different dental luting cements.

PubMed

Milutinović-Nikolić, Aleksandra D; Medić, Vesna B; Vuković, Zorica M

2007-06-01

The aim of this in vitro study was to compare open porosity and pore size distribution of different types of luting cements (zinc phosphate and polycarboxylate produced by Harvard Cement, Great Britain, glass-ionomer product GC Fuji I, GC Corporation, Japan, and Panavia F, resin based composite cement, Kurraray Co. Ltd. Japan) using mercury intrusion porosimetry and use it as an additional parameter for ranging the quality of cements used in prosthetics. Samples were hand mixed in accordance with the manufacturer's instructions and formed in cylindrical test specimens. Density of samples was determined using a pycnometer while porous structure was estimated using high pressure mercury intrusion porosimeter enabling estimation of pore diameters in interval 7.5-15,000 nm. The polycarboxylate cement posses the highest porosity and specific pore volume among investigated cements. By comparison of the results obtained for zinc phosphate and glass-ionomer cement, it can be observed that according to some textural properties zinc phosphate cement is better choice (smaller specific pore volume and absence of macropores larger than 1 microm) while according to other textural properties the glass-ionomer has advantage (smaller porosity). The resin based composite cement poses the most desired porous structure for prosthetic application among the investigated cements (the lowest porosity and specific pore volume and all identified pores are smaller than 20 nm). Based on results of this study, it is possible to estimate the efficiency of luting cements to protect the interior of tooth from penetration of oral fluids, bacteria and bacterial toxins into unprotected dentine.

[Cement augmentation on the spine : Biomechanical considerations].

PubMed

Kolb, J P; Weiser, L; Kueny, R A; Huber, G; Rueger, J M; Lehmann, W

2015-09-01

Vertebral compression fractures are the most common osteoporotic fractures. Since the introduction of vertebroplasty and screw augmentation, the management of osteoporotic fractures has changed significantly. The biomechanical characteristics of the risk of adjacent fractures and novel treatment modalities for osteoporotic vertebral fractures, including pure cement augmentation by vertebroplasty, and cement augmentation of screws for posterior instrumentation, are explored. Eighteen human osteoporotic lumbar spines (L1-5) adjacent to vertebral bodies after vertebroplasty were tested in a servo-hydraulic machine. As augmentation compounds we used standard cement and a modified low-strength cement. Different anchoring pedicle screws were tested with and without cement augmentation in another cohort of human specimens with a simple pull-out test and a fatigue test that better reflects physiological conditions. Cement augmentation in the osteoporotic spine leads to greater biomechanical stability. However, change in vertebral stiffness resulted in alterations with the risk of adjacent fractures. By using a less firm cement compound, the risk of adjacent fractures is significantly reduced. Both screw augmentation techniques resulted in a significant increase in the withdrawal force compared with the group without cement. Augmentation using perforated screws showed the highest stability in the fatigue test. The augmentation of cement leads to a significant change in the biomechanical properties. Differences in the stability of adjacent vertebral bodies increase the risk of adjacent fractures, which could be mitigated by a modified cement compound with reduced strength. Screws that were specifically designed for cement application displayed greatest stability in the fatigue test.

Experimental Study on Artificial Cemented Sand Prepared with Ordinary Portland Cement with Different Contents.

PubMed

Li, Dongliang; Liu, Xinrong; Liu, Xianshan

2015-07-02

Artificial cemented sand test samples were prepared by using ordinary Portland cement (OPC) as the cementing agent. Through uniaxial compression tests and consolidated drained triaxial compression tests, the stress-strain curves of the artificial cemented sand with different cementing agent contents (0.01, 0.03, 0.05 and 0.08) under various confining pressures (0.00 MPa, 0.25 MPa, 0.50 MPa and 1.00 MPa) were obtained. Based on the test results, the effect of the cementing agent content ( C v ) on the physical and mechanical properties of the artificial cemented sand were analyzed and the Mohr-Coulomb strength theory was modified by using C v . The research reveals that when C v is high (e.g., C v = 0.03, 0.05 or 0.08), the stress-strain curves of the samples indicate a strain softening behavior; under the same confining pressure, as C v increases, both the peak strength and residual strength of the samples show a significant increase. When C v is low (e.g., C v = 0.01), the stress-strain curves of the samples indicate strain hardening behavior. From the test data, a function of C v (the cementing agent content) with c ' (the cohesion force of the sample) and Δϕ' (the increment of the angle of shearing resistance) is obtained. Furthermore, through modification of the Mohr-Coulomb strength theory, the effect of cementing agent content on the strength of the cemented sand is demonstrated.

A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation

PubMed Central

Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen

2016-01-01

AIM: To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. MATERIALS AND METHOD: The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. RESULTS: GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. CONCLUSION: It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation. PMID:28028417

Microleakage along Glassix glass fibre posts cemented with three different materials assessed using a fluid transport system.

PubMed

Rogić-Barbić, M; Segović, S; Pezelj-Ribarić, S; Borcić, J; Jukić, S; Anić, I

2006-05-01

To evaluate the microleakage along Glassix fibre posts cemented with three different materials. The root canals of maxillary central incisor teeth were filled and restored with Glassix posts (Harald Nordin sa, Chailly/Montreux, Switzerland) cemented with either a zinc-phosphate Harvard cement (Richter & Hoffmann, Harvard Dental GmbH, Berlin, Germany), Fuji PLUS cement (GC Corporation, Tokyo, Japan) or Variolink II cement (Vivadent, Schaan, Lichtenstein) in three groups of 15 canals each. Twenty unrestored canals served as a control group, 10 filled with gutta-percha and sealer (negative control group), the remaining 10 with gutta-percha only (positive control group). Coronal microleakage was evaluated using a fluid transport system. The movement of an air bubble in a capillary glass tube connected to the apex of the experimental root section was measured over 5-min periods. Measurements were performed four times for each specimen and the mean values recorded. ANOVA and Duncan's test were performed. The positive control group had the highest values of microleakage. Amongst experimental groups, the highest values of microleakage occurred in the group with the posts cemented with Harvard cement, followed by Fuji PLUS and Variolink II cements. Groups with Fuji PLUS, Variolink II and the negative control group had significantly (P < 0.00001) less microleakage compared with the Harvard cement group and the positive control group. Canals with Glassix posts cemented with Variolink II and Fuji PLUS cement had the least leakage when assessed using a fluid transport system.

Retention of metal-ceramic crowns with contemporary dental cements.

PubMed

Johnson, Glen H; Lepe, Xavier; Zhang, Hai; Wataha, John C

2009-09-01

New types of crown and bridge cement are in use by practitioners, and independent studies are needed to assess their effectiveness. The authors conducted a study in three parts (study A, study B, and study C) and to determine how well these new cements retain metal-ceramic crowns. The authors prepared teeth with a 20-degree taper and a 4-millimeter length. They cast high-noble metal-ceramic copings, then fitted and cemented them with a force of 196 newtons. The types of cements they used were zinc phosphate, resin-modified glass ionomer, conventional resin and self-adhesive modified resin. They thermally cycled the cemented copings, then removed them. They recorded the removal force and calculated the stress of dislodgment by using the surface area of each preparation. They used a single-factor analysis of variance to analyze the data (alpha = .05). The mean stresses necessary to remove crowns, in megapascals, were 8.0 for RelyX Luting (3M ESPE, St. Paul, Minn.), 7.3 for RelyX Unicem (3M ESPE), 5.7 for Panavia F (Kuraray America, New York) and 4.0 for Fuji Plus (GC America, Alsip, Ill.) in study A; 8.1 for RelyX Luting, 2.6 for RelyX Luting Plus (3M ESPE) and 2.8 for Fuji CEM (GC America) in study B; and 4.9 for Maxcem (Kerr, Orange, Calif.), 4.0 for BisCem (Bisco, Schaumburg, Ill.), 3.7 for RelyX Unicem Clicker (3M ESPE), 2.9 for iCEM (Heraeus Kulzer, Armonk, N.Y.) and 2.3 for Fleck's Zinc Cement (Keystone Industries, Cherry Hill, N.J.) in study C. Powder-liquid versions of new cements were significantly more retentive than were paste-paste versions of the same cements. The mean value of crown removal stress for the new self-adhesive modified-resin cements varied appreciably among the four cements tested. All cements retained castings as well as or better than did zinc phosphate cement. Powder-liquid versions of cements, although less convenient to mix, may be a better clinical choice when crown retention is an issue. All cements tested will retain castings adequately on ideal preparations because the corresponding removal stresses are comparable with or higher than those associated with zinc phosphate. Powder-liquid resin-modified glass ionomer cement, selected self-adhesive modified-resin cements and conventional resin cements provide additional retention when desired.

Cementing a wellbore using cementing material encapsulated in a shell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.

A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in themore » space between the wellbore and the pipe.« less

Crushed cement concrete substitution for construction aggregates; a materials flow analysis

USGS Publications Warehouse

Kelly, Thomas

1998-01-01

An analysis of the substitution of crushed cement concrete for natural construction aggregates is performed by using a materials flow diagram that tracks all material flows into and out of the cement concrete portion of the products made with cement concrete: highways, roads, and buildings. Crushed cement concrete is only one of the materials flowing into these products, and the amount of crushed cement concrete substituted influences the amount of other materials in the flow. Factors such as availability and transportation costs, as well as physical properties, that can affect stability and finishability, influence whether crushed cement concrete or construction aggregates should be used or predominate for a particular end use.

Assessment of Physical and Mechanical Properties of Cement Panel Influenced by Treated and Untreated Coconut Fiber Addition

NASA Astrophysics Data System (ADS)

Abdullah, Alida; Jamaludin, Shamsul Baharin; Anwar, Mohamed Iylia; Noor, Mazlee Mohd; Hussin, Kamarudin

This project was conducted to produce a cement panel with the addition of treated and untreated coconut fiber in cement panel. Coconut fiber was added to replace coarse aggregate (sand) in this cement panel. In this project, the ratios used to design the mixture were 1:1:0, 1:0.97:0.03, 1:0.94:0.06, 1:0.91:0.09 (cement: sand: coconut fiber). The water cement ratio was constant at 0.55. The sizes of sample tested were, 160 mm x 40 mm x 40 mm for compression test, and 100 mm x 100 mm x 40 mm for density, moisture content and water absorption tests. After curing samples for 28 days, it was found that the addition of coconut fiber, further increase in compressive strength of cement panel with untreated coconut fiber. Moisture content of cement panel with treated coconut fiber increased with increasing content of coconut fiber whereas water absorption of cement panel with untreated coconut fiber increased with increasing content of coconut fiber. The density of cement panel decreased with the addition of untreated and treated coconut fiber.

Influence of Blended Cements with Calcareous Fly Ash on Chloride Ion Migration and Carbonation Resistance of Concrete for Durable Structures

PubMed Central

Glinicki, Michał A.; Jóźwiak-Niedźwiedzka, Daria; Gibas, Karolina; Dąbrowski, Mariusz

2016-01-01

The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement—ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash. PMID:28787821

Evaluation of the strength and radiopacity of Portland cement with varying additions of bismuth oxide.

PubMed

Saliba, E; Abbassi-Ghadi, S; Vowles, R; Camilleri, J; Hooper, S; Camilleri, J

2009-04-01

To study the effect of addition of various proportions of bismuth oxide on compressive strength and radiopacity of Portland cement. The compressive strength of white Portland cement and cement replaced with 10, 15, 20, 25 and 30% bismuth oxide was evaluated by testing cylinders 6 mm in diameter and 12 mm high. Twelve cylinders were tested for each material under study. The radiopacity of the cements tested was evaluated using an aluminium step-wedge and densitometer. The optical density was compared with the relevant thickness of aluminium (Al). Statistical analysis was performed using Analysis of Variance (ANOVA) with P = 0.05 and Tukey test to perform multiple comparison tests. Various additions of bismuth oxide had no significant effect on the strength of the material when compared with the unmodified Portland cement (P > 0.05). The radiopacity of the cements tested ranged from 2.02 mm Al for Portland cement to 9.79 mm Al for the highest bismuth replacement. Addition of bismuth oxide did not affect the compressive strength of Portland cement. All the bismuth oxide cement mixtures had radio-opacities higher than 3 mm thickness of aluminium.

The Effect of Curing Temperature on the Properties of Cement Pastes Modified with TiO2 Nanoparticles

PubMed Central

Pimenta Teixeira, Karine; Perdigão Rocha, Isadora; De Sá Carneiro, Leticia; Flores, Jessica; Dauer, Edward A.; Ghahremaninezhad, Ali

2016-01-01

This paper investigates the effect of curing temperature on the hydration, microstructure, compressive strength, and transport of cement pastes modified with TiO2 nanoparticles. These characteristics of cement pastes were studied using non-evaporable water content measurement, X-ray diffraction (XRD), compressive strength test, electrical resistivity and porosity measurements, and scanning electron microscopy (SEM). It was shown that temperature enhanced the early hydration. The cement pastes cured at elevated temperatures generally showed an increase in compressive strength at an early age compared to the cement paste cured at room temperature, but the strength gain decreased at later ages. The electrical resistivity of the cement pastes cured at elevated temperatures was found to decrease more noticeably at late ages compared to that of the room temperature cured cement paste. SEM examination indicated that hydration product was more uniformly distributed in the microstructure of the cement paste cured at room temperature compared to the cement pastes cured at elevated temperatures. It was observed that high temperature curing decreased the compressive strength and electrical resistivity of the cement pastes at late ages in a more pronounced manner when higher levels of TiO2 nanoparticles were added. PMID:28774073

Substantial global carbon uptake by cement carbonation

NASA Astrophysics Data System (ADS)

Xi, Fengming; Davis, Steven J.; Ciais, Philippe; Crawford-Brown, Douglas; Guan, Dabo; Pade, Claus; Shi, Tiemao; Syddall, Mark; Lv, Jie; Ji, Lanzhu; Bing, Longfei; Wang, Jiaoyue; Wei, Wei; Yang, Keun-Hyeok; Lagerblad, Björn; Galan, Isabel; Andrade, Carmen; Zhang, Ying; Liu, Zhu

2016-12-01

Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 2013. Considerable attention has been paid to quantifying these industrial process emissions from cement production, but the natural reversal of the process--carbonation--has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO2, increasing from 0.10 GtC yr-1 in 1998 to 0.25 GtC yr-1 in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories.

Effect of Self-Adhesive and Separate Etch Adhesive Dual Cure Resin Cements on the Bond Strength of Fiber Post to Dentin at Different Parts of the Root.

PubMed

Amiri, Ehsan Mohamadian; Balouch, Fariba; Atri, Faezeh

2017-05-01

Bonding of fiber posts to intracanal dentin is challenging in the clinical setting. This study aimed to compare the effect of self-adhesive and separate etch adhesive dual cure resin cements on the bond strength of fiber post to dentin at different parts of the root. This in-vitro experimental study was conducted on 20 single-rooted premolars. The teeth were decoronated at 1mm coronal to the cementoenamel junction (CEJ), and the roots underwent root canal treatment. Post space was prepared in the roots. Afterwards, the samples were randomly divided into two groups. In group 1, the fiber posts were cemented using Rely X Unicem cement, while in group 2, the fiber posts were cemented using Duo-Link cement, according to the manufacturer's instructions. The intracanal post in each root was sectioned into three segments of coronal, middle, and apical, and each cross-section was subjected to push-out bond strength test at a crosshead speed of 1mm/minute until failure. Push-out bond strength data were analyzed using independent t-test and repeated measures ANOVA. The bond strength at the middle and coronal segments in separate etch adhesive cement group was higher than that in self-adhesive cement group. However, the bond strength at the apical segment was higher in self-adhesive cement group compared to that in the other group. Overall, the bond strength in separate etch adhesive cement group was significantly higher than that in self-adhesive cement group (P<0.001). Bond strength of fiber post to intracanal dentin is higher after the use of separate etch adhesive cement compared to self-adhesive cement.

Preparation and evaluation of a novel glass-ionomer cement with antibacterial functions.

PubMed

Xie, Dong; Weng, Yiming; Guo, Xia; Zhao, Jun; Gregory, Richard L; Zheng, Cunge

2011-05-01

The objective of this study was to use the newly synthesized poly(quaternary ammonium salt) (PQAS)-containing polyacid to formulate the light-curable glass-ionomer cements and study the effect of the PQAS on the compressive strength and antibacterial activity of the formed cements. The functional QAS and their constructed PQAS were synthesized, characterized and formulated into the experimental high-strength cements. Compressive strength (CS) and Streptococcus mutans viability were used to evaluate the mechanical strength and antibacterial activity of the cements. Fuji II LC cement was used as control. The specimens were conditioned in distilled water at 37°C for 24 h prior to testing. The effects of the substitute chain length, loading as well as grafting ratio of the QAS and aging on CS and S. mutans viability were investigated. All the PQAS-containing cements showed a significant antibacterial activity, accompanying with an initial CS reduction. The effects of the chain length, loading and grafting ratio of the QAS were significant. Increasing chain length, loading, grafting ratio significantly enhanced antibacterial activity but reduced the initial CS. Under the same substitute chain length, the cements containing QAS bromide were found to be more antibacterial than those containing QAS chloride although the CS values of the cements were not statistically different from each other, suggesting that we can use QAS bromide directly without converting bromide to chloride. The experimental cement showed less CS reduction and higher antibacterial activity than Fuji II LC. The long-term aging study suggests that the cements may have a long-lasting antibacterial function. This study developed a novel antibacterial glass-ionomer cement. Within the limitations of this study, it appears that the experimental cement is a clinically attractive dental restorative due to its high mechanical strength and antibacterial function. Published by Elsevier Ltd.

Porosity and Permeability Evolution in Cemented Rock Cores under Reactive Flowing Conditions: Comparative Analysis between Limestone and Sandstone Host Rocks

NASA Astrophysics Data System (ADS)

Cao, P.; Karpyn, Z.; Li, L.

2013-12-01

CO2-brine has the potential to alter wellbore cement in depleted oil and gas reservoirs under geological CO2 sequestration conditions. A better understanding of CO2-brine-cement-rock interaction is needed to evaluate the seal integrity of candidate sequestration formation in the long run. This work investigates possible alteration of wellbore cement when bonded by different host formation rock upon exposure to CO2-saturated brine. Composite cement-sandstone and cement-limestone core samples were created to perform reactive coreflood experiments. After an eight-day dynamic flow-through period, both cores had a similar extent of porosity increase, while the cement-limestone core experienced a ten-fold higher increase in permeability. With the aid of X-ray Micro-CT imaging and Scanning Electron Microscopy, it is observed that cement underwent greater degradation at the cement-sandstone interface. Degradation of cement-limestone core mainly took place on the host rock matrix. Worm holes were developed and a solution channel was formed in the limestone, creating a dominant flow path that altered both flow and reaction behavior. Limestone buffered the injected acidic brine preventing further deterioration of cement near the core outlet. Changes in fluid chemistry of limestone and sandstone coreflood effluents are compared. Results from this work are aimed at assisting the development and validation of robust reactive transport models through direct measurement of cemented rock core porosity and permeability evolution as well as the effluent aqueous chemistry change. This will subsequently improve predictive capabilities of reactive transport models associated with CO2 sequestration in geologic environments. Permeability Evolution of Cement-Rock Core Sample during Dynamic Flow of CO2-Brine

Cement Leakage in Percutaneous Vertebral Augmentation for Osteoporotic Vertebral Compression Fractures: Analysis of Risk Factors.

PubMed

Xie, Weixing; Jin, Daxiang; Ma, Hui; Ding, Jinyong; Xu, Jixi; Zhang, Shuncong; Liang, De

2016-05-01

The risk factors for cement leakage were retrospectively reviewed in 192 patients who underwent percutaneous vertebral augmentation (PVA). To discuss the factors related to the cement leakage in PVA procedure for the treatment of osteoporotic vertebral compression fractures. PVA is widely applied for the treatment of osteoporotic vertebral fractures. Cement leakage is a major complication of this procedure. The risk factors for cement leakage were controversial. A retrospective review of 192 patients who underwent PVA was conducted. The following data were recorded: age, sex, bone density, number of fractured vertebrae before surgery, number of treated vertebrae, severity of the treated vertebrae, operative approach, volume of injected bone cement, preoperative vertebral compression ratio, preoperative local kyphosis angle, intraosseous clefts, preoperative vertebral cortical bone defect, and ratio and type of cement leakage. To study the correlation between each factor and cement leakage ratio, bivariate regression analysis was employed to perform univariate analysis, whereas multivariate linear regression analysis was employed to perform multivariate analysis. The study included 192 patients (282 treated vertebrae), and cement leakage occurred in 100 vertebrae (35.46%). The vertebrae with preoperative cortical bone defects generally exhibited higher cement leakage ratio, and the leakage is typically type C. Vertebrae with intact cortical bones before the procedure tend to experience type S leakage. Univariate analysis showed that patient age, bone density, number of fractured vertebrae before surgery, and vertebral cortical bone were associated with cement leakage ratio (P<0.05). Multivariate analysis showed that the main factors influencing bone cement leakage are bone density and vertebral cortical bone defect, with standardized partial regression coefficients of -0.085 and 0.144, respectively. High bone density and vertebral cortical bone defect are independent risk factors associated with bone cement leakage.

Radiopacity of portland cement associated with different radiopacifying agents.

PubMed

Húngaro Duarte, Marco Antonio; de Oliveira El Kadre, Guâniara D'arc; Vivan, Rodrigo Ricci; Guerreiro Tanomaru, Juliane Maria; Tanomaru Filho, Mário; de Moraes, Ivaldo Gomes

2009-05-01

This study evaluated the radiopacity of Portland cement associated with the following radiopacifying agents: bismuth oxide, zinc oxide, lead oxide, bismuth subnitrate, bismuth carbonate, barium sulfate, iodoform, calcium tungstate, and zirconium oxide. A ratio of 20% radiopacifier and 80% white Portland cement by weight was used for analysis. Pure Portland cement and dentin served as controls. Cement/radiopacifier and dentin disc-shaped specimens were fabricated, and radiopacity testing was performed according to the ISO 6876/2001 standard for dental root sealing materials. Using Insight occlusal films, the specimens were radiographed near to a graduated aluminum stepwedge varying from 2 to 16 mm in thickness. The radiographs were digitized and radiopacity compared with the aluminum stepwedge using Digora software (Orion Corporation Soredex, Helsinki, Finland). The radiographic density data were converted into mmAl and analyzed statistically by analysis of variance and Tukey-Kramer test (alpha = 0.05). The radiopacity of pure Portland cement was significantly lower (p < 0.05) than that of dentin, whereas all cement/radiopacifier mixtures were significantly more radiopaque than dentin and Portland cement alone (p < 0.05). Portland cement/bismuth oxide and Portland cement/lead oxide presented the highest radiopacity values and differed significantly from the other materials (p < 0.05), whereas Portland cement/zinc oxide presented the lowest radiopacity values of all mixtures (p < 0.05). All tested substances presented higher radiopacity than that of dentin and may potentially be added to the Portland cement as radiopacifying agents. However, the possible interference of the radiopacifiers with the setting chemistry, biocompatibility, and physical properties of the Portland cement should be further investigated before any clinical recommendation can be done.

Validation of a measuring technique with computed tomography for cement penetration into trabecular bone underneath the tibial tray in total knee arthroplasty on a cadaver model

PubMed Central

2014-01-01

Background In total knee arthroplasty (TKA), cement penetration between 3 and 5 mm beneath the tibial tray is required to prevent loosening of the tibia component. The objective of this study was to develop and validate a reliable in vivo measuring technique using CT imaging to assess cement distribution and penetration depth in the total area underneath a tibia prosthesis. Methods We defined the radiodensity ranges for trabecular tibia bone, polymethylmethacrylate (PMMA) cement and cement-penetrated trabecular bone and measured the percentages of cement penetration at various depths after cementing two tibia prostheses onto redundant femoral heads. One prosthesis was subsequently removed to examine the influence of the metal tibia prostheses on the quality of the CT images. The percentages of cement penetration in the CT slices were compared with percentages measured with photographs of the corresponding transversal slices. Results Trabecular bone and cement-penetrated trabecular bone had no overlap in quantitative scale of radio-density. There was no significant difference in mean HU values when measuring with or without the tibia prosthesis. The percentages of measured cement-penetrated trabecular bone in the CT slices of the specimen were within the range of percentages that could be expected based on the measurements with the photographs (p = 0.04). Conclusions CT scan images provide valid results in measuring the penetration and distribution of cement into trabecular bone underneath the tibia component of a TKA. Since the proposed method does not turn metal elements into artefacts, it enables clinicians to assess the width and density of the cement mantle in vivo and to compare the results of different cementing methods in TKA. PMID:25158996

Effect of different resin luting cements on the marginal fit of lithium disilicate pressed crowns.

PubMed

Mounajjed, Radek; Salinas, Thomas J; Ingr, Tomas; Azar, Basel

2017-11-15

The vertical marginal discrepancy of restorations can increase upon cementation, and poor marginal fit can lead to cement dissolution, marginal discoloration, microleakage, and secondary caries. The amount of increase is related to the type of luting cement used, but how lithium disilicate pressed crowns are affected by different resin cements is unclear. The purpose of this in vitro study was to compare the effect of using different resin luting cements on the vertical marginal discrepancy of lithium disilicate pressed crowns. A total of 18 intact extracted mandibular third molars were disinfected in a solution of 10% formalin for 7 days and were then prepared to receive a ceramic crown. Impressions were made with polyvinyl siloxane and lithium disilicate pressed crowns made and cemented with 1 of 3 resin luting cements. The marginal discrepancy was measured at 4 points on the finishing line of each tooth, with optical microscopy at ×200 magnification before and after cementation. Statistical analysis was done with the Kruskal-Wallis test to compare the median marginal increase among the 3 groups. The least amount of marginal increase after cementation was with Harvard PremiumFlow cement, with an average marginal increase of 42 ±11 μm. RelyX Ultimate cement increased the margins by an average 45 ±29 μm. The highest marginal increase was found in the Enamel Plus HRi preheated composite resin group (116 ±47 μm). The marginal increase of pressed crowns cemented with preheated composite resin (Enamel Plus HRi) exceeded the clinically acceptable range of marginal discrepancy. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

[Correlation analysis of cement leakage with volume ratio of intravertebral bone cement to vertebral body and vertebral body wall incompetence in percutaneous vertebroplasty for osteoporotic vertebral compression fractures].

PubMed

Liang, De; Ye, Linqiang; Jiang, Xiaobing; Huang, Weiquan; Yao, Zhensong; Tang, Yongchao; Zhang, Shuncong; Jin, Daxiang

2014-11-01

To investigate the risk factors of cement leakage in percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fracture (OVCF). Between March 2011 and March 2012, 98 patients with single level OVCF were treated by PVP, and the clinical data were analyzed retrospectively. There were 13 males and 85 females, with a mean age of 77.2 years (range, 54-95 years). The mean disease duration was 43 days (range, 15-120 days), and the mean T score of bone mineral density (BMD) was -3.8 (range, -6.7- -2.5). Bilateral transpedicular approach was used in all the patients. The patients were divided into cement leakage group and no cement leakage group by occurrence of cement leakage based on postoperative CT. Single factor analysis was used to analyze the difference between 2 groups in T score of BMD, operative level, preoperative anterior compression degree of operative vertebrae, preoperative middle compression degree of operative vertebrae, preoperative sagittal Cobb angle of operative vertebrae, preoperative vertebral body wall incompetence, cement volume, and volume ratio of intravertebral bone cement to vertebral body. All relevant factors were introduced to logistic regression analysis to analyze the risk factors of cement leakage. All procedures were performed successfully. The mean operation time was 40 minutes (range, 30-50 minutes), and the mean volume ratio of intravertebral bone cement to vertebral body was 24.88% (range, 7.84%-38.99%). Back pain was alleviated significantly in all the patients postoperatively. All patients were followed up with a mean time of 8 months (range, 6-12 months). Cement leakage occurred in 49 patients. Single factor analysis showed that there were significant differences in the volume ratio of intravertebral bone cement to vertebral body and preoperative vertebral body wall incompetence between 2 groups (P < 0.05), while no significant difference in T score of BMD, operative level, preoperative anterior compression degree of operative vertebrae, preoperative middle compression degree of operative vertebrae, preoperative sagittal Cobb angle of operative vertebrae, and cement volume (P > 0.05). The logistic regression analysis showed that the volume ratio of intravertebral bone cement to vertebral body (P < 0.05) and vertebral body wall incompetence (P < 0.05) were the risk factors for occurrence of cement leakage. The volume ratio of intravertebral bone cement to vertebral body and vertebral body wall incompetence are risk factors of cement leakage in PVP for OVCF. Cement leakage is easy to occur in operative level with vertebral body wall incompetence and high volume ratio of intravertebral bone cement to vertebral body.

The performance of three vacuum-mixing cement guns--a comparison of the fatigue properties of simplex P cement.

PubMed

Yau, W P; Ng, T P; Chiu, K Y; Poon, K C; Ho, W Y; Luk, D K

2001-01-01

We tested three commercially available cement-mixing systems (Howmedica, Summit and Stryker). After mixing the cement was allowed to cure in metal moulds under standard conditions. Sixty-nine cement blocks were produced. The fatigue behavior of the blocks was tested until failure. A wide scattering of results was observed in all the three systems. Uneven mixing of the polymer and monomer was observed in the Howmedica system. A significantly stronger cement (P=0.018) was produced with the Stryker system.

Prevention of cement leakage into the hip joint by a standard cement plug during PFN-A cement augmentation: a technical note.

PubMed

Hanke, M; Djonov, V; Tannast, M; Keel, M J; Bastian, J D

2016-06-01

Medial penetration of the helical blade into the hip joint after fixation of trochanteric fractures using the proximal femur nail antirotation (PFN-A) is a potential failure mode. In low demand patients a blade exchange with cement augmentation may be an option if conversion to total hip arthroplasty is unfeasible to salvage the cut-through. This article describes a technique to avoid intraarticular cement leakage using a cement plug to close the defect in the femoral head caused by the cut-through.

Mounting system for optical frequency reference cavities

NASA Technical Reports Server (NTRS)

Notcutt, Mark (Inventor); Hall, John L. (Inventor); Ma, Long-Sheng (Inventor)

2008-01-01

A technique for reducing the vibration sensitivity of laser-stabilizing optical reference cavities is based upon an improved design and mounting method for the cavity, wherein the cavity is mounted vertically. It is suspended at one plane, around the spacer cylinder, equidistant from the mirror ends of the cavity. The suspension element is a collar of an extremely low thermal expansion coefficient material, which surrounds the spacer cylinder and contacts it uniformly. Once the collar has been properly located, it is cemented in place so that the spacer cylinder is uniformly supported and does not have to be squeezed at all. The collar also includes a number of cavities partially bored into its lower flat surface, around the axial bore. These cavities are support points, into which mounting base pins will be inserted. Hence the collar is supported at a minimum of three points.

Evaluation of tensile retention of Y-TZP crowns cemented on resin composite cores: effect of the cement and Y-TZP surface conditioning.

PubMed

Rippe, M P; Amaral, R; Oliveira, F S; Cesar, P F; Scotti, R; Valandro, L F; Bottino, M A

2015-01-01

This study evaluated the effect of the cement type (adhesive resin, self-adhesive, glass ionomer, and zinc phosphate) on the retention of crowns made of yttria-stabilized polycrystalline tetragonal zirconia (Y-TZP). Therefore, 108 freshly extracted molars were embedded in acrylic resin, perpendicular to their long axis, and prepared for full crowns: the crown preparations were removed and reconstructed using composite resin plus fiber posts with dimensions identical to the prepared dentin. The preparations were impressed using addition silicone, and Y-TZP copings were produced, which presented a special setup for the tensile testing. Cementation was performed with two adhesive resin cements (Multilink Automix, Ivoclar-Vivadent; RelyX ARC, 3M ESPE, St Paul, MN, USA), one self-adhesive resin cement (RelyX U100, 3M ESPE), one glass ionomer based cement (RelyX Luting, 3M ESPE), and one zinc phosphate cement (Cimento de Zinco, SS White, Rio de Janeiro, Brazil). For the resin cement groups, the inner surfaces of the crowns were subjected to three surface treatments: cleaning with isopropyl alcohol, tribochemical silica coating, or application of a thin low-fusing glass porcelain layer plus silanization. After 24 hours, all groups were subjected to thermocycling (6000 cycles) and included in a special device for tensile testing in a universal testing machine to test the retention of the infrastructure. After testing, the failure modes of all samples were analyzed under a stereomicroscope. The Kruskal-Wallis test showed that the surface treatment and cement type (α=0.05) affected the tensile retention results. The Multilink cement presented the highest tensile retention values, but that result was not statistically different from RelyX ARC. The surface treatment was statistically relevant only for the Multilink cement. The cement choice was shown to be more important than the crown surface treatment for cementation of a Y-TZP crown to a composite resin substrate.

Evaluation of effectiveness of cement removal from implant-retained crowns using a proposed circular crisscross flossing technique.

PubMed

Ferreira, Cimara Fortes; Shafter, Mohamed Amer; Jain, Vinay; Wicks, Russel Anthony; Linder, Erno; Ledo, Carlos Alberto da Silva

2018-02-13

Extruded cement during dental implant crown cementation may cause peri-implant diseases if not removed adequately. Evaluate the efficiency of removal of cement after cementation of implant crowns using an experimental "circular crisscross flossing technique (CCCFT) flossing technique, compared to the conventional "C" shape flossing technique (CSFT). Twenty-four patients rendered 29 experimental and 29 control crowns. Prefabricated abutments were secured to the implant with the margins at least 1 mm subgingivally. The abutments were scanned using CADCAM technology and Emax crowns were fabricated in duplicates. Each crown was cemented separately and excess cement was removed using the CSFT and the CCFT techniques. After completion of cementation was completed, the screw access holes were accessed and the crown was unscrewed along with the abutment. The samples were disinfected using 70% ethanol for 10 minutes. Crowns were divided into 4 parts using a marker in order to facilitate measurement data collection. Vertical and horizontal measurements were made for extruded cement for each control and experimental groups by means of a digital microscope. One-hundred and seventeen measurements were made for each group. Mann-Whitney test was applied to verify statistical significance between the groups. The CCFT showed a highly statistically significant result (104.8 ± 13.66, p<0.0001) for cement removal compared with the CSFT (291.8 ± 21.96, p<0.0001). The vertical lengths of the extruded cement showed a median of 231.1 µm (IQR = 112.79 -398.39) and 43.62 µm (IQR = 0 - 180.21) for the control and the experimental flossing techniques, respectively. The horizontal length of the extruded cement showed a median of 987.1 µm (IQR = 476.7 - 1,933.58) and 139.2 µm (IQR = 0 - 858.28) for the control and the experimental flossing techniques, respectively. The CCFT showed highly statistically significant less cement after implant crowns cementation when compared with the CSFT.

Comparative Evaluation of Antibacterial Effect of Dental Luting Cements on Streptococcus mutans and Lactobacillus acidophilus: An In vitro Study.

PubMed

Feroz, Sma; Bhoyar, A; Khan, S

2016-12-01

This study aimed at evaluating and comparing the antibacterial activity of six types of dental luting cements on Streptococcus mutans and Lactobacillus acidophilus using the agar diffusion test (ADT) and the direct-contact test (DCT). The antibacterial activity in ADT was measured based on the diameter of the zone of inhibition formed, whereas in DCT the density of the bacterial suspension was measured. The lower the density of the suspension, the more antibacterial activity the cement possesses. Agar diffusion test was carried out on the bacteria. After an incubation period of 24 hours, the plates were checked for the presence of zone of inhibition. In DCT the cement was mixed and applied. Once the cement was set, bacterial suspension and brain-heart infusion medium was poured and incubated for 24 hours. After 24 hours, the plate was placed in the enzyme-linked immunosorbent assay plate reader, which measured the optical density of the fluid. The first set of data was recorded approximately 1 hour after incubation. Overall, three sets of data were recorded. Additional experiments were performed on set test materials that were allowed to age for 24 hours, 1 week, 1, 3, and 6 months. When using ADT only two cements zinc oxide eugenol (ZOE) and zinc polycarboxylate (ZPC) cement showed antibacterial activity against the test organisms. When using DCT, all cements showed some amount of antibacterial activity. Zinc oxide eugenol and ZPC cement showed highest amount of antibacterial activity against S. mutans and L. acidophilus respectively. Within the limitations of study, ZOE cement and ZPC cement were most effective against the tested microorganisms followed by the newer resin cement. The glass ionomer cement was the weakest of all. Patients with high caries index can be treated more effectively using the abovementioned cements.

Preparation and Characterization of Injectable Brushite Filled-Poly (Methyl Methacrylate) Bone Cement

PubMed Central

Rodriguez, Lucas C.; Chari, Jonathan; Aghyarian, Shant; Gindri, Izabelle M.; Kosmopoulos, Victor; Rodrigues, Danieli C.

2014-01-01

Powder-liquid poly (methyl methacrylate) (PMMA) bone cements are widely utilized for augmentation of bone fractures and fixation of orthopedic implants. These cements typically have an abundance of beneficial qualities, however their lack of bioactivity allows for continued development. To enhance osseointegration and bioactivity, calcium phosphate cements prepared with hydroxyapatite, brushite or tricalcium phosphates have been introduced with rather unsuccessful results due to increased cement viscosity, poor handling and reduced mechanical performance. This has limited the use of such cements in applications requiring delivery through small cannulas and in load bearing. The goal of this study is to design an alternative cement system that can better accommodate calcium-phosphate additives while preserving cement rheological properties and performance. In the present work, a number of brushite-filled two-solution bone cements were prepared and characterized by studying their complex viscosity-versus-test frequency, extrusion stress, clumping tendency during injection through a syringe, extent of fill of a machined void in cortical bone analog specimens, and compressive strength. The addition of brushite into the two-solution cement formulations investigated did not affect the pseudoplastic behavior and handling properties of the materials as demonstrated by rheological experiments. Extrusion stress was observed to vary with brushite concentration with values lower or in the range of control PMMA-based cements. The materials were observed to completely fill pre-formed voids in bone analog specimens. Cement compressive strength was observed to decrease with increasing concentration of fillers; however, the materials exhibited high enough strength for consideration in load bearing applications. The results indicated that partially substituting the PMMA phase of the two-solution cement with brushite at a 40% by mass concentration provided the best combination of the properties investigated. This alternative material may find applications in systems requiring highly injectable and viscous cements such as in the treatment of spinal fractures and bone defects. PMID:28788212

Does adding antibiotics to cement reduce the need for early revision in total knee arthroplasty?

PubMed

Bohm, Eric; Zhu, Naisu; Gu, Jing; de Guia, Nicole; Linton, Cassandra; Anderson, Tammy; Paton, David; Dunbar, Michael

2014-01-01

There is considerable debate about whether antibiotic-loaded bone cement should be used for fixation of TKAs. While antibiotics offer the theoretical benefit of lowering early revision due to infection, they may weaken the cement and thus increase the likelihood of aseptic loosening, perhaps resulting in a higher revision rate. We (1) compared the frequency of early knee revision arthroplasty in patients treated with antibiotic-loaded or non-antibiotic-loaded cement for initial fixation, (2) determined effects of age, sex, comorbidities, and surgeons' antibiotic-loaded cement usage patterns on revision rate, and (3) compared causes of revision (aseptic or septic) between groups. Our study sample was taken from the Canadian Joint Replacement Registry and Canada's Hospital Morbidity Database and included cemented TKAs performed between April 1, 2003, and March 31, 2008, including 20,016 TKAs inserted with non-antibiotic-loaded cement and 16,665 inserted with antibiotic-loaded cement. Chi-square test was used to compare the frequency of early revisions between groups. Cox regression modeling was used to determine whether revision rate would change by age, sex, comorbidities, or use of antibiotic-loaded cement. Similar Cox regression modeling was used to compare cause of revision between groups. Two-year revision rates were similar between the groups treated with non-antibiotic-loaded cement and antibiotic-loaded cement (1.40% versus 1.51%, p = 0.41). When controlling for age, sex, comorbidities, diabetes, and surgeons' antibiotic-loaded cement usage patterns, the revision risk likewise was similar between groups. Revision rates for infection were similar between groups; however, there were more revisions for aseptic loosening in the group treated with non-antibiotic-loaded cement (p = 0.02). The use of antibiotic-loaded cement in TKAs performed for osteoarthritis has no clinically significant effect on reducing revision within 2 years in patients who received perioperative antibiotics. Longer followup and confirmation of these findings with other national registries are warranted.

Influence of preheating the bonding agent of a conventional three-step adhesive system and the light activated resin cement on dentin bond strength

PubMed Central

Holanda, Daniel Brandão Vilela; França, Fabiana Mantovani Gomes; do Amaral, Flávia Lucisano Botelho; Flório, Flávia Martão; Basting, Roberta Tarkany

2013-01-01

Aims: to evaluate the influence of preheating the bonding agent (Scotchbond Multipurpose Adhesive/3M ESPE) and the light-activated resin cement (RelyX Venner/3M ESPE) on dentin microtensile bond strength. Materials and Methods: The exposed flat dentin surface of 40 human third molars were randomly distributed into four groups for cementation (SR Adoro/Ivoclar Vivadent) (n = 10): G1-bond and resin cement, both at room temperature (22°C), G2-bond preheated to 58°C and cement at room temperature (22°C), G3-bond at room temperature (22°C) and the cement preheated to 58°C, G4-bond preheated to 58°C and cement preheated to 58°C. Sticks of dentin/block set measuring approximately 1 mm2 were obtained and used for the microtensile bond strength test. All sticks had their failure mode classified. Statistical analysis used: Factorial analysis of variance was applied, 2 × 2 (bond × cement) (P < 0.05). Results: Preheating the bonding agent (P = 0.8411) or the cement (P = 0.7155), yielded no significant difference. The interaction bond × cement was not significant (P = 0.9389). Conclusions: Preheating the bond and/or the light-activated resin cement did not influence dentin bond strength or fracture failure mode. PMID:24347889

Probabilistic analysis of the influence of the bonding degree of the stem-cement interface in the performance of cemented hip prostheses.

PubMed

Pérez, M A; Grasa, J; García-Aznar, J M; Bea, J A; Doblaré, M

2006-01-01

The long-term behavior of the stem-cement interface is one of the most frequent topics of discussion in the design of cemented total hip replacements, especially with regards to the process of damage accumulation in the cement layer. This effect is analyzed here comparing two different situations of the interface: completely bonded and debonded with friction. This comparative analysis is performed using a probabilistic computational approach that considers the variability and uncertainty of determinant factors that directly compromise the damage accumulation in the cement mantle. This stochastic technique is based on the combination of probabilistic finite elements (PFEM) and a cumulative damage approach known as B-model. Three random variables were considered: muscle and joint contact forces at the hip (both for walking and stair climbing), cement damage and fatigue properties of the cement. The results predicted that the regions with higher failure probability in the bulk cement are completely different depending on the stem-cement interface characteristics. In a bonded interface, critical sites appeared at the distal and medial parts of the cement, while for debonded interfaces, the critical regions were found distally and proximally. In bonded interfaces, the failure probability was higher than in debonded ones. The same conclusion may be established for stair climbing in comparison with walking activity.

Elaborating the History of Our Cementing Societies: An in-Use Stock Perspective.

PubMed

Cao, Zhi; Shen, Lei; Løvik, Amund N; Müller, Daniel B; Liu, Gang

2017-10-03

Modern cities and societies are built fundamentally based on cement and concrete. The global cement production has risen sharply in the past decades due largely to urbanization and construction. Here we deployed a top-down dynamic material flow analysis (MFA) model to quantify the historical development of cement in-use stocks in residential, nonresidential, and civil engineering sectors of all world countries. We found that global cement production spreads unevenly among 184 countries, with China dominating the global production and consumption after the 1990s. Nearly all countries have shown an increasing trend of per capita cement in-use stock in the past century. The present per capita cement in-use stocks vary from 10 to 40 tonnes in major industrialized and transiting countries and are below 10 tonnes in developing countries. Evolutionary modes identified from historical patterns suggest that per capita in-use cement stock growth generally complies with an S-shape curve and relates closely to affluence and urbanization of a country, but more in-depth and bottom-up investigations are needed to better understand socioeconomic drivers behind stock growth. These identified in-use stock patterns can help us better estimate future demand of cement, explore strategies for emissions reduction in the cement industry, and inform CO 2 uptake potentials of cement based products and infrastructure in service.

Comparative evaluation of compressive strength, diametral tensile strength and shear bond strength of GIC type IX, chlorhexidine-incorporated GIC and triclosan-incorporated GIC: An in vitro study.

PubMed

Jaidka, Shipra; Somani, Rani; Singh, Deepti J; Shafat, Shazia

2016-04-01

To comparatively evaluate the compressive strength, diametral tensile strength, and shear bond strength of glass ionomer cement type IX, chlorhexidine-incorporated glass ionomer cement, and triclosan-incorporated glass ionomer cement. In this study, glass ionomer cement type IX was used as a control. Chlorhexidine diacetate, and triclosan were added to glass ionomer cement type IX powder, respectively, in order to obtain 0.5, 1.25, and 2.5% concentrations of the respective experimental groups. Compressive strength, diametral tensile strength, and shear bond strength were evaluated after 24 h using Instron Universal Testing Machine. The results obtained were statistically analyzed using the independent t-test, Dunnett test, and Tukey test. There was no statistical difference in the compressive strength, diametral tensile strength, and shear bond strength of glass ionomer cement type IX (control), 0.5% triclosan-glass ionomer cement, and 0.5% chlorhexidine-glass ionomer cement. The present study suggests that the compressive strength, diametral tensile strength, and shear bond strength of 0.5% triclosan-glass ionomer cement and 0.5% chlorhexidine-glass ionomer cement were similar to those of the glass ionomer cement type IX, discernibly signifying that these can be considered as viable options for use in pediatric dentistry with the additional value of antimicrobial property along with physical properties within the higher acceptable range.

Mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells following their exposure to a discoloration-free calcium aluminosilicate cement.

PubMed

Niu, Li-Na; Pei, Dan-Dan; Morris, Matthew; Jiao, Kai; Huang, Xue-Qing; Primus, Carolyn M; Susin, Lisiane F; Bergeron, Brian E; Pashley, David H; Tay, Franklin R

2016-10-01

An experimental discoloration-free calcium aluminosilicate cement has been developed with the intention of maximizing the beneficial attributes of tricalcium silicate cements and calcium aluminate cements. The present study examined the effects of this experimental cement (Quick-Set2) on the mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells (hDPSCs), by comparing the cellular responses with a commercially available tricalcium silicate cement (white mineral trioxide aggregate (ProRoot(®) MTA); WMTA). The osteogenic potential of hDPSCs exposed to the cements was examined using qRT-PCR for osteogenic gene expressions, Western blot for osteogenic-related protein expressions, alkaline phosphatase enzyme activity, Alizarin red S staining, Fourier transform infrared spectroscopy and transmission electron microscopy of extracellular calcium deposits. Results of the six assays indicated that osteogenic differentiation of hDPSCs was significantly enhanced after exposure to the tricalcium silicate cement or the experimental calcium aluminosilicate cement, with the former demonstrating better mineralogenic stimulation capacity. The better osteogenic stimulating effect of the tricalcium silicate cement on hDPSCs may be due to its relatively higher silicate content, or higher OH(-) and Ca(2+) release. Further investigations with the use of in vivo animal models are required to validate the potential augmenting osteogenic effects of the experimental discoloration-free calcium aluminosilicate cement. Published by Elsevier Ltd.

Characterization and analyses of acid-extractable and leached trace elements in dental cements.

PubMed

Camilleri, J; Kralj, P; Veber, M; Sinagra, E

2012-08-01

Determination of the elemental constitution and investigation of the total and leachable arsenic, chromium and lead in Portland cement, pure tricalcium silicate, Biodentine, Bioaggregate and mineral trioxide aggregate (MTA) Angelus. The chemical composition of Portland cement, MTA Angelus, tricalcium silicate cement, Biodentine and Bioaggregate was determined using X-ray fluorescence (XRF). Measurements of arsenic, lead and chromium were taken with inductively coupled plasma-mass spectrometry (ICP-MS), following acid digestion on the hydrated material and on leachates of cements soaked in Hank's balanced salt solution (HBSS). All the cements investigated had a similar oxide composition with the main oxide being calcium and silicon oxide. Both the Portland cement and MTA Angelus had an additional aluminium oxide. The dental cements included a radiopacifying material. All the materials tested had higher acid-extractable arsenic content than the level set by ISO 9917-1 (2007) and an acceptable level of lead. Regardless these high levels of trace elements present in the materials, the leaching in HBSS was minimal for all the dental material tested in contrast to the high levels displayed by Portland cement. Dental materials based on tricalcium silicate cement and MTA Angelus release minimal quantities of trace elements when in contact with simulated body fluids. The results of acid extraction could be affected by nonspecific matrix effects by the cement. © 2012 International Endodontic Journal.

Biomechanical Evaluation of All-Polyethylene Pegged Bony Ingrowth Glenoid Fixation Techniques on Implant Micromotion.

PubMed

Wiater, Brett P; Moravek, James E; Kurdziel, Michael D; Baker, Kevin C; Wiater, J Michael

2016-01-01

Newer glenoid components that allow for hybrid cement fixation via traditional cementation of peripheral pegs and bony ingrowth into an interference-fit central peg introduce the possibility of long-term biological fixation. However, little biomechanical work has been done on the initial stability of these components and the various fixation options. We conducted a study in which all-polyethylene glenoid components with a centrally fluted peg were implanted in polyurethane blocks with interference-fit, hybrid cement, and fully cemented fixation (5 per fixation group). Biomechanical evaluation of glenoid loosening, according to ASTM Standard F-2028-12, subjected the glenoids to 50,000 cycles of rim loading, and glenoid component motion was recorded with 2 differential variable reluctance transducers fixed to each glenoid prosthesis. Fully cemented fixation exhibited significantly less mean distraction in comparison with interference-fit fixation (P < .001) and hybrid cement fixation (P < .001). Hybrid cement fixation exhibited significantly less distraction (P < .001), more compression (P < .001), and no significant difference in glenoid translation (P = .793) in comparison with interference-fit fixation. Fully cemented fixation exhibited the most resistance to glenoid motion in comparison with hybrid cement fixation and interference-fit fixation. However, hybrid cement fixation and interference-fit fixation exhibited equivocal motion. Given these results, cementation of peripheral pegs may confer no additional initial stability over that provided by uncemented interference-fit fixation.

Bond strengths of custom cast and prefabricated posts luted with two cements.

PubMed

Aleisa, Khalil Ibrahim

2011-02-01

This in vitro study evaluated the bond strength of custom cast and prefabricated posts luted with resin or zinc phosphate cements into unobturated canals of extracted teeth. Forty-eight custom cast and prefabricated posts were placed into extracted single-rooted human teeth. Post-cavity preparation was 1.5 mm in diameter and 10 mm in depth. Specimens were randomly divided into 4 groups of 12 each. Two of the groups were then luted with resin cement, while the other two groups were luted with zinc phosphate cement. A pull-out bond strength evaluation was performed using a universal testing machine. The Kolmogorov-Smirnov test was used to prove normal distribution. Data were statistically analyzed using two-way ANOVA and the Student t test (alpha = .05). For both luting agents, the prefabricated posts group exhibited significantly less bond strength than the custom cast posts group (P = .0001). There were statistically significant differences in mean bond strength for the prefabricated posts group luted with resin cement vs the group cemented with zinc phosphate cement (P = .002). There was no significant difference between the mean bond strength values of custom cast posts luted with resin cement or zinc phosphate cement. Custom cast posts showed significantly greater bond strength than prefabricated posts when luted with either resin or zinc phosphate cements. The type of cement had less significance on the retention of custom cast posts.

LEACHING BOUNDARY IN CEMENT-BASED WASTE FORMS

EPA Science Inventory

Cement-based fixation systems are among the most commonly employed stabilization/solidification techniques. These cement haste mixtures, however, are vulnerable to ardic leaching solutions. Leaching of cement-based waste forms in acetic acid solutions with different acidic streng...

Microstructural characterization of catalysis product of nanocement based materials: A review

NASA Astrophysics Data System (ADS)

Sutan, Norsuzailina Mohamed; Izaitul Akma Ideris, Nur; Taib, Siti Noor Linda; Lee, Delsye Teo Ching; Hassan, Alsidqi; Kudnie Sahari, Siti; Mohamad Said, Khairul Anwar; Rahman Sobuz, Habibur

2018-03-01

Cement as an essential element for cement-based products contributed to negative environmental issues due to its high energy consumption and carbon dioxide emission during its production. These issues create the need to find alternative materials as partial cement replacement where studies on the potential of utilizing silica based materials as partial cement replacement come into picture. This review highlights the effectiveness of microstructural characterization techniques that have been used in the studies that focus on characterization of calcium hydroxide (CH) and calcium silicate hydrate (C-S-H) formation during hydration process of cement-based product incorporating nano reactive silica based materials as partial cement replacement. Understanding the effect of these materials as cement replacement in cement based product focusing on the microstructural development will lead to a higher confidence in the use of industrial waste as a new non-conventional material in construction industry that can catalyse rapid and innovative advances in green technology.

IMPACT OF PHYSICAL AND CHEMICAL MUD CONTAMINATION ON WELLBORE CEMENT- FORMATION SHEAR BOND STRENGTH Authors: Arome Oyibo1 and Mileva Radonjic1 * 1. Craft and Hawkins Department of Petroleum Engineering, 2131 Patrick F. Taylor Hall, Louisiana State University, Baton Rouge, LA 70803, aoyibo1@tigers.lsu.edu, mileva@lsu.edu

NASA Astrophysics Data System (ADS)

Oyibo, A. E.

2013-12-01

Wellbore cement has been used to provide well integrity through zonal isolation in oil & gas wells and geothermal wells. Cementing is also used to provide mechanical support for the casing and protect the casing from corrosive fluids. Failure of cement could be caused by several factors ranging from poor cementing, failure to completely displace the drilling fluids to failure on the path of the casing. A failed cement job could result in creation of cracks and micro annulus through which produced fluids could migrate to the surface which could lead to sustained casing pressure, contamination of fresh water aquifer and blow out in some cases. In addition, cement failures could risk the release of chemicals substances from hydraulic fracturing into fresh water aquifer during the injection process. To achieve proper cementing, the drilling fluid should be completely displaced by the cement slurry. However, this is hard to achieve in practice, some mud is usually left on the wellbore which ends up contaminating the cement afterwards. The purpose of this experimental study is to investigate the impact of both physical and chemical mud contaminations on cement-formation bond strength for different types of formations. Physical contamination occurs when drilling fluids (mud) dries on the surface of the formation forming a mud cake. Chemical contamination on the other hand occurs when the drilling fluids which is still in the liquid form interacts chemically with the cement during a cementing job. We investigated the impact of the contamination on the shear bond strength and the changes in the mineralogy of the cement at the cement-formation interface to ascertain the impact of the contamination on the cement-formation bond strength. Berea sandstone and clay rich shale cores were bonded with cement cores with the cement-formation contaminated either physically or chemically. For the physically contaminated composite cores, we have 3 different sample designs: clean/not contaminated, scrapped and washed composite cores. Similarly, for the chemically contaminated samples we had 3 different sample designs: 0%, 5% and 10% mud contaminated composite cores. Shear test were performed on the composite cores to determine the shear bond strength and the results suggested that the detrimental impact of the contamination is higher when the cores are physically contaminated i.e. when we have mud cake present at the surface of the wellbore before a cement job is performed. Also, the results showed that shear bond strength is higher for sandstone formations as compared to shale formations. Material characterization analysis was carried out to determine the micro structural changes at the cement-formation interface. The results obtained from the SEM and micro CT images taken at the bond interface confirmed that chemical contamination caused substantial changes in the spatial distribution of minerals that impacted bond strength. Keywords: Cement-Formation bond strength, mud contamination, shale, sandstone and material characterization *Corresponding author

The Interaction of Implant Luting Cements and Oral Bacteria Linked to Peri-Implant Disease: An In Vitro Analysis of Planktonic and Biofilm Growth--A Preliminary Study.

PubMed

Raval, Neal C; Wadhwani, Chandur P K; Jain, Sumita; Darveau, Richard P

2015-12-01

There is little consensus on the most appropriate cement to use when restoring a cement-retained, implant-supported restoration. One consideration should be the interaction of pathogenic oral bacteria with restorative cements. To determine how oral bacteria associated with peri-implant disease grow in the presence of implant cements. Five test cements with varying composition (zinc oxide-eugenol [TBO], eugenol-free zinc oxide [TBNE], zinc orthophosphate [FL], and two resin cements [PIC and ML]) were used to fabricate specimen disks. The disks were submerged in bacterial suspensions of either Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, or Porphyromonas gingivalis. Planktonic bacterial growth within the test media was measured by determining the optical density of the cultures (OD600 ). Positive controls (media and bacteria without cement disks) and negative controls (media alone) were similarly evaluated. The mean and standard deviations (SD) were calculated for planktonic growth from three separate experiments. ANOVA statistical analysis with post hoc Tukey tests was performed where differences existed (p < .05). Selected cement disks (TBO and ML) were further examined for bacterial biofilm growth. Surface bacteria were removed and grown on agar media, and colony-forming units (CFUs) were quantified. Planktonic growth for both A. actinomycetemcomitans and P. gingivalis was significantly inhibited (p < .05) when grown in the presence of cement disks consisting of TBNE, PIC, FL, and TBO. In contrast, neither of these bacteria displayed growth inhibition in the presence of ML cement disks. F. nucleatum growth was also significantly inhibited by PIC, FL. and TBO (p < .05), but not by ML and TBNE cement disks. CFU counts for the biofilm study for TBO gave minimal and, in some instances, no bacterial adherence and growth, in contrast to ML, which supported substantially greater bacterial biofilm growth. Cements display differing abilities to inhibit both planktonic and biofilm bacterial growth. Cements with the ability to reduce planktonic or biofilm growth of the test bacteria may be advantageous in reducing peri-implant disease. Understanding the microbial growth-inhibiting characteristics of different cement types should be considered important in the selection criteria. © 2014 Wiley Periodicals, Inc.

The influence of temporary cements on dental adhesive systems for luting cementation.

PubMed

Ribeiro, José C V; Coelho, Paulo G; Janal, Malvin N; Silva, Nelson R F A; Monteiro, André J; Fernandes, Carlos A O

2011-03-01

This study tested the hypothesis that bond strength of total- and self-etching adhesive systems to dentine is not affected by the presence of remnants from either eugenol-containing (EC) or eugenol-free (EF) temporary cements after standardized cleaning procedures. Thirty non-carious human third molars were polished flat to expose dentine surfaces. Provisional acrylic plates were fabricated and cemented either with EC, EF or no temporary cements. All specimens were incubated for 7 days in water at 37°C. The restorations were then taken out and the remnants of temporary cements were mechanically removed with a dental instrument. The dentine surfaces were cleaned with pumice and treated with either total-etching (TE) or self-etching (SE) dental adhesive systems. Atomic force microscopy was used to examine the presence of remnants of temporary cements before and after dentine cleaning procedures. Composite resin build-ups were fabricated and cemented to the bonded dentine surfaces with a resin luting cement. The specimens were then sectioned to obtain 0.9mm(2) beams for microtensile bond strength testing. Fractographic analysis was performed by optical and scanning electron microscopy. ANOVA showed lower mean microtensile bond strength in groups of specimens treated with EC temporary cement than in groups treated with either no cement or an EF cement (p<0.05). Mean microtensile bond strength was lower in groups employing the SE rather than the TE adhesive system (p<0.001). SE samples were also more likely to fail during initial processing of the samples. There was no evidence of interaction between cement and adhesive system effects on tensile strength. Fractographic analysis indicated different primary failure modes for SE and TE bonding systems, at the dentine-adhesive interface and at the resin cement-resin composite interface, respectively. The use of eugenol-containing temporary cements prior to indirect bonding restorations reduce, to a statistically similar extent, the bond strength of both total- and self-etching adhesive systems to dentine. Copyright © 2011 Elsevier Ltd. All rights reserved.

Antibacterial properties of aged dental cements evaluated by direct-contact and agar diffusion tests.

PubMed

Lewinstein, Israel; Matalon, Shlomo; Slutzkey, Shimshon; Weiss, Ervin I

2005-04-01

Since failure of fixed partial dentures is most frequently caused by caries, it would be advantageous if cements possessed antibacterial properties. The purpose of this study was to evaluate the antibacterial properties of 3 dental cements using the direct-contact test and agar diffusion test. For the direct-contact test, wells (n = 4) of microtiter plates were coated with the tested cements (Harvard cement, Duralon, and Ketac-Cem) while Streptococcus mutans suspension was placed directly on the cements. Bacterial growth was evaluated by a temperature-controlled microplate spectrophotometer. Eight wells of bacteria without the tested cements served as the positive control. Six wells of the tested cement without bacteria served as the negative control. For the agar diffusion test, triplicate specimens of freshly mixed cements were poured into uniform wells (5 mm in diameter) punched in the agar plates inoculated with Streptococcus mutans . After incubation at 37 degrees C for 24 hours, the agar plates were examined for bacterial growth and the diameter of the halo formed in the bacterial lawn was measured. In both tests, each cement was mixed in 2 different powder/liquid ratios. For the direct-contact test, data were initially recorded after 1 hour of incubation. Additional experiments were performed on specimens that were aged for 24 hours, 1 week, 1 month, and 3 months before assessment by either direct-contact test or agar diffusion test. The data were subjected to 1-way ANOVA with the Tukey post hoc test (alpha=.05). Compared with the control group, Duralon and Harvard cements demonstrated antibacterial properties even after 3 months with the direct-contact test (P <.002), while Ketac-Cem exhibited no antibacterial properties. In the agar diffusion test, no antibacterial activity was observed for any of the tested cements. The different powder/liquid ratios had a negligible effect on the antibacterial properties of the tested cements. Within the limitations of this study, Duralon and Harvard cements possessed prolonged antibacterial properties, while Ketac-Cem exhibited no antibacterial activity. The direct-contact test may be a more suitable test than the agar diffusion test to evaluate antibacterial properties of definitive cements.

Micro Mechanics and Microstructures of Major Subsurface Hydraulic Barriers: Shale Caprock vs Wellbore Cement

NASA Astrophysics Data System (ADS)

Radonjic, M.; Du, H.

2015-12-01

Shale caprocks and wellbore cements are two of the most common subsurface impermeable barriers in the oil and gas industry. More than 60% of effective seals for geologic hydrocarbon bearing formations as natural hydraulic barriers constitute of shale rocks. Wellbore cements provide zonal isolation as an engineered hydraulic barrier to ensure controlled fluid flow from the reservoir to the production facilities. Shale caprocks were deposited and formed by squeezing excess formation water and mineralogical transformations at different temperatures and pressures. In a similar process, wellbore cements are subjected to compression during expandable tubular operations, which lead to a rapid pore water propagation and secondary mineral precipitation within the cement. The focus of this research was to investigate the effect of wellbore cement compression on its microstructure and mechanical properties, as well as a preliminary comparison of shale caprocks and hydrated cement. The purpose of comparative evaluation of engineered vs natural hydraulic barrier materials is to further improve wellbore cement durability when in contact with geofluids. The micro-indentation was utilized to evaluate the change in cement mechanical properties caused by compression. Indentation experiments showed an overall increase in hardness and Young's modulus of compressed cement. Furthermore, SEM imaging and Electron Probe Microanalysis showed mineralogical alterations and decrease in porosity. These can be correlated with the cement rehydration caused by microstructure changes as a result of compression. The mechanical properties were also quantitatively compared to shale caprock samples in order to investigate the similarities of hydraulic barrier features that could help to improve the subsurface application of cement in zonal isolation. The comparison results showed that the poro-mechanical characteristics of wellbore cement appear to be improved when inherent pore sizes are shifted to predominantly nano-scale range as characteristic of pore-size distribution typical for shale rocks. The effect of compression on cement appears to petrophysically alter cement towards the properties of shale caprocks, although the process is achieved much faster than in the case of shale diagenesis over geological times.

The differences between soil grouting with cement slurry and cement-water glass slurry

NASA Astrophysics Data System (ADS)

Zhu, Mingting; Sui, Haitong; Yang, Honglu

2018-01-01

Cement slurry and cement-water glass slurry are the most widely applied for soil grouting reinforcement project. The viscosity change of cement slurry is negligible during grouting period and presumed to be time-independent while the viscosity of cement-water glass slurry increases with time quickly and is presumed to be time-dependent. Due to the significantly rheology differences between them, the grouting quality and the increasing characteristics of grouting parameters may be different, such as grouting pressure, grouting surrounding rock pressure, i.e., the change of surrounding rock pressure deduced by grouting pressure. Those are main factors for grouting design. In this paper, a large-scale 3D grouting simulation device was developed to simulate the surrounding curtain grouting for a tunnel. Two series of surrounding curtain grouting experiments under different geo-stress of 100 kPa, 150 kPa and 200 kPa were performed. The overload test on tunnel was performed to evaluate grouting effect of all surrounding curtain grouting experiments. In the present results, before 240 seconds, the grouting pressure increases slowly for both slurries; after 240 seconds the increase rate of grouting pressure for cement-water glass slurry increases quickly while that for cement slurry remains roughly constant. The increasing trend of grouting pressure for cement-water glass is similar to its viscosity. The setting time of cement-water glass slurry obtained from laboratory test is less than that in practical grouting where grout slurry solidifies in soil. The grouting effect of cement-water glass slurry is better than that of cement slurry and the grouting quality decreases with initial pressure.

Cement-based stabilization/solidification of oil refinery sludge: Leaching behavior of alkanes and PAHs.

PubMed

Karamalidis, Athanasios K; Voudrias, Evangelos A

2007-09-05

Stabilization/solidification is a process widely applied for the immobilization of inorganic constituents of hazardous wastes, especially for metals. Cement is usually one of the most common binders for that purpose. However, limited results have been presented on immobilization of hydrocarbons in cement-based stabilized/solidified petroleum solid waste. In this study, real oil refinery sludge samples were stabilized and solidified with various additions of I42.5 and II42.5 cement (Portland and blended cement, respectively) and subject to leaching. The target analytes were total petroleum hydrocarbons, alkanes and 16 polycyclic aromatic hydrocarbons of the EPA priority pollutant list. The experiments showed that the waste was confined in the cement matrix by macroencapsulation. The rapture of the cement structure led to the increase of leachability for most of the hydrocarbons. Leaching of n-alkanes from II42.5 cement-solidified samples was lower than that from I42.5 solidified samples. Leaching of alkanes in the range of n-C(10) to n-C(27) was lower than that of long chain alkanes (>n-C(27)), regardless the amount of cement addition. Generally, increasing the cement content in the solidified waste samples, increased individual alkane leachability. This indicated that cement addition resulted in destabilization of the waste. Addition of I42.5 cement favored immobilization of anthracene, benzo[a]anthracene, benzo[b]fluoroanthene, benzo[k]fluoroanthene, benzo[a]pyrene and dibenzo[a,h]anthracene. However, addition of II42.5 favored 5 out of 16, i.e., naphthalene, anthracene, benzo[b]fluoroanthene, benzo[k]fluoroanthene and dibenzo[a,h]anthracene.

Impact of implant size on cement filling in hip resurfacing arthroplasty.

PubMed

de Haan, Roel; Buls, Nico; Scheerlinck, Thierry

2014-01-01

Larger proportions of cement within femoral resurfacing implants might result in thermal bone necrosis. We postulate that smaller components are filled with proportionally more cement, causing an elevated failure rate. A total of 19 femoral heads were fitted with polymeric replicas of ReCap (Biomet) resurfacing components fixed with low-viscosity cement. Two specimens were used for each even size between 40 and 56 mm and one for size 58 mm. All specimens were imaged with computed tomography, and the cement thickness and bone density were analyzed. The average cement mantle thickness was 2.63 mm and was not correlated with the implant size. However, specimen with low bone density had thicker cement mantles regardless of size. The average filling index was 36.65% and was correlated to both implant size and bone density. Smaller implants and specimens with lower bone density contained proportionally more cement than larger implants. According to a linear regression model, bone density but not implant size influenced cement thickness. However, both implant size and bone density had a significant impact on the filling index. Large proportions of cement within the resurfacing head have the potential to generate thermal bone necrosis and implant failure. When considering hip resurfacing in patients with a small femoral head and/or osteoporotic bone, extra care should be taken to avoid thermal bone necrosis, and alternative cementing techniques or even cementless implants should be considered. This study should help delimiting the indications for hip resurfacing and to choose an optimal cementing technique taking implant size into account.

Effect of a bonding agent on in vitro biochemical activities of remineralizing resin-based calcium phosphate cements.

PubMed

Dickens, Sabine H; Flaim, Glenn M

2008-09-01

To test whether fluoride in a resin-based Ca-PO4 ion releasing cement or coating with an acidic bonding agent for improved adhesion compromised the cement remineralization potential. Cements were formulated without fluoride (Cement A) or with fluoride (Cement B). The treatment groups were A=Cement A; A2=Cement A+bonding agent; B=Cement B; B2=Cement B+bonding agent. The calcium, phosphate, and fluoride ion release in saliva-like solution (SLS) was determined from hardened cement disks without or with a coating of bonding agent. For the remineralization, two cavities were prepared in dentin of extracted human molars and demineralized. One cavity received composite resin (control); the other received treatment A, A2, B or B2. After 6 week incubation in SLS, 180 microm cross-sections were cut. The percentage remineralization was determined by transverse microradiography comparing the dentin mineral density under the cement to that under the control. The percentage of remineralization (mean+/-S.D.) was A (39+/-14)=B (37+/-18), A2 (23+/-13), B2 (14+/-7). Two-way analysis of variance (ANOVA) and Holm-Sidak test showed a significant effect from the presence of bonding agent (p<0.05), but not from fluoride (p>0.05). The ion solution concentrations of all groups showed undersaturation with respect to dicalcium phosphate dihydrate and calcium fluoride and supersaturation for fluorapatite and hydroxyapatite suggesting a positive remineralization potential. Compared to the control all treatments resulted in mineral increase. The remineralization was negatively affected by the presence of the bonding agent.

Fracture resistance of aluminium oxide and lithium disilicate-based crowns using different luting cements: an in vitro study.

PubMed

Al-Wahadni, Ahed M; Hussey, David L; Grey, Nicholas; Hatamleh, Muhanad M

2009-03-01

The aim of this study was to investigate the fracture resistance of two types of ceramic crowns cemented with two different cements. Forty premolar crowns were fabricated using lithium-disilicate (IPS Empress-2) and glass-infiltrated aluminium-oxide (In-Ceram) ceramic systems. The crowns were divided into four groups (n=10) with Group 1 (IPS Empress-2) and Group 2 (In-Ceram) cemented with glass ionomer cement. Group 3 (IPS Empress-2) and Group 4 (In-Ceram) were cemented with resin cement. Crowns were tested in a universal testing machine at a compressive-load speed of 10 mm/min. Fracture modes were grouped into five categories. One way analysis of variance (ANOVA) and Bonferroni post-hoc tests were used to detect statistical significances (p<0.05). The mean (SD) fracture resistance (Newtons) for Groups 1 to 4 were: 245.35 (82.69), 390.48 (67.03), 269.69 (10.33), and 418.36 (26.24). The cement type had no statistical significant effect (p>0.05) on fracture resistance within each ceramic system tested. In-Ceram crowns cemented with either glass ionomer or resin cements exhibited a statistically significantly higher fracture-resistance than IPS Empress-2 crowns (p<0.05). Minimal fracture in the test crowns was the common mode exhibited. Fracture resistance of IPS Empress-2 and In-Ceram crowns was not affected by the type of cement used for luting. Both In-Ceram and IPS Empress-2 crowns can be successfully luted with the cements tested with In-Ceram exhibiting higher fracture resistance than IPS Empress-2.

Self-healing polymer cement composites for geothermal wellbore applications

NASA Astrophysics Data System (ADS)

Rod, K. A.; Fernandez, C.; Childers, I.; Koech, P.; Um, W.; Roosendaal, T.; Nguyen, M.; Huerta, N. J.; Chun, J.; Glezakou, V. A.

2017-12-01

Cement is vital for controlling leaks from wellbores employed in oil, gas, and geothermal operations by sealing the annulus between the wellbore casing and geologic formation. Wellbore cement failure due to physical and chemical stresses is common and can result in significant environmental consequences and ultimately significant financial costs due to remediation efforts. To date numerous alternative cement blends have been proposed for the oil and gas industry. Most of these possess poor mechanical properties, or are not designed to work in high temperature environments. This research investigates novel polymer-cement composites which could function at most geothermal temperatures. Thermal stability and mechanical strength of the polymer is attributed to the formation of a number of chemical interactions between the polymer and cement matrix including covalent bonds, hydrogen bonding, and van der Waals interactions. It has been demonstrated that the bonding between cement and casing is more predictable when polymer is added to cement and can even improve healing of adhesion break when subjected to stresses such as thermal shock. Fractures have also been healed, effectively reducing permeability with fractures up to 0.3-0.5mm apertures, which is two orders of magnitude larger than typical wellbore fractures. Additionally, tomography analysis was used to determine internal structure of the cement polymer composite and imaging reveals that polymers fill fractures in the cement and between the cement and casing. By plugging fractures that occur in wellbore cement, reducing permeability of fractures, both environmental safety and economics of subsurface operations will be improved for geothermal energy and oil and gas production.

Marginal Fit of Metal-Ceramic Copings: Effect of Luting Cements and Tooth Preparation Design.

PubMed

de Almeida, Juliana Gomes Dos Santos Paes; Guedes, Carlos Gramani; Abi-Rached, Filipe de Oliveira; Trindade, Flávia Zardo; Fonseca, Renata Garcia

2017-12-22

To evaluate the effect of the triad finish line design, axial wall convergence angle, and luting cement on the marginal fit of metal copings used in metal-ceramic crowns. Schematic dies and their respective copings were cast in NiCr alloy. The dies exhibited the following finish line/convergence angle combinations: sloping shoulder/6°, sloping shoulder/20°, shoulder/6°, shoulder/20°. Marginal fit was evaluated under a stereomicroscope, before and after cementation. Copings were air-abraded with 50 μm Al 2 O 3 particles and cemented with Cimento de Zinco, RelyX U100, or Panavia F cements (n = 10/group). Data were square-root transformed and analyzed by 3-way factorial random effect model and Tukey's post hoc test (α = 0.05). Statistical analysis showed significance for the interactions finish line and convergence angle (p < 0.05), convergence angle and time (p < 0.001), and luting cement and time (p < 0.001). Sloping shoulder/20° provided the highest marginal discrepancy when compared to the other finish line/convergence angle combinations, which were statistically similar among each other. For both convergence angles and for all luting cements, the marginal discrepancy was significantly higher after cementation. Before and after cementation, 6° provided better marginal fit than 20°. After cementation, Panavia F provided higher marginal discrepancy than Cimento de Zinco. Lower convergence angle combined with shoulder and a low-consistency luting cement is preferable to cement metal copings. © 2017 by the American College of Prosthodontists.

Cements and adhesives for all-ceramic restorations.

PubMed

Manso, Adriana P; Silva, Nelson R F A; Bonfante, Estevam A; Pegoraro, Thiago A; Dias, Renata A; Carvalho, Ricardo M

2011-04-01

Dental cements are designed to retain restorations, prefabricated or cast posts and cores, and appliances in a stable, and long-lasting position in the oral environment. Resin-based cements were developed to overcome drawbacks of nonresinous materials, including low strength, high solubility, and opacity. Successful cementation of esthetic restorations depends on appropriate treatment to the tooth substrate and intaglio surface of the restoration, which in turn, depends on the ceramic characteristics. A reliable resin cementation procedure can only be achieved if the operator is aware of the mechanisms involved to perform the cementation and material properties. This article addresses current knowledge of resin cementation concepts, exploring the bonding mechanisms that influence long-term clinical success of all-ceramic systems. Copyright © 2011 Elsevier Inc. All rights reserved.

Results of the freeze resistance test, swelling index and coefficient of permeability of finegrained mining waste reinforced with cements

NASA Astrophysics Data System (ADS)

Morman, Justyna

2018-04-01

The article presents the result of laboratory tests for mining waste with grain size of 0 to 2 mm stabilized with cement. Used for stabilization of cement CEM I 42.5 R and blast furnace cement CEM III / A 42.5N - LH / HSR / NA and a plasticizer sealant. Cement was added to the mining waste test in the proportions of 5 - 8% in relation to the skeleton's weight. For the cemented samples, the freeze resistance test, swelling index, coefficient of permeability and pH of water leachate were tested. The addition of a cement binder resulted in diminishing the water permeability of mining waste and limiting the leaching of fine particles from the material.

A critical assessment of proximal macrotexturing on cemented femoral components.

PubMed

Duffy, G P; Muratoglu, O K; Biggs, S A; Larson, S L; Lozynsky, A J; Harris, W H

2001-12-01

We analyzed the cement-metal interface of 3 different types of femoral components that had proximal macrotexturing after in vitro insertion and after fatigue testing designed to produce debonding and micromotion. These components were compared with clinical retrieval specimens. The cement did not flow into the macrotexturing; rather, hollow, brittle volcanoes or calderas were formed. These fragile protrusions of cement become worn down or abraded by debonded components. This abrasion of cement may contribute to the early and aggressive osteolysis seen in some of these early failures with proximal macrotextured components. The formation of these volcanos and calderas can be aborted by placing bone-cement onto the macrotexturing before stem insertion. This simple technique allows the macrotexturing to be filled with cement.

Development of design parameters for virtual cement and concrete testing : [summary].

DOT National Transportation Integrated Search

2013-12-01

At its most basic, concrete is made from cement : and aggregate, often Portland cement and gravel : (or in Florida, limestone). Varying ingredients and : their proportions directly influences the behavior : of the final cement and concrete products. ...

A descriptive study of the radiographic density of implant restorative cements.

PubMed

Wadhwani, Chandur; Hess, Timothy; Faber, Thomas; Piñeyro, Alfonso; Chen, Curtis S K

2010-05-01

Cementation of implant prostheses is a common practice. Excess cement in the gingival sulcus may harm the periodontal tissues. Identification of the excess cement may be possible with the use of radiographs if the cement has sufficient radiopacity. The purpose of this study was to compare the radiographic density of different cements used for implant prostheses. Eight different cements were compared: TempBond Original (TBO), TempBond NE (TBN), Fleck's (FL), Dycal (DY), RelyX Unicem (RXU), RelyX Luting (RXL), Improv (IM), and Premier Implant Cement (PIC). Specimen disks, 2 mm in thickness, were radiographed. Images were made using photostimulable phosphor (PSP) plates with standardized exposure values. The average grey level of the central area of each specimen disk was selected and measured in pixels using a software analysis program, ImageTool, providing an average grey level value representative of radiodensity for each of the 8 cements. The radiodensity was determined using the grey level values of the test materials, which were recorded and compared to a standard aluminum step wedge. An equivalent thickness of aluminum in millimeters was calculated using best straight line fit estimates. To assess contrast effects by varying the exposure settings, a second experiment using 1-mm-thick cement specimens radiographed at both 60 kVp and 70 kVp was conducted. The PSP plates with specimens were measured for a grey level value comparison to the standard aluminum step wedge, using the same software program. The highest grey level values were recorded for the zinc cements (TBO, TBN, and FL), with the 1-mm specimen detectable at both 60- and 70-kVp settings. A lower grey level was recorded for DY, indicative of a lower radiodensity compared to the zinc cements, but higher than RXL and RXU. The implant-specific cements had the lowest grey level values. IM could only be detected in 2-mm-thick sections with a lower aluminum equivalence value than the previously mentioned cements. PIC could not be detected radiographically for either the 1-mm or 2-mm thicknesses at either of the kVp settings. Some types of cement commonly used for the cementation of implant-supported prostheses have poor radiodensity and may not be detectable following radiographic examination.

In Vitro Evaluation of Cell Compatibility of Dental Cements Used with Titanium Implant Components.

PubMed

Marvin, Jason C; Gallegos, Silvia I; Parsaei, Shaida; Rodrigues, Danieli C

2018-03-09

To evaluate the biocompatibility of five dental cement compositions after directly exposing human gingival fibroblast (HGF) and MC3T3-E1 preosteoblast cells to cement alone and cement applied on commercially pure titanium (cpTi) specimens. Nanostructurally integrated bioceramic (NIB), resin (R), resin-modified glass ionomer (RMGIC), zinc oxide eugenol (ZOE), and zinc phosphate (ZP) compositions were prepared according to the respective manufacturer's instructions. Samples were prepared in cylindrical Teflon molds or applied over the entire surface of polished cpTi discs. All samples were cured for 0.5, 1, 12, or 24 hours post-mixing. Direct contact testing was conducted according to ISO 10993 by seeding 6-well plates at 350,000 cells/well. Plates were incubated at 37°C in a humidified atmosphere with 5% CO 2 for 24 hours before individually plating samples and cpTi control discs. Plates were then incubated for an additional 24 hours. Microtetrazolium (MTT) cell viability assays were used to measure sample cytotoxicity. For samples that cured for 24 hours prior to direct contact exposure, only NIB and ZP cements when cemented on cpTi demonstrated cell viability percentages above the minimum biocompatibility requirement (≥70%) for both the investigative cell lines. R, RMGIC, and ZOE cements exhibited moderate to severe cytotoxic effects on both cell lines in direct contact and when cemented on cpTi specimens. For HGF cells, ZOE cemented-cpTi specimens exhibited significantly decreased cytotoxicity, whereas RMGIC cemented-cpTi specimens exhibited significantly increased cytotoxicity. Despite previous studies that showed enhanced cpTi corrosion activity for fluoride-containing compositions (NIB and ZP), there was no significant difference in cytotoxicity between cement alone and cemented-cpTi. In general, the MC3T3-E1 preosteoblast cells were more sensitive than HGF cells to cement composition. Ultimately, cement composition played a significant role in maintaining host cell compatibility. Results of this work help illustrate the impact of different cement formulations on host cell health and emphasize the need for understanding material properties when selecting certain formulations of dental cements, which can ultimately influence the survival of dental implant systems. © 2018 by the American College of Prosthodontists.

Effect of different power settings of Er,Cr:YSGG laser before or after tribosilicatization on the microshear bond strength between zirconia and two types of cements.

PubMed

Zeidan, Leonardo C; Esteves, Camila M; Oliveira, Juliana A; Brugnera, Aldo; Cassoni, Alessandra; Rodrigues, José Augusto

2018-02-01

The aim of this study was to evaluate the effect of different output powers of Er,Cr:YSGG laser and the association with tribochemical silica coating on the bond strength between zirconia ceramic and two resin cements. One hundred ninety-two zirconia ceramic bars (IPS e-max ZirCAD Ivoclar Vivadent-) were sectioned (6 × 6 × 4 mm), sintered, and randomly divided into 12 groups for each cement system according to the surface treatment (n = 8): C-without treatment (control); R-tribochemical coating + resin cement (control); 2L-laser (2.0 W) + resin cement; 2LR-laser (2.0 W) + tribochemical coating + resin cement; R2L-tribochemical coating + laser (2.0 W) + resin cement; 2.5L-laser (2.5 W) + resin cement; 2.5LR-laser (2.5 W) + tribochemical coating + resin cement; R2.5L-tribochemical coating + laser (2.5 W) + resin cement; 3L-laser (3.0 W) + resin cement; 3LR-laser (3.0 W) + tribochemical coating + resin cement, R3L-tribochemical coating + laser (3.0 W) + resin cement; and RPHO-tribochemical + resin cement + photoactivation (control). After the surface treatment, the respective primers were applied, and resin cements, Multilink N, Ivoclar Vivadent (M), and Panavia F 2.0, Kuraray Medical Inc. (P), were inserted into Tygon molds which were bonded to the zirconia bars. Each specimen received two cements bars. After 24 h of storage in a relative humidity (100%) at 37 °C, they were evaluated by the microshear test speed of 1 mm/min. The microshear values were analyzed by one-way ANOVA and Tukey's test (α = 0.05). ANOVA showed statistically significant differences among the evaluated groups. The highest bond strength was observed in RPHO, which statistically differed from all groups. The lowest bond strength was observed in M2.5L (Multilink N) and in P3LR (Panavia F 2.0). It can be concluded that the lowest power output tested was suitable and showed bond strength values similar to tribochemical silica deposition. The light curing is important to adhesion and the tribosilicatizated surface achieves similar microshear values to untreated surface in absence of light.

Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steshenko, Aleksei, E-mail: steshenko.alexey@gmail.com; Kudyakov, Aleksander; Konusheva, Viktoriya

The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significantmore » change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.« less

Use of waste brick as a partial replacement of cement in mortar.

PubMed

Naceri, Abdelghani; Hamina, Makhloufi Chikouche

2009-08-01

The aim of this study is to investigate the use of waste brick as a partial replacement for cement in the production of cement mortar. Clinker was replaced by waste brick in different proportions (0%, 5%, 10%, 15% and 20%) by weight for cement. The physico-chemical properties of cement at anhydrous state and the hydrated state, thus the mechanical strengths (flexural and compressive strengths after 7, 28 and 90 days) for the mortar were studied. The microstructure of the mortar was investigated using scanning electron microscopy (SEM), the mineralogical composition (mineral phases) of the artificial pozzolan was investigated by the X-ray diffraction (XRD) and the particle size distributions was obtained from laser granulometry (LG) of cements powders used in this study. The results obtained show that the addition of artificial pozzolan improves the grinding time and setting times of the cement, thus the mechanical characteristics of mortar. A substitution of cement by 10% of waste brick increased mechanical strengths of mortar. The results of the investigation confirmed the potential use of this waste material to produce pozzolanic cement.

[A comparative study of marginal microleakage using different cements in porcelain-fused-to-metal crown].

PubMed

Jiang, Ming-Xin; Huang, Ke-Qiang; Li, Zhi-Gang; Gao, Xiu-Qiu; Li, Chun-Shan

2011-04-01

To evaluate the marginal microleakage of porcelain-fused-to-metal crown using four different cements. Sixteen porcelain-fused-to-metal crowns were built and randomly divided into 4 group, luted onto standard prepared human forward molars using four different cements (glass ionomer cement, resin-modified glass ionomer cement, PanaviaF, Super-Bond C&B adhesive luting system). After temperature cycling test, all the crowns were then submerged in 2% fuchsin for 24 h. The marginal microleakage at tooth cement interfaces was observed using light stereomicroscopy and evaluated in classification index. The marginal microleakage grade of 4 groups were analyzed by SPSS 13.0. The PanaviaF demonstrated the least marginal microleakage, Super-Bond C&B adhesive luting system, resin-modified glass ionomer cement showed an intermediate level of marginal microleakage, glass ionomer cement was associated with severe marginal microleakage (total, Chi2 = 157.60, P < 0.01; among the different groups, P<0.05). Adhesive resin luting system which is the first selection in clinical is better than glass ionomer cement and is good at porcelain-fused-to-metal crown.

[Bonding interfaces of three kinds of cements and root canal dentin: a scanning electron microscope observation].

PubMed

Chen, Lei; Lei, Hui-yun; Xu, Guo-fu; Liang, Xiao-peng; Li, Ji-jia

2010-04-01

To compare the bonding properties of three kinds of cements by observing the bonding inteffaces of cements and root canal dentin. 15 extracted mandibular premolars were divided into 3 groups, and were cemented by Rely X luting, Panavia F and Paracore 5 mL, respectively. Each tooth was sectioned into two parts and the dentin-cement interfaces at the coronal, middle and apical parts of the fiber post were oberved by scanning electron microscope (SEM). The length of hybrid layer was also recorded. Hybrid layer was not clearly found in group one, which could be seen on the dentin-cement interfaces of group two and three. Resin tags and lateral adhesives were also observed in group three. From the apical to the coronal part, microgaps seemed gradually smaller in group one, while the hybrid layer became thicker in both group two and three. The total-etch resin cement bounds tightly with dentin, and owns a more superior bonding property than self-etch resin cement and resin modified glass ionomer cement.

The role of calcium and magnesium in the concrete tubes of the sandcastle worm.

PubMed

Sun, ChengJun; Fantner, Georg E; Adams, Jonathan; Hansma, Paul K; Waite, J Herbert

2007-04-01

Sandcastle worms Phragmatopoma californica build mound-like reefs by sticking together large numbers of sand grains with cement secreted from the building organ. The cement consists of protein plus substantial amounts of calcium and magnesium, which are not invested in any mineral form. This study examined the effect of calcium and magnesium depletion on the structural and mechanical properties of the cement. Divalent ion removal by chelating with EDTA led to a partial collapse of cement architecture and cement dislodgement from silica surfaces. Mechanical properties examined were sand grain pull-out force, tube resistance to compression and cement adhesive force. EDTA treatment reduced sand grain pull-out forces by 60% and tube compressive strength by 50% relative to controls. EDTA lowered both the maximal adhesive force and energy dissipation of cement by up to an order of magnitude. The adhesiveness of calcium- and magnesium-depleted cement could not be restored by re-exposure to the ions. The results suggest that divalent ions play a complex and multifunctional role in maintaining the structure and stickiness of Phragmatopoma cement.

The effect of lime-dried sewage sludge on the heat-resistance of eco-cement.

PubMed

Li, Wen-Quan; Liu, Wei; Cao, Hai-Hua; Xu, Jing-Cheng; Liu, Jia; Li, Guang-Ming; Huang, Juwen

2016-01-01

The treatment and disposal of sewage sludge is a growing problem for sewage treatment plants. One method of disposal is to use sewage sludge as partial replacement for raw material in cement manufacture. Although this process has been well researched, little attention has been given to the thermal properties of cement that has had sewage sludge incorporated in the manufacturing process. This study investigated the fire endurance of eco-cement to which lime-dried sludge (LDS) had been added. LDS was added in proportions of 0%, 3%, 6%, 9%, and 12% (by weight) to the raw material. The eco-cement was exposed to 200, 400, or 600 °C for 3 h. The residual strength and the microstructural properties of eco-cement were then studied. Results showed that the eco-cement samples suffered less damage than conventional cement at 600 °C. The microstructural studies showed that LDS incorporation could reduce Ca(OH)(2) content. It was concluded that LDS has the potential to improve the heat resistance of eco-cement products.

Use of waste brick as a partial replacement of cement in mortar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naceri, Abdelghani; Hamina, Makhloufi Chikouche

2009-08-15

The aim of this study is to investigate the use of waste brick as a partial replacement for cement in the production of cement mortar. Clinker was replaced by waste brick in different proportions (0%, 5%, 10%, 15% and 20%) by weight for cement. The physico-chemical properties of cement at anhydrous state and the hydrated state, thus the mechanical strengths (flexural and compressive strengths after 7, 28 and 90 days) for the mortar were studied. The microstructure of the mortar was investigated using scanning electron microscopy (SEM), the mineralogical composition (mineral phases) of the artificial pozzolan was investigated by themore » X-ray diffraction (XRD) and the particle size distributions was obtained from laser granulometry (LG) of cements powders used in this study. The results obtained show that the addition of artificial pozzolan improves the grinding time and setting times of the cement, thus the mechanical characteristics of mortar. A substitution of cement by 10% of waste brick increased mechanical strengths of mortar. The results of the investigation confirmed the potential use of this waste material to produce pozzolanic cement.« less

Handbook: Approaches for the Remediation of Federal Facility Sites Contaminated with Explosive or Radioactive Wastes

DTIC Science & Technology

1993-09-01

ash, and incinerator fly ash in modified sulfur cement and Portland cement waste forms ................................. 70 6-10 Drawing of full-scale...6-17 Economic analysis of encapsulating sodium nitrate at Rocky Flats Plant ..................... 74 6-18 Portland cement and modified sulfur cement...environment. DP-1629. Savannah and modified sulfur cement encapsulation. Both methods River Laboratory, Aiken, South Carolina. have advantages over

Glass ionomer cements: chemistry of erosion.

PubMed

Crisp, S; Lewis, B G; Wilson, A D

1976-01-01

A three-month study of the chemistry of the water erosion of two forms of ASPA cement has been made. The effect of varying cement consistency and cure time was investigated. The results are discussed in terms of the known chemistry and structure of the cement. The erosion behavior is compared to that of silicate, silicophosphate, and zinc polycarboxylate dental cements. The state of absorbed water and the mechanism of erosion is discussed.

Effect of cement/wood ratios and wood storage conditions on hydration temperature, hydration time, and compressive strength of wood-cement mixtures

Treesearch

Andy W.C. Lee; Zhongli Hong; Douglas R. Phillips; Chung-Yun Hse

1987-01-01

This study investigated the effect of cement/wood ratios and wood storage conditions on hydration temperature, hydration time, and compressive strength of wood-cement mixtures made from six wood species: southern pine, white oak, southern red oak, yellow-poplar, sweetgum, and hickory. Cement/wood ratios varied from 13/1 to 4/1. Wood storage conditions consisted of air-...

Bone Repair and Military Readiness

DTIC Science & Technology

2015-10-01

Even though commercial bone cements have not significantly changed in the past 50 years and have been used throughout the world, there are...generation. In addition, it appears that this new bone cement is actually supportive of new bone formation. A cement that can achieve true integration...problem. As the proposed bone cement prototype polymerizes at a much lower temperature, antibiotics that are sensitive to heat can be added to the cement

Carbonation-induced weathering effect on cesium retention of cement paste

NASA Astrophysics Data System (ADS)

Park, S. M.; Jang, J. G.

2018-07-01

Carbonation is inevitable for cement and concrete in repositories over an extended period of time. This study investigated the carbonation-induced weathering effect on cesium retention of cement. Cement paste samples were exposed to accelerated carbonation for different durations to simulate the extent of weathering among samples. The extent of carbonation in cement was characterized by XRD, TG and NMR spectroscopy, while the retention capacity for cesium was investigated by zeta potential measurement and batch adsorption tests. Though carbonation led to decalcification from the binder gel, it negatively charged the surface of cement hydrates and enhanced their cesium adsorption capacity.

Physical and thermal behavior of cement composites reinforced with recycled waste paper fibers

NASA Astrophysics Data System (ADS)

Hospodarova, Viola; Stevulova, Nadezda; Vaclavik, Vojtech; Dvorsky, Tomas

2017-07-01

In this study, three types of recycled waste paper fibers were used to manufacture cement composites reinforced with recycled cellulosic fibers. Waste cellulosic fibers in quantity of 0.2, 0.3, and 0.5 wt.% were added to cement mixtures. Physical properties such as density, water capillarity, water absorbability and thermal conductivity of fiber cement composites were studied after 28 days of hardening. However, durability of composites was tested after their water storage up to 90 days. Final results of tested properties of fiber cement composites were compared with cement reference sample without cellulosic fibers.

Polymer-Cement Composites with Self-Healing Ability for Geothermal and Fossil Energy Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Childers, M. Ian; Nguyen, Manh-Thuong; Rod, Kenton A.

Sealing of wellbores in geothermal and tight oil/gas reservoirs by filling the annulus with cement is a well-established practice. Failure of the cement as a result of physical and/or chemical stress is a common problem with serious environmental and financial consequences. Numerous alternative cement blends have been proposed for the oil and gas industry. Most of these possess poor mechanical properties, or are not designed to work in high temperature environments. This work reports on a novel polymer-cement composite with remarkable self-healing ability that maintains the required properties of typical wellbore cements and may be stable at most geothermal temperatures.more » We combine for the first time experimental analysis of physical and chemical properties with density functional theory simulations to evaluate cement performance. The thermal stability and mechanical strength are attributed to the formation of a number of chemical interactions between the polymer and cement matrix including covalent bonds, hydrogen bonding, and van der Waals interactions. Self-healing was demonstrated by sealing fractures with 0.3–0.5 mm apertures, 2 orders of magnitude larger than typical wellbore fractures. This polymer-cement composite represents a major advance in wellbore cementing that could improve the environmental safety and economics of enhanced geothermal energy and tight oil/gas production.« less

Relationship between operational variables, fundamental physics and foamed cement properties in lab and field generated foamed cement slurries

DOE PAGES

Glosser, D.; Kutchko, B.; Benge, G.; ...

2016-03-21

Foamed cement is a critical component for wellbore stability. The mechanical performance of a foamed cement depends on its microstructure, which in turn depends on the preparation method and attendant operational variables. Determination of cement stability for field use is based on laboratory testing protocols governed by API Recommended Practice 10B-4 (API RP 10B-4, 2015). However, laboratory and field operational variables contrast considerably in terms of scale, as well as slurry mixing and foaming processes. Here in this paper, laboratory and field operational processes are characterized within a physics-based framework. It is shown that the “atomization energy” imparted by themore » high pressure injection of nitrogen gas into the field mixed foamed cement slurry is – by a significant margin – the highest energy process, and has a major impact on the void system in the cement slurry. There is no analog for this high energy exchange in current laboratory cement preparation and testing protocols. Quantifying the energy exchanges across the laboratory and field processes provides a basis for understanding relative impacts of these variables on cement structure, and can ultimately lead to the development of practices to improve cement testing and performance.« less

Analysis of the properties of dental cements after exposure to incubation media containing Streptococcus mutans.

PubMed

de Menezes, Fernando Carlos Hueb; Junior, Geraldo Thedei; de Oliveira, Wildomar Jose; Paulino, Tony de Paiva; de Moura, Marcelo Boaventura; da Silva, Igor Lima; de Moura, Marcos Boaventura

2011-09-01

Indirect restorations are increasingly used in dentistry, and the cementation interface is possibly the most critical region of the work. The objective of the present work was to evaluate the influence of exposure to a culture medium containing S. mutans on the hardness and solubility of four different cementing agents (zinc phosphate, glass ionomer, glass ionomer modified with resin and resin cement). Test specimens composed of these cements were exposed for 30 days in a culture medium containing S. mutans. After leaching, the test materials were assessed in terms of their solubility (loss of mass) and Knoop (KHN) microhardness. Changes in surface morphology were identified using scanning electron microscopy (SEM). The resin cement showed no significant solubility and its hardness increased following exposure and leaching, while the zinc phosphate cement was the most soluble and its hardness decreased after exposure to the culture medium. SEM analyses identified morphological alterations on the surfaces of the test materials that were compatible with the solubility results. It is concluded that resinous cements perform better than water-based cements when exposed to acidic conditions. The effects of acids from Streptococcus mutans can interfere with the efficiency and properties of some cements used for fixation of indirect restorations, exposed to the buccal environment.

Evaluation of load at fracture of Procera AllCeram copings using different luting cements.

PubMed

Al-Makramani, Bandar M A; Razak, A A A; Abu-Hassan, M I

2008-02-01

The current study investigated the effect of different luting agents on the fracture resistance of Procera AllCeram copings. Six master dies were duplicated from the prepared maxillary first premolar tooth using nonprecious metal alloy (Wiron 99). Thirty copings (Procera AllCeram) of 0.6-mm thickness were manufactured. Three types of luting media were used: zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and dual-cured composite resin cement (Panavia F). Ten copings were cemented with each type. Two master dies were used for each group, and each of them was used to lute five copings. All groups were cemented according to manufacturer's instructions and received a static load of 5 kg during cementation. After 24 hours of distilled water storage at 37 degrees C, the copings were vertically compressed using a universal testing machine at a crosshead speed of 1 mm/min. ANOVA revealed significant differences in the load at fracture among the three groups (p < 0.001). The fracture strength results showed that the mean fracture strength of zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and resin luting cement (Panavia F) were 1091.9 N, 784.8 N, and 1953.5 N, respectively. Different luting agents have an influence on the fracture resistance of Procera AllCeram copings.

The effect of fly ash and coconut fibre ash as cement replacement materials on cement paste strength

NASA Astrophysics Data System (ADS)

Bayuaji, R.; Kurniawan, R. W.; Yasin, A. K.; Fatoni, H. AT; Lutfi, F. M. A.

2016-04-01

Concrete is the backbone material in the construction field. The main concept of the concrete material is composed of a binder and filler. Cement, concrete main binder highlighted by environmentalists as one of the industry are not environmentally friendly because of the burning of cement raw materials in the kiln requires energy up to a temperature of 1450° C and the output air waste CO2. On the other hand, the compound content of cement that can be utilized in innovation is Calcium Hydroxide (CaOH), this compound will react with pozzolan material and produces additional strength and durability of concrete, Calcium Silicate Hydrates (CSH). The objective of this research is to explore coconut fibers ash and fly ash. This material was used as cement replacement materials on cement paste. Experimental method was used in this study. SNI-03-1974-1990 is standard used to clarify the compressive strength of cement paste at the age of 7 days. The result of this study that the optimum composition of coconut fiber ash and fly ash to substitute 30% of cement with 25% and 5% for coconut fibers ash and fly ash with similar strength if to be compared normal cement paste.

Evaluation of retentive strength of four luting cements with stainless steel crowns in primary molars: An in vitro study.

PubMed

Parisay, Iman; Khazaei, Yegane

2018-01-01

Stainless steel crown (SSC) is the most reliable restoration for primary teeth with extensive caries. Retention is of great importance for a successful restoration and is provided by various factors such as luting cements. The aim of this study was to evaluate the retentive strength of SSC cemented with four different luting cements. In this in vitro study, A total of 55 extracted primary first molars were selected. Following crown selection and cementation (one with no cement and four groups cemented with resin, glass ionomer, zinc phosphate, and polycarboxylate), all the specimens were incubated and thermocycled in 5°C-55°C. Retentive properties of SSCs were tested with a mechanical test machine. First dislodgement of each specimen and full crown removal were recorded. One-way ANOVA test followed by least significant difference test and Kruskal-Wallis test was used for retentive strength comparison at the level of significance of P < 0.05. The results of the study showed that the specimens cemented with zinc phosphate exhibited higher retentive strength as compared to glass ionomer and polycarboxylate ( P < 0.001 and P = 0.023, respectively). Zinc phosphate cement showed the most promising results; thus, it can be preferably used for cementation of the teeth with no grossly broken down crowns.

Mechanical, material, and antimicrobial properties of acrylic bone cement impregnated with silver nanoparticles.

PubMed

Slane, Josh; Vivanco, Juan; Rose, Warren; Ploeg, Heidi-Lynn; Squire, Matthew

2015-03-01

Prosthetic joint infection is one of the most serious complications that can lead to failure of a total joint replacement. Recently, the rise of multidrug resistant bacteria has substantially reduced the efficacy of antibiotics that are typically incorporated into acrylic bone cement. Silver nanoparticles (AgNPs) are an attractive alternative to traditional antibiotics resulting from their broad-spectrum antimicrobial activity and low bacterial resistance. The purpose of this study, therefore, was to incorporate metallic silver nanoparticles into acrylic bone cement and quantify the effects on the cement's mechanical, material and antimicrobial properties. AgNPs at three loading ratios (0.25, 0.5, and 1.0% wt/wt) were incorporated into a commercial bone cement using a probe sonication technique. The resulting cements demonstrated mechanical and material properties that were not substantially different from the standard cement. Testing against Staphylococcus aureus and Staphylococcus epidermidis using Kirby-Bauer and time-kill assays demonstrated no antimicrobial activity against planktonic bacteria. In contrast, cements modified with AgNPs significantly reduced biofilm formation on the surface of the cement. These results indicate that AgNP-loaded cement is of high potential for use in primary arthroplasty where prevention of bacterial surface colonization is vital. Copyright © 2014 Elsevier B.V. All rights reserved.

Natural cement in the nineteenth century city of Madrid. Identification of their application, conservation status and their compatibility with moderns cements.

NASA Astrophysics Data System (ADS)

Corrochano, Cristina Mayo; Lasheras Merino, Felix; Sanz-Arauz, David

2016-04-01

Roman cement was patented in 1796 and it arrived to Spain in 1835. Although the natural cement used in Madrid came mainly from Guipúzcoa's factories, there were a few small factories producing natural cement in the area. In the south east of Madrid, in "Morata de Tajuña", are the marl quarries of the Madrid Community. Natural cement was extensively used to decorate buildings in Madrid during the 19th century and the beginning of the 20th. It was highly demanded in various sectors of civil engineering: sewerage, water supply, canals, ports and tunnels. In the building sector, at first the use of cements was limited to building foundations and masonry mortars, but never as render mortar because it was considered an unsightly and vulgar material. For renders still traditional lime mortar was used. And is not till the end of the 19th century when it was used in facade decorations for the first time. We have analysed 25 buildings in Madrid built in that period of time. It was used microscopy techniques for the identification of these cements, checking how many of them used natural cement, how they used it, what is its conservation status and their compatibility with modern cements.

The physical properties of accelerated Portland cement for endodontic use.

PubMed

Camilleri, J

2008-02-01

To investigate the physical properties of a novel accelerated Portland cement. The setting time, compressive strength, pH and solubility of white Portland cement (Lafarge Asland; CEM 1, 52.5 N) and accelerated Portland cement (Proto A) produced by excluding gypsum from the manufacturing process (Aalborg White) and a modified version with 4 : 1 addition of bismuth oxide (Proto B) were evaluated. Proto A set in 8 min. The compressive strength of Proto A was comparable with that of Portland cement at all testing periods (P > 0.05). Additions of bismuth oxide extended the setting time and reduced the compressive strength (P < 0.05). Both cements and storage solution were alkaline. All cements tested increased by >12% of their original weight after immersion in water for 1 day with no further absorption after 28 days. Addition of bismuth oxide increased the water uptake of the novel cement (P < 0.05). The setting time of Portland cement can be reduced by excluding the gypsum during the last stage of the manufacturing process without affecting its other properties. Addition of bismuth oxide affected the properties of the novel cement. Further investigation on the effect that bismuth oxide has on the properties of mineral trioxide aggregate is thus warranted.

Biomineralization in metakaolin modified cement mortar to improve its strength with lowered cement content.

PubMed

Li, Mengmeng; Zhu, Xuejiao; Mukherjee, Abhijit; Huang, Minsheng; Achal, Varenyam

2017-05-05

The role of industrial byproduct as supplementary cementitious material to partially replace cement has greatly contributed to sustainable environment. Metakaolin (MK), one of such byproduct, is widely used to partial replacement of cement; however, during cement replacement at high percentage, it may not be a good choice to improve the strength of concrete. Thus, in the present study, biocement, a product of microbially induced carbonate precipitation is utilized in MK-modified cement mortars to improve its compressive strength. Despite of cement replacement with MK as high as 50%, the presented technology improved compressive strength of mortars by 27%, which was still comparable to those mortars with 100% cement. The results proved that biomineralization could be effectively used in reducing cement content without compromising compressive strength of mortars. Biocementation also reduced the porosity of mortars at all ages. The process was characterized by SEM-EDS to observe bacterially-induced carbonate crystals and FTIR spectroscopy to predict responsible bonding in the formation of calcium carbonate. Further, XRD analysis identified bio/minerals formed in the MK-modified mortars. The study also encourages combining biological role in construction engineering to solve hazardous nature of cement and at same time solve the disposal problem of industrial waste for sustainable environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Biomechanical comparison of the strength of adhesion of polymethylmethacrylate cement to zirconia ceramic and cobalt-chromium alloy components in a total knee arthroplasty.

PubMed

Kumahashi, Nobuyuki; Uchio, Yuji; Kitamura, Nobuto; Satake, Shigeru; Iwamoto, Mikio; Yasuda, Kazunori

2014-11-01

The purpose of this study was to clarify the biomechanical characteristics of cement-material interfaces for the zirconia ceramic and cobalt-chromium (Co-Cr) alloy femoral components used for total knee arthroplasty. In the first sub-study, we compared the strength of adhesion of the cement to flat plates, by tensile testing under dry and moistened conditions. In the second sub-study, we compared the maximum load of the cement-component complex by tensile testing. In the third sub-study, we compared the fatigue characteristics of the cement-component complex by use of a dynamic tensile testing machine. Under dry conditions, the maximum strength of adhesion to the zirconia ceramic plate was the same as that to the Co-Cr alloy plate. Under moistened conditions, however, the strength of adhesion to the zirconia ceramic plate was significantly lower (p = 0.0017) whereas the strength of adhesion to the Co-Cr alloy plate was not reduced. Maximum load for the cement-component complexes for zirconia ceramic and Co-Cr alloy was no different under both dry and moistened conditions. Fatigue testing showed that cement-zirconia adhesion was stronger than cement-Co-Cr alloy adhesion (p = 0.0161). The strength of adhesion of cement to zirconia ceramic is substantially weaker under wet conditions than under dry conditions. The mechanical properties of cement-zirconia ceramic component complexes and cement-Co-Cr alloy component complexes are equivalent.

Research on a Defects Detection Method in the Ferrite Phase Shifter Cementing Process Based on a Multi-Sensor Prognostic and Health Management (PHM) System.

PubMed

Wan, Bo; Fu, Guicui; Li, Yanruoyue; Zhao, Youhu

2016-08-10

The cementing manufacturing process of ferrite phase shifters has the defect that cementing strength is insufficient and fractures always appear. A detection method of these defects was studied utilizing the multi-sensors Prognostic and Health Management (PHM) theory. Aiming at these process defects, the reasons that lead to defects are analyzed in this paper. In the meanwhile, the key process parameters were determined and Differential Scanning Calorimetry (DSC) tests during the cure process of resin cementing were carried out. At the same time, in order to get data on changing cementing strength, multiple-group cementing process tests of different key process parameters were designed and conducted. A relational model of cementing strength and cure temperature, time and pressure was established, by combining data of DSC and process tests as well as based on the Avrami formula. Through sensitivity analysis for three process parameters, the on-line detection decision criterion and the process parameters which have obvious impact on cementing strength were determined. A PHM system with multiple temperature and pressure sensors was established on this basis, and then, on-line detection, diagnosis and control for ferrite phase shifter cementing process defects were realized. It was verified by subsequent process that the on-line detection system improved the reliability of the ferrite phase shifter cementing process and reduced the incidence of insufficient cementing strength defects.

Modelling the minislump spread of superplasticized PPC paste using RLS with the application of Random Kitchen sink

NASA Astrophysics Data System (ADS)

Sathyan, Dhanya; Anand, K. B.; Jose, Chinnu; Aravind, N. R.

2018-02-01

Super plasticizers(SPs) are added to the concrete to improve its workability with out changing the water cement ratio. Property of fresh concrete is mainly governed by the cement paste which depends on the dispersion of cement particle. Cement dispersive properties of the SP depends up on its dosage and the family. Mini slump spread diameter with different dosages and families of SP is taken as the measure of workability characteristic of cement paste chosen for measuring the rheological properties of cement paste. The main purpose of this study includes measure the dispersive ability of different families of SP by conducting minislump test and model the minislump spread diameter of the super plasticized Portland Pozzolona Cement (PPC)paste using regularized least square (RLS) approach along with the application of Random kitchen sink (RKS) algorithm. For preparing test and training data for the model 287 different mixes were prepared in the laboratory at a water cement ratio of 0.37 using four locally available brand of Portland Pozzolona cement (PPC) and SP belonging to four different families. Water content, cement weight and amount of SP (by considering it as seven separate input based on their family and brand) were the input parameters and mini slump spread diameter was the output parameter for the model. The variation of predicted and measured values of spread diameters were compared and validated. From this study it was observed that, the model could effectively predict the minislump spread of cement paste

The effect of N-acetylcysteine on mechanical fatigue resistance of antibiotic-loaded bone cement.

PubMed

Sukur, Erhan; Akar, Abdulhalim; Topcu, Huseyin Nevzat; Cicekli, Ozgur; Kochai, Alauddin; Turker, Mehmet

2018-05-31

This biomechanical study evaluates the effect of N-acetylcysteine alone and in combination with the most commonly used antibiotic-loaded bone cement mixtures. We mixed eight bone cement mixture groups including combinations of N-acetylcysteine, gentamicin, teicoplanin, and vancomycin and applied a four-point bending test individually to each sample on days 1 and 15 using an MTS Acumen test device. The result was less than 50 MPa-the limit declared by the ISO (International Standards Organization)-in only the "gentamicin + bone cement + N-acetylcysteine" group. Mechanical fatigue resistance of the bone cement decreased significantly with the addition of N-acetylcysteine both on day 1 and day 15 (p <  0.001). With the addition of N-acetylcysteine into the "gentamicin + bone cement" and "vancomycin + bone cement" mixtures, a significant decrease in mechanical fatigue resistance was observed both on day 1 and day 15 (p <  0.001). In contrast, with the addition of N-acetylcysteine into the "teicoplanin + bone cement" mixture, no significant difference in mechanical fatigue resistance was observed on days 1 and 15 (p = 0.093, p = 0.356). Preliminary results indicate that adding N-acetylcysteine to teicoplanin-loaded bone cement does not significantly affect the cement's mechanical resistance, potentially leading to a new avenue for preventing and treating peri-prosthetic joint infection. N-acetylcysteine may, therefore, be considered as an alternative agent to be added to antibiotic-loaded bone cement mixtures used in the prevention of peri-prosthetic joint infection.

Direct Tensile Strength and Characteristics of Dentin Restored with All-Ceramic, Resin-Composite, and Cast Metal Prostheses Cemented with Resin Adhesives

PubMed Central

Piemjai, Morakot; Nakabayashi, Nobuo

2015-01-01

A dentin-cement-prosthesis complex restored with either all-porcelain, cured resin-composite, or cast base metal alloy and cemented with either of the different resin cements was trimmed into a mini-dumbbell shape for tensile testing. The fractured surfaces and characterization of the dentin-cement interface of bonded specimens were investigated using a Scanning Electron Microscope. A significantly higher tensile strength of all-porcelain (12.5 ± 2.2 MPa) than that of cast metal (9.2 ± 3.5 MPa) restorations was revealed with cohesive failure in the cement and failure at the prosthesis-cement interface in Super-Bond C&B group. No significant difference in tensile strength was found among the types of restorations using the other three cements with adhesive failure on the dentin side and cohesive failure in the cured resin. SEM micrographs demonstrated the consistent hybridized dentin in Super-Bond C&B specimens that could resist degradation when immersed in hydrochloric acid followed by NaOCl solutions whereas a detached and degraded interfacial layer was found for the other cements. The results suggest that when complete hybridization of resin into dentin occurs tensile strength at the dentin-cement is higher than at the cement-prosthesis interfaces. The impermeable hybridized dentin can protect the underlying dentin and pulp from acid demineralization, even if detachment of the prosthesis has occurred. PMID:26539520

A 3-D view of field-scale fault-zone cementation from geologically ground-truthed electrical resistivity

NASA Astrophysics Data System (ADS)

Barnes, H.; Spinelli, G. A.; Mozley, P.

2015-12-01

Fault-zones are an important control on fluid flow, affecting groundwater supply, hydrocarbon/contaminant migration, and waste/carbon storage. However, current models of fault seal are inadequate, primarily focusing on juxtaposition and entrainment effects, despite the recognition that fault-zone cementation is common and can dramatically reduce permeability. We map the 3D cementation patterns of the variably cemented Loma Blanca fault from the land surface to ~40 m depth, using electrical resistivity and induced polarization (IP). The carbonate-cemented fault zone is a region of anomalously low normalized chargeability, relative to the surrounding host material. Zones of low-normalized chargeability immediately under the exposed cement provide the first ground-truth that a cemented fault yields an observable IP anomaly. Low-normalized chargeability extends down from the surface exposure, surrounded by zones of high-normalized chargeability, at an orientation consistent with normal faults in the region; this likely indicates cementation of the fault zone at depth, which could be confirmed by drilling and coring. Our observations are consistent with: 1) the expectation that carbonate cement in a sandstone should lower normalized chargeability by reducing pore-surface area and bridging gaps in the pore space, and 2) laboratory experiments confirming that calcite precipitation within a column of glass beads decreases polarization magnitude. The ability to characterize spatial variations in the degree of fault-zone cementation with resistivity and IP has exciting implications for improving predictive models of the hydrogeologic impacts of cementation within faults.

Influence of curing protocol and ceramic composition on the degree of conversion of resin cement.

PubMed

Lanza, Marcos Daniel Septimio; Andreeta, Marcello Rubens Barsi; Pegoraro, Thiago Amadei; Pegoraro, Luiz Fernando; Carvalho, Ricardo Marins De

2017-01-01

Due to increasing of aesthetic demand, ceramic crowns are widely used in different situations. However, to obtain long-term prognosis of restorations, a good conversion of resin cement is necessary. To evaluate the degree of conversion (DC) of one light-cure and two dual-cure resin cements under a simulated clinical cementation of ceramic crowns. Prepared teeth were randomly split according to the ceramic's material, resin cement and curing protocol. The crowns were cemented as per manufacturer's directions and photoactivated either from occlusal suface only for 60 s; or from the buccal, occlusal and lingual surfaces, with an exposure time of 20 s on each aspect. After cementation, the specimens were stored in deionized water at 37°C for 7 days. Specimens were transversally sectioned from occlusal to cervical surfaces and the DC was determined along the cement line with three measurements taken and averaged from the buccal, lingual and approximal aspects using micro-Raman spectroscopy (Alpha 300R/WITec®). Data were analyzed by 3-way ANOVA and Tukey test at =5%. Statistical analysis showed significant differences among cements, curing protocols and ceramic type (p<0.001). The curing protocol 3x20 resulted in higher DC for all tested conditions; lower DC was observed for Zr ceramic crowns; Duolink resin cement culminated in higher DC regardless ceramic composition and curing protocol. The DC of resin cement layers was dependent on the curing protocol and type of ceramic.

Characterization of Cement Particles Found in Peri-implantitis-Affected Human Biopsy Specimens.

PubMed

Burbano, Maria; Wilson, Thomas G; Valderrama, Pilar; Blansett, Jonathan; Wadhwani, Chandur P K; Choudhary, Pankaj K; Rodriguez, Lucas C; Rodrigues, Danieli C

2015-01-01

Peri-implantitis is a disease characterized by soft tissue inflammation and continued loss of supporting bone, which can result in implant failure. Peri-implantitis is a multifactorial disease, and one of its triggering factors may be the presence of excess cement in the soft tissues surrounding an implant. This descriptive study evaluated the composition of foreign particles from 36 human biopsy specimens with 19 specimens selected for analysis. The biopsy specimens were obtained from soft tissues affected by peri-implantitis around cement-retained implant crowns and compared with the elemental composition of commercial luting cement. Nineteen biopsy specimens were chosen for the comparison, and five test cements (TempBond, Telio, Premier Implant Cement, Intermediate Restorative Material, and Relyx) were analyzed using scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. This enabled the identification of the chemical composition of foreign particles embedded in the tissue specimens and the composition of the five cements. Statistical analysis was conducted using classification trees to pair the particles present in each specimen with the known cements. The particles in each biopsy specimen could be associated with one of the commercial cements with a level of probability ranging between .79 and 1. TempBond particles were found in one biopsy specimen, Telio particles in seven, Premier Implant Cement particles in four, Relyx particles in four, and Intermediate Restorative Material particles in three. Particles found in human soft tissue biopsy specimens around implants affected by peri-implant disease were associated with five commercially available dental cements.

Effect of amorphous silica ash used as a partial replacement for cement on the compressive and flexural strengths cement mortar.

NASA Astrophysics Data System (ADS)

Usman, Aliyu; Ibrahim, Muhammad B.; Bala, Nura

2018-04-01

This research is aimed at investigating the effect of using amorphous silica ash (ASA) obtained from rice husk as a partial replacement of ordinary Portland cement (OPC) on the compressive and flexural strength of mortar. ASA was used in partial replacement of ordinary Portland cement in the following percentages 2.5 percent, 5 percent, 7.5 percent and 10 percent. These partial replacements were used to produce Cement-ASA mortar. ASA was found to contain all major chemical compounds found in cement with the exception of alumina, which are SiO2 (91.5%), CaO (2.84%), Fe2O3 (1.96%), and loss on ignition (LOI) was found to be 9.18%. It also contains other minor oxides found in cement. The test on hardened mortar were destructive in nature which include flexural strength test on prismatic beam (40mm x 40mm x 160mm) and compressive strength test on the cube size (40mm x 40mm, by using the auxiliary steel plates) at 2,7,14 and 28 days curing. The Cement-ASA mortar flexural and compressive strengths were found to be increasing with curing time and decreases with cement replacement by ASA. It was observed that 5 percent replacement of cement with ASA attained the highest strength for all the curing ages and all the percentage replacements attained the targeted compressive strength of 6N/mm2 for 28 days for the cement mortar

40 CFR 427.20 - Applicability; description of the asbestos-cement sheet subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... asbestos-cement sheet subcategory. 427.20 Section 427.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Sheet Subcategory § 427.20 Applicability; description of the asbestos-cement sheet...

40 CFR 427.10 - Applicability; description of the asbestos-cement pipe subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... asbestos-cement pipe subcategory. 427.10 Section 427.10 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Pipe Subcategory § 427.10 Applicability; description of the asbestos-cement pipe...

40 CFR 427.10 - Applicability; description of the asbestos-cement pipe subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... asbestos-cement pipe subcategory. 427.10 Section 427.10 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Pipe Subcategory § 427.10 Applicability; description of the asbestos-cement pipe...

40 CFR 427.20 - Applicability; description of the asbestos-cement sheet subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... asbestos-cement sheet subcategory. 427.20 Section 427.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Sheet Subcategory § 427.20 Applicability; description of the asbestos-cement sheet...

Research Of The Influence Of Reftinskii SDPP’S Ash On The Processes Of Cement Stone’S Structure Forming

NASA Astrophysics Data System (ADS)

Zimakova, G. A.; Solonina, V. A.; Zelig, M. P.

2017-01-01

The article describes the experimental research of cement stone. Cement stone forming involves highly dispersive mineral additive - ground ash. It is stated that the substitution of some part of cement with activated ash leaves cement strength high. This is possible due to the activity of ash in structure forming processes. Activation of ash provides the increase in its puzzolanic activity, complete hydration processes. it is stated that ash grinding leads to a selective crystallization hydrated neoformations. Their morthology is different on outer and inner surfaces of ash spheres. The usage of ash can provide cement economy on condition that rheological characteristics of concrete stay constant. Besides, the usage of ash will improve physical and mechanic characteristics of cement stone and concrete.

Physical and mechanical properties of PMMA bone cement reinforced with nano-sized titania fibers.

PubMed

Khaled, S M Z; Charpentier, Paul A; Rizkalla, Amin S

2011-02-01

X-ray contrast medium (BaSO(4) or ZrO(2)) used in commercially available PMMA bone cements imparts a detrimental effect on mechanical properties, particularly on flexural strength and fracture toughness. These lower properties facilitate the chance of implant loosening resulting from cement mantle failure. The present study was performed to examine the mechanical properties of a commercially available cement (CMW1) by introducing novel nanostructured titania fibers (n-TiO(2) fibers) into the cement matrix, with the fibers acting as a reinforcing phase. The hydrophilic nature of the n-TiO(2) fibers was modified by using a bifunctional monomer, methacrylic acid. The n-TiO(2) fiber content of the cement was varied from 0 to 2 wt%. Along with the mechanical properties (fracture toughness (K (IC)), flexural strength (FS), and flexural modulus (FM)) of the reinforced cements the following properties were investigated: complex viscosity-versus-time, maximum polymerization temperature (T (max)), dough time (t (dough)), setting time (t (set)), radiopacity, and in vitro biocompatibility. On the basis of the determined mechanical properties, the optimized composition was found at 1 wt% n-TiO(2) fibers, which provided a significant increase in K (IC) (63%), FS (20%), and FM (22%), while retaining the handling properties and in vitro biocompatibility compared to that exhibited by the control cement (CMW1). Moreover, compared to the control cement, there was no significant change in the radiopacity of any of the reinforced cements at p = 0.05. This study demonstrated a novel pathway to augment the mechanical properties of PMMA-based cement by providing an enhanced interfacial interaction and strong adhesion between the functionalized n-TiO( 2) fibers and PMMA matrix, which enhanced the effective load transfer within the cement.

Regional cement stratigraphy and diagenetic history of Waulsortian Limestones, eastern Midlands, Republic of Ireland

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, D.E.; Meyers, W.J.

1985-02-01

The Lower Carboniferous Waulsortian Limestones, eastern Midlands, Republic of Ireland, contain 7 distinct luminescent zones in clear calcite cements that overlie inclusion-rich, marine cements in cavities and also fill fractures and aragonite-skeleton molds. The luminescent sequence, which records precipitation from increasingly reducing pore waters, is regionally and stratigraphically consistent over an interval more than 1200 ft thick. Zone 1 cements are nonluminescent; zone 2 cements are brightly luminescent; and zones 3-7 cements are ferroan with a moderate to dull luminescence. Zone 1 cements (mean -2.6% delta/sup 18/O/ +3.3% delta/sup 13/C PDB) are slightly depleted in oxygen relative to radiaxial-fibrous cementsmore » (mean -1.8% delta/sup 18/O/ +3.5% delta/sup 13/C PDB) which have a composition that reflects Lower Carboniferous seawater. Zone 4 cements (mean -4.1% delta/sup 18/O/ +3.1% delta/sup 13/C PDB) are depleted in oxygen relative to zone 1, whereas zone 5 cements (mean -11.8% delta/sup 18/O/ +1.1 delta/sup 13/C PDB) are extremely depleted in oxygen and somewhat in carbon. Locally intense dolomitization includes 2 regionally extensive generations of ferroan saddle dolomite. Petrographic relationships demonstrate these dolomite generations were replaced by zone 5 cement. Sulfide mineralization, principally pyrite and sphalerite, occurred after the precipitation of zone 5 cement. Much of diagenesis occurred during a brief period in the Lower Carboniferous. Zones 1-6 and saddle dolomites are contained in Chadian (upper Osagean), shallow-marine facies overlying the Waulsortian. Fractures filled by zone 5 cements are truncated at the margins of Waulsortian clasts contained in a conglomerate overlying an early Arundian (early Meramecian) unconformity.« less

Proton Range Uncertainty Due to Bone Cement Injected Into the Vertebra in Radiation Therapy Planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Young Kyung; Hwang, Ui-Jung; Shin, Dongho, E-mail: dongho@ncc.re.kr

2011-10-01

We wanted to evaluate the influence of bone cement on the proton range and to derive a conversion factor predicting the range shift by correcting distorted computed tomography (CT) data as a reference to determine whether the correction is needed. Two CT datasets were obtained with and without a bone cement disk placed in a water phantom. Treatment planning was performed on a set of uncorrected CT images with the bone cement disk, and the verification plan was applied to the same set of CT images with an effective CT number for the bone cement disk. The effective CT numbermore » was determined by measuring the actual proton range with the bone cement disk. The effects of CT number, thicknesses, and position of bone cement on the proton range were evaluated in the treatment planning system (TPS) to draw a conversion factor predicting the range shift by correcting the CT number of bone cement. The effective CT number of bone cement was 260 Hounsfield units (HU). The calculated proton range for native CT data was significantly shorter than the measured proton range. However, the calculated range for the corrected CT data with the effective CT number coincided exactly with the measured range. The conversion factor was 209.6 [HU . cm/mm] for bone cement and predicted the range shift by approximately correcting the CT number. We found that the heterogeneity of bone cement could cause incorrect proton ranges in treatment plans using CT images. With an effective CT number of bone cement derived from the proton range and relative stopping power, a more actual proton range could be calculated in the TPS. The conversion factor could predict the necessity for CT data correction with sufficient accuracy.« less

Bond strength and interactions of machined titanium-based alloy with dental cements.

PubMed

Wadhwani, Chandur; Chung, Kwok-Hung

2015-11-01

The most appropriate luting agent for restoring cement-retained implant restorations has yet to be determined. Leachable chemicals from some types of cement designed for teeth may affect metal surfaces. The purpose of this in vitro study was to evaluate the shear bond strength and interactions of machined titanium-based alloy with dental luting agents. Eight dental luting agents representative of 4 different compositional classes (resin, polycarboxylate, glass ionomer, and zinc oxide-based cements) were used to evaluate their effect on machined titanium-6 aluminum-4 vanadium (Ti-6Al-4V) alloy surfaces. Ninety-six paired disks were cemented together (n=12). After incubation in a 37°C water bath for 7 days, the shear bond strength was measured with a universal testing machine (Instron) and a custom fixture with a crosshead speed of 5 mm/min. Differences were analyzed statistically with 1-way ANOVA and Tukey HSD tests (α=.05). The debonded surfaces of the Ti alloy disks were examined under a light microscope at ×10 magnification to record the failure pattern, and the representative specimens were observed under a scanning electron microscope. The mean ±SD of shear failure loads ranged from 3.4 ±0.5 to 15.2 ±2.6 MPa. The retention provided by both polycarboxylate cements was significantly greater than that of all other groups (P<.05). The scanning electron microscope examination revealed surface pits only on the bonded surface cemented with the polycarboxylate cements. Cementation with polycarboxylate cement obtained higher shear bond strength. Some chemical interactions occurred between the machined Ti-6Al-4V alloy surface and polycarboxylate cements during cementation. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Bond Strength of Resin Cements to Zirconia Ceramic Using Adhesive Primers.

PubMed

Stefani, Ariovaldo; Brito, Rui Barbosa; Kina, Sidney; Andrade, Oswaldo Scopin; Ambrosano, Gláucia Maria Bovi; Carvalho, Andreia Assis; Giannini, Marcelo

2016-07-01

To evaluate the influence of adhesive primers on the microshear bond strength of resin cements to zirconia ceramic. Fifty zirconia plates (12 mm × 5 mm × 1.5 mm thick) of a commercially available zirconium oxide ceramic (ZirCad) were sintered, sandblasted with aluminum oxide particles, and cleaned ultrasonically before bonding. The plates were randomly divided into five groups of 10. Three resin cements were selected (RelyX ARC, Multilink Automix, Clearfil SA Cement self-adhesive resin cement), along with two primers (Metal-Zirconia Primer, Alloy Primer) and one control group. The primers and resin cements were used according to manufacturers' recommendations. The control group comprised the conventional resin cement (RelyX ARC) without adhesive primer. Test cylinders (0.75 mm diameter × 1 mm high) were formed on zirconia surfaces by filling cylindrical Tygon tube molds with resin cement. The specimens were stored in distilled water for 24 hours at 37°C, then tested for shear strength on a Shimadzu EZ Test testing machine at 0.5 mm/min. Bond strength data were analyzed statistically by two-way ANOVA and Dunnett's test (5%). The bond strength means in MPa (± s.d.) were: RelyX ARC: 28.1 (6.6); Multilink Automix: 37.6 (4.5); Multilink Automix + Metal-Zirconia Primer: 55.7 (4.0); Clearfil SA Cement: 46.2 (3.3); and Clearfil SA Cement + Alloy Primer: 47.0 (4.1). Metal-Zirconia Primer increased the bond strength of Multilink Automix resin cement to zirconia, but no effect was observed for Alloy Primer using Clearfil SA Cement. RelyX ARC showed the lowest bond strength to zirconia. © 2015 by the American College of Prosthodontists.

Comparison of Film Thickness of Two Commercial Brands of Glass lonomer Cement and One Dual-cured Composite: An in vitro Study.

PubMed

Khajuria, Rajat R; Singh, Rishav; Barua, Pranamee; Hajira, Nausheen; Gupta, Naveen; Thakkar, Rohit R

2017-08-01

The present study is undertaken to examine the film thickness of three most commonly used luting cements and to determine their usage as a luting agent. This study was carried out strictly according to the guidelines of American Dental Association (ADS) specification no. 8. Two glass slabs of 5 cm in length and 2 cm in width were used. One glass slab was kept over the other glass slab and the space between the two glass slabs was measured using metallurgical microscope at the power of 10*. Two brands of glass ionomer cement (GIC) and one dual-cured resin cement were used in this study. The test cement is sandwiched between two glass slabs. A static load of 15 kg was applied using universal testing machine on the glass slabs for 1 hour and the space present between the two glass slabs was measured using metallurgical microscope at the power of 10*. Greatest film thickness was found in group III (Paracore) followed by group II (micron) and lowest in group I (GC luting and lining cement). All the tested samples can be used for luting purposes. Greatest film thickness was observed in Paracore followed by micron and lowest in GC luting and lining cement. This suggests that the 25 to 27°C is ideal for mixing of the cement when used for luting consistency. The cement with film thickness more than 30 urn should never be used for luting purposes. The dentist should choose the luting cement with utmost care noting the film thickness and bond strength of the cement. The cement with low exothermic heat production and good bond strength should be encouraged.

Sample environment for in situ synchrotron XRD measurements for CO2 interaction with subsurface materials

NASA Astrophysics Data System (ADS)

Elbakhshwan, M.; Gill, S.; Weidner, R.; Ecker, L.

2017-12-01

Sequestration of CO2 in geological formations requires a deep understanding of its interaction with the cement-casing components in the depleted oil and gas wells. Portland cement is used to seal the wellbores; however it tends to interact with the CO2. Therefore it is critical to investigate the wellbore integrity over long term exposure to CO2. Studies showed that, CO2 leakage is due to the flow through the casing-cement microannulus, cement-cement fractures, or the cement-caprock interface. The objective of this work is to gain a better understanding of the dissolution process of the cement-casing in the CO2 flow channels alongside with the carbonation reactions at the interfaces using XRF, XANES and X-ray tomography techniques. In this study, a synthetic wellbore system, consisting of cement with an embedded rectangular length of steel casing that had grooves to accommodate fluid flow, was used to investigate the casing-cement microannulus through core-flood experiments. The objective of this work is to gain a better understanding of the dissolution process of the cement-casing in the CO2 flow channels alongside with the carbonation reactions at the interfaces using a sample environment designed and built for in situ X-ray diffraction in the National Synchrotron Light Source II (NSLS II). The formation of carbonate phases at cement -fluid and cement-steel/fluid interfaces will be monitored in real time. Samples may be exposed to super critical CO2 at pressures above 1100 psi and temperatures around 50°C. The reaction cell is built from hastealloy to provide corrosion resistance, while the experimental temperature and pressure are controlled with thermocouples and pressure vessel.

Quartz cement in sandstones: a review

NASA Astrophysics Data System (ADS)

McBride, Earle F.

Quartz cement as syntaxial overgrowths is one of the two most abundant cements in sandstones. The main factors that control the amount of quartz cement in sandstones are: framework composition; residence time in the "silica mobility window"; and fluid composition, flow volume and pathways. Thus, the type of sedimentary basin in which a sand was deposited strongly controls the cementation process. Sandstones of rift basins (arkoses) and collision-margin basins (litharenites) generally have only a few percent quartz cement; quartzarenites and other quartzose sandstones of intracratonic, foreland and passive-margin basins have the most quartz cement. Clay and other mineral coatings on detrital quartz grains and entrapment of hydrocarbons in pores retard or prevent cementation by quartz, whereas extremely permeable sands that serve as major fluid conduits tend to sequester the greatest amounts of quartz cement. In rapidly subsiding basins, like the Gulf Coast and North Sea basins, most quartz cement is precipitated by cooling, ascending formation water at burial depths of several kilometers where temperatures range from 60° to 100° C. Cementation proceeds over millions of years, often under changing fluid compositions and temperatures. Sandstones with more than 10% imported quartz cement pose special problems of fluid flux and silica transport. If silica is transported entirely as H 4SiO 4, convective recycling of formation water seems to be essential to explain the volume of cement present in most sandstones. Precipitation from single-cycle, upward-migrating formation water is adequate to provide the volume of cement only if significant volumes of silica are transported in unidentified complexes. Modeling suggests that quartz cementation of sandstones in intracratonic basins is effected by advecting meteoric water, although independent petrographic, isotopic or fluid inclusion data are lacking. Silica for quartz cement comes from both shale and sandstone beds within the depositional basin, including possibly deeply buried rocks undergoing low-grade metamorphism, but the relative importance of potential sources remains controversial and likely differs for different formations. The most likely important silica sources within unmetamorphosed shales include clay transformation (chiefly illitization of smectite), dissolution/pressure solution of detrital grains, and dissolution of opal skeletal grains; the most likely important sources of silica within unmetamorphosed sandstones include pressure solution of detrital quartz grains at grain contacts and at stylolites, feldspar alteration/dissolution, and perhaps carbonate replacement of silicate minerals and the margins of some quartz grains. Silica released by pressure solution in many sandstones post-dates the episode of cementation by quartz; thus, this silica must migrate and cement shallower sandstones in the basin or escape altogether. Some quartz-cemented sandstones are separated vertically from potential silica source beds by a kilometer or more, requiring silica transport over long distances. The similarity of diagenetic sequences in sandstones of different composition and ages apparently is the result of the normal temperature and time-dependent maturation of sediments, organic matter and pore fluids during burial in sedimentary basins. Silica that forms overgrowths is released by one or more diagenetic processes that apparently are controlled by temperature and time. Most cementation by quartz takes place when sandstone beds were in the silica mobility window specific to a particular sedimentary basin. Important secondary controls are introduced by compartmentalized domains produced by faults (e.g., North Sea) or overpressure boundaries (e.g., Gulf Coast Tertiary). Shallow meteoric water precipitates only small amounts of silica cement (generally less than 5% in most fluvial and colian sandstones), except in certain soils and at water tables in high-flux sand aquifers. Soil silcretes are chiefly cemented by opal and microcrystalline quartz, whereas water-table silcretes have abundant normal syntaxial quartz overgrowths. Silica for silcrete cements and replacements comes from quartz, silicate minerals, and locally volcanic glass, in alluvium and bedrock.

Effect of bioglass 45S5 addition on properties, microstructure and cellular response of tetracalcium phosphate/monetite cements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stulajterova, R., E-mail: rstulajterova@saske.sk

Tetracalcium phosphate/nanomonetite (TTCPMH) cement composites with 7.5 and 15 wt% addition of melt-derived 45S5 bioactive glass were prepared by mechanical homogenization of powder components and 2% NaH{sub 2}PO{sub 4} solution was used as a hardening liquid. The properties of composites with the acidic (Ca/P ratio equal 1.5) or basic (Ca/P ratio equal 1.67) TTCPMH component were compared. Addition of glass component caused rapid rise in pH of composites up to 10. In microstructure of basic cement composite, the large bioglass particles weakly bounded to surrounding cement matrix were found contrary to a more compact microstructure of acidic cement composites withmore » the high number of spherical silica particles. Both the significant refinement of hydroxyapatite particles and the change to needle-like morphology with rise in the content of bioglass were identified in hydroxyapatite coatings created during soaking of composites in phosphate buffered saline. In acidic cement mixtures, the increase of compressive strength with an amount of bioglass was found whereas the opposite tendency was revealed in the case of basic cement mixtures. The higher concentrations of ions were verified in solutions after immersion of acidic cement composites. The severe cytotoxicity of extracts and composite cement substrates containing 15 wt% of bioglass demonstrated adverse effects of both the ionic concentrations and unappropriate surface texture on proliferation of mesenchymal stem cells. The enhanced ALP activities of cells cultured on composite cements confirmed the positive effect of bioactive glass addition on differentiation of mesenchymal stem cells. - Highlights: • Novel B45S5 bioglass/tetracalcium phosphate/nanomonetite cement composites • Cement basicity negatively affected their microstructure. • Acid composite cements had higher compressive strengths than basic composites. • Fast differentiation of MSC to osteoblast line on composite with 7.5 wt% of bioglass • Severe cytotoxicity of 24 h extracts from composites with 15 wt% of bioglass.« less

Bone preserving techniques for explanting the well-fixed cemented acetabular component.

PubMed

Stevens, Jarrad; Macpherson, Gavin; Howie, Colin

2018-06-01

Removal of a well-fixed, cemented acetabular component at the time of revision hip surgery can be complex. It is essential to remove the implant and cement mantle in a timely fashion while preserving bone stock and osseous integrity. The biomechanical properties of polymethylmethacrylate cement and polyethylene can be utilised to aid with the removal of well cemented implants which are often harder than the surrounding bone. While removal of loose components may be relatively straightforward, the challenge for the revision arthroplasty surgeon often involves the removal of well-fixed implants. Here, we present three established techniques for the removal of a well-fixed cemented acetabular component and one novel modification we have described before. We collate and review four techniques for removing well-fixed cemented acetabular implants that utilise the different biomechanical properties of bone cement and polyethylene. These techniques are illustrated with a photographic series utilising saw bones. A step-by-step approach to our new technique is shown in photographs, both in the clinical setting and with a "Sawbone". This is accompanied by a clinical video that details the surgical technique in its entirety. These techniques utilise different biomechanical principles to extract the acetabular component. Each technique has advantages and disadvantages. Our new technique is a simplification of a previously published extraction manoeuvre that utilises tensile force between cement and the implant to remove the polyethylene cup. This is a safe and reproducible technique in patients with a well-fixed cemented acetabular implant. Understanding the biomechanical properties of polymethylmethacrylate bone cement and polyethylene can aid in the safe removal of a well-fixed cemented acetabular component in revision hip surgery. The optimal technique for removal of a cemented acetabular component varies depending on a number of patient and implant factors. This summary of the available techniques will be of interest to revision arthroplasty surgeons.

The comparison of properties and cost of material use of natural rubber and sand in manufacturing cement mortar for construction sub-base layer

NASA Astrophysics Data System (ADS)

Rahman, R.; Nemmang, M. S.; Hazurina, Nor; Shahidan, S.; Khairul Tajuddin Jemain, Raden; Abdullah, M. E.; Hassan, M. F.

2017-11-01

The main issue related to this research was to examine the feasibility of natural rubber SMR 20 in the manufacturing of cement mortar for sub-base layer construction. Subbase layers have certain functions that need to be fulfilled in order to assure strong and adequate permeability of pavement performance. In a pavement structure, sub-base is below the base and serves as the foundation for the overall pavement structure, transmitting traffic loads to the sub-grade and providing drainage. Based on this research, the natural rubber, SMR 20 was with the percentages of 0%, 5%, 10% and 15% to mix with sand in the manufacture of the cement mortar. This research describes some of the properties and cost of the materials for the natural rubber and sand in cement mortar manufacturing by laboratory testing. Effects of the natural rubber replacement on mechanical properties of mortar were investigated by laboratory testing such as compressive strength test and density. This study obtained the 5% of natural rubber replaced in sand can achieved the strength of normal mortar after 7 days and 28 days. The strength of cement mortar depends on the density of cement mortar. According to the cost of both materials, sand shows the lower cost in material for the cement mortar manufacturing than the uses of natural rubber. Thus, the convectional cement mortar which used sand need lower cost than the modified rubber cement mortar and the most economical to apply in industrial. As conclusion, the percentage of 5% natural rubber in the cement mortar would have the same with normal cement mortar in terms of the strength. However, in terms of the cost of the construction, it will increase higher than cost of normal cement mortar production. So that, this modified cement mortar is not economical for the road sub-base construction.

The Use of Micro and Nano Particulate Fillers to Modify the Mechanical and Material Properties of Acrylic Bone Cement

NASA Astrophysics Data System (ADS)

Slane, Joshua A.

Acrylic bone cement (polymethyl methacrylate) is widely used in total joint replacements to provide long-term fixation of implants. In essence, bone cement acts as a grout by filling in the voids left between the implant and the patient's bone, forming a mechanical interlock. While bone cement is considered the `gold standard' for implant fixation, issues such as mechanical failure of the cement mantle (aseptic loosening) and the development of prosthetic joint infection (PJI) still plague joint replacement procedures and often necessitate revision arthroplasty. In an effort to address these failures, various modifications are commonly made to bone cement such as mechanical reinforcement with particles/fibers and the addition of antibiotics to mitigate PJI. Despite these attempts, issues such as poor particle interfacial adhesion, inadequate drug release, and the development of multidrug resistant bacteria limit the effectiveness of bone cement modifications. Therefore, the overall goal of this work was to use micro and nanoparticles to enhance the properties of acrylic bone cement, with particular emphasis placed on improving the mechanical properties, cumulative antibiotic release, and antimicrobial properties. An acrylic bone cement (Palacos R) was modified with three types of particles in various loading ratios: mesoporous silica nanoparticles (for mechanical reinforcement), xylitol microparticles (for increased antibiotic release), and silver nanoparticles (as an antimicrobial agent). These particles were used as sole modifications, not in tandem with one another. The resulting cement composites were characterized using a variety of mechanical (macro to nano, fatigue, fracture, and dynamic), imaging, chemical, thermal, biological, and antimicrobial testing techniques. The primary outcomes of this dissertation demonstrate that: (1) mesoporous silica, as used in this work, is a poor reinforcement phase for acrylic bone cement, (2) xylitol can significantly increase the cumulative antibiotic release from acrylic cement, and (3) silver nanoparticles are a potential alternative to traditional antibiotics in cement, such as gentamicin.

Gentamicin release from commercially-available gentamicin-loaded PMMA bone cements in a prosthesis-related interfacial gap model and their antibacterial efficacy.

PubMed

Neut, Daniëlle; Kluin, Otto S; Thompson, Jonathan; van der Mei, Henny C; Busscher, Henk J

2010-11-10

Around about 1970, a gentamicin-loaded poly (methylmethacrylate) (PMMA) bone cement brand (Refobacin Palacos R) was introduced to control infection in joint arthroplasties. In 2005, this brand was replaced by two gentamicin-loaded follow-up brands, Refobacin Bone Cement R and Palacos R + G. In addition, another gentamicin-loaded cement brand, SmartSet GHV, was introduced in Europe in 2003. In the present study, we investigated differences in gentamicin release and the antibacterial efficacy of the eluent between these four cement brands. 200 μm-wide gaps were made in samples of each cement and filled with buffer in order to measure the gentamicin release. Release kinetics were related to bone cement powder particle characteristics and wettabilities of the cement surfaces. Gaps were also inoculated with bacteria isolated from infected prostheses for 24 h and their survival determined. Gentamicin release and bacterial survival were statistically analysed using the Student's t-test. All three Palacos variants showed equal burst releases but each of the successor Palacos cements showed significantly higher sustained releases. SmartSet GHV showed a significantly higher burst release, while its sustained release was comparable with original Palacos. A gentamicin-sensitive bacterium did not survive in the high gentamicin concentrations in the interfacial gaps, while a gentamicin-resistant strain did, regardless of the type of cement used. Survival was independent of the level of burst release by the bone cement. Although marketed as the original gentamicin-loaded Palacos cement, orthopaedic surgeons should be aware that the successor cements do not appear to have the same release characteristics as the original one. Overall, high gentamicin concentrations were reached inside our prosthesis-related interfacial gap model. These concentrations may be expected to effectively decontaminate the prosthesis-related interfacial gap directly after implantation, provided that these bacteria are sensitive for gentamicin.

Design of Fit-for-Purpose Cement to Restore Cement-Caprock Seal Integrity

NASA Astrophysics Data System (ADS)

Provost, R.

2015-12-01

This project aims to study critical research needs in the area of rock-cement interfaces, with a special focus on crosscutting applications in the Wellbore Integrity Pillar of the SubTER initiative. This study will focus on design and test fit-for-purpose cement formulations. The goals of this project are as follows: 1) perform preliminary study of dispersing nanomaterial admixtures in Ordinary Portland Cement (OPC) mixes, 2) characterize the cement-rock interface, and 3) identify potential high-performance cement additives that can improve sorption behavior, chemical durability, bond strength, and interfacial fracture toughness, as appropriate to specific subsurface operational needs. The work presented here focuses on a study of cement-shale interfaces to better understand failure mechanisms, with particular attention to measuring bond strength at the cement-shale interface. Both experimental testing and computational modeling were conducted to determine the mechanical behavior at the interface representing the interaction of cement and shale of a typical wellbore environment. Cohesive zone elements are used in the finite element method to computationally simulate the interface of the cement and rock materials with varying properties. Understanding the bond strength and mechanical performance of the cement-formation interface is critical to wellbore applications such as sequestration, oil and gas production and exploration and nuclear waste disposal. Improved shear bond strength is an indication of the capability of the interface to ensure zonal isolation and prevent zonal communication, two crucial goals in preserving wellbore integrity. Understanding shear bond strength development and interface mechanics will provide an idea as to how the cement-formation interface can be altered under environmental changes (temperature, pressure, chemical degradation, etc.) so that the previously described objectives can be achieved. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND #: SAND2015-6523 A

Addition of a Fluoride-containing Radiopacifier Improves Micromechanical and Biological Characteristics of Modified Calcium Silicate Cements.

PubMed

Antonijevic, Djordje; Jeschke, Anke; Colovic, Bozana; Milovanovic, Petar; Jevremovic, Danimir; Kisic, Danilo; vom Scheidt, Annika; Hahn, Michael; Amling, Michael; Jokanovic, Vukoman; Busse, Björn; Djuric, Marija

2015-12-01

Calcium silicate cements (CSCs) with the addition of nanohydroxyapatite and calcium carbonate play a critical role in dental applications. To further improve their properties, particularly radiopacity and biointeractivity, the fluoride-containing radiopacifier ytterbium trifluoride (YbF3) was added to their composition, and biological and mechanical characteristics were evaluated. YbF3 was added to 3 different CSCs: cement I (CSC + calcium carbonate), cement II (CSC + nanohydroxyapatite), and Portland cement. Material characterization encompassed measurements of pH, calcium, ytterbium, and fluoride ion release; radiopacity; setting time; porosity; microindentation properties; wettability; and Fourier transform infrared spectroscopic, x-ray diffraction, and scanning electron microscopic analyses. Osteoblast- and osteoclast-like cells were grown on the materials' surface to evaluate their adherence. The addition of calcium carbonate, nanohydroxyapatite, and 30 wt% of YbF3 improved radiopacity and the setting time of experimental cements. The pH values did not differ among the groups. The greatest ytterbium and fluoride releases occurred in the Portland cement + YbF3 group. Combined x-ray diffraction and Fourier transform infrared spectroscopic analysis showed the presence of calcium hydroxide and calcium silicate hydrates. In addition, the presence of calcium ytterbium fluoride and ytterbium oxide proved that YbF3 reacted with cement compounds. Wettability of cement I + YbF3 was superior to other formulations, but its porosity and microindentation properties were weaker than in the Portland cement + YbF3 mixture. Cement II + YbF3 presented micromechanical indentation and porosity characteristics similar to the Portland-based cement formulation. Osteoclast- and osteoblast-like cells adhered to the cements' surfaces without alteration of the cell structural integrity. YbF3-containing CSCs with nanostructured hydroxyapatite and calcium carbonate are well suited for dental application. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Comparative study of the marginal microleakage of six cements in fixed provisional crowns.

PubMed

Baldissara, P; Comin, G; Martone, F; Scotti, R

1998-10-01

In many situations, provisional restorations require a long-term permanence in the oral cavity. During this period, the abutments need the best possible biologic and mechanical protection. In this way, the vitality of the pulp and the integrity of mineralized tissues can be preserved. The luting cement used to fix interim restorations should have good mechanical properties, low solubility, and good adhesion to resist bacterial and molecular penetration. However, because of its provisional nature, the prosthesis should be easy to remove from the abutments. These contrasting requirements may lead to a compromise in cement behavior, particularly in its mechanical properties. This in vitro study evaluated the marginal microleakage of 4 provisional cements, a cavity base compound and a zinc-phosphate luting cement in provisional acrylic resin crowns fixed on extracted human teeth. Thirty acrylic resin crowns were made and fitted on intact human premolars with the 6 cements. All restorations were applied in a standardized manner by means of an axial load of 10 kg. Specimens were thermocycled then submerged in a 5% basic fuchsin solution, then sectioned and observed under a light stereomicroscope. A 5-level scale was used to score dye penetration in the tooth/cement interface. A high dye penetration in the tooth/cement interface was present in all 4 provisional cements. Microleakage existed in specimens where zinc-phosphate and cavity base compounds were used; however, it was lower than the other materials. A significant difference (P < .05) was found between zinc-phosphate and one eugenol-free cement and between cavity base and the same eugenol-free cement. All materials tested demonstrated different degrees of microleakage. Zinc-phosphate and cavity base compound cements had the best sealing properties. This latter, even if conceived as a cavity base, may be considered a good provisional cement as far as microleakage is concerned.

21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device... metallic prosthetic implants to living bone. (b) Classification. Class II (special controls). The special...

21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device... metallic prosthetic implants to living bone. (b) Classification. Class II (special controls). The special...

21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device... metallic prosthetic implants to living bone. (b) Classification. Class II (special controls). The special...

21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device... metallic prosthetic implants to living bone. (b) Classification. Class II (special controls). The special...

21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device... metallic prosthetic implants to living bone. (b) Classification. Class II (special controls). The special...

40 CFR 427.10 - Applicability; description of the asbestos-cement pipe subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... asbestos-cement pipe subcategory. 427.10 Section 427.10 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Pipe Subcategory § 427.10 Applicability; description of the asbestos-cement pipe...

40 CFR 427.10 - Applicability; description of the asbestos-cement pipe subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... asbestos-cement pipe subcategory. 427.10 Section 427.10 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Pipe Subcategory § 427.10 Applicability; description of the asbestos-cement pipe...

40 CFR 427.20 - Applicability; description of the asbestos-cement sheet subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... asbestos-cement sheet subcategory. 427.20 Section 427.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Sheet Subcategory § 427.20 Applicability; description of the asbestos-cement sheet...

40 CFR 427.20 - Applicability; description of the asbestos-cement sheet subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... asbestos-cement sheet subcategory. 427.20 Section 427.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Sheet Subcategory § 427.20 Applicability; description of the asbestos-cement sheet...

40 CFR 427.20 - Applicability; description of the asbestos-cement sheet subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... asbestos-cement sheet subcategory. 427.20 Section 427.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Sheet Subcategory § 427.20 Applicability; description of the asbestos-cement sheet...

40 CFR 427.10 - Applicability; description of the asbestos-cement pipe subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... asbestos-cement pipe subcategory. 427.10 Section 427.10 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos-Cement Pipe Subcategory § 427.10 Applicability; description of the asbestos-cement pipe...

Cement Mason's Curriculum. Instructional Units.

ERIC Educational Resources Information Center

Hendirx, Laborn J.; Patton, Bob

To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

75 FR 7303 - Drake Cement, LLC-Acquisition Exemption-Clarkdale Arizona Central Railroad, LLC

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-18

... DEPARTMENT OF TRANSPORTATION Surface Transportation Board [STB Finance Docket No. 35350] Drake Cement, LLC--Acquisition Exemption--Clarkdale Arizona Central Railroad, LLC Drake Cement, LLC (DC), a..., Drake Switching Company, LLC --Operation Exemption-- Drake Cement, LLC. DC certifies that the projected...

[A study on alpha-tricalcium phosphate bone cement carbon fiber-reinforced].

PubMed

Wu, Wenjin; Yang, Weizhong; Zhou, Dali; Ma, Jiang; Xiao, Bin

2006-06-01

In order to improve the mechanical properties of alpha-tricalcium phosphate (alpha-TCP), we prepared surface-modified carbon fibers (CF) reinforced alpha-TCP composite bone cement. Bone cement was soaked in Ringer's body solution to test its capacity of fast formation of hydroxyapatite crystals and self-solidification. Scan electronic microscope (SEM) observation and compressive strength measurement were taken to analyze the mechanical properties and the micro- morphological structure of CF reinforced alpha-TCP bone cement. The results showed that the bone cement was transferred into hydroxyapatite plates after being soaked in Ringer's simulated body fluid for 5 days. Suitable amount of carbon fibers could well spread in and bond with the matrix of the bone cement. The mechanical properties of the bone cement have been improved by CF reinforcing; the compressive strength reaches 46.7 MPa when the amount of carbon fibers is 0.5% in weight percent, which is 22% higher than that of the non-reinforced alpha-TCP bone cement.

Microleakage under orthodontic bands cemented with nano-hydroxyapatite-modified glass ionomer.

PubMed

Enan, Enas T; Hammad, Shaza M

2013-11-01

To estimate the in vivo effect of nano-hydroxyapatite (HA) modification of banding glass-ionomer cement on microleakage under orthodontic bands. Eighty noncarious premolars scheduled for extraction in 20 orthodontic patients were randomly divided into four groups. Grouping was based on the ratio of nano-HA (0%, 5%, 10%, 15% by weight) added to the luting glass-ionomer cement (GIC) Ketac-Cem, which was used for cementation of prefabricated micro-etched orthodontic bands. Dye penetration method was used for microleakage evaluation at the cement-band and cement-enamel interfaces. Statistical evaluation was performed with a Kruskal-Wallis test and a Mann-Whitney U-test, and a Bonferroni-adjusted significance level was calculated. Bands cemented with conventional GIC showed the highest microleakage scores in comparison to those cemented with nano-HA-modified GIC. No significant difference was found between teeth banded with 10% and 15% modified GIC. Modification of the banding GIC with 15% nano-HA revealed a positive effect on reducing microleakage around orthodontic bands.

Dose response effect of cement dust on respiratory muscles competence in cement mill workers.

PubMed

Meo, Sultan A; Azeem, Muhammad A; Qureshi, Aijaz A; Ghori, G Moinudin; Al-Drees, Abdul Majeed; Feisal Subhan, Mirza Muhammad

2006-12-01

Electromyography (EMG) of respiratory muscles is a reliable method of assessing the ventilatory muscle function, but still its use has not been fully utilized to determine the occupational and environmental hazards on respiratory muscles. Therefore, EMG of intercostal muscles was performed to determine the dose response effect of cement dust on respiratory muscles competence. Matched cross-sectional study of EMG in 50 non-smoking cement mill workers with an age range of 20 - 60 years, who worked without the benefit of cement dust control ventilation or respiratory protective devices. EMG was performed by using surface electrodes and chart recorder. Significant reduction was observed in number of peaks (p < 0.0005), maximum peak amplitude (p < 0.0005), peak-to-peak amplitude (p < 0.0005) and duration of response (p < 0.0005) in cement mill workers compared to their matched control. Cement dust impairs the intercostal muscle competence and stratification of results shows a dose-effect of years of exposure in cement mill.

Preferential adsorption of polycarboxylate superplasticizers on cement and silica fume in ultra-high performance concrete (UHPC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroefl, Ch.; Gruber, M.; Plank, J., E-mail: sekretariat@bauchemie.ch.tum.de

2012-11-15

UHPC is fluidized particularly well when a blend of MPEG- and APEG-type PCEs is applied. Here, the mechanism for this behavior was investigated. Testing individual cement and micro silica pastes revealed that the MPEG-PCE disperses cement better than silica whereas the APEG-PCE fluidizes silica particularly well. This behavior is explained by preferential adsorption of APEG-PCE on silica while MPEG-PCEs exhibit a more balanced affinity to both cement and silica. Adsorption data obtained from individual cement and micro silica pastes were compared with those found for the fully formulated UHPC containing a cement/silica blend. In the UHPC formulation, both PCEs stillmore » exhibit preferential and selective adsorption similar as was observed for individual cement and silica pastes. Preferential adsorption of PCEs is explained by their different stereochemistry whereby the carboxylate groups have to match with the steric position of calcium ions/atoms situated at the surfaces of cement hydrates or silica.« less

Revision total hip arthroplasty: the femoral side using cemented implants.

PubMed

Holt, Graeme; Hook, Samantha; Hubble, Matthew

2011-02-01

Advances in surgical technique and implant technology have improved the ten-year survival after primary total hip arthroplasty (THA). Despite this, the number of revision procedures has been increasing in recent years, a trend which is predicted to continue into the future. Revision THA is a technically demanding procedure often complicated by a loss of host bone stock which may be compounded by the need to remove primary implants. Both cemented and uncemented implant designs are commonly used in the United Kingdom for primary and revision THA and much controversy still exists as to the ideal method of stem fixation. In this article we discuss revision of the femur using cemented components during revision THA. We focus on three clinical scenarios including femoral cement-in-cement revision where the primary femoral cement-bone interface remains well fixed, femoral cement-in-cement revision for peri-prosthetic femoral fractures, and femoral impaction grafting. We discuss the clinical indications, surgical techniques and clinical outcomes for each of these procedures.

Comparative study of methods to measure the density of Cementious powders.

PubMed

Helsel, Michelle A; Ferraris, Chiara F; Bentz, Dale

2016-11-01

The accurate measurement of the density of hydraulic cement has an essential role in the determination of concrete mixture proportions. As more supplementary cementitious materials (SCM), such as fly ash, and slag, or cement replacements materials such as limestone and calcium carbonate are used in blended cements, knowledge of the density of each powder or of the blended cement would allow a more accurate calculation of the proportions of a concrete mixture by volume instead of by mass. The current ASTM standard for measuring cement density is the "Test Method for Density of Hydraulic Cements" (ASTM C188-14), which utilizes a liquid displacement method to measure the volume of the cement. This paper will examine advantageous modifications of the current ASTM test, by alcohol substitutions for kerosene. In addition, a gas (helium) pycnometry method is evaluated as a possible alternative to the current standard. The described techniques will be compared to determine the most precise and reproducible method for measuring the density of hydraulic cements and other powders.

The crucial effect of early-stage gelation on the mechanical properties of cement hydrates

NASA Astrophysics Data System (ADS)

Ioannidou, Katerina; Kanduč, Matej; Li, Lunna; Frenkel, Daan; Dobnikar, Jure; Del Gado, Emanuela

2016-07-01

Gelation and densification of calcium-silicate-hydrate take place during cement hydration. Both processes are crucial for the development of cement strength, and for the long-term evolution of concrete structures. However, the physicochemical environment evolves during cement formation, making it difficult to disentangle what factors are crucial for the mechanical properties. Here we use Monte Carlo and Molecular Dynamics simulations to study a coarse-grained model of cement formation, and investigate the equilibrium and arrested states. We can correlate the various structures with the time evolution of the interactions between the nano-hydrates during the preparation of cement. The novel emerging picture is that the changes of the physicochemical environment, which dictate the evolution of the effective interactions, specifically favour the early gel formation and its continuous densification. Our observations help us understand how cement attains its unique strength and may help in the rational design of the properties of cement and related materials.

The crucial effect of early-stage gelation on the mechanical properties of cement hydrates

PubMed Central

Ioannidou, Katerina; Kanduč, Matej; Li, Lunna; Frenkel, Daan; Dobnikar, Jure; Del Gado, Emanuela

2016-01-01

Gelation and densification of calcium–silicate–hydrate take place during cement hydration. Both processes are crucial for the development of cement strength, and for the long-term evolution of concrete structures. However, the physicochemical environment evolves during cement formation, making it difficult to disentangle what factors are crucial for the mechanical properties. Here we use Monte Carlo and Molecular Dynamics simulations to study a coarse-grained model of cement formation, and investigate the equilibrium and arrested states. We can correlate the various structures with the time evolution of the interactions between the nano-hydrates during the preparation of cement. The novel emerging picture is that the changes of the physicochemical environment, which dictate the evolution of the effective interactions, specifically favour the early gel formation and its continuous densification. Our observations help us understand how cement attains its unique strength and may help in the rational design of the properties of cement and related materials. PMID:27417911

Novel cemented cup-holding technique while performing total hip arthroplasty with navigation system.

PubMed

Takai, Hirokazu; Takahashi, Tomoki

2017-09-01

Recently, navigation systems have been more widely utilized in total hip arthroplasty. However, almost all of these systems have been developed for cementless cups. In the case of cemented total hip arthroplasty using a navigation system, a special-ordered cemented holder is needed. We propose a novel cemented cup-holding technique for navigation systems using readily available articles. We combine a cementless cup holder with an inverted cementless trial cup. The resulting apparatus is used as a cemented cup holder. The upside-down cup-holding technique is useful and permits cemented cup users to utilize a navigation system for placement of the acetabular component.

A comparison of distal canal restrictors in primary cemented femoral hip arthroplasty.

PubMed

Smith, Eric L; Wohlrab, Kurt P; Matzkin, Elizabeth G; Providence, Bertram C

2004-08-01

A retrospective study evaluated 75 total hip arthroplasties performed over a 4-year period using 4 different cement restrictors. A harvested bone restrictor, polyethylene restrictor (Smith & Nephew, Richards Inc, Memphis, Tenn), Biostop G (Depuy Orthopaedics, Warsaw, Ind), and polymethylmethacrylate (PMMA) (Wright Medical Technology, Arlington, Tex) were compared for the percentage of failures, the average length of the cement mantle, and the width of the femoral canal compared to the cement grade. Patient age, sex, and cement type were also evaluated for their influence on cement grade. The PMMA restrictor and bone performed better than the Richards plug and Biostop G restrictor.

Effects of Using Pozzolan and Portland Cement in the Treatment of Dispersive Clay

PubMed Central

Vakili, A. H.; Selamat, M. R.; Moayedi, H.

2013-01-01

Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable of reducing dispersion potential to almost zero percent in only 7 days; and a 2% cement content was capable of achieving similar result in 14 days. However, treatment by cement alone is costly and could jeopardize the long term performance. Thus, a combined 5% pozzolan and 1.5% cement content was found capable of reducing dispersion potential from 100% to zero percent in 14 days. The results indicate that although simultaneous treatment with pozzolan and cement would extend the required curing time in comparison to treatment by cement alone of a higher content, the task could still be carried out in a reasonable period of curing time while avoiding the drawbacks of using either pozzolan or cement alone. PMID:23864828

Revealing the influence of water-cement ratio on the pore size distribution in hydrated cement paste by using cyclohexane

NASA Astrophysics Data System (ADS)

Bede, Andrea; Ardelean, Ioan

2017-12-01

Varying the amount of water in a concrete mix will influence its final properties considerably due to the changes in the capillary porosity. That is why a non-destructive technique is necessary for revealing the capillary pore distribution inside hydrated cement based materials and linking the capillary porosity with the macroscopic properties of these materials. In the present work, we demonstrate a simple approach for revealing the differences in capillary pore size distributions introduced by the preparation of cement paste with different water-to-cement ratios. The approach relies on monitoring the nuclear magnetic resonance transverse relaxation distribution of cyclohexane molecules confined inside the cement paste pores. The technique reveals the whole spectrum of pores inside the hydrated cement pastes, allowing a qualitative and quantitative analysis of different pore sizes. The cement pastes with higher water-to-cement ratios show an increase in capillary porosity, while for all the samples the intra-C-S-H and inter-C-S-H pores (also known as gel pores) remain unchanged. The technique can be applied to various porous materials with internal mineral surfaces.

Development of Carbon Nanotube Modified Cement Paste with Microencapsulated Phase-Change Material for Structural–Functional Integrated Application

PubMed Central

Cui, Hongzhi; Yang, Shuqing; Memon, Shazim Ali

2015-01-01

Microencapsulated phase-change materials (MPCM) can be used to develop a structural–functional integrated cement paste having high heat storage efficiency and suitable mechanical strength. However, the incorporation of MPCM has been found to degrade the mechanical properties of cement based composites. Therefore, in this research, the effect of carbon nanotubes (CNTs) on the properties of MPCM cement paste was evaluated. Test results showed that the incorporation of CNTs in MPCM cement paste accelerated the cement hydration reaction. SEM micrograph showed that CNTs were tightly attached to the cement hydration products. At the age of 28 days, the percentage increase in flexural and compressive strength with different dosage of CNTs was found to be up to 41% and 5% respectively. The optimum dosage of CNTs incorporated in MPCM cement paste was found to be 0.5 wt %. From the thermal performance test, it was found that the cement paste panels incorporated with different percentages of MPCM reduced the temperature measured at the center of the room by up to 4.6 °C. Inverse relationship was found between maximum temperature measured at the center of the room and the dosage of MPCM. PMID:25867476

Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?

PubMed

Walling, Sam A; Provis, John L

2016-04-13

This review examines the detailed chemical insights that have been generated through 150 years of work worldwide on magnesium-based inorganic cements, with a focus on both scientific and patent literature. Magnesium carbonate, phosphate, silicate-hydrate, and oxysalt (both chloride and sulfate) cements are all assessed. Many such cements are ideally suited to specialist applications in precast construction, road repair, and other fields including nuclear waste immobilization. The majority of MgO-based cements are more costly to produce than Portland cement because of the relatively high cost of reactive sources of MgO and do not have a sufficiently high internal pH to passivate mild steel reinforcing bars. This precludes MgO-based cements from providing a large-scale replacement for Portland cement in the production of steel-reinforced concretes for civil engineering applications, despite the potential for CO2 emissions reductions offered by some such systems. Nonetheless, in uses that do not require steel reinforcement, and in locations where the MgO can be sourced at a competitive price, a detailed understanding of these systems enables their specification, design, and selection as advanced engineering materials with a strongly defined chemical basis.

A novel antibacterial orthodontic cement containing a quaternary ammonium monomer dimethylaminododecyl methacrylate

PubMed Central

Melo, Mary A.S.; Wu, Junling; Weir, Michael D.; Xu, Hockin H. K.

2015-01-01

Demineralized lesions in tooth enamel around orthodontic brackets are caused by acids from cariogenic biofilm. This study aimed to develop a novel antibacterial orthodontic cement by incorporating a quaternary ammonium monomer dimethylaminododecyl methacrylate (DMADDM) into a commercial orthodontic cement, and to investigate the effects on microcosm biofilm response and enamel bond strength. DMADDM, a recently-synthetized antibacterial monomer, was incorporated into orthodontic cement at 0%, 1.5%, 3% and 5% mass fractions. Bond strength of brackets to enamel was measured. A microcosm biofilm model was used to measure metabolic activity, lactic acid production, and colony-forming units (CFU) on orthodontic cements. Shear bond strength was not reduced at 3% DAMDDM (p > 0.1), but was slightly reduced at 5% DMADDM, compared to 0% DMADDM. Biofilm viability was substantially inhibited when in contact with orthodontic cement containing 3% DMADDM. Biofilm metabolic activity, lactic acid production, and CFU were much lower on orthodontic cement containing DMADDM than control cement (p < 0.05). Therefore, the novel antibacterial orthodontic cement containing 3% DMADDM inhibited oral biofilms without compromising the enamel bond strength, and is promising to reduce or eliminate demineralization in enamel around orthodontic brackets. PMID:25035230

Influence of increasing amount of recycled concrete powder on mechanical properties of cement paste

NASA Astrophysics Data System (ADS)

Topič, Jaroslav; Prošek, Zdeněk; Plachý, Tomáš

2017-09-01

This paper deals with using fine recycled concrete powder in cement composites as micro-filler and partial cement replacement. Binder properties of recycled concrete powder are given by exposed non-hydrated cement grains, which can hydrate again and in small amount replace cement or improve some mechanical properties. Concrete powder used in the experiments was obtained from old railway sleepers. Infrastructure offer more sources of old concrete and they can be recycled directly on building site and used again. Experimental part of this paper focuses on influence of increasing amount of concrete powder on mechanical properties of cement paste. Bulk density, shrinkage, dynamic Young’s modulus, compression and flexural strength are observed during research. This will help to determine limiting amount of concrete powder when decrease of mechanical properties outweighs the benefits of cement replacement. The shrinkage, dynamic Young’s modulus and flexural strength of samples with 20 to 30 wt. % of concrete powder are comparable with reference cement paste or even better. Negative effect of concrete powder mainly influenced the compression strength. Only a 10 % cement replacement reduced compression strength by about 25 % and further decrease was almost linear.

Effects of using pozzolan and Portland cement in the treatment of dispersive clay.

PubMed

Vakili, A H; Selamat, M R; Moayedi, H

2013-01-01

Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable of reducing dispersion potential to almost zero percent in only 7 days; and a 2% cement content was capable of achieving similar result in 14 days. However, treatment by cement alone is costly and could jeopardize the long term performance. Thus, a combined 5% pozzolan and 1.5% cement content was found capable of reducing dispersion potential from 100% to zero percent in 14 days. The results indicate that although simultaneous treatment with pozzolan and cement would extend the required curing time in comparison to treatment by cement alone of a higher content, the task could still be carried out in a reasonable period of curing time while avoiding the drawbacks of using either pozzolan or cement alone.

A comparison of high viscosity bone cement and low viscosity bone cement vertebroplasty for severe osteoporotic vertebral compression fractures.

PubMed

Zhang, Liang; Wang, Jingcheng; Feng, Xinmin; Tao, Yuping; Yang, Jiandong; Wang, Yongxiang; Zhang, Shengfei; Cai, Jun; Huang, Jijun

2015-02-01

To compare the clinical outcome and complications of high viscosity and low viscosity poly-methyl methacrylate bone cement PVP for severe OVCFs. From December 2010 to December 2012, 32 patients with severe OVCFs were randomly assigned to either group H using high viscosity cement (n=14) or group L using low viscosity cement (n=18). The clinical outcomes were assessed by the Visual Analog Scale (VAS), Oswestry Disability Index (ODI), Short Form-36 General Health Survey (SF-36), kyphosis Cobb's angle, vertebral height, and complications. Significant improvement in the VAS, ODI, SF-36 scores, kyphosis Cobb's angle, and vertebral height were noted in both the groups, and there were no significant differences between the two groups. Cement leakage was seen less in group H. Postoperative assessment using computed tomography identified cement leakage in 5 of 17 (29.4%) vertebrae in group H and in 15 of 22 (68.2%) vertebrae in group L (P=0.025). The PVP using high viscosity bone cement can provide the same clinical outcome and fewer complications compared with PVP using low viscosity bone cement. Copyright © 2014. Published by Elsevier B.V.

Rigidity and retention of ceramic root canal posts.

PubMed

Purton, D G; Love, R M; Chandler, N P

2000-01-01

Ceramic root-canal posts offer potential advantages over other types with respect to aesthetics and biocompatibility. Any post must be sufficiently rigid and retentive to withstand functional forces. Ceraposts (1.2 mm coronal diameter, ceramic, tapering, smooth posts) and Paraposts (1.25 mm, stainless-steel, parallel, serrated posts) were tested for rigidity by means of a three-point bending test. To test retention in roots, ceramic posts were cemented using one of three protocols: (1) glass-ionomer cement, (2) silane coupling agent and resin cement, or (3) sandblasted post surface, silane coupling agent, and resin cement. Stainless-steel posts were cemented with resin. The tensile force required to dislodge the posts, following four weeks of storage in water, was recorded. Data were compared using Student's t-test and Mann-Whitney U analysis. Ceraposts were significantly more rigid than Paraposts (p < 0.001). Paraposts cemented with resin were significantly more strongly retained than Ceraposts following any cementation protocol (p < 0.001). Retention of the ceramic posts was significantly greater with a silane coupling agent and resin cement than with glass-ionomer cement (p < 0.001). Sandblasting the ceramic posts produced variable results and needs further investigation before it could be recommended.

Low force cementation.

PubMed

Wilson, P R

1996-07-01

The marginal adaptation of full coverage restorations is adversely affected by the introduction of luting agents of various minimum film thicknesses during the cementation process. The increase in the marginal opening may have long-term detrimental effects on the health of both pulpal and periodontal tissues. The purpose of this study was to determine the effects of varying seating forces (2.5, 12.5, 25 N), venting, and cement types on post-cementation marginal elevation in cast crowns. A standardized cement space of 40 microns was provided between a machined gold crown and a stainless steel die. An occlusal vent was placed that could be opened or closed. The post-cementation crown elevation was measured, following the use of two commercially available capsulated dental cements (Phosphacap, and Ketac-cem Applicap). The results indicate that only the combination of Ketac-Cem Applicap and crown venting produced post-cementation crown elevation of less than 20 microns when 12.5 N seating force was used. Higher forces (25 N) and venting were required for comparable seating when using Phosphacap (19 microns). The amount of force required to allow maximum seating of cast crowns appears to be cement specific, and is reduced by effective venting procedures.

Influence of dunite mineral additive on strength of cement

NASA Astrophysics Data System (ADS)

Vasilyeva, A. A.; Moskvitina, L. V.; Moskvitin, S. G.; Lebedev, M. P.; Fedorova, G. D.

2017-12-01

The work studies the applicability of dunite rocks from Inagli massif (South Yakutia) for the production of mixed (composite) cement. The paper reviews the implementation of dunite for manufacturing materials and products. The chemical and mineral compositions of Inagli massif dunite rocks are presented, which relegate the rocks to magnesia-silicate rocks of low-quality in terms of its application as refractory feedstock due to appreciable serpentinization of dunite. The work presents the results of dunite study in terms of its applicability as an additive to Portland cement. The authors have established that dunite does not feature hydraulicity and can be used as a filling additive to Portland cement in the amount of up to 40%. It was unveiled that the mixed grinding of Portland cement and dunite sand with specific surface area of 5500 cm2/g yields the cement that complies with GOST 31108-2016 for CEM II and CEM V normal-cured cements with strength grades of 32.5 and 42.5. The work demonstrates the benefits of the studies of dunite as a filling additive for producing both Portland cement with mineral component and composite (mixed) cement.

Fracture mechanics analysis of the dentine-luting cement interface.

PubMed

Ryan, A K; Mitchell, C A; Orr, J F

2002-01-01

The objectives of this study were to determine the fracture toughness of adhesive interfaces between dentine and clinically relevant, thin layers of dental luting cements. Cements tested included a conventional glass-ionomer, F (Fuji 1), a resin-modified glass-ionomer, FP (Fuji Plus) and a compomer cement, D (DyractCem). Ten miniature short-bar chevron notch specimens were manufactured for each cement, each comprising a 40 microm thick chevron of lute, between two 1.5 mm thick blocks of bovine dentine, encased in resin composite. The interfacial K(IC) results (MN/m3/2) were median (range): F; 0.152 (0.14-0.16), FP; 0.306 (0.27-0.37), D; 0.351 (0.31-0.37). Non-parametric statistical analysis showed that the fracture toughness of F was significantly lower (p <0.05) than those of FP or D, and all were significantly lower than values for monolithic cement specimens. Scanning electron microscopy of the specimens suggested crack propagation along the interface. However, energy dispersive X-ray analysis indicated that failure was cohesive within the cement. It is concluded that the fracture toughness of luting cement was lowered by cement-dentine interactions.

Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets.

PubMed

Lu, Liulei; Ouyang, Dong

2017-07-20

In this work, the effect of graphene oxide nanosheet (GONS) additives on the properties of cement mortar and ultra-high strength concrete (UHSC) is reported. The resulting GONS-cement composites were easy to prepare and exhibited excellent mechanical properties. However, their fluidity decreased with increasing GONS content. The UHSC specimens were prepared with various amounts of GONSs (0-0.03% by weight of cement). Results indicated that using 0.01% by weight of cement GONSs caused a 7.82% in compressive strength after 28 days of curing. Moreover, adding GONSs improved the flexural strength and deformation ability, with the increase in flexural strength more than that of compressive strength. Furthermore, field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hardened cement paste and UHSC samples. FE-SEM observations showed that the GONSs were well dispersed in the matrix and the bonding of the GONSs and the surrounding cement matrix was strong. Furthermore, FE-SEM observation indicated that the GONSs probably affected the shape of the cement hydration products. However, the growth space for hydrates also had an important effect on the morphology of hydrates. The true hydration mechanism of cement composites with GONSs needs further study.

In vitro effects of dental cements on hard and soft tissues associated with dental implants.

PubMed

Rodriguez, Lucas C; Saba, Juliana N; Chung, Kwok-Hung; Wadhwani, Chandur; Rodrigues, Danieli C

2017-07-01

Dental cements for cement-retained restorations are often chosen based on clinician preference for the product's material properties, mixing process, delivery mechanism, or viscosity. The composition of dental cement may play a significant role in the proliferation or inhibition of different bacterial strains associated with peri-implant disease, and the effect of dental cements on host cellular proliferation may provide further insight into appropriate cement material selection. The purpose of this in vitro study was to investigate the cellular host response of bone cells (osteoblasts) and soft tissue cells (gingival fibroblasts) to dental cements. Zinc oxide (eugenol and noneugenol), zinc phosphate, and acrylic resin cements were molded into pellets and directly applied to confluent preosteoblast (cell line MC3T3 E1) or gingival fibroblast cell cultures (cell line HGF) to determine cellular viability after exposure. Controls were defined as confluent cell cultures with no cement exposure. Direct contact cell culture testing was conducted following International Organization for Standardization 10993 methods, and all experiments were performed in triplicate. To compare either the MC3T3 E1 cell line, or the HGF cell line alone, a 1-way ANOVA test with multiple comparisons was used (α=.05). To compare the MC3T3 E1 cell line results and the HGF cell line results, a 2-way ANOVA test with multiple comparisons was used (α=.05). The results of this study illustrated that while both bone and soft tissue cell lines were vulnerable to the dental cement test materials, the soft tissue cell line (human gingival fibroblasts) was more susceptible to reduced cellular viability after exposure. The HGF cell line was much more sensitive to cement exposure. Here, the acrylic resin, zinc oxide (eugenol), and zinc phosphate cements significantly reduced cellular viability after exposure with respect to HGF cells only. Within the limitation of this in vitro cellular study, the results indicated that cell response to various implant cements varied significantly, with osteoblast proliferation much less affected than gingival fibroblast cells. Furthermore, the zinc oxide noneugenol dental cement appeared to affect the cell lines significantly less than the other test cements. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Cement-based materials' characterization using ultrasonic attenuation

NASA Astrophysics Data System (ADS)

Punurai, Wonsiri

The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct relationship between attenuation and water to cement (w/c) ratio. A phenomenological model based on the existence of fluid-filled capillary voids is used to help explain the experimentally observed behavior. Overall this research shows the potential of using ultrasonic attenuation to quantitatively characterize cement paste. The absorption and scattering losses can be related to the individual microstructural elements of hardened cement paste. By taking a fundamental, mechanics-based approach, it should be possible to add additional components such as scattering by aggregates or even microcracks in a systematic fashion and eventually build a realistic model for ultrasonic wave propagation study for concrete.

High temperature lightweight foamed cements

DOEpatents

Sugama, Toshifumi

1989-01-01

Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed.

21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in commercial...

21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in commercial...

21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in commercial...

21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in commercial...

21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in commercial...

Cements for Structural Concrete in Cold Regions.

DTIC Science & Technology

1977-10-01

ability to reduce the early evolu- tion of heat: slag and obsidian, pumicite and calcined shale, fly-ash , tuff and calcined diatomite , natural cement...and uncalcined diatomite . Variations in initial set times of cements can be controlled ‘cy varying the percentages of different cement mixtures . Wh it

WATER QUALITY AND TREATMENT CONSIDERATIONS FOR CEMENT-LINED AND A-C PIPE

EPA Science Inventory

Both cement mortar lined (CML) and asbestos-cement pipes (A-C) are widely used in many water systems. Cement linings are also commonly applied in-situ after pipe cleaning, usually to prevent the recurrence of red water or tuberculation problems. Unfortunately, little consideratio...

Density and mechanical properties of calcium aluminate cement

NASA Astrophysics Data System (ADS)

Ahmed, Syed Taqi Uddin; Ahmmad, Shaik Kareem

2018-04-01

Calcium aluminate cements are a special type of cements which have their composition mainly dominated by the presence of Monocalcium Aluminates. In the present paper for the first time we have shown theoretical density and elastic constants for various calcium aluminate cements. The density of the present CAS decrease with aluminates presents in the cement. Using the density data, the elastic moduli namely Young's modulus, bulk and shear modulus show strong linear dependence as a function of compositional parameter.

Marginal Integrity of Glass Ionomer and All Ceramic Restorations

DTIC Science & Technology

2016-06-01

from ceramic blocks, and cemented with a dual-cured resin cement . Following thennocycling (10,000 cycles, 5°/55°C), the restorations were examined...final result by using resin cements .26 There is an increasing range of shades in resin cements that can be used to modify the shade and value of the...restoration. The resin cement can also block out any potential imperfections present in the prepared tooth from being externally visible.27 Modern

Microstructural Properties of Cement Paste and Mortar Modified by Low Cost Nanoplatelets Sourced from Natural Materials.

PubMed

Huang, Piao; Lv, Liming; Liao, Wei; Lu, Chunhua; Xu, Zhongzi

2018-05-11

Nanomaterials have been widely used in cement-based materials. Graphene has excellent properties for improving the durability of cement-based materials. Given its high production budget, it has limited its wide potential for application in the field of engineering. Hence, it is very meaningful to obtain low cost nanoplatelets from natural materials that can replace graphene nanoplatelets (GNPs) The purpose of this paper is to improve the resistance to chloride ion penetration by optimizing the pore structure of cement-based materials, and another point is to reduce investment costs. The results illustrated that low cost CaCO₃ nanoplatelets (CCNPs) were successfully obtained under alkali treatment of seashell powder, and the chloride ion permeability of cement-based materials significantly decreased by 15.7% compared to that of the control samples when CCNPs were incorporated. Furthermore, the compressive strength of cement pastes at the age of 28 days increased by 37.9% than that of the plain sample. Improvement of performance of cement-based materials can be partly attributed to the refinement of the pore structure. In addition, AFM was employed to characterize the nanoplatelet thickness of CCNPs and the pore structures of the cement-based composites were analyzed by MIP, respectively. CCNPs composite cement best performance could lay the foundation for further study of the durability of cement-based materials and the application of decontaminated seashells.

Resistance against bacterial leakage of four luting agents used for cementation of complete cast crowns.

PubMed

Zmener, Osvaldo; Pameijer, Cornelis H; Hernández, Sandra

2014-02-01

To assess the sealing properties of four luting materials used for cementation of full cast crowns. 40 human premolars were prepared with a chamfer finish line. Stone dies were fabricated and copings were waxed, invested and cast in gold. Ten samples (n = 10) were randomly assigned to four groups. In two groups, resin modified glass-ionomer cements were used, ACTIVA BioACTIVE-CEMENT/BASE/LINER and FujiCem2; the third group received the self-adhesive resin cement Embrace WetBond, while the fourth group served as control with a zinc phosphate cement. After cementation, excess cement was removed followed by bench-set for 10 minutes. All samples were stored in water at 37 degrees C and subjected to thermal cycling (x2000 between 5 and 55 degrees C). Subsequently the occlusal surface was reduced exposing the dentin. After sterilization the specimens were subjected to bacterial microleakage with E. faecalis in a dual chamber apparatus for a period of 60 days. Bacterial leakage was checked daily. Data were analyzed using the Kaplan-Meyer survival test. Significant pairwise differences were analyzed using the Log Rank test and the Fishers' exact test at P < 0.05. ACTIVA BioACTIVE-CEMENT/BASE/LINER, FujiCem2 and Embrace WetBond showed the lowest microleakage scores and differed statistically significantly (P < 0.05) from zinc phosphate cement.

Investigation on the potential of waste cooking oil as a grinding aid in Portland cement.

PubMed

Li, Haoxin; Zhao, Jianfeng; Huang, Yuyan; Jiang, Zhengwu; Yang, Xiaojie; Yang, Zhenghong; Chen, Qing

2016-12-15

Although there are several methods for managing waste cooking oil (WCO), a significant result has not been achieved in China. A new method is required for safe WCO management that minimizes the environmental threat. In this context, this work was developed in which cement clinker and gypsum were interground with various WCOs, and their properties, such as grindability, water-cement ratio required to achieve a normal consistency, setting times, compressive strength, contents of calcium hydroxide and ettringite in the hardened paste, microstructure and economic and environmental considerations, were addressed in detail. The results show that, overall, WCO favorably improves cement grinding. WCO prolonged the cement setting times and resulted in longer setting times. Additionally, more remarkable effects were found in cements in which WCO contained more unsaturated fatty acid. WCOs increased the cement strength. However, this enhancement was rated with respect to the WCO contents and components. WCOs decreased the CH and AFt contents in the cement hardened paste. Even the AFt content at later ages was reduced when WCO was used. WCO also densify microstructure of the hardened cement paste. It is economically and environmentally feasible to use WCOs as grinding aids in the cement grinding process. These results contribute to the application of WCOs as grinding aids and to the safe management of WCO. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microstructural Properties of Cement Paste and Mortar Modified by Low Cost Nanoplatelets Sourced from Natural Materials

PubMed Central

Lv, Liming; Liao, Wei; Lu, Chunhua; Xu, Zhongzi

2018-01-01

Nanomaterials have been widely used in cement-based materials. Graphene has excellent properties for improving the durability of cement-based materials. Given its high production budget, it has limited its wide potential for application in the field of engineering. Hence, it is very meaningful to obtain low cost nanoplatelets from natural materials that can replace graphene nanoplatelets (GNPs) The purpose of this paper is to improve the resistance to chloride ion penetration by optimizing the pore structure of cement-based materials, and another point is to reduce investment costs. The results illustrated that low cost CaCO3 nanoplatelets (CCNPs) were successfully obtained under alkali treatment of seashell powder, and the chloride ion permeability of cement-based materials significantly decreased by 15.7% compared to that of the control samples when CCNPs were incorporated. Furthermore, the compressive strength of cement pastes at the age of 28 days increased by 37.9% than that of the plain sample. Improvement of performance of cement-based materials can be partly attributed to the refinement of the pore structure. In addition, AFM was employed to characterize the nanoplatelet thickness of CCNPs and the pore structures of the cement-based composites were analyzed by MIP, respectively. CCNPs composite cement best performance could lay the foundation for further study of the durability of cement-based materials and the application of decontaminated seashells. PMID:29751666

Impedance methodology: A new way to characterize the setting reaction of dental cements.

PubMed

Villat, Cyril; Tran, Xuan-Vinh; Tran, V X; Pradelle-Plasse, Nelly; Ponthiaux, Pierre; Wenger, François; Grosgogeat, Brigitte; Colon, Pierre

2010-12-01

Impedance spectroscopy is a non-destructive, quantitative method, commonly used nowadays for industrial research on cement and concrete. The aim of this study is to investigate the interest of impedance spectroscopy in the characterization of setting process of dental cements. Two types of dental cements are used in this experiment: a new Calcium Silicate cement Biodentine™ (Septodont, Saint Maur-des Fossés, France) and a glass ionomer cement resin modified or not (Fuji II(®) LC Improved Capsules and Fuji IX(®) GP Fast set Capsules, GC Corp., Tokyo, Japan). The conductivity of the dental cements was determined by impedance spectroscopy measurements carried out on dental cement samples immersed in a 0.1M potassium chloride solution (KCl) in a "like-permeation" cell connected to a potentiostat and a Frequency Response Analyzer. The temperature of the solution is 37°C. From the moment of mixing of powder and liquid, the experiments lasted 2 weeks. The results obtained for each material are relevant of the setting process. For GIC, impedance values are stabilized after 5 days while at least 14 days are necessary for the calcium silicate based cement. In accordance with the literature regarding studies of cements and concrete, impedance spectroscopy can characterize ion mobility, porosity and hardening process of dental hydrogel materials. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Bonding quality of contemporary dental cements to sandblasted esthetic crown copings.

PubMed

Abdelaziz, Khalid M; Al-Qahtani, Nasser M; Al-Shehri, Abdulrahman S; Abdelmoneam, Adel M

2012-05-01

To evaluate the shear bond strength of current luting cements to sandblasted crown-coping substrates. Specimens of nickel-chromium, pressable glass ceramic, and zirconia crown-coping substrates were sandblasted in three groups (n = 30 each) with 50 (group 1), 110 (group 2), and 250 μm (group 3) alumina particles at a pressure of 250 kPa. Cylinders of glass ionomer, universal resin, and self-adhesive resin cements were then built up on the sandblasted substrate surfaces of each group (n = 10). All bonded specimens were stressed to evaluate the cement-substrate shear bond strength. Both the mode and incidence of bond failure were also considered. No difference was noticed between all test groups in terms of cement-substrate bond strength. In comparison to self-adhesive type, the universal resin cement provided lower bond strengths to both metal and glass-ceramic substrates in group 1. The self-adhesive resin cement provided the highest bond strengths to the zirconia substrates in groups 2 and 3. The adhesive type of bond failure was common in the metal and zirconia substrates in all groups. Cement-substrate bonding quality is not affected by the size of sandblasting particles. Resin cements bond better to different coping substrates. Self-adhesive resin cement is the best choice to bond zirconia-based substrates. © 2011 Blackwell Publishing Asia Pty Ltd.

Physical characteristics, antimicrobial and odontogenesis potentials of calcium silicate cement containing hinokitiol.

PubMed

Huang, Ming-Hsien; Shen, Yu-Fang; Hsu, Tuan-Ti; Huang, Tsui-Hsien; Shie, Ming-You

2016-08-01

Hinokitiol is a natural material and it has antibacterial and anti-inflammatory effects. The purpose of this study was to evaluate the material characterization, cell viability, antibacterial and anti-inflammatory abilities of the hinokitiol-modified calcium silicate (CS) cement as a root end filling material. The setting times, diametral tensile strength (DTS) values and XRD patterns of CS cements with 0-10mM hinokitiol were examined. Then, the antibacterial effect and the expression levels of cyclooxygenase 2 (COX-2) and interleukin-1 (IL-1) of the hinokitiol-modified CS cements were evaluated. Furthermore, the cytocompatibility, the expression levels of the markers of odontoblastic differentiation, mineralized nodule formation and calcium deposition of human dental pulp cells (hDPCs) cultured on hinokitiol-modified CS cements were determined. The hinokitiol-modified CS cements had better antibacterial and anti-inflammatory abilities and cytocompatibility than non-modified CS cements. Otherwise, the hinokitiol-modified CS cements had suitable setting times and better odontoblastic potential of hDPCs. Previous report pointed out that the root-end filling materials may induce inflammatory cytokines reaction. In our study, hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility, antimicrobial properties and active ability of odontoblastic differentiation of hDPCs. Therefore, the hinokitiol-modified CS cement may be a potential root end filling material for clinic. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of retentive strength of four luting cements with stainless steel crowns in primary molars: An in vitro study

PubMed Central

Parisay, Iman; Khazaei, Yegane

2018-01-01

Background: Stainless steel crown (SSC) is the most reliable restoration for primary teeth with extensive caries. Retention is of great importance for a successful restoration and is provided by various factors such as luting cements. The aim of this study was to evaluate the retentive strength of SSC cemented with four different luting cements. Materials and Methods: In this in vitro study, A total of 55 extracted primary first molars were selected. Following crown selection and cementation (one with no cement and four groups cemented with resin, glass ionomer, zinc phosphate, and polycarboxylate), all the specimens were incubated and thermocycled in 5°C–55°C. Retentive properties of SSCs were tested with a mechanical test machine. First dislodgement of each specimen and full crown removal were recorded. One-way ANOVA test followed by least significant difference test and Kruskal–Wallis test was used for retentive strength comparison at the level of significance of P < 0.05. Results: The results of the study showed that the specimens cemented with zinc phosphate exhibited higher retentive strength as compared to glass ionomer and polycarboxylate (P < 0.001 and P = 0.023, respectively). Conclusion: Zinc phosphate cement showed the most promising results; thus, it can be preferably used for cementation of the teeth with no grossly broken down crowns. PMID:29922339

Improvement in engineering properties of soft-soil using cement and lime additives: A case study of southern Vietnam

NASA Astrophysics Data System (ADS)

To-Anh Phan, Vu; Ngoc-Anh Pham, Kha

2018-04-01

This paper presents the experimental results of using two additives to improve natural soft soil properties in southern Vietnam (i.g., cement and cement-lime mixture). The specimens were prepared by compacting method. Firstly, the natural soil was mixed with cement or cement-lime to determine the optimum water contents of various additive contents. Then, optimum water content was used to produce samples to test some engineering properties such as unconfined compressive strength, splitting tensile strength, and Young’s modulus. The specimens were tested by various curing duration of 7, 14, and 28 days. Results indicated that using cement additive is suitable for improvement of soft soil in the local area and cement-soil stabilization can be replaced as the subbase layer of the flexible pavement according to current Vietnamese standard. In addition, a higher cement content has a greater compressive strength as well as tensile strength. Besides, the Young’ modulus has significantly increased with a long-term curing age and more cement content. No evidences of increasing in strength and modulus are found with the cement-lime-soil stabilization. Finally, the best-fit power function is established by the relationships between unconfined compressive strength and splitting tensile strength as well unconfined compressive strength and Young’s Modulus, with the coefficient of determination, R2>0.999.

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

PubMed Central

Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

2016-01-01

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns. PMID:27023532

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate.

PubMed

Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

2016-03-25

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

Experimental study on compressive strength of sediment brick masonry

NASA Astrophysics Data System (ADS)

Woen, Ean Lee; Malek, Marlinda Abdul; Mohammed, Bashar S.; Chao-Wei, Tang; Tamunif, Muhammad Thaqif

2018-02-01

The effects of pre-wetted unit bricks, mortar type and slenderness ratio of prisms on the compressive strength and failure mode of newly developed sediment brick have been evaluated and compared to clay brick and cement-sand bricks. The results show that pre-wetted sediment brick masonry exhibits higher compressive strength of up to 20% compared to the dry sediment masonry. Using cement-lime mortar leads to lower compressive strength compared to cement mortar. However, the sediment brick masonry with the cement lime mortar exhibit higher compressive strength in comparison with cement mortar masonry. More of diagonal shear cracks have been observed in the failure mode of the sediment bricks masonry compared to clay and cement-sand bricks masonry that show mostly vertical cracks and crushing. The sediment unit bricks display compressive strength in between clay and cement-sand bricks.

1H NMR Cryoporometry Study of the Melting Behavior of Water in White Cement

NASA Astrophysics Data System (ADS)

Boguszyńska, Joanna; Tritt-Goc, Jadwiga

2004-09-01

The pore size of white cement samples is studied by the melting behaviour of water confined in it, using 1H NMR cryopormetry. The influence of the preparing method and antifreeze admixture on the pore size and distribution in cement samples is investigated at 283 K. The addition of an antifreeze admixture [containing 1% Sika Rapid 2 by weight of the dry cement] influences the porosity. In wet prepared samples we observed a significant increase in the quantity of mesopores between 0.8 and 5 nm and a smaller increase of mesopores between 5 and 10 nm, when compared to cement without admixture. The compressive strength is related to the porosity of the cement. Therefore the cement with Sika Rapid 2, wet prepared at 278 K shows a higher strength than all other measured samples.

Modification of Wood Fiber for Use in Cement Board

NASA Astrophysics Data System (ADS)

Han, F. Q.; Tan, X.; Zhao, F. Q.

2017-12-01

When ordinary Portland cement is used for wood fiber cement (WFC) board, the setting time is too long, even hard to solidify. Three methods can be used for wood fiber modification, i.e., soaking in water, treated with alkali solution and coated with some substances on the fiber surface. The results show that the proper water-cement ratio of WFC paste is 1:1.3 in the case of wood cement ratio being 1:1. The WFC board from modified wood fiber and cement is better than the control samples, in which the combined treatment, i.e. soaking in hot water and then coating with alkali-BFS-EVA slurry, behaves best. It is proved that ordinary Portland cement can be used to produce WFC board, with the modified wood fiber, which can greatly reduce production costs.

Predictive Mechanical Characterization of Macro-Molecular Material Chemistry Structures of Cement Paste at Nano Scale - Two-phase Macro-Molecular Structures of Calcium Silicate Hydrate, Tri-Calcium Silicate, Di-Calcium Silicate and Calcium Hydroxide

NASA Astrophysics Data System (ADS)

Padilla Espinosa, Ingrid Marcela

Concrete is a hierarchical composite material with a random structure over a wide range of length scales. At submicron length scale the main component of concrete is cement paste, formed by the reaction of Portland cement clinkers and water. Cement paste acts as a binding matrix for the other components and is responsible for the strength of concrete. Cement paste microstructure contains voids, hydrated and unhydrated cement phases. The main crystalline phases of unhydrated cement are tri-calcium silicate (C3S) and di-calcium silicate (C2S), and of hydrated cement are calcium silicate hydrate (CSH) and calcium hydroxide (CH). Although efforts have been made to comprehend the chemical and physical nature of cement paste, studies at molecular level have primarily been focused on individual components. Present research focuses on the development of a method to model, at molecular level, and analysis of the two-phase combination of hydrated and unhydrated phases of cement paste as macromolecular systems. Computational molecular modeling could help in understanding the influence of the phase interactions on the material properties, and mechanical performance of cement paste. Present work also strives to create a framework for molecular level models suitable for potential better comparisons with low length scale experimental methods, in which the sizes of the samples involve the mixture of different hydrated and unhydrated crystalline phases of cement paste. Two approaches based on two-phase cement paste macromolecular structures, one involving admixed molecular phases, and the second involving cluster of two molecular phases are investigated. The mechanical properties of two-phase macromolecular systems of cement paste consisting of key hydrated phase CSH and unhydrated phases C3S or C2S, as well as CSH with the second hydrated phase CH were calculated. It was found that these cement paste two-phase macromolecular systems predicted an isotropic material behavior. Also, these systems exhibited a high bulk modulus, compared to the elastic modulus. These results are an indication and concur with the high compression strength of cement paste seen at engineering length scale. In addition, the bulk modulus of two-phase systems consisting of hydrated CSH and unhydrated C3S or C2S was found to increase with higher levels of unhydrated components. The interaction energies of two-phase cement paste molecular structures studied in the present work were calculated, showing that a higher interaction is attained when the two phases are admixed as small components instead of cluster of phases. Finally, the mechanical behavior under shear deformation was predicted by using a quasi-static deformation method and analyzed for a representative two-phase (CSH and C2S) macromolecular structure of cement paste.

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements.

PubMed

Pereira, Jefferson Ricardo; Rosa, Ricardo Abreu da; Só, Marcus Vinícius Reis; Afonso, Daniele; Kuga, Milton Carlos; Honório, Heitor Marques; Valle, Accácio Lins do; Vidotti, Hugo Alberto

2014-01-01

The purpose of this study was to assess the push-out bond strength of glass fiber posts to root dentin after cementation with glass ionomer (GICs) and resinmodified glass ionomer cements (RMGICs). Fifty human maxillary canines were transversally sectioned at 15 mm from the apex. Canals were prepared with a step back technique until the application of a #55 K-file and filled. Post spaces were prepared and specimens were divided into five groups according to the cement used for post cementation: Luting & Lining Cement; Fuji II LC Improved; RelyX Luting; Ketac Cem; and Ionoseal. After cementation of the glass fiber posts, all roots were stored at 100% humidity until testing. For push-out test, 1-mm thick slices were produced. The push-out test was performed in a universal testing machine at a crosshead speed of 0.5 mm/minute and the values (MPa) were analyzed by Kolmogorov-Smirnov and Levene's tests and by two-way ANOVA and Tukey's post hoc test at a significance level of 5%. Fiber posts cemented using Luting & Lining Cement, Fuji II LC Improved, and Ketac Cem presented the highest bond strength to root dentin, followed by RelyX Luting. Ionoseal presented the lowest bond strength values (P>0.05). The post level did not influence the bond strength of fiber posts to root dentin (P=0.148). The major cause of failure was cohesive at the cement for all GICs and RMGICs. Except for Ionoseal, all cements provided satisfactory bond strength values.

Hydration and leaching characteristics of cement pastes made from electroplating sludge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Ying-Liang; Sustainable Environment Research Center, National Cheng Kung University, No. 1, University Rd., Tainan City 70101, Taiwan; Ko, Ming-Sheng

2011-06-15

The purpose of this study was to investigate the hydration and leaching characteristics of the pastes of belite-rich cements made from electroplating sludge. The compressive strength of the pastes cured for 1, 3, 7, 28, and 90 days was determined, and the condensation of silicate anions in hydrates was examined with the {sup 29}Si nuclear magnetic resonance (NMR) technology. The leachabilities of the electroplating sludge and the hardened pastes were studied with the multiple toxicity characteristic leaching procedure (MTCLP) and the tank leaching test (NEN 7345), respectively. The results showed that the electroplating sludge continued to leach heavy metals, includingmore » nickel, copper, and zinc, and posed a serious threat to the environment. The belite-rich cement made from the electroplating sludge was abundant in hydraulic {beta}-dicalcium silicate, and it performed well with regard to compressive-strength development when properly blended with ordinary Portland cements. The blended cement containing up to 40% the belite-rich cement can still satisfy the compressive-strength requirements of ASTM standards, and the pastes cured for 90 days had comparable compressive strength to an ordinary Portland cement paste. It was also found that the later hydration reaction of the blended cements was relatively more active, and high fractions of belite-rich cement increased the chain length of silicate hydrates. In addition, by converting the sludge into belite-rich cements, the heavy metals became stable in the hardened cement pastes. This study thus indicates a viable alternative approach to dealing with heavy metal bearing wastes, and the resulting products show good compressive strength and heavy-metal stability.« less

Micro- and nano-scale characterization to study the thermal degradation of cement-based materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Seungmin, E-mail: lim76@illinois.edu; Mondal, Paramita

2014-06-01

The degradation of hydration products of cement is known to cause changes in the micro- and nano-structure, which ultimately drive thermo-mechanical degradation of cement-based composite materials at elevated temperatures. However, a detailed characterization of these changes is still incomplete. This paper presents results of an extensive experimental study carried out to investigate micro- and nano-structural changes that occur due to exposure of cement paste to high temperatures. Following heat treatment of cement paste up to 1000 °C, damage states were studied by compressive strength test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) atomic force microscopy (AFM) and AFM image analysis.more » Using experimental results and research from existing literature, new degradation processes that drive the loss of mechanical properties of cement paste are proposed. The development of micro-cracks at the interface between unhydrated cement particles and paste matrix, a change in C–S–H nano-structure and shrinkage of C–S–H, are considered as important factors that cause the thermal degradation of cement paste. - Highlights: • The thermal degradation of hydration products of cement is characterized at micro- and nano-scale using scanning electron microscopy (SEM) and atomic force microscopy (AFM). • The interface between unhydrated cement particles and the paste matrix is considered the origin of micro-cracks. • When cement paste is exposed to temperatures above 300 ºC, the nano-structure of C-S-H becomes a more loosely packed globular structure, which could be indicative of C-S-H shrinkage.« less

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements

PubMed Central

PEREIRA, Jefferson Ricardo; da ROSA, Ricardo Abreu; SÓ, Marcus Vinícius Reis; AFONSO, Daniele; KUGA, Milton Carlos; HONÓRIO, Heitor Marques; do VALLE, Accácio Lins; VIDOTTI, Hugo Alberto

2014-01-01

Objective The purpose of this study was to assess the push-out bond strength of glass fiber posts to root dentin after cementation with glass ionomer (GICs) and resin-modified glass ionomer cements (RMGICs). Material and Methods Fifty human maxillary canines were transversally sectioned at 15 mm from the apex. Canals were prepared with a step back technique until the application of a #55 K-file and filled. Post spaces were prepared and specimens were divided into five groups according to the cement used for post cementation: Luting & Lining Cement; Fuji II LC Improved; RelyX Luting; Ketac Cem; and Ionoseal. After cementation of the glass fiber posts, all roots were stored at 100% humidity until testing. For push-out test, 1-mm thick slices were produced. The push-out test was performed in a universal testing machine at a crosshead speed of 0.5 mm/minute and the values (MPa) were analyzed by Kolmogorov-Smirnov and Levene's tests and by two-way ANOVA and Tukey's post hoc test at a significance level of 5%. Results Fiber posts cemented using Luting & Lining Cement, Fuji II LC Improved, and Ketac Cem presented the highest bond strength to root dentin, followed by RelyX Luting. Ionoseal presented the lowest bond strength values (P>0.05). The post level did not influence the bond strength of fiber posts to root dentin (P=0.148). The major cause of failure was cohesive at the cement for all GICs and RMGICs. Conclusions Except for Ionoseal, all cements provided satisfactory bond strength values. PMID:25004052

Cytotoxicity and biocompatibility of Zirconia (Y-TZP) posts with various dental cements

PubMed Central

Shin, Hyeongsoon; Ko, Hyunjung

2016-01-01

Objectives Endodontically treated teeth with insufficient tooth structure are often restored with esthetic restorations. This study evaluated the cytotoxicity and biological effects of yttria partially stabilized zirconia (Y-TZP) blocks in combination with several dental cements. Materials and Methods Pairs of zirconia cylinders with medium alone or cemented with three types of dental cement including RelyX U200 (3M ESPE), FujiCEM 2 (GC), and Panavia F 2.0 (Kuraray) were incubated in medium for 14 days. The cytotoxicity of each supernatant was determined using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays on L929 fibroblasts and MC3T3-E1 osteoblasts. The levels of interleukin-6 (IL-6) mRNA were evaluated by reverse transcription polymerase chain reaction (RT-PCR), and IL-6 protein was evaluated by enzyme-linked immunosorbent assays (ELISA). The data were analyzed using one-way ANOVA and Tukey post-hoc tests. A p < 0.05 was considered statistically significant. Results The MTT assays showed that MC3T3-E1 osteoblasts were more susceptible to dental cements than L929 fibroblasts. The resin based dental cements increased IL-6 expression in L929 cells, but reduced IL-6 expression in MC3T3-E1 cells. Conclusions Zirconia alone or blocks cemented with dental cement showed acceptable biocompatibilities. The results showed resin-modified glass-ionomer based cement less produced inflammatory cytokines than other self-adhesive resin-based cements. Furthermore, osteoblasts were more susceptible than fibroblasts to the biological effects of dental cement. PMID:27508157

Marginal gap, cement thickness, and microleakage of 2 zirconia crown systems luted with glass ionomer and MDP-based cements.

PubMed

Sener, Isil; Turker, Begum; Valandro, Luiz Felipe; Ozcan, Mutlu

2014-01-01

This in vitro study evaluated the marginal gap, cement thickness, and microleakage of glass-ionomer cement (GIC) and phosphate monomer-containing resin cement (MDP-RC) under 2 zirconia crown systems (Cercon and DC-Zirkon). Forty human premolars were prepared for all-ceramic zirconia crowns with a 1 mm circumferential finish line and a 1.5 mm occlusal reduction. The crowns (n = 10 per group) from each zirconia system were randomly divided into 2 groups and cemented either with GIC (Vivaglass CEM) or MDP-RC (Panavia F 2.0) cement. The cemented crowns were thermocycled 5000 times (5°-55°C). The crowns were immersed in 0.5% basic fuchsine dye solution for 24 hours and sectioned buccolingually and mesiodistally. Specimens were examined under optical microscope (100X). Data were analyzed using Student t-test and chi-square tests (α = 0.05). Mean marginal gap values for Cercon (85 ± 11.4 μm) were significantly higher than for DC-Zircon (75.3 ± 13.2 μm) (P = 0.018). The mean cement thickness values of GIC (81.7 ± 13.9 μm) and MDP-RC (78.5 ± 12.5 μm) were not significantly different (P = 0.447). Microleakage scores did not demonstrate significant difference between GIC (P = 0.385) and MDP-RC (P = 0.631) under Cercon or DC-Zircon. Considering the cement thickness values and microleakage scores obtained, both zirconia crown systems could be cemented in combination with either GIC or MDP-RC.

Cytotoxicity and biocompatibility of Zirconia (Y-TZP) posts with various dental cements.

PubMed

Shin, Hyeongsoon; Ko, Hyunjung; Kim, Miri

2016-08-01

Endodontically treated teeth with insufficient tooth structure are often restored with esthetic restorations. This study evaluated the cytotoxicity and biological effects of yttria partially stabilized zirconia (Y-TZP) blocks in combination with several dental cements. Pairs of zirconia cylinders with medium alone or cemented with three types of dental cement including RelyX U200 (3M ESPE), FujiCEM 2 (GC), and Panavia F 2.0 (Kuraray) were incubated in medium for 14 days. The cytotoxicity of each supernatant was determined using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays on L929 fibroblasts and MC3T3-E1 osteoblasts. The levels of interleukin-6 (IL-6) mRNA were evaluated by reverse transcription polymerase chain reaction (RT-PCR), and IL-6 protein was evaluated by enzyme-linked immunosorbent assays (ELISA). The data were analyzed using one-way ANOVA and Tukey post-hoc tests. A p < 0.05 was considered statistically significant. The MTT assays showed that MC3T3-E1 osteoblasts were more susceptible to dental cements than L929 fibroblasts. The resin based dental cements increased IL-6 expression in L929 cells, but reduced IL-6 expression in MC3T3-E1 cells. Zirconia alone or blocks cemented with dental cement showed acceptable biocompatibilities. The results showed resin-modified glass-ionomer based cement less produced inflammatory cytokines than other self-adhesive resin-based cements. Furthermore, osteoblasts were more susceptible than fibroblasts to the biological effects of dental cement.

Complexity in modeling of residual stresses and strains during polymerization of bone cement: effects of conversion, constraint, heat transfer, and viscoelastic property changes.

PubMed

Gilbert, Jeremy L

2006-12-15

Aseptic loosening of cemented joint prostheses remains a significant concern in orthopedic biomaterials. One possible contributor to cement loosening is the development of porosity, residual stresses, and local fracture of the cement that may arise from the in-situ polymerization of the cement. In-situ polymerization of acrylic bone cement is a complex set of interacting processes that involve polymerization reactions, heat generation and transfer, full or partial mechanical constraint, evolution of conversion- and temperature-dependent viscoelastic material properties, and thermal and conversion-driven changes in the density of the cement. Interactions between heat transfer and polymerization can lead to polymerization fronts moving through the material. Density changes during polymerization can, in the presence of mechanical constraint, lead to the development of locally high residual strain energy and residual stresses. This study models the interactions during bone cement polymerization and determines how residual stresses develop in cement and incorporates temperature and conversion-dependent viscoelastic behavior. The results show that the presence of polymerization fronts in bone cement result in locally high residual strain energies. A novel heredity integral approach is presented to track residual stresses incorporating conversion and temperature dependent material property changes. Finally, the relative contribution of thermal- and conversion-dependent strains to residual stresses is evaluated and it is found that the conversion-based strains are the major contributor to the overall behavior. This framework provides the basis for understanding the complex development of residual stresses and can be used as the basis for developing more complex models of cement behavior.

Influence of curing protocol and ceramic composition on the degree of conversion of resin cement

PubMed Central

Lanza, Marcos Daniel Septimio; Andreeta, Marcello Rubens Barsi; Pegoraro, Thiago Amadei; Pegoraro, Luiz Fernando; Carvalho, Ricardo Marins De

2017-01-01

Abstract Due to increasing of aesthetic demand, ceramic crowns are widely used in different situations. However, to obtain long-term prognosis of restorations, a good conversion of resin cement is necessary. Objective: To evaluate the degree of conversion (DC) of one light-cure and two dual-cure resin cements under a simulated clinical cementation of ceramic crowns. Material and Methods: Prepared teeth were randomly split according to the ceramic's material, resin cement and curing protocol. The crowns were cemented as per manufacturer's directions and photoactivated either from occlusal suface only for 60 s; or from the buccal, occlusal and lingual surfaces, with an exposure time of 20 s on each aspect. After cementation, the specimens were stored in deionized water at 37°C for 7 days. Specimens were transversally sectioned from occlusal to cervical surfaces and the DC was determined along the cement line with three measurements taken and averaged from the buccal, lingual and approximal aspects using micro-Raman spectroscopy (Alpha 300R/WITec®). Data were analyzed by 3-way ANOVA and Tukey test at =5%. Results: Statistical analysis showed significant differences among cements, curing protocols and ceramic type (p<0.001). The curing protocol 3x20 resulted in higher DC for all tested conditions; lower DC was observed for Zr ceramic crowns; Duolink resin cement culminated in higher DC regardless ceramic composition and curing protocol. Conclusion: The DC of resin cement layers was dependent on the curing protocol and type of ceramic. PMID:29211292

High temperature lightweight foamed cements

DOEpatents

Sugama, Toshifumi.

1989-10-03

Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed. 3 figs.

21 CFR 888.3210 - Finger joint metal/metal constrained cemented prosthesis.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint metal/metal constrained cemented... metal/metal constrained cemented prosthesis. (a) Identification. A finger joint metal/metal constrained..., 1996 for any finger joint metal/metal constrained cemented prosthesis that was in commercial...

21 CFR 888.3210 - Finger joint metal/metal constrained cemented prosthesis.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Finger joint metal/metal constrained cemented... metal/metal constrained cemented prosthesis. (a) Identification. A finger joint metal/metal constrained..., 1996 for any finger joint metal/metal constrained cemented prosthesis that was in commercial...

21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Wrist joint metal constrained cemented prosthesis... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is a...

21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Wrist joint metal constrained cemented prosthesis... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is a...

High-Temperature Inorganic Self-Healing Inorganic Cement Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyatina, Tatiana; Sugama, Toshifumi

The data files below summarize the results from various experiments testing properties of high-temperature self-healing inorganic cement composites. These properties include cement-carbon steel bond strength, Young's modulus recovery, matrix recovery strength, and compressive strength and Yonug's modulus for cement composites modified with Pozzolanic Clay additives.

21 CFR 888.4230 - Cement ventilation tube.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cement ventilation tube. 888.4230 Section 888.4230...) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4230 Cement ventilation tube. (a) Identification. A cement ventilation tube is a tube-like device usually made of plastic intended to be inserted into...

21 CFR 888.4230 - Cement ventilation tube.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cement ventilation tube. 888.4230 Section 888.4230...) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4230 Cement ventilation tube. (a) Identification. A cement ventilation tube is a tube-like device usually made of plastic intended to be inserted into...

21 CFR 888.4230 - Cement ventilation tube.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cement ventilation tube. 888.4230 Section 888.4230...) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4230 Cement ventilation tube. (a) Identification. A cement ventilation tube is a tube-like device usually made of plastic intended to be inserted into...

21 CFR 888.4230 - Cement ventilation tube.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cement ventilation tube. 888.4230 Section 888.4230...) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4230 Cement ventilation tube. (a) Identification. A cement ventilation tube is a tube-like device usually made of plastic intended to be inserted into...

40 CFR 147.2104 - Requirements for all wells.

Code of Federal Regulations, 2010 CFR

2010-07-01

... (PVC, ABS, or others) casings shall: (1) Not construct a well deeper than 500 feet; (2) Use cement and additives compatible with such casing material; and (3) Cement the annular space above the injection... feet below the lowermost USDW; (ii) Cementing surface casing by recirculating the cement to the surface...

40 CFR 147.305 - Requirements for all wells.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., and others) casings shall: (1) Not construct a well deeper than 500 feet; (2) Use cement and additives compatible with such casing material; (3) Cement the annular space above the injection interval from the... base of the lowermost USDW; (ii) Cementing surface casing by recirculating the cement to the surface...

40 CFR 147.2104 - Requirements for all wells.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (PVC, ABS, or others) casings shall: (1) Not construct a well deeper than 500 feet; (2) Use cement and additives compatible with such casing material; and (3) Cement the annular space above the injection... feet below the lowermost USDW; (ii) Cementing surface casing by recirculating the cement to the surface...

40 CFR 147.305 - Requirements for all wells.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., and others) casings shall: (1) Not construct a well deeper than 500 feet; (2) Use cement and additives compatible with such casing material; (3) Cement the annular space above the injection interval from the... base of the lowermost USDW; (ii) Cementing surface casing by recirculating the cement to the surface...

40 CFR 146.32 - Construction requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... would result. The casing and cement used in the construction of each newly drilled well shall be... and confining zones; and (7) Type and grade of cement. (b) Appropriate logs and other tests shall be... pilot holes and reaming are used, unless the hole will be cased and cemented by circulating cement to...

21 CFR 888.4230 - Cement ventilation tube.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement ventilation tube. 888.4230 Section 888.4230...) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4230 Cement ventilation tube. (a) Identification. A cement ventilation tube is a tube-like device usually made of plastic intended to be inserted into...

76 FR 12370 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-Portland Cement...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-07

... Production Act of 1993--Portland Cement Association Notice is hereby given that, on February 02, 2011... seq. (``the Act''), Portland Cement Association (``PCA'') has filed written notifications..., Praxair, Danbury, CT; Metso Minerals, York, PA; Lehigh Cement Company LLC, Allentown, PA; Lehigh Northwest...

Assessment of high early strength limestone blended cement for next generation transportation structures : final report.

DOT National Transportation Integrated Search

2016-12-01

This research on Type IL cements for high early strength concretes demonstrated that Type IL cements satisfying AASHTO M 240 specifications may be used in place of Type I/II cements which satisfy AASHTO M 85 specifications for construction of transpo...

ELIMINATION OF WATER POLLUTION BY RECYCLING CEMENT PLANT KILN DUST

EPA Science Inventory

Excessive amounts of alkalies can have deleterious effects upon the process of cement manufacture and the product. Normally much of the alkali present in cement raw materials is volatilized in the cement kiln and condenses on the particles of kiln dust which are carried out of th...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verba, Circe; Montross, Scott; Spaulding, Richard

Geologic carbon storage (GCS) is a potentially viable strategy to reduce greenhouse emissions. Understanding the risks to engineered and geologic structures associated with GCS is an important first step towards developing practices for safe and effective storage. The widespread utilization of foamed cement in wells may mean that carbon dioxide (CO 2)/brine/foamed cement reactions may occur within these GCS sites. Characterizing the difference in alteration rates as well as the physical and mechanical impact of CO 2/brine/foamed cement is an important preliminary step to ensuring offshore and onshore GCS is a prudent anthropogenic CO 2 mitigation choice. In a typicalmore » oil and gas well, cement is placed in the annulus between the steel casing and formation rock for both zonal isolation and casing support. The cement must have sufficient strength to secure the casing in the hole and withstand the stress of drilling, perforating, and fracturing (e.g. API, 1997, 2010 Worldwide Cementing Practices). As such, measuring the mechanical and properties of cement is an important step in predicting cement behavior under applied downhole stresses (Nelson, 2006). Zonal isolation is the prevention of fluids migrating to different zones outside of the casing and is strongly impacted by the permeability of the wellbore cement (Nelson, 2006). Zonal isolation depends on both the mechanical behavior and permeability (a physical property) of the cement (Mueller and Eid, 2006; Nelson, 2006). Long-term integrity of cement depends on the mechanical properties of the cement sheath, such as Young’s Modulus (Griffith et al., 2004). The cement sheath’s ability to withstand the stresses from changes in pressure and temperature is predominantly determined by the mechanical properties, including Young’s modulus, Poisson’s ratio, and tensile strength. Any geochemical alteration may impact both the mechanical and physical properties of the cement, thus ultimately impacting the structural integrity of the wellbore. In this study, atmospheric foamed cements were generated using a neat cement and three foam qualities (volume of entrained gas in the cement) - 10%, 20%, and 30 % gas volume. The samples were immersed in a 0.25 M NaCl brine followed by the injection of supercritical CO 2 at 28.9 MPa and 50°C. Petrophysical properties were examined for representative samples using computed tomography (CT) and scanning electron microscopy (SEM). CT scanning of representative samples across the range of reacted cements revealed macroscopic changes in structure due to brine/CO 2/cement interactions. The high foam quality samples resulted in more CO 2-saturated brine infiltrating radially deeper into the cement and thus were more susceptible to alteration. After 56 days of exposure, the 30% foam quality sample had the most reaction resulting in an alteration depth of 8.35 ± 0.13 mm with a calculated 34.6 ± 0.2% reacted area and 5.76 ± 0.2% reacted pore space area. The neat sample on the other hand, had a reaction depth of 0.31 ± 0.13 mm with a calculated 0.15 ± 0.08% reacted area and 0.57 ± 0.05% reacted pore area. Physical measurements of the exposed samples were consistent with this degree of alteration having 47.02% porosity and the highest permeability of 0.041 mD. These results indicate that the greater surface area provided by the increase of pore space in the higher quality foam coupled with carbonate diffusion reactions enabled greater alteration.« less

Effects of Curing Temperature and Pressure on the Chemical, Physical, and Mechanical Properties of Portland Cement

NASA Astrophysics Data System (ADS)

Pang, Xueyu

This dissertation mainly focuses on studying the fundamental hydration kinetics and mechanisms of Portland cement as well as the effects of curing temperature and pressure on its various properties. An innovative test apparatus has been developed in this study to cure and test cement paste specimens under in-situ conditions, such as down-hole in oil wells with high temperature and high pressure. Two series of tests were performed using cement pastes prepared with four different classes of oilwell cement (namely Class A, C, G, and H cements). Specimens in groups of four were cured at temperatures ranging from ambient to 60 °C and pressures ranging from 0.69 to 51.7 MPa for a period of 48 or 72 hours. The density and w/c ratio of the specimens at the time of casting as well as at the end of the curing period were recorded. Total chemical shrinkage of the cement paste was measured continuously during the entire hydration period while tensile strength was obtained at the end of the curing period using both water pressure and splitting tension test methods. Due to capacity limitations of the test equipment, in-situ tensile strength was obtained for only one test series with a highest curing pressure of 13.1 MPa. Specimens from the other test series were depressurized before the tensile strength tests. Chemical shrinkage test is an important method of measuring cement hydration kinetics in that the normalized total chemical shrinkage is approximately equal to the degree of cement hydration. By studying the correlations between the chemical shrinkage and the non-evaporable water content of cement during hydration, a multi-linear model is first proposed to estimate the normalization factors for different types of cement under different curing conditions. Based on the hydration kinetics data obtained from chemical shrinkage test results, a new approach of modeling the effect of curing temperature and pressure on cement hydration kinetics is proposed. It is found that when a hydration kinetics curve is represented by an unknown function, the effect of curing condition on the curve can be modeled by incorporating a simple scale factor in this function. The relationship between this scale factor and curing condition is described by chemical kinetics laws. While the proposed new approach of modeling cement hydration kinetics has the advantage of being widely applicable to different types of cement, it only explains one influence factor of cement hydration (i.e. the curing condition). In order to take into account other influence factors and to further understand the fundamental mechanisms of cement hydration, a more complex particle-based numerical hydration model is developed by combining the two well-known cement hydration mechanisms, namely the nucleation and growth controlled mechanism and the diffusion controlled mechanism. The model is applied to experimental data of both C3S hydration in dilute suspensions and Class H cement paste hydration. Excellent agreement is observed between experimental and modeled results. Three rate-controlling parameters with clear physical meanings can be identified from the proposed model. Fitted model parameters are found to be in reasonable agreement with experimental observation. The dependencies of these parameters on particle size, cement composition, w/c ratio, and curing condition are also investigated. Finally, the importance of cement hydration kinetics is illustrated by showing their close correlations with the physical and mechanical properties. The various influence factors, including the curing temperature and pressure, of physical and mechanical property test results (particularly density and tensile strength) are evaluated. Potential damage mechanisms of cement paste specimens during depressurization are studied by analyzing the deformation behavior of the entire system consisting of the cement paste and pressurizing water.

Cemented Volcanic Soils, Martian Spectra and Implications for the Martian Climate

NASA Technical Reports Server (NTRS)

Bishop, J. L.; Schiffman, P.; Drief, A.; Southard, R. J.

2004-01-01

Cemented soils formed via reactions with salts are studied here and provide information about the climate when they formed. Spectroscopic and microprobe studies have been performed on cemented volcanic crusts in order to learn about the composition of these materials, how they formed, and what they can tell us about climatic interactions with surface material on Mars to form cemented soils. These crusts include carbonate, sulfate and opaline components that may all be present in cemented soil units on Mars.

Effect of Fly Ash and Silica Fume on the Mechanical Properties of Cement Paste at Different Stages of Hydration

DTIC Science & Technology

2015-08-10

All materials were placed in a clean, labeled stainless steel mixing bowl and weighed to the nearest ten thousandth of a pound. The cement and fly...on the Mechanical Properties of Cement Paste at Different Stages of Hydration This thesis investigates the effect of fly ash and silica fume on... cement paste hydration. Percentages of each additive will replace the cement by volume to be studied at five ages. These percentages will be compared

Natural Cellulose Nanofibers As Sustainable Enhancers in Construction Cement

PubMed Central

Jiao, Li; Su, Ming; Chen, Liao; Wang, Yuangang; Zhu, Hongli; Dai, Hongqi

2016-01-01

Cement is one of the mostly used construction materials due to its high durability and low cost, but it suffers from brittle fracture and facile crack initiation. This article describes the use of naturally-derived renewable cellulose nanofibers (CNFs) to reinforce cement. The effects of CNFs on the mechanical properties, degree of hydration (DOH), and microstructure of cement pastes have been studied. It is found that an addition of 0.15% by weight of CNFs leads to a 15% and 20% increase in the flexural and compressive strengths of cement paste. The enhancement in mechanical strength is attributed to high DOH and dense microstructure of cement pastes after adding CNFs. PMID:28005917

Dental Cements for Luting and Bonding Restorations: Self-Adhesive Resin Cements.

PubMed

Manso, Adriana P; Carvalho, Ricardo M

2017-10-01

Self-adhesive resin cements combine easy application of conventional luting materials with improved mechanical properties and bonding capability of resin cements. The presence of functional acidic monomers, dual cure setting mechanism, and fillers capable of neutralizing the initial low pH of the cement are essential elements of the material and should be understood when selecting the ideal luting material for each clinical situation. This article addresses the most relevant aspects of self-adhesive resin cements and their potential impact on clinical performance. Although few clinical studies are available to establish solid clinical evidence, the information presented provides clinical guidance in the dynamic environment of material development. Copyright © 2017 Elsevier Inc. All rights reserved.

Production and construction technology of C100 high strength concrete filled steel tube

NASA Astrophysics Data System (ADS)

Wu, Yanli; Sun, Jinlin; Yin, Suhua; Liu, Yu

2017-10-01

In this paper, the effect of the amount of cement, water cement ratio and sand ratio on compressive strength of C100 concrete was studied. The optimum mix ratio was applied to the concrete filled steel tube for the construction of Shenyang Huangchao Wanxin mansion. The results show that the increase of amount of cement, water cement ratio can improve the compressive strength of C100 concrete but increased first and then decreased with the increase of sand ratio. The compressive strength of C100 concrete can reach 110MPa with the amount of cement 600kg/m3, sand ratio 40% and water cement ratio 0.25.

The influence of carbon nanotubes on the properties of water solutions and fresh cement pastes

NASA Astrophysics Data System (ADS)

Leonavičius, D.; Pundienė, I.; Girskas, G.; Pranckevičienė, J.; Kligys, M.; Sinica, M.

2017-10-01

It is known, that the properties of cement-based materials can be significantly improved by addition of carbon nanotubes (CNTs). The dispersion of CNTs is an important process due to an extremely high specific surface area. This aspect is very relevant and is one of the main factors for the successful use of CNTs in cement-based materials. The influence of CNTs in different amounts (from 0 to 0.5 percent) on the pH values of water solutions and fresh cement pastes, and also on rheological properties, flow characteristics, setting time and EXO reaction of the fresh cement pastes was analyzed in this work. It was found that the increment of the amount of CNTs leads to decreased pH values of water solutions and fresh cement pastes, and also increases viscosity, setting times and EXO peak times of fresh cement pastes.

Effects of mechanical properties of adhesive resin cements on stress distribution in fiber-reinforced composite adhesive fixed partial dentures.

PubMed

Yokoyama, Daiichiro; Shinya, Akikazu; Gomi, Harunori; Vallittu, Pekka K; Shinya, Akiyoshi

2012-01-01

Using finite element analysis (FEA), this study investigated the effects of the mechanical properties of adhesive resin cements on stress distributions in fiber-reinforced resin composite (FRC) adhesive fixed partial dentures (AFPDs). Two adhesive resin cements were compared: Super-Bond C&B and Panavia Fluoro Cement. The AFPD consisted of a pontic to replace a maxillary right lateral incisor and retainers on a maxillary central incisor and canine. FRC framework was made of isotropic, continuous, unidirectional E-glass fibers. Maximum principal stresses were calculated using finite element method (FEM). Test results revealed that differences in the mechanical properties of adhesive resin cements led to different stress distributions at the cement interfaces between AFPD and abutment teeth. Clinical implication of these findings suggested that the safety and longevity of an AFPD depended on choosing an adhesive resin cement with the appropriate mechanical properties.

Hybrid Polyvinyl Alcohol and Cellulose Fiber Pulp Instead of Asbestos Fibers in Cement-Based Composites

NASA Astrophysics Data System (ADS)

Shokrieh, M. M.; Mahmoudi, A.; Shadkam, H. R.

2015-05-01

The Taguchi method was used to determine the optimum content of a four-parameters cellulose fiber pulp, polyvinyl alcohol (PVA) fibers, a silica fume, and bentonite for cement-based composite sheets. Then cement composite sheets from the hybrid of PVA and the cellulose fiber pulp were manufactured, and their moduli of rapture were determined experimentally. The result obtained showed that cement composites with a hybrid of PVA and cellulose fiber pulp had a higher flexural strength than cellulose-fiber- reinforced cement ones, but this strength was rather similar to that of asbestos-fiber-reinforced cement composites. Also, using the results of flexural tests and an analytical method, the tensile and compressive moduli of the hybrid of PVA and cement sheet were calculated. The hybrid of PVA and cellulose fiber pulp is proposed as an appropriate alternative for substituting asbestos in the Hatschek process.