The Shock and Vibration Bulletin. Part 3: Structure Medium Interaction, Case Studies in Dynamics

NASA Technical Reports Server (NTRS)

1979-01-01

Structure and medium interactions topics are addressed. Topics include: a failure analysis of underground concrete structures subjected to blast loadings, an optimization design procedure for concrete slabs, and a discussion of the transient response of a cylindrical shell submerged in a fluid. Case studies in dynamics are presented which include an examination of a shock isolation platform for a seasparrow launcher, a discussion of hydrofoil fatigue load environments, and an investigation of the dynamic characteristics of turbine generators and low tuned foundations.

Mitigating Joint Reflective Cracks using Stone Interlayers : Case Study on Louisiana Highway 5, Desoto Parish : Research Project Capsule

DOT National Transportation Integrated Search

2017-12-01

When Portland cement concrete (PCC) pavement reaches an intolerable level of service, it is commonly overlaid with asphaltic concrete (AC) and is referred to as a composite pavement. Even though AC overlays are designed to resist failure mechanisms s...

Effects of climate and corrosion on concrete behaviour

NASA Astrophysics Data System (ADS)

Ismail, Mohammad; Egba, Ernest Ituma

2017-11-01

Corrosion of steel is a damaging agent that reduces the functional and structural responsibilities of reinforced concrete structures. Accordingly, reinforced concrete members in the environments that are prone to concrete carbonation or chloride attack coupled with high temperature and relative humidity suffer from accelerated corrosion of reinforcing material. Also, literature proves that climate influences corrosion of concrete, and suggests investigation of impact of corrosion on concrete based on climate zone. Therefore, this paper presents the effects of climate and corrosion on concrete behavior, using bond strength of concrete as a case study. Concrete specimens were prepared form concrete mix that was infested with 3.5 kgm-3 of sodium chloride to accelerate corrosion. The specimens were cured sodium chloride solution 3.5% by weight of water for 28 days before placing them in the exposure conditions. Pull-out tests were conducted at time intervals for one year to measure the impact of exposure condition and corrosion on bond strength of concrete. The results show reduction of bond strength of concrete by 32%, 28% and 8% after one year of subjection of the specimens to the unsheltered natural climate, sheltered natural climate, and laboratory ambient environment respectively. The findings indicate that the climate influences corrosion, which reduces the interlocking bond between the reinforcing bar and the adjacent concrete.

Study of the Technical Feasibility of Increasing the Amount of Recycled Concrete Waste Used in Ready-Mix Concrete Production.

PubMed

Fraile-Garcia, Esteban; Ferreiro-Cabello, Javier; López-Ochoa, Luis M; López-González, Luis M

2017-07-18

The construction industry generates a considerable amount of waste. Faced with this undesirable situation, the ready-mix concrete sector, in particular, has invested energy and resources into reusing its own waste in its production process as it works towards the goal of more sustainable construction. This study examines the feasibility of incorporating two types of concrete waste, which currently end up in landfill, into the production process of ready-mix concrete: the waste generated during the initial production stage (ready-mix concrete waste), and waste created when demolition waste is treated to obtain artificial aggregate. The first phase of the study's methodology corroborates the suitability of the recycled aggregate through characterization tests. After this phase, the impact of incorporating different percentages of recycled coarse aggregate is evaluated by examining the performance of the produced concrete. The replacement rate varied between 15% and 50%. The results indicate that recycled aggregates are, indeed, suitable to be incorporated into ready-mix concrete production. The impact on the final product's performance is different for the two cases examined herein. Incorporating aggregates from generic concrete blocks led to a 20% decrease in the produced concrete's strength performance. On the other hand, using recycled aggregates made from the demolition waste led to a smaller decrease in the concrete's performance: about 8%. The results indicate that with adequate management and prior treatment, the waste from these plants can be re-incorporated into their production processes. If concrete waste is re-used, concrete production, in general, becomes more sustainable for two reasons: less waste ends up as landfill and the consumption of natural aggregates is also reduced.

Performance of an unbonded concrete overlay on I-74

DOT National Transportation Integrated Search

2002-04-01

In Illinois, the typical rehabilitation for a concrete pavement is full-depth patching of the distressed concrete, and overlaying the pavement with 3.25 inches of bituminous concrete. In cases where there are poor joints or extensive durability crack...

Characterization of the punching shear capacity of thin ultra-high performance concrete slabs.

DOT National Transportation Integrated Search

2005-01-01

Ultra-high performance concrete (UHPC) is a relatively new type of concrete that exhibits mechanical properties that are far superior to those of conventional concrete and in some cases rival those of steel. The main characteristics that distinguish ...

Analysis, prediction, and case studies of early-age cracking in bridge decks

NASA Astrophysics Data System (ADS)

ElSafty, Adel; Graeff, Matthew K.; El-Gharib, Georges; Abdel-Mohti, Ahmed; Mike Jackson, N.

2016-06-01

Early-age cracking can adversely affect strength, serviceability, and durability of concrete bridge decks. Early age is defined as the period after final setting, during which concrete properties change rapidly. Many factors can cause early-age bridge deck cracking including temperature change, hydration, plastic shrinkage, autogenous shrinkage, and drying shrinkage. The cracking may also increase the effect of freeze and thaw cycles and may lead to corrosion of reinforcement. This research paper presents an analysis of causes and factors affecting early-age cracking. It also provides a tool developed to predict the likelihood and initiation of early-age cracking of concrete bridge decks. Understanding the concrete properties is essential so that the developed tool can accurately model the mechanisms contributing to the cracking of concrete bridge decks. The user interface of the implemented computer Excel program enables the user to input the properties of the concrete being monitored. The research study and the developed spreadsheet were used to comprehensively investigate the issue of concrete deck cracking. The spreadsheet is designed to be a user-friendly calculation tool for concrete mixture proportioning, temperature prediction, thermal analysis, and tensile cracking prediction. The study also provides review and makes recommendations on the deck cracking based mainly on the Florida Department of Transportation specifications and Structures Design Guidelines, and Bridge Design Manuals of other states. The results were also compared with that of other commercially available software programs that predict early-age cracking in concrete slabs, concrete pavement, and reinforced concrete bridge decks. The outcome of this study can identify a set of recommendations to limit the deck cracking problem and maintain a longer service life of bridges.

Cross-infrastructure learnings for alternative bridge system designs : a case study on the hybrid composite bridge system.

DOT National Transportation Integrated Search

2015-04-30

The hybrid composite beam (HCB) technology has been presented as a system for short and medium span beam bridges as an alternative to traditional materials such as concrete and steel. A HCB consists of a concrete tied arch encased in a fiber-reinforc...

Corrosion control of cement-matrix and aluminum-matrix composites

NASA Astrophysics Data System (ADS)

Hou, Jiangyuan

Corrosion control of composite materials, particularly aluminum-matrix and cement-matrix composites, was addressed by surface treatment, composite formulation and cathodic protection. Surface treatment methods studied include anodization in the case of aluminum-matrix composites and oxidation treatment (using water) in the case of steel rebar for reinforcing concrete. The effects of reinforcement species (aluminum nitride (AIN) versus silicon carbide (SiC) particles) in the aluminum-matrix composites and of admixtures (carbon fibers, silica fume, latex and methylcellulose) in concrete on the corrosion resistance of composites were addressed. Moreover, the effect of admixtures in concrete and of admixtures in mortar overlay (as anode on concrete) on the efficiency of cathodic protection of steel reinforced concrete was studied. For SiC particle filled aluminum, anodization was performed successfully in an acid electrolyte, as for most aluminum alloys. However, for AlN particle filled aluminum, anodization needs to be performed in an alkaline (0.7 N NaOH) electrolyte instead. The concentration of NaOH in the electrolyte was critical. It was found that both silica fume and latex improved the corrosion resistance of rebar in concrete in both Ca(OH)sb2 and NaCl solutions, mainly because these admixtures decreased the water absorptivity. Silica fume was more effective than latex. Methylcellulose improved the corrosion resistance of rebar in concrete a little in Ca(OH)sb2 solution. Carbon fibers decreased the corrosion resistance of rebar in concrete, but this effect could be made up for by either silica fume or latex, such that silica fume was more effective than latex. Surface treatment in the form of water immersion for two days was found to improve the corrosion resistance of rebar in concrete. This treatment resulted in a thin uniform layer of black iron oxide (containing Fesp{2+}) on the entire rebar surface except on the cross-sectional surface. Prior to the treatment, the surface was non-uniform due to rusting. Sand blasting also made the surface uniform, but is an expensive process, compared to the water immersion method. For cathodic protection of steel rebar reinforced concrete, mortar overlay containing carbon fibers and latex needed 11% less driving voltage to protect the rebar in concrete than plain mortar overlay. However, multiple titanium electrical contacts were necessary, whether the overlay contained carbon fibers or not. For the same overlay (containing carbon fibers and latex), admixtures in the concrete also made a significant difference on the effect of cathodic protection; concrete with carbon fibers and silica fume needed 18% less driving voltage than plain concrete and 28% less than concrete containing silica fume.

Evaluation of heavy metal leaching from coal ash-versus conventional concrete monoliths and debris.

PubMed

Gwenzi, Willis; Mupatsi, Nyarai M

2016-03-01

Application of coal ash in construction materials is constrained by the potential risk of heavy metal leaching. Limited information is available on the comparative heavy metal leaching from coal ash-versus conventional concrete. The current study compared total and leached heavy metal concentrations in unbound coal ash, cement and sand; and investigated the effect of initial leachant pH on heavy metal leaching from coal-ash versus conventional concrete monoliths and their debris. Total Pb, Mn and Zn in coal ash were lower than or similar to that of other materials, while Cu and Fe showed the opposite trend. Leached concentrations of Zn, Pb, Mn, Cu and Fe in unbound coal ash, its concrete and debris were comparable and in some cases even lower than that for conventional concrete. In all cases, leached concentrations accounted for just <1% of the total concentrations. Log-log plots of concentration and cumulative release of Fe versus time based on tank leaching data showed that leaching was dominated by diffusion. Overall, the risk of Zn, Pb, Mn, Cu and Fe leaching from coal ash and its concrete was minimal and comparable to that of conventional concrete, a finding in contrast to widely held public perceptions and earlier results reported in other regions such as India. In the current study the coal ash, and its concrete and debris had highly alkaline pH indicative of high acid neutralizing and pH buffering capacity, which account for the stabilization of Zn, Pb, Mn, Cu and Fe. Based on the low risk of Zn, Pb, Mn, Cu and Fe leaching from the coal ash imply that such coal ash can be incorporated in construction materials such as concrete without adverse impacts on public and environmental health from these constituents. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of Elevated Temperature on Mechanical Assets of Metakaolin Base Steel Fiber Reinforced Concrete

NASA Astrophysics Data System (ADS)

Vijay Anand, M.; Ibrahim, Azmi; Patil, Anand A.; Muthu, K. U.

2017-06-01

The fact of vast usage of concrete leads to important problems regarding its design and preparation of eco-friendly to obtain an economic cost of the product on varieties of time periods. Conventional ordinary Portland concrete may not able to meet its functional requisites as it found inconsistency in high temperature. The exposing of concrete structure to elevated temperature may be in case of rocket launching space ships, nuclear power plants. In this experiment, to enhance the high temperature resistance, pozzolanic materials and steel fibres are added to preserve the strength characteristics of concrete structure. In this analysis, the pozzolanic admixture MK is used as partial replacement of cementatious materials. The volume fraction of steel fibre is varied 0.25%, 0.5%, 0.75% and 1% by preserving MK as stationary for 10% replacement of cement. The strength parameters of concrete such as compressive strength, split tensile strength and flexural strength are studied.

An assessment of the CORCON-MOD3 code. Part 1: Thermal-hydraulic calculations

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

Strizhov, V.; Kanukova, V.; Vinogradova, T.

1996-09-01

This report deals with the subject of CORCON-Mod3 code validation (thermal-hydraulic modeling capability only) based on MCCI (molten core concrete interaction) experiments conducted under different programs in the past decade. Thermal-hydraulic calculations (i.e., concrete ablation, melt temperature, melt energy, concrete temperature, and condensible and non-condensible gas generation) were performed with the code, and compared with the data from 15 experiments, conducted at different scales using both simulant (metallic and oxidic) and prototypic melt materials, using different concrete types, and with and without an overlying water pool. Sensitivity studies were performed in a few cases involving, for example, heat transfer frommore » melt to concrete, condensed phase chemistry, etc. Further, special analysis was performed using the ACE L8 experimental data to illustrate the differences between the experimental and the reactor conditions, and to demonstrate that with proper corrections made to the code, the calculated results were in better agreement with the experimental data. Generally, in the case of dry cavity and metallic melts, CORCON-Mod3 thermal-hydraulic calculations were in good agreement with the test data. For oxidic melts in a dry cavity, uncertainties in heat transfer models played an important role for two melt configurations--a stratified geometry with segregated metal and oxide layers, and a heterogeneous mixture. Some discrepancies in the gas release data were noted in a few cases.« less

Cost-effective and rapid concrete repair techniques.

DOT National Transportation Integrated Search

2016-02-08

Concrete is a principal component of many transportation structures. While highly durable, a : variety of processes degrade and damage concrete. Replacement is expensive. Many cases : warrant repair instead of replacement. Since many damage processes...

Case study #3 -- severe scaling of an interstate bridge deck, and Potentially reactive carbonate aggregates, progress report #6 (partial): an example of bridge deterioration promoted by alkali-carbonate reaction.

DOT National Transportation Integrated Search

1971-01-01

The project designated "Concrete Durability Studies" comprises case studies of unusual durability, either in kind or extent. These case studies are directed toward situations in which appearances suggest materials or construction rather than structur...

Learning with Technology: Video Modeling with Concrete-Representational-Abstract Sequencing for Students with Autism Spectrum Disorder

ERIC Educational Resources Information Center

Yakubova, Gulnoza; Hughes, Elizabeth M.; Shinaberry, Megan

2016-01-01

The purpose of this study was to determine the effectiveness of a video modeling intervention with concrete-representational-abstract instructional sequence in teaching mathematics concepts to students with autism spectrum disorder (ASD). A multiple baseline across skills design of single-case experimental methodology was used to determine the…

Assessment of mitigating transverse joint faulting on portland cement concrete pavement with polyurethane foam on LA 1 Bypass, state project number 034-30-0023.

DOT National Transportation Integrated Search

2015-02-01

A case study was conducted by the Louisiana Transportation Research Center (LTRC) to assess the effectiveness of reducing faulting on jointed concrete : pavement (JCP) with polyurethane foam (PF) on LA 1 Bypass, S.P. 034-30-0023. The PF fault correct...

Evaluation of the Carrying Capacity of Rectangular Steel-Concrete Columns

NASA Astrophysics Data System (ADS)

Vatulia, Glib; Rezunenko, Maryna; Petrenko, Dmytro; Rezunenko, Sergii

2018-06-01

Experimental studies of rectangular steel-concrete columns under centric compression with random eccentricity were conducted. The stress-strain state and the carrying capacity exhaustion have been assessed. The regression dependence is proposed to determine the maximum carrying capacity of such columns. The mathematical model takes into account the combined influence of the physical and geometric characteristics of the columns, such as their length, crosssectional area, casing thickness, prism strength of concrete, yield strength of steel, modulus of elasticity of both steel and concrete. The correspondence of the obtained model to the experimental data, as well as the significance of the regression parameters are confirmed by the Fisher and Student criteria.

The effect of various pozzolanic additives on the concrete strength index

NASA Astrophysics Data System (ADS)

Vitola, L.; Sahmenko, G.; Erdmane, D.; Bumanis, G.; Bajare, D.

2017-10-01

The concrete industry is searching continuously for new effective mineral additives to improve the concrete properties. Replacing cement with the pozzolanic additives in most cases has resulted not only in positive impact on the environment but also has improved strength and durability of the concrete. Effective pozzolanic additives can be obtained from natural resources such as volcanic ashes, kaolin and other sediments as well as from different production industries that create various by-products with high pozzolanic reactivity. Current research deals with effectiveness evaluation of various mineral additives/wastes, such as coal combustion bottom ash, barley bottom ash, waste glass and metakaolin containing waste as well as calcined illite clays as supplementary cementitious materials, to be used in concrete production as partial cement replacement. Most of the examined materials are used as waste stream materials with potential reactive effect on the concrete. Milling time and fineness of the tested supplementary material has been evaluated and effectiveness was detected. Results indicate that fineness of the tested materials has crucial effect on the concrete compressive strength index. Not in all cases the prolonged milling time can increase fineness and reactivity of the supplementary materials; however the optimal milling time and fineness of the pozolanic additives increased the strength index of concrete up to 1.16 comparing to reference, even in cases when cement was substituted by 20 w%.

WeSaySo Case Study: Designing and Implementing a Case Study for Use in an Instructional Design Class.

ERIC Educational Resources Information Center

Graves, Rick; Barnett, Mardee; Gamble, Yolanda; Kolak, Mike

A case study was used in an instructional design class to facilitate the transfer of conceptual knowledge to concrete concerns and to aid instructional technology graduate students' understanding of the steps involved in designing, analyzing, and implementing an effective needs analysis. The case study involved real events at fictitious company…

[Toxic ulcerative contact dermatitis due to prefabricated concrete (cement burns)].

PubMed

Bandmann, H J; Agathos, M

1977-01-01

In the present report the case of a toxic ulcerous contact dermatitis (cement burns) by pre-fabricated concrete is described. This can be clearly distinguished by anamnesis, findings and development from the allergic and cumulative-toxic contact dermatitis caused by cement and related substances. It is pointed out, that in the few cases of "cement burns" made known up to now, pre-fabricated concrete was always the triggering agent.

Dynamic Impact Analyses and Tests of Concrete Overpacks - 13638

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

Lee, Sanghoon; Cho, Sang-Soon; Kim, Ki-Young

Concrete cask is an option for spent nuclear fuel interim storage which is prevailingly used in US. A concrete cask usually consists of metallic canister which confines the spent nuclear fuel and concrete overpack. When the overpack undergoes a severe missile impact which might be caused by a tornado or an aircraft crash, it should sustain acceptable level of structural integrity so that its radiation shielding capability and the retrievability of canister are maintained. Missile impact against a concrete overpack involves two damage modes, local damage and global damage. Local damage of concrete is usually evaluated by empirical formulas whilemore » the global damage is evaluated by finite element analysis. In many cases, those two damage modes are evaluated separately. In this research, a series of numerical simulations are performed using finite element analysis to evaluate the global damage of concrete overpack as well as its local damage under high speed missile impact. We consider two types of concrete overpack, one with steel in-cased concrete without reinforcement and the other with partially-confined reinforced concrete. The numerical simulation results are compared with test results and it is shown that appropriate modeling of material failure is crucial in this analysis and the results are highly dependent on the choice of failure parameters. (authors)« less

Corrosion Behavior of Steel Reinforcement in Concrete with Recycled Aggregates, Fly Ash and Spent Cracking Catalyst.

PubMed

Gurdián, Hebé; García-Alcocel, Eva; Baeza-Brotons, Francisco; Garcés, Pedro; Zornoza, Emilio

2014-04-21

The main strategy to reduce the environmental impact of the concrete industry is to reuse the waste materials. This research has considered the combination of cement replacement by industrial by-products, and natural coarse aggregate substitution by recycled aggregate. The aim is to evaluate the behavior of concretes with a reduced impact on the environment by replacing a 50% of cement by industrial by-products (15% of spent fluid catalytic cracking catalyst and 35% of fly ash) and a 100% of natural coarse aggregate by recycled aggregate. The concretes prepared according to these considerations have been tested in terms of mechanical strengths and the protection offered against steel reinforcement corrosion under carbonation attack and chloride-contaminated environments. The proposed concrete combinations reduced the mechanical performance of concretes in terms of elastic modulus, compressive strength, and flexural strength. In addition, an increase in open porosity due to the presence of recycled aggregate was observed, which is coherent with the changes observed in mechanical tests. Regarding corrosion tests, no significant differences were observed in the case of the resistance of these types of concretes under a natural chloride attack. In the case of carbonation attack, although all concretes did not stand the highly aggressive conditions, those concretes with cement replacement behaved worse than Portland cement concretes.

Detection of cracks on concrete surfaces by hyperspectral image processing

NASA Astrophysics Data System (ADS)

Santos, Bruno O.; Valença, Jonatas; Júlio, Eduardo

2017-06-01

All large infrastructures worldwide must have a suitable monitoring and maintenance plan, aiming to evaluate their behaviour and predict timely interventions. In the particular case of concrete infrastructures, the detection and characterization of crack patterns is a major indicator of their structural response. In this scope, methods based on image processing have been applied and presented. Usually, methods focus on image binarization followed by applications of mathematical morphology to identify cracks on concrete surface. In most cases, publications are focused on restricted areas of concrete surfaces and in a single crack. On-site, the methods and algorithms have to deal with several factors that interfere with the results, namely dirt and biological colonization. Thus, the automation of a procedure for on-site characterization of crack patterns is of great interest. This advance may result in an effective tool to support maintenance strategies and interventions planning. This paper presents a research based on the analysis and processing of hyper-spectral images for detection and classification of cracks on concrete structures. The objective of the study is to evaluate the applicability of several wavelengths of the electromagnetic spectrum for classification of cracks in concrete surfaces. An image survey considering highly discretized wavelengths between 425 nm and 950 nm was performed on concrete specimens, with bandwidths of 25 nm. The concrete specimens were produced with a crack pattern induced by applying a load with displacement control. The tests were conducted to simulate usual on-site drawbacks. In this context, the surface of the specimen was subjected to biological colonization (leaves and moss). To evaluate the results and enhance crack patterns a clustering method, namely k-means algorithm, is being applied. The research conducted allows to define the suitability of using clustering k-means algorithm combined with hyper-spectral images highly discretized for crack detection on concrete surfaces, considering cracking combined with the most usual concrete anomalies, namely biological colonization.

For Example? A Philosophical Case Study of Some Problems When Abstract Educational Theory Ignores Concrete Practice

ERIC Educational Resources Information Center

Golding, Clinton

2017-01-01

In Philosophy of Education we frequently argue for or against different educational theories. Yet, as I illustrate in this analysis of two articles, in order to maintain the abstract theoretical distinctions, we are liable to ignore the concrete details of practice, caricature the theories we reject and make false distinctions. The two articles…

Repair, Evaluation, Maintenance, and Rehabilitation Research Program: Plastic Concrete Cutoff Walls for Earth Dams

DTIC Science & Technology

1991-03-01

Vicksburg, MS 39180-6199 REMR-GT-15 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10 . SPONSORINGIMONITORING AGENCY REPORT NUMBER US Army Corps...6 PART II: LITERATURE REVIEW ............................................. 10 General Observations of Recent...Plastic Concrete Research ......... 10 Major Plastic Concrete Research Programs ............................ 13 Plastic Concrete Cutoff Wall Field Case

Repair, Evaluation, Maintenance, and Rehabilitation Research Program Overlays on Horizontal Concrete Surfaces: Case Histories

DTIC Science & Technology

1994-02-01

ash, silica-fume, polymer -modified, polymer , and fiber - reinforced concretes. For some nonstructural repairs, unbonded overlays have been employed in an...which silica fume was included; polymer -modified concrete overlay, one in which a polymer admixture had been included; and fiber - reinforced concrete...of pumps. However, a determination has not been made for the source of leakage. 56 Chapter 6 Polymer -Modified Concrete Overlays 7 Fiber - Reinforced

Equivalent Quantum Equations in a System Inspired by Bouncing Droplets Experiments

NASA Astrophysics Data System (ADS)

Borghesi, Christian

2017-07-01

In this paper we study a classical and theoretical system which consists of an elastic medium carrying transverse waves and one point-like high elastic medium density, called concretion. We compute the equation of motion for the concretion as well as the wave equation of this system. Afterwards we always consider the case where the concretion is not the wave source any longer. Then the concretion obeys a general and covariant guidance formula, which leads in low-velocity approximation to an equivalent de Broglie-Bohm guidance formula. The concretion moves then as if exists an equivalent quantum potential. A strictly equivalent free Schrödinger equation is retrieved, as well as the quantum stationary states in a linear or spherical cavity. We compute the energy (and momentum) of the concretion, naturally defined from the energy (and momentum) density of the vibrating elastic medium. Provided one condition about the amplitude of oscillation is fulfilled, it strikingly appears that the energy and momentum of the concretion not only are written in the same form as in quantum mechanics, but also encapsulate equivalent relativistic formulas.

Reclamation chain of waste concrete: A case study of Shanghai.

PubMed

Xiao, Jianzhuang; Ma, Zhiming; Ding, Tao

2016-02-01

A mass of construction and demolition (C&D) waste are generated in Shanghai every year, and it has become a serious environment problem. Reclaiming the waste concrete to produce recycled aggregate (RA) and recycled aggregate concrete (RAC) is an effective method to reduce the C&D waste. This paper develops a reclamation chain of waste concrete based on the researches and practices in Shanghai. C&D waste management, waste concrete disposition, RA production and RAC preparation are discussed respectively. In addition, technical suggestions are also given according to the findings in practical engineering, which aims to optimize the reclamation chain. The results show that the properties of RA and RAC can well meet the requirement of design and practical application through a series of technical measures. The reclamation chain of waste concrete is necessary and appropriate for Shanghai, which provides more opportunities for the wider application of RA and RAC, and it shows a favorable environmental benefit. Copyright © 2015 Elsevier Ltd. All rights reserved.

Reuse of municipal solid wastes incineration fly ashes in concrete mixtures.

PubMed

Collivignarelli, Carlo; Sorlini, Sabrina

2002-01-01

This study is aimed at assessing the feasibility of concrete production using stabilized m.s.w. (municipal solid waste) incineration fly ashes in addition to natural aggregates. The tested fly ashes were washed and milled, then stabilized by a cement-lime process and finally were reused as a "recycled aggregate" for cement mixture production, in substitution of a natural aggregate (with dosage of 200-400 kg m(-3)). These mixtures, after curing, were characterized with conventional physical-mechanical tests (compression, traction, flexure, modulus of elasticity, shrinkage). In samples containing 200 kg(waste) m(-3)(concrete), a good compressive strength was achieved after 28 days of curing. Furthermore, concrete leaching behavior was evaluated by means of different leaching tests, both on milled and on monolithic samples. Experimental results showed a remarkable reduction of metal leaching in comparison with raw waste. In some cases, similar behavior was observed in "natural" concrete (produced with natural aggregates) and in "waste containing" concrete.

Investigation on the Rheological Behavior of Fly Ash Cement Composites at Paste and Concrete Level

NASA Astrophysics Data System (ADS)

Thiyagarajan, Hemalatha; Mapa, Maitri; Kushwaha, Rakhi

2018-06-01

Towards developing sustainable concrete, nowadays, high volume replacement of cement with fly ash (FA) is more common. Though the replacement of fly ash at 20-30% is widely accepted due to its advantages at both fresh and hardened states, applicability and acceptability of high volume fly ash (HVFA) is not so popular due to some adverse effects on concrete properties. Nowadays to suit various applications, flowing concretes such as self compacting concrete is often used. In such cases, implications of usage of HVFA on fresh properties are required to be investigated. Further, when FA replacement is beyond 40% in cement, it results in the reduction of strength and in order to overcome this drawback, additions such as nano calcium carbonate (CC), lime sludge (LS), carbon nano tubes (CNT) etc. are often incorporated to HVFA concrete. Hence, in this study, firstly, the influence of replacement level of 20-80% FA on rheological property is studied for both cement and concrete. Secondly, the influence of additions such as LS, CC and CNT on rheological parameters are discussed. It is found that the increased FA content improved the flowability in paste as well as in concrete. In paste, the physical properties such as size and shape of fly ash is the reason for increased flowability whereas in concrete, the paste volume contributes dominantly for the flowability rather than the effect due to individual FA particle. Reduced density of FA increases the paste volume in FA concrete thus reducing the interparticle friction by completely coating the coarse aggregate.

Microsilica modified concrete for bridge deck overlays : second-year interim report.

DOT National Transportation Integrated Search

1994-10-01

This report summarizes the performance of microsilica concrete (MC) overlays on seven distressed portland cement concrete bridge decks at three sites in Oregon. This report emphasizes the overlays' condition after two, or in some cases, three years o...

Economics of Concrete and Wood Tie Track Structures

DOT National Transportation Integrated Search

1978-08-01

This report presents results from an evaluation of the economic benefits of concrete- versus wood-tie track. The analysis includes the life-cycle capital, maintenance, and renewal costs for concrete- and wood-tie track for four specific test cases an...

PFC2D simulation of thermally induced cracks in concrete specimens

NASA Astrophysics Data System (ADS)

Liu, Xinghong; Chang, Xiaolin; Zhou, Wei; Li, Shuirong

2013-06-01

The appearance of cracks exposed to severe environmental conditions can be critical for concrete structures. The research is to validate Particle Flow Code(PFC2D) method in the context of concrete thermally-induced cracking simulations. First, concrete was discreted as meso-level units of aggregate, cement mortar and the interfaces between them. Parallel bonded-particle model in PFC2D was adapted to describe the constitutive relation of the cementing material. Then, the concrete mechanics meso-parameters were obtained through several groups of biaxial tests, in order to make the numerical results comply with the law of the indoor test. The concrete thermal meso-parameters were determined by compared with the parameters in the empirical formula through the simulations imposing a constant heat flow to the left margin of concrete specimens. At last, a case of 1000mm×500mm concrete specimen model was analyzed. It simulated the formation and development process of the thermally-induced cracks under the cold waves of different durations and temperature decline. Good agreements in fracture morphology and process were observed between the simulations, previous studies and laboratory data. The temperature decline limits during cold waves were obtained when its tensile strength was given as 3MPa. And it showed the feasibility of using PFC2D to simulate concrete thermally-induced cracking.

Study of the Technical Feasibility of Increasing the Amount of Recycled Concrete Waste Used in Ready-Mix Concrete Production

PubMed Central

Ferreiro-Cabello, Javier; López-González, Luis M.

2017-01-01

The construction industry generates a considerable amount of waste. Faced with this undesirable situation, the ready-mix concrete sector, in particular, has invested energy and resources into reusing its own waste in its production process as it works towards the goal of more sustainable construction. This study examines the feasibility of incorporating two types of concrete waste, which currently end up in landfill, into the production process of ready-mix concrete: the waste generated during the initial production stage (ready-mix concrete waste), and waste created when demolition waste is treated to obtain artificial aggregate. The first phase of the study’s methodology corroborates the suitability of the recycled aggregate through characterization tests. After this phase, the impact of incorporating different percentages of recycled coarse aggregate is evaluated by examining the performance of the produced concrete. The replacement rate varied between 15% and 50%. The results indicate that recycled aggregates are, indeed, suitable to be incorporated into ready-mix concrete production. The impact on the final product’s performance is different for the two cases examined herein. Incorporating aggregates from generic concrete blocks led to a 20% decrease in the produced concrete’s strength performance. On the other hand, using recycled aggregates made from the demolition waste led to a smaller decrease in the concrete’s performance: about 8%. The results indicate that with adequate management and prior treatment, the waste from these plants can be re-incorporated into their production processes. If concrete waste is re-used, concrete production, in general, becomes more sustainable for two reasons: less waste ends up as landfill and the consumption of natural aggregates is also reduced. PMID:28773183

Evaluation of concrete recycling system efficiency for ready-mix concrete plants.

PubMed

Vieira, Luiz de Brito Prado; Figueiredo, Antonio Domingues de

2016-10-01

The volume of waste generated annually in concrete plants is quite large and has important environmental and economic consequences. The use of fresh concrete recyclers is an interesting way for the reuse of aggregates and water in new concrete production. This paper presents a study carried out for over one year by one of the largest ready-mix concrete producers in Brazil. This study focused on the evaluation of two recyclers with distinct material separation systems, herein referred to as drum-type and rotary sieve-type equipment. They were evaluated through characterization and monitoring test programs to verify the behaviour of recovered materials (aggregates, water, and slurry). The applicability of the recovered materials (water and aggregates) was also evaluated in the laboratory and at an industrial scale. The results obtained with the two types of recyclers used were equivalent and showed no significant differences. The only exception was in terms of workability. The drum-type recycler generated fewer cases that required increased pumping pressure. The analysis concluded that the use of untreated slurry is unfeasible because of its intense negative effects on the strength and workability of concrete. The reclaimed water, pre-treated to ensure that its density is less than 1.03g/cm(3), can be used on an industrial scale without causing any harm to the concrete. The use of recovered aggregates consequently induces an increase in water demand and cement consumption to ensure the workability conditions of concrete that is proportional to the concrete strength level. Therefore, the viability of their use is restricted to concretes with characteristic strengths lower than 25MPa. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of Air Entraining Method on the Resistance of Concrete to Internal Cracking

NASA Astrophysics Data System (ADS)

Wawrzeńczyk, Jerzy; Molendowska, Agnieszka

2017-10-01

This paper presents the test results of air entrained concrete mixtures made at a constant W/C ratio of 0.44. Three different air entraining agents were used: polymer microspheres, glass microspheres and a conventional air entraining admixture. The aim of this study was to compare the effectiveness of the air entraining methods. Concrete mixture tests were performed for consistency (slump test), density and, in the case of AEA series, air content by pressure method. Hardened concrete tests were performed for compressive strength, water absorption, resistance to chloride ingress, and freeze-thaw durability - resistance to internal cracking tests were conducted in accordance with PN-88/B-06250 on cube specimens and with the modified ASTM C666 A test method on beam specimens; porosity characteristics (A, A300, \\bar L) were determined to PN-EN 480-11:1998. No significant mass and length changes were recorded for the concrete air entrained with the conventional methods or with polymer microspheres. The results indicate that polymer microspheres are a very good alternative to traditional air entraining methods for concrete, providing effective air entrainment and protection from freezing and thawing. The glass microsphere-based concretes showed insufficient freeze-thaw resistance. The test results indicate that both the conventional methods (AEA) and the air entrainment by polymer microspheres are effective air entraining methods. It has to be noted that in the case of the use of polymer microspheres, a comparable value of \\bar L and a very good freeze-thaw resistance can be achieved at a noticeably lower air and micropore contents and at lower strength loss.

Application of Natural Mineral Additives in Construction

NASA Astrophysics Data System (ADS)

Linek, Malgorzata; Nita, Piotr; Wolka, Paweł; Zebrowski, Wojciech

2017-12-01

The article concerns the idea of using selected mineral additives in the pavement quality concrete composition. The basis of the research paper was the modification of cement concrete intended for airfield pavements. The application of the additives: metakaolonite and natural zeolite was suggested. Analyses included the assessment of basic physical properties of modifiers. Screening analysis, assessment of micro structure and chemical microanalysis were conducted in case of these materials. The influence of the applied additives on the change of concrete mix parameters was also presented. The impact of zeolite and metakaolinite on the mix density, oxygen content and consistency class was analysed. The influence of modifiers on physical and mechanical changes of the hardened cement concrete was discussed (concrete density, compressive strength and bending strength during fracturing) in diversified research periods. The impact of the applied additives on the changes of internal structure of cement concrete was discussed. Observation of concrete micro structure was conducted using the scanning electron microscope. According to the obtained lab test results, parameters of the applied modifiers and their influence on changes of internal structure of cement concrete are reflected in the increase of mechanical properties of pavement quality concrete. The increase of compressive and bending strength in case of all analysed research periods was proved.

Corrosion Behavior of Steel Reinforcement in Concrete with Recycled Aggregates, Fly Ash and Spent Cracking Catalyst

PubMed Central

Gurdián, Hebé; García-Alcocel, Eva; Baeza-Brotons, Francisco; Garcés, Pedro; Zornoza, Emilio

2014-01-01

The main strategy to reduce the environmental impact of the concrete industry is to reuse the waste materials. This research has considered the combination of cement replacement by industrial by-products, and natural coarse aggregate substitution by recycled aggregate. The aim is to evaluate the behavior of concretes with a reduced impact on the environment by replacing a 50% of cement by industrial by-products (15% of spent fluid catalytic cracking catalyst and 35% of fly ash) and a 100% of natural coarse aggregate by recycled aggregate. The concretes prepared according to these considerations have been tested in terms of mechanical strengths and the protection offered against steel reinforcement corrosion under carbonation attack and chloride-contaminated environments. The proposed concrete combinations reduced the mechanical performance of concretes in terms of elastic modulus, compressive strength, and flexural strength. In addition, an increase in open porosity due to the presence of recycled aggregate was observed, which is coherent with the changes observed in mechanical tests. Regarding corrosion tests, no significant differences were observed in the case of the resistance of these types of concretes under a natural chloride attack. In the case of carbonation attack, although all concretes did not stand the highly aggressive conditions, those concretes with cement replacement behaved worse than Portland cement concretes. PMID:28788613

Repair and Rehabilitation of Dams: Case Studies

DTIC Science & Technology

1999-09-01

with fiber - reinforced , acrylic- polymer modi- fied concrete (FRAPMC) and eliminating leakage into the trunnion recesses. FRAPMC consists of mortar...coarse aggregate, and reinforcement fibers . It is mixed in a mortar mixer as a two-component system consisting of a liquid polymer emulsion of...seat was removed and replaced with fiber - reinforced , acrylic- polymer modified concrete (FRAPMC). New bridge seats were installed, allowing for more

Open cycle ocean thermal energy conversion system

DOEpatents

Wittig, J. Michael

1980-01-01

An improved open cycle ocean thermal energy conversion system including a flash evaporator for vaporizing relatively warm ocean surface water and an axial flow, elastic fluid turbine having a vertical shaft and axis of rotation. The warm ocean water is transmitted to the evaporator through a first prestressed concrete skirt-conduit structure circumferentially situated about the axis of rotation. The unflashed warm ocean water exits the evaporator through a second prestressed concrete skirt-conduit structure located circumferentially about and radially within the first skirt-conduit structure. The radially inner surface of the second skirt conduit structure constitutes a cylinder which functions as the turbine's outer casing and obviates the need for a conventional outer housing. The turbine includes a radially enlarged disc element attached to the shaft for supporting at least one axial row of radially directed blades through which the steam is expanded. A prestressed concrete inner casing structure of the turbine has upstream and downstream portions respectively situated upstream and downstream from the disc element. The radially outer surfaces of the inner casing portions and radially outer periphery of the axially interposed disc cooperatively form a downwardly radially inwardly tapered surface. An annular steam flowpath of increasing flow area in the downward axial direction is radially bounded by the inner and outer prestressed concrete casing structures. The inner casing portions each include a transversely situated prestressed concrete circular wall for rotatably supporting the turbine shaft and associated structure. The turbine blades are substantially radially coextensive with the steam flowpath and receive steam from the evaporator through an annular array of prestressed concrete stationary vanes which extend between the inner and outer casings to provide structural support therefor and impart a desired flow direction to the steam.

Concrete Open-Wall Systems Wrapped with FRP under Torsional Loads

PubMed Central

Mancusi, Geminiano; Feo, Luciano; Berardi, Valentino P.

2012-01-01

The static behavior of reinforced concrete (RC) beams plated with layers of fiber-reinforced composite material (FRP) is widely investigated in current literature, which deals with both its numerical modeling as well as experiments. Scientific interest in this topic is explained by the increasing widespread use of composite materials in retrofitting techniques, as well as the consolidation and upgrading of existing reinforced concrete elements to new service conditions. The effectiveness of these techniques is typically influenced by the debonding of the FRP at the interface with concrete, where the transfer of stresses occurs from one element (RC member) to the other (FRP strengthening). In fact, the activation of the well-known premature failure modes can be regarded as a consequence of high peak values of the interfacial interactions. Until now, typical applications of FRP structural plating have included cases of flexural or shear-flexural strengthening. Within this context, the present study aims at extending the investigation to the case of wall-systems with open cross-section under torsional loads. It includes the results of some numerical analyses carried out by means of a finite element approximation.

A Business Casebook for Young Decision Makers.

ERIC Educational Resources Information Center

Tedesco, Paul H., Ed.; And Others

Ten case studies taken from the business world are presented to help secondary school students develop a realistic understanding of economic problems. Discussion of the cases can be integrated into economics or social studies programs. By studying concrete examples of business reacting to changing economic conditions, students should learn to…

Structural Effects of Reinforced Concrete Beam Due to Corrosion

NASA Astrophysics Data System (ADS)

Noh, Hamidun Mohd; Idris, Nur'ain; Noor, Nurazuwa Md; Sarpin, Norliana; Zainal, Rozlin; Kasim, Narimah

2018-03-01

Corrosion of steel in reinforced concrete is one of the main issues among construction stakeholders. The main consequences of steel corrosion include loss of cross section of steel area, generation of expansive pressure which caused cracking of concrete, spalling and delaminating of the concrete cover. Thus, it reduces the bond strength between the steel reinforcing bar and concrete, and deteriorating the strength of the structure. The objective of this study is to investigate the structural effects of corrosion damage on the performance of reinforced concrete beam. A series of corroded reinforced concrete beam with a corrosion rate of 0%, 20% and 40% of rebar corrosion is used in parametric study to assess the influence of different level of corrosion rate to the structural performance. As a result, the used of interface element in the finite element modelling predicted the worst case of corrosion analysis since cracks is induced and generate at this surface. On the other hand, a positive linear relationship was sketched between the increase of expansive pressure and the corrosion rate. Meanwhile, the gradient of the graph is decreased with the increase of steel bar diameter. Furthermore, the analysis shows that there is a significant effect on the load bearing capacity of the structure where the higher corrosion rate generates a higher stress concentration at the mid span of the beam. This study could predict the residual strength of reinforced concrete beam under the corrosion using the finite element analysis. The experimental validation is needed on the next stage to investigate the quantitative relation between the corrosion rate and its influence on the mechanical properties.

AN OPTIMAL MAINTENANCE MANAGEMENT MODEL FOR AIRPORT CONCRETE PAVEMENT

NASA Astrophysics Data System (ADS)

Shimomura, Taizo; Fujimori, Yuji; Kaito, Kiyoyuki; Obama, Kengo; Kobayashi, Kiyoshi

In this paper, an optimal management model is formulated for the performance-based rehabilitation/maintenance contract for airport concrete pavement, whereby two types of life cycle cost risks, i.e., ground consolidation risk and concrete depreciation risk, are explicitly considered. The non-homogenous Markov chain model is formulated to represent the deterioration processes of concrete pavement which are conditional upon the ground consolidation processes. The optimal non-homogenous Markov decision model with multiple types of risk is presented to design the optimal rehabilitation/maintenance plans. And the methodology to revise the optimal rehabilitation/maintenance plans based upon the monitoring data by the Bayesian up-to-dating rules. The validity of the methodology presented in this paper is examined based upon the case studies carried out for the H airport.

Seismic Behaviour of Composite Steel Fibre Reinforced Concrete Shear Walls

NASA Astrophysics Data System (ADS)

Boita, Ioana-Emanuela; Dan, Daniel; Stoian, Valeriu

2017-10-01

In this paper is presented an experimental study conducted at the “Politehnica” University of Timisoara, Romania. This study provides results from a comprehensive experimental investigation on the behaviour of composite steel fibre reinforced concrete shear walls (CSFRCW) with partially or totally encased profiles. Two experimental composite steel fibre reinforced concrete walls (CSFRCW) and, as a reference specimen, a typical reinforced concrete shear wall (RCW), (without structural reinforcement), were fabricated and tested under constant vertical load and quasi-static reversed cyclic lateral loads, in displacement control. The tests were performed until failure. The tested specimens were designed as 1:3 scale steel-concrete composite elements, representing a three storeys and one bay element from the base of a lateral resisting system made by shear walls. Configuration/arrangement of steel profiles in cross section were varied within the specimens. The main objective of this research consisted in identifying innovative solutions for composite steel-concrete shear walls with enhanced performance, as steel fibre reinforced concrete which was used in order to replace traditional reinforced concrete. A first conclusion was that replacing traditional reinforcement with steel fibre changes the failure mode of the elements, as from a flexural mode, in case of element RCW, to a shear failure mode for CSFRCW. The maximum lateral force had almost similar values but test results indicated an improvement in cracking response, and a decrease in ductility. The addition of steel fibres in the concrete mixture can lead to an increase of the initial cracking force, and can change the sudden opening of a crack in a more stable process.

Vibrated and self-compacting fibre reinforced concrete: experimental investigation on the fibre orientation

NASA Astrophysics Data System (ADS)

Conforti, A.; Plizzari, G. A.; Zerbino, R.

2017-09-01

In addition to the fibre type and content, the residual properties of fibre reinforced concrete are influenced by fibre orientation. Consequently, the performance fibre reinforced concrete can be affected by its fresh properties (workability, flowing capacity) and by casting and compaction processes adopted. This paper focuses on the study of the orientation of steel or macro-synthetic fibres in two materials characterized by very different fresh properties: vibrated and self-compacting concrete. Four rectangular slabs 1800 mm long, 925 mm wide and 100 mm high were produced changing concrete and fibre type. From each slab, eighteen small prisms (550 mm long) were firstly cut either orthogonal or parallel to casting direction and, secondly, notched and tested in bending according to EN 14651. Experimental results showed that the toughness properties of a thin slab significantly varies both in vibrated and self-compacting concrete, even if in case of self-compacting concrete this variation resulted higher. Steel fibres led to greater variability of results compared to polymer one, underlining a different fibre orientation. A discussion on the relative residual capacity measured on the prisms sawn from the slabs and the parameters obtained from standard specimens is performed.

Finite element simulation of ultrasonic waves in corroded reinforced concrete for early-stage corrosion detection

NASA Astrophysics Data System (ADS)

Tang, Qixiang; Yu, Tzuyang

2017-04-01

In reinforced concrete (RC) structures, corrosion of steel rebar introduces internal stress at the interface between rebar and concrete, ultimately leading to debonding and separation between rebar and concrete. Effective early-stage detection of steel rebar corrosion can significantly reduce maintenance costs and enable early-stage repair. In this paper, ultrasonic detection of early-stage steel rebar corrosion inside concrete is numerically investigated using the finite element method (FEM). Commercial FEM software (ABAQUS) was used in all simulation cases. Steel rebar was simplified and modeled by a cylindrical structure. 1MHz ultrasonic elastic waves were generated at the interface between rebar and concrete. Two-dimensional plain strain element was adopted in all FE models. Formation of surface rust in rebar was modeled by changing material properties and expanding element size in order to simulate the rust interface between rebar and concrete and the presence of interfacial stress. Two types of surface rust (corroded regions) were considered. Time domain and frequency domain responses of displacement were studied. From our simulation result, two corrosion indicators, baseline (b) and center frequency (fc) were proposed for detecting and quantifying corrosion.

Evaluation of the fatigue and toughness of fiber reinforced concrete for use as a new highway pavement design.

DOT National Transportation Integrated Search

2016-04-01

Concrete pavement design is currently centered on steel reinforcement, whether that reinforcement be in the : form of dowel bars, as is the case in jointed plain concrete pavement (JPCP), or in the form of continuous rebar : reinforcement, continuous...

Performance of Hydrophobisation Techniques in Case of Reinforced Concrete Structures

NASA Astrophysics Data System (ADS)

Błaszczyński, Tomasz; Osesek, Mateusz; Gwozdowski, Błażej; Ilski, Mirosław

2017-10-01

Concrete is, unchangeably, one of the most frequently applied building materials, also in the case of bridges, overpasses or viaducts. Along with the aging of such structures, the degradation of concrete, which may accelerate the corrosion of reinforcing steel and drastically decrease the load-bearing capacity of the structure, becomes an important issue. The paper analyzes the possibilities of using deep hydrophobisation in repairing reinforced concrete engineering structures. The benefits of properly securing reinforced concrete structures from the damaging effects of UV radiation, the influence of harmful gases, or progression of chlorine induced corrosion have been presented, especially in regards to bridge structures. The need to calculate the costs of carrying out investments along with the expected costs of maintaining such structures, as well as the high share of costs connected with logistics, has also been indicated in the total costs of repair works.

Organic compounds in concrete from demolition works.

PubMed

Van Praagh, M; Modin, H; Trygg, J

2015-11-01

This study aims to verify the effect of physically removing the outer surface of contaminated concrete on total contents and on potential mobility of pollutants by means of leaching tests. Reclaimed concrete from 3 industrial sites in Sweden were included: A tar impregnated military storage, a military tar track-depot, as well as concrete constructions used for disposing of pesticide production surplus and residues. Solid materials and leachates from batch and column leaching tests were analysed for metals, Cl, F, SO4, DOC and contents of suspected organic compounds (polycyclic aromatic hydrocarbons, PAH, and pesticides/substances for pesticide production such as phenoxy acids, chlorophenols and chlorocresols, respectively). In case of PAH contaminated concrete, results indicate that removing 1 or 5 mm of the surface lead to total concentrations below the Swedish guidelines for recycling of aggregates and soil in groundwork constructions. 3 out of 4 concrete samples contaminated with pesticides fulfilled Swedish guidelines for contaminated soil. Results from batch and column leaching tests indicated, however, that concentrations above environmental quality standards for certain PAH and phenoxy acids, respectively, might occur at site when the crushed concrete is recycled in groundwork constructions. As leaching tests engaged in the study deviated from leaching test standards with a limited number of samples, the potential impact of the leaching tests' equipment on measured PAH and pesticide leachate concentrations has to be evaluated in future work. Copyright © 2015. Published by Elsevier Ltd.

Sustainable management and utilisation of concrete slurry waste: A case study in Hong Kong.

PubMed

Hossain, Md Uzzal; Xuan, Dongxing; Poon, Chi Sun

2017-03-01

With the promotion of environmental protection in the construction industry, the mission to achieve more sustainable use of resources during the production process of concrete is also becoming important. This study was conducted to assess the environmental sustainability of concrete slurry waste (CSW) management by life cycle assessment (LCA) techniques, with the aim of identifying a resource-efficient solution for utilisation of CSW in the production of partition wall blocks. CSW is the dewatered solid residues deposited in the sedimentation tank after washing out over-ordered/rejected fresh concrete and concrete trucks in concrete batching plants. The reuse of CSW as recycled aggregates or a cementitious binder for producing partition wall blocks, and the life cycle environmental impact of the blocks were assessed and compared with the conventional one designed with natural materials. The LCA results showed that the partition wall blocks prepared with fresh CSW and recycled concrete aggregates achieved higher sustainability as it consumed 59% lower energy, emitted 66% lower greenhouse gases, and produced lesser amount of other environmental impacts than that of the conventional one. When the mineral carbonation technology was further adopted for blocks curing using CO 2 , the global warming potential of the corresponding blocks production process was negligible, and hence the carbonated blocks may be considered as carbon neutral eco-product. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impact properties of geopolymeric concrete: a state-of-the-art review

NASA Astrophysics Data System (ADS)

Fang, Chi; Xie, Jianhe; Zhang, Bingxue; Yuan, Bing; Wang, Chonghao

2018-01-01

The application of geopolymer instead of cement in construction engineering provides an effective way to achieve sustainable development. A large number of studies have shown that geopolymeric concrete (GC) has excellent static performance. However, there are relatively few studies on the dynamic performance of GC which is of dominate importance in cases such as explosion, earthquake and other impact loads. This paper presents a brief review of recent research on the impact properties of GC, in order to facilitate the research development in this field. The effects of strain rate, fiber type, alkali type, elevated temperature, water environment and flow state on the impact resistance performance of GC were analysed. Research findings revealed that GC exhibited better impact properties than ordinary Portland concrete (OPC).

A statistical approach to optimizing concrete mixture design.

PubMed

Ahmad, Shamsad; Alghamdi, Saeid A

2014-01-01

A step-by-step statistical approach is proposed to obtain optimum proportioning of concrete mixtures using the data obtained through a statistically planned experimental program. The utility of the proposed approach for optimizing the design of concrete mixture is illustrated considering a typical case in which trial mixtures were considered according to a full factorial experiment design involving three factors and their three levels (3(3)). A total of 27 concrete mixtures with three replicates (81 specimens) were considered by varying the levels of key factors affecting compressive strength of concrete, namely, water/cementitious materials ratio (0.38, 0.43, and 0.48), cementitious materials content (350, 375, and 400 kg/m(3)), and fine/total aggregate ratio (0.35, 0.40, and 0.45). The experimental data were utilized to carry out analysis of variance (ANOVA) and to develop a polynomial regression model for compressive strength in terms of the three design factors considered in this study. The developed statistical model was used to show how optimization of concrete mixtures can be carried out with different possible options.

A Statistical Approach to Optimizing Concrete Mixture Design

PubMed Central

Alghamdi, Saeid A.

2014-01-01

A step-by-step statistical approach is proposed to obtain optimum proportioning of concrete mixtures using the data obtained through a statistically planned experimental program. The utility of the proposed approach for optimizing the design of concrete mixture is illustrated considering a typical case in which trial mixtures were considered according to a full factorial experiment design involving three factors and their three levels (33). A total of 27 concrete mixtures with three replicates (81 specimens) were considered by varying the levels of key factors affecting compressive strength of concrete, namely, water/cementitious materials ratio (0.38, 0.43, and 0.48), cementitious materials content (350, 375, and 400 kg/m3), and fine/total aggregate ratio (0.35, 0.40, and 0.45). The experimental data were utilized to carry out analysis of variance (ANOVA) and to develop a polynomial regression model for compressive strength in terms of the three design factors considered in this study. The developed statistical model was used to show how optimization of concrete mixtures can be carried out with different possible options. PMID:24688405

Energy Efficiency Improvement and Cost Saving Oportunities for the Concrete Industry

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

Kermeli, Katerina; Worrell, Ernst; Masanet, Eric

2011-12-01

The U.S. concrete industry is the main consumer of U.S.-produced cement. The manufacturing of ready mixed concrete accounts for more than 75% of the U.S. concrete production following the manufacturing of precast concrete and masonry units. The most significant expenditure is the cost of materials accounting for more than 50% of total concrete production costs - cement only accounts for nearly 24%. In 2009, energy costs of the U.S. concrete industry were over $610 million. Hence, energy efficiency improvements along with efficient use of materials without negatively affecting product quality and yield, especially in times of increased fuel and materialmore » costs, can significantly reduce production costs and increase competitiveness. The Energy Guide starts with an overview of the U.S. concrete industry’s structure and energy use, a description of the various manufacturing processes, and identification of the major energy consuming areas in the different industry segments. This is followed by a description of general and process related energy- and cost-efficiency measures applicable to the concrete industry. Specific energy and cost savings and a typical payback period are included based on literature and case studies, when available. The Energy Guide intends to provide information on cost reduction opportunities to energy and plant managers in the U.S. concrete industry. Every cost saving opportunity should be assessed carefully prior to implementation in individual plants, as the economics and the potential energy and material savings may differ.« less

Teaching the Holocaust through Case Study

ERIC Educational Resources Information Center

Misco, Thomas

2009-01-01

This article responds to the curricular challenges teachers face with Holocaust education, including cursory treatments and a lack of focus on individual experiences. First, the author argues for a case-study approach to help students reengage concrete and complex features of the Holocaust as a point of departure for subsequent inquiry. In…

Dynamics of layered reinforced concrete beam on visco-elastic foundation with different resistances of concrete and reinforcement to tension and compression

NASA Astrophysics Data System (ADS)

Nemirovsky, Y. V.; Tikhonov, S. V.

2018-03-01

Originally, fundamentals of the theory of limit equilibrium and dynamic deformation of building metal and reinforced concrete structures were created by A. A. Gvozdev [1] and developed by his followers [4, 5, 6, 7, 11, 12]. Forming the basis for the calculation, the model of an ideal rigid-plastic material has enabled to determine in many cases the ultimate load bearing capacity and upper (kinematically possible) or lower (statically valid) values for a wide class of different structures with quite simple methods. At the same time, applied to concrete structures the most important property of concrete to significantly differently resist tension and compression was not taken into account [10]. This circumstance was considered in [3] for reinforced concrete beams under conditions of quasistatic loading. The deformation is often accompanied by resistance of the environment in construction practice [8, 9]. In [2], the dynamics of multi-layered concrete beams on visco-elastic foundation under the loadings of explosive type is considered. In this work we consider the case which is often encountered in practical applications when the loadings weakly change in time.

Characterization of concrete from Roman theatre and amphitheater in Emerita Augusta (Mérida, Spain)

NASA Astrophysics Data System (ADS)

Mota-Lopez, Maria Isabel; Fort, Rafael; Alvarez de Buergo, Monica; Pizzo, Antonio; Maderuelo-Sanz, Ruben; Meneses-Rodríguez, Juan Miguel

2016-04-01

The restoration of historical buildings is very important for the history and culture of the cities and their population. It requires an advanced knowledge of the building materials used for the construction of these structures. Previously to any intervention in historical buildings, it is necessary a historic-scientific study of the original material. Historic mortars or concretes can reveal us different composition and the dependence on the geographical location and the time period of its construction. Historical concretes are complex systems that contain aerial or hydraulic binders or a blend of them, with aggregates, not always crystalline, and others elements that interact with the binder. The use of different techniques for microstructural characterization of materials, like optical microscopy, X-ray diffractometry or petrophysical analysis, allows the determination of the composition and some properties of these concretes. However, each technique has its own limits and, in many cases, several characterization techniques must be used to obtain coherent and reliable results. The present study focuses on the compositional characterization of Roman concrete from Roman buildings for public spectacles of Emerita Augusta, Mérida, Spain. An advanced knowledge of the Roman concrete composition is required to get a reliable restoration and preservation of these ancient monuments. Various samples of concrete were extracted from different zones from this archaeological site. The concrete was studied through mineralogical analysis (petrographic microscope and XRD) and petrophysical properties determination (bulk and real density, open porosity, mercury porosimetry intrusion, compressive strength and Ultrasound propagation velocity). The results obtained allow us to know the original composition of the concrete and the provenance of the aggregates used in it. Acknowledgements: Community of Madrid for financing Geomateriales2 program (P2013/MIT2914), to the funding provided by BIA 2014-53911-R project and to the Consortium for the Monumental City of Merida for the permission granted to collect concrete samples.

Upgrading Basements for Combined Nuclear Weapons Effects: Expedient Options

DTIC Science & Technology

1976-05-01

reinforced concrete stairwell walls can be expected to be substantial in these cases, since they are supporting an axial load from higher floors. F...desirability) include: a. Stacked concrete block or brick b. Stacked timber * The latter situation is likely to occur only in load - bearing wall...concrete flat slab 4 Reinforced concrete flat plate 4 Load - bearing wall 3 The analysis of the floor systems for the 34 NSS buildings required the dynamic

Bi-directional evolutionary structural optimization for strut-and-tie modelling of three-dimensional structural concrete

NASA Astrophysics Data System (ADS)

Shobeiri, Vahid; Ahmadi-Nedushan, Behrouz

2017-12-01

This article presents a method for the automatic generation of optimal strut-and-tie models in reinforced concrete structures using a bi-directional evolutionary structural optimization method. The methodology presented is developed for compliance minimization relying on the Abaqus finite element software package. The proposed approach deals with the generation of truss-like designs in a three-dimensional environment, addressing the design of corbels and joints as well as bridge piers and pile caps. Several three-dimensional examples are provided to show the capabilities of the proposed framework in finding optimal strut-and-tie models in reinforced concrete structures and verifying its efficiency to cope with torsional actions. Several issues relating to the use of the topology optimization for strut-and-tie modelling of structural concrete, such as chequerboard patterns, mesh-dependency and multiple load cases, are studied. In the last example, a design procedure for detailing and dimensioning of the strut-and-tie models is given according to the American Concrete Institute (ACI) 318-08 provisions.

Demonstration of EnergyNest thermal energy storage (TES) technology

NASA Astrophysics Data System (ADS)

Hoivik, Nils; Greiner, Christopher; Tirado, Eva Bellido; Barragan, Juan; Bergan, Pâl; Skeie, Geir; Blanco, Pablo; Calvet, Nicolas

2017-06-01

This paper presents the experimental results from the EnergyNest 2 × 500 kWhth thermal energy storage (TES) pilot system installed at Masdar Institute of Science & Technology Solar Platform. Measured data are shown and compared to simulations using a specially developed computer program to verify the stability and performance of the TES. The TES is based on a solid-state concrete storage medium (HEATCRETE®) with integrated steel tube heat exchangers cast into the concrete. The unique concrete recipe used in the TES has been developed in collaboration with Heidelberg Cement; this material has significantly higher thermal conductivity compared to regular concrete implying very effective heat transfer, at the same time being chemically stable up to 450 °C. The demonstrated and measured performance of the TES matches the predictions based on simulations, and proves the operational feasibility of the EnergyNest concrete-based TES. A further case study is analyzed where a large-scale TES system presented in this article is compared to two-tank indirect molten salt technology.

On intuitional stability: the clear, the strong, and the paradigmatic.

PubMed

Wright, Jennifer Cole

2010-06-01

Skepticism about the epistemic value of intuition in theoretical and philosophical inquiry has recently been bolstered by empirical research suggesting that people's concrete-case intuitions are vulnerable to irrational biases (e.g., the order effect). What is more, skeptics argue that we have no way to "calibrate" our intuitions against these biases and no way of anticipating intuitional instability. This paper challenges the skeptical position, introducing data from two studies that suggest not only that people's concrete-case intuitions are often stable, but also that people have introspective awareness of this stability, providing a promising means by which to assess the epistemic value of our intuitions.

The Case Method in Teacher Education: Alaskan Models. ERIC Digest.

ERIC Educational Resources Information Center

Kleinfeld, Judith

This ERIC digest discusses the theoretical basis of case teaching and examines its strengths and limitations as a tool for teacher education. Case teaching presents authentic, concrete teaching problems for students to analyze. The study of a classroom fight, for example, might draw discussion of racial, ethical, political, and other community…

Exploring Pre-Operational and Concrete Operational Children's Thinking on Nutrition: A Case Study

ERIC Educational Resources Information Center

Brouse, Corey H.; Chow, Tracy H. F.

2009-01-01

Objective: In this exploratory study, we observed the process in which children make food choices from a cognitive development perspective and the implications that these choices have on the areas of cognitive development and health and nutrition education. Design: This was a cross-sectional case study that involved an in-depth examination of the…

Refractory Access Disorders and the Organization of Concrete and Abstract Semantics: Do they Differ?

PubMed Central

Hamilton, A. Cris; Coslett, H. Branch

2010-01-01

Patients with “refractory semantic access deficits” demonstrate several unique features that make them important sources of insight into the organization of semantic representations. Here we attempt to replicate several novel findings from single-case studies reported in the literature. Patient UM– 103 displays the cardinal features of a “refractory semantic access deficit” and showed many of the same effects of semantic relatedness reported in the literature. However, when probing concrete and abstract words, this patient revealed very different patterns of performance compared to two previously reported patients. We discuss the implications of our data for models of semantic organization of abstract and concrete words. PMID:18569737

Durable fiber reinforced self-compacting concrete

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

Corinaldesi, V.; Moriconi, G

2004-02-01

In order to produce thin precast elements, a self-compacting concrete was prepared. When manufacturing these elements, homogenously dispersed steel fibers instead of ordinary steel-reinforcing mesh were added to the concrete mixture at a dosage of 10% by mass of cement. An adequate concrete strength class was achieved with a water to cement ratio of 0.40. Compression and flexure tests were carried out to assess the safety of these thin concrete elements. Moreover, serviceability aspects were taken into consideration. Firstly, drying shrinkage tests were carried out in order to evaluate the contribution of steel fibers in counteracting the high concrete strainsmore » due to a low aggregate-cement ratio. Secondly, the resistance to freezing and thawing cycles was investigated on concrete specimens in some cases superficially treated with a hydrophobic agent. Lastly, both carbonation and chloride penetration tests were carried out to assess durability behavior of this concrete mixture.« less

Corrosion of steel in locally deficient concrete.

DOT National Transportation Integrated Search

2009-02-28

This investigation confirmed prior noted trends of extensive preferential chloride intrusion at preexisitng cracks in a majority of cases of substructure members in Florida bridges built with low permeability conventional concrete.

Crack identification for reinforced concrete using PZT based smart rebar active sensing diagnostic network

NASA Astrophysics Data System (ADS)

Song, N. N.; Wu, F.

2016-04-01

An active sensing diagnostic system using PZT based smart rebar for SHM of RC structure has been currently under investigation. Previous test results showed that the system could detect the de-bond of concrete from reinforcement, and the diagnostic signals were increased exponentially with the de-bonding size. Previous study also showed that the smart rebar could function well like regular reinforcement to undertake tension stresses. In this study, a smart rebar network has been used to detect the crack damage of concrete based on guided waves. Experimental test has been carried out for the study. In the test, concrete beams with 2 reinforcements have been built. 8 sets of PZT elements were mounted onto the reinforcement bars in an optimized way to form an active sensing diagnostic system. A 90 kHz 5-cycle Hanning-windowed tone burst was used as input. Multiple cracks have been generated on the concrete structures. Through the guided bulk waves propagating in the structures from actuators and sensors mounted from different bars, crack damage could be detected clearly. Cases for both single and multiple cracks were tested. Different crack depths from the surface and different crack numbers have been studied. Test result shows that the amplitude of sensor output signals is deceased linearly with a propagating crack, and is decreased exponentially with increased crack numbers. From the study, the active sensing diagnostic system using PZT based smart rebar network shows a promising way to provide concrete crack damage information through the "talk" among sensors.

Analysis of the microbial communities on corroded concrete sewer pipes--a case study.

PubMed

Vincke, E; Boon, N; Verstraete, W

2001-12-01

Conventional as well as molecular techniques have been used to determine the microbial communities present on the concrete walls of sewer pipes. The genetic fingerprint of the microbiota on corroded concrete sewer pipes was obtained by means of denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. The DGGE profiles of the bacterial communities present on the concrete surface changed as observed by shifts occurring at the level of the dominance of bands from non-corroded places to the most severely corroded places. By means of statistical tools, it was possible to distinguish two different groups, corresponding to the microbial communities on corroded and non-corroded surfaces, respectively. Characterization of the microbial communities indicated that the sequences of typical bands showed the highest level of identity to sequences from the bacterial strains Thiobacillus thiooxidans, Acidithiobacillus sp., Mycobacterium sp. and different heterotrophs belonging to the alpha-, beta- and gamma-Proteobacteria, Acidobacteria and Actinobacteria. In addition, the presence of N-acyl-homoserine lactone signal molecules was shown by two bio-assays of the biofilm on the concrete under the water level and at the most severely corroded places on the concrete surface of the sewer pipe.

The Greenhouse Gas Emission from Portland Cement Concrete Pavement Construction in China.

PubMed

Ma, Feng; Sha, Aimin; Yang, Panpan; Huang, Yue

2016-06-24

This study proposes an inventory analysis method to evaluate the greenhouse gas (GHG) emissions from Portland cement concrete pavement construction, based on a case project in the west of China. The concrete pavement construction process was divided into three phases, namely raw material production, concrete manufacture and pavement onsite construction. The GHG emissions of the three phases are analyzed by a life cycle inventory method. The CO₂e is used to indicate the GHG emissions. The results show that for 1 km Portland cement concrete pavement construction, the total CO₂e is 8215.31 tons. Based on the evaluation results, the CO₂e of the raw material production phase is 7617.27 tons, accounting for 92.7% of the total GHG emissions; the CO₂e of the concrete manufacture phase is 598,033.10 kg, accounting for 7.2% of the total GHG emissions. Lastly, the CO₂e of the pavement onsite construction phase is 8396.59 kg, accounting for only 0.1% of the total GHG emissions. The main greenhouse gas is CO₂ in each phase, which accounts for more than 98% of total emissions. N₂O and CH₄ emissions are relatively insignificant.

Concreteness and relational effects on recall of adjective-noun pairs.

PubMed

Paivio, A; Khan, M; Begg, I

2000-09-01

Extending previous research on the problem, we studied the effects of concreteness and relatedness of adjective-noun pairs on free recall, cued recall, and memory integration. Two experiments varied the attributes in paired associates lists or sentences. Consistent with predictions from dual coding theory and prior results with noun-noun pairs, both experiments showed that the effects of concreteness were strong and independent of relatedness in free recall and cued recall. The generally positive effects of relatedness were absent in the case of free recall of sentences. The two attributes also had independent (additive) effects on integrative memory as measured by conditionalized free recall of pairs. Integration as measured by the increment from free to cued recall occurred consistently only when pairs were high in both concreteness and relatedness. Explanations focused on dual coding and relational-distinctiveness processing theories as well as task variables that affect integration measures.

Experimental Study on Welded Headed Studs Used In Steel Plate-Concrete Composite Structures Compared with Contactless Method of Measuring Displacement

NASA Astrophysics Data System (ADS)

Kisała, Dawid; Tekieli, Marcin

2017-10-01

Steel plate-concrete composite structures are a new innovative design concept in which a thin steel plate is attached to the reinforced concrete beam by means of welded headed studs. The comparison between experimental studies and theoretical analysis of this type of structures shows that their behaviour is dependent on the load-slip relationship of the shear connectors used to ensure sufficient bond between the concrete and steel parts of the structure. The aim of this paper is to describe an experimental study on headed studs used in steel plate-concrete composite structures. Push-out tests were carried out to investigate the behaviour of shear connectors. The test specimens were prepared according to standard push-out tests, however, instead of I-beam, a steel plate 16 mm thick was used to better reflect the conditions in the real structure. The test specimens were produced in two batches using concrete with significantly different compressive strength. The experimental study was carried out on twelve specimens. Besides the traditional measurements based on LVDT sensors, optical measurements based on the digital image correlation method (DIC) and pattern tracking methods were used. DIC is a full-field contactless optical method for measuring displacements in experimental testing, based on the correlation of the digital images taken during test execution. With respect to conventional methods, optical measurements offer a wider scope of results and can give more information about the material or construction behaviour during the test. The ultimate load capacity and load-slip curves obtained from the experiments were compared with the values calculated based on Eurocodes, American and Chinese design specifications. It was observed that the use of the relationships developed for the traditional steel-concrete composite structures is justified in the case of ultimate load capacity of shear connectors in steel plate-concrete composite structures.

Locomotion and claw disorders in Norwegian dairy cows housed in freestalls with slatted concrete, solid concrete, or solid rubber flooring in the alleys.

PubMed

Fjeldaas, T; Sogstad, A M; Osterås, O

2011-03-01

This study was part of a cross-sectional project on freestall housing, and the aim was to compare locomotion and claw disorders in freestall dairy cattle herds with slatted concrete, solid concrete, or solid rubber flooring in the alleys. The final population for studying claw disorders consisted of 66 dairy herds with 2,709 dry or lactating cows, whereas the population for studying locomotion consisted of 54 herds with 2,216 cows. All herds used Norwegian Red as the main breed. The herds were visited by 15 trained claw trimmers one time during the period from the beginning of February to summer let-out onto pasture in 2008. The trimmers assessed locomotion scores (LocS) of all cows before trimming. At trimming, claw disorders were diagnosed and recorded in the Norwegian Claw Health Card. Estimates describing locomotion and claw disorders in the hind feet were identified by use of multivariable models fit with LocS and each claw disorder as dependent variables, respectively. Herd nested within claw trimmer was included in the model as random effects. The odds ratio (OR) of having LocS >2 and LocS >3 was 1.9 and 2.1, respectively, on slatted concrete compared with solid concrete. Fewer cases of dermatitis were found on slatted than solid concrete (OR=0.70) and a tendency was observed for fewer heel horn erosions on slatted concrete than solid rubber (OR=0.47). Hemorrhages of the white line and sole were more prevalent in herds housed on slatted and solid concrete than in those housed on solid rubber (OR=2.6 and OR=2.1, respectively). White line fissures were also more prevalent in herds housed on slatted and solid concrete than in those housed on solid rubber (OR=2.1 and OR=2.0, respectively). Double soles were more prevalent on solid concrete than solid rubber (OR=4.4). However, sole ulcers were less prevalent in herds with slatted and solid concrete than solid rubber (OR=0.39 and OR=0.53, respectively). Fewer corkscrewed claws were found on slatted concrete than both solid rubber and solid concrete (OR=0.60 and OR=0.44, respectively). More white line crossing fissures were recorded on slatted and solid concrete than solid rubber (OR=3.6 and OR=3.1, respectively). This shows that solid rubber flooring was favorable when most laminitis-related lesions were considered, whereas slatted concrete was favorable for infectious claw lesions and corkscrewed claws but not for locomotion. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Best Practices Case Study: Tindall Homes - Princeton, NJ, Legends at Mansfield, Columbus, NJ

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

None

2011-09-01

Case Study of Tindall Homes, who worked with Building America to design an optimal package including advanced framing, insulated precast concrete basement walls, polyurethane foam in the walls, and R-49 of batt plus blown cellulose in the attics. Some homes included a detached garden shed with photovoltaic panel-covered roofs.

Analysis of Transparent Concrete as an Innovative Material Used in Civil Engineering

NASA Astrophysics Data System (ADS)

Zielińska, Monika; Ciesielski, Albert

2017-10-01

Since the dawn of history concrete has been, right behind stone and brick, one of the oldest building materials. The ancient Romans took advantage of its opportunities. They constructed amazing architectural objects, which survived centuries as whole buildings or parts of them. Concrete is so ubiquitous, that when we are walking in a newer districts of cities we are virtually surrounded by concrete from everywhere. Sometimes we do not realize in how many cases and various ways concrete is used in towns and cities. As we know, human curiosity and quest for newer and newer solutions and capabilities does not leave such amazing material as concrete alone. There are many varieties of concrete, depending on what people want to achieve. By changing its chemical composition, technological process and adding various other materials, we receive various types of concrete. We use them to create durable supporting structures, a variety of concrete which is resistant to constant moisture or different chemical types. Additionally, some aspects of aesthetics in architecture are made with the help of concrete.

Correlation of rates of tritium migration through porous concrete

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

Fukada, S.; Katayama, K.; Takeishi, T.

In a nuclear facility when tritium leaks from a glovebox to room accidentally, an atmosphere detritiation system (ADS) starts operating, and HTO released is recovered by ADS. ADS starts when tritium activity in air becomes higher than its controlled level. Before ADS operates, the laboratory walls are the final enclosure facing tritium and are usually made of porous concrete coated with a hydrophobic paint. In the present study, previous data on the diffusivity and adsorption coefficient of concrete and paints are reviewed. Tritium penetrates and migrates into concrete by following 3 ways. First, gaseous HT or T{sub 2} easily penetratesmore » into porous concrete. Its diffusivity is almost equal to that of H{sub 2}. When a gaseous molecule diffuses through pores with a smaller diameter than a mean free path, its migration rate is described by the Knudsen diffusion formula. The second mechanism is H{sub 2}O vapor diffusion in pores. Concrete holds a lot of structural water. Therefore, H{sub 2}O or HTO vapor can diffuse inside concrete pores along with adsorption-desorption and isotopic exchange with structural water, which is the third mechanism. Literature shows that the diffusivity of HTO through the epoxy-resin paint is determined as D(HTO)=1.0*10{sup -16} m{sup 2}/s. We have used this data to set a model and we have applied it to estimate residual tritium in laboratory walls. We have considered 2 accidental cases and a normal case: first, ADS starts operating 1 hour after 100 Ci HTO is released in the room, secondly, ADS starts 24 hours after 100 Ci HTO release and thirdly, when the walls are exposed to HTO for 10 years of normal operation. It appears that the immediate start up of ADS is indispensable for safety.« less

Influence of synthetic calcium silicates on the strength properties of fine-grained concrete

NASA Astrophysics Data System (ADS)

Yarusova, S. B.; Gordienko, P. S.; Kozin, A. V.; Zhevtun, I. G.; Perfilev, A. V.

2018-04-01

The effect of additives based on acicular calcium hydrosilicates (xonotlite and tobermorite) and wollastonite, obtained from boric acid production waste in autoclave synthesis at a temperature of 220 °C, on the strength of fine-grained concrete, has been studied in this paper. It was shown that when the calcium hydrosilicates and wollastonite are introduced, an increase in the strength characteristics of concrete is observed. After heat and moisture treatment, the maximum increase in strength is observed with the addition of 4% of mass content of calcium hydrosilicates and 6% of mass content of wollastonite. After 28 days of hardening under normal conditions, the maximum increase in strength of concrete is observed with the addition of 4% of mass content of both types of additives. It was shown that the water absorption of concrete decreases with a maximum when 4% of mass content is added, as in the case of the introduction of calcium hydrosilicates, and wollastonite. With a further increase in the number of additives, the amount of water absorption increases, but these values remain below the values for the control sample without additives.

Proposal of Environmental Impact Assessment Method for Concrete in South Korea: An Application in LCA (Life Cycle Assessment)

PubMed Central

Kim, Tae Hyoung; Tae, Sung Ho

2016-01-01

This study aims to develop a system for assessing the impact of the substances discharged from concrete production process on six environmental impact categories, i.e., global warming (GWP), acidification (AP), eutrophication (EP), abiotic depletion (ADP), ozone depletion (ODP), and photochemical oxidant creation (POCP), using the life a cycle assessment (LCA) method. To achieve this, this study proposed an LCA method specifically applicable to the Korean concrete industry by adapting the ISO standards to suit the Korean situations. The proposed LCA method involves a system that performs environmental impact assessment on the basis of input information on concrete mix design, transport distance, and energy consumption in a batch plant. The Concrete Lifecycle Assessment System (CLAS) thus developed provides user-friendly support for environmental impact assessment with specialized database for concrete mix materials and energy sources. In the case analysis using the CLAS, among the substances discharged from the production of 24 MPa concrete, those contributing to GWP, AP, EP, ADP, ODP, and POCP were assessed to amount to 309 kg-CO2 eq/m3, 28.7 kg-SO2 eq/m3, 5.21 kg-PO43− eq/m3, 0.000049 kg-CFC11 eq/m3, 34 kg/m3, and 21 kg-Ethylene eq/m3, respectively. Of these six environmental impact categories selected for the LCA in this study, ordinary Portland cement (OPC) was found to contribute most intensely to GWP and POCP, and aggregates, to AP, EP, ODP, and ADP. It was also found that the mix design with increased prop proportion of recycled aggregate was found to contribute to reducing the impact in all other categories. PMID:27827843

Proposal of Environmental Impact Assessment Method for Concrete in South Korea: An Application in LCA (Life Cycle Assessment).

PubMed

Kim, Tae Hyoung; Tae, Sung Ho

2016-11-02

This study aims to develop a system for assessing the impact of the substances discharged from concrete production process on six environmental impact categories, i.e., global warming (GWP), acidification (AP), eutrophication (EP), abiotic depletion (ADP), ozone depletion (ODP), and photochemical oxidant creation (POCP), using the life a cycle assessment (LCA) method. To achieve this, this study proposed an LCA method specifically applicable to the Korean concrete industry by adapting the ISO standards to suit the Korean situations. The proposed LCA method involves a system that performs environmental impact assessment on the basis of input information on concrete mix design, transport distance, and energy consumption in a batch plant. The Concrete Lifecycle Assessment System (CLAS) thus developed provides user-friendly support for environmental impact assessment with specialized database for concrete mix materials and energy sources. In the case analysis using the CLAS, among the substances discharged from the production of 24 MPa concrete, those contributing to GWP, AP, EP, ADP, ODP, and POCP were assessed to amount to 309 kg-CO₂ eq/m³, 28.7 kg-SO₂ eq/m³, 5.21 kg-PO₄ 3- eq/m³, 0.000049 kg-CFC 11 eq/m³, 34 kg/m³, and 21 kg-Ethylene eq/m³, respectively. Of these six environmental impact categories selected for the LCA in this study, ordinary Portland cement (OPC) was found to contribute most intensely to GWP and POCP, and aggregates, to AP, EP, ODP, and ADP. It was also found that the mix design with increased prop proportion of recycled aggregate was found to contribute to reducing the impact in all other categories.

[Conceiling the cadaver in masonry and cement].

PubMed

Madea, Burkhard; Cremer, Ulrich; Schiwy-Bochat, Karl Heinz

2003-01-01

Encasing with concrete and/or bricks are relatively rare forms of hiding or disposing of a body; criminologically, cases of this kind are often treated as "matters involving a missing person" at first. The article describes the circumstances and findings of 2 cases in which bodies were encased with concrete. Under the aspects of reconstruction it is of importance that bodies may be preserved quite well in concrete, which allows not only identification of the victim but also determination of the cause of death even after a prolonged post-mortem interval, the more so as occasionally tools used for committing the offense are also encased together with the body.

Diagnostic imaging learning resources evaluated by students and recent graduates.

PubMed

Alexander, Kate; Bélisle, Marilou; Dallaire, Sébastien; Fernandez, Nicolas; Doucet, Michèle

2013-01-01

Many learning resources can help students develop the problem-solving abilities and clinical skills required for diagnostic imaging. This study explored veterinary students' perceptions of the usefulness of a variety of learning resources. Perceived resource usefulness was measured for different levels of students and for academic versus clinical preparation. Third-year (n=139) and final (fifth) year (n=105) students and recent graduates (n=56) completed questionnaires on perceived usefulness of each resource. Resources were grouped for comparison: abstract/low complexity (e.g., notes, multimedia presentations), abstract/high complexity (e.g., Web-based and film case repositories), concrete/low complexity (e.g., large-group "clicker" workshops), and concrete/high complexity (e.g., small-group interpretation workshops). Lower-level students considered abstract/low-complexity resources more useful for academic preparation and concrete resources more useful for clinical preparation. Higher-level students/recent graduates also considered abstract/low-complexity resources more useful for academic preparation. For all levels, lecture notes were considered highly useful. Multimedia slideshows were an interactive complement to notes. The usefulness of a Web-based case repository was limited by accessibility problems and difficulty. Traditional abstract/low-complexity resources were considered useful for more levels and contexts than expected. Concrete/high-complexity resources need to better represent clinical practice to be considered more useful for clinical preparation.

Numerical Analysis of Effectiveness of Strengthening Concrete Slab in Tension of the Steel-Concrete Composite Beam Using Pretensioned CFRP Strips

NASA Astrophysics Data System (ADS)

Jankowiak, Iwona; Madaj, Arkadiusz

2017-12-01

One of the methods to increase the load carrying capacity of the reinforced concrete (RC) structure is its strengthening by using carbon fiber (CFRP) strips. There are two methods of strengthening using CFRP strips - passive method and active method. In the passive method a strip is applied to the concrete surface without initial strains, unlike in the active method a strip is initially pretensioned before its application. In the case of a steel-concrete composite beam, strips may be used to strengthen the concrete slab located in the tension zone (in the parts of beams with negative bending moments). The finite element model has been developed and validated by experimental tests to evaluate the strengthening efficiency of the composite girder with pretensioned CFRP strips applied to concrete slab in its tension zone.

Deterioration of Pracana Dam due to ASR. Main features and repair works

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

Matos, D.S.; Camelo, S.; Silva, H.S.

1995-12-31

Some of the Portuguese concrete dams show evidences of ASR. In majority the phenomena is still benign. However, in a few cases some significant deterioration of ASR type have malfunctions arose. In such cases deteriorations of ASR type have been detected while in the others the ASSR type prevail, depending on the type of aggregate. The paper reports the most important case of ASR in Portuguese concrete dams. Pracana dam is a buttress structures built in 1948-51, being the aggregates predominantly of quartzitic and metapellitic nature. Subsequently to the intense fracturing due to a quick concrete cooling during the firstmore » filling of the reservoir, high levels of expansion rates had been detected by means of monitoring system. After 8 years emptied reservoir, rehabilitation works took place in 1991-92 aiming at the concrete mass regeneration and the installation of an upstream face membrane, the improvement of spillway capacity and of the foundation performances. The behaviour of the dam as well as the performed tests (petrographic, mechanic, ultrasonic and expansibility ones) and repair works are described in the paper.« less

Novel Concrete Chemistry Achieved with Low Dose Gamma Radiation Curing and Resistance to Neutron Activation

NASA Astrophysics Data System (ADS)

Burnham, Steven Robert

As much as 50% of ageing-related problems with concrete structures can be attributed to con-struction deficiencies at the time of placement. The most influential time affecting longevity of concrete structures is the curing phase, or commonly the initial 28 days following its placement. A novel advanced atomistic analysis of novel concrete chemistry is presented in this dissertation with the objective to improve concrete structural properties and its longevity. Based on experiments and computational models, this novel concrete chemistry is discussed in two cases: (a) concrete chemistry changes when exposed to low-dose gamma radiation in its early curing stage, thus improving its strength in a shorter period of time then curing for the conventional 28 days; (b) concrete chemistry is controlled by its atomistic components to assure strength is not reduced but that its activation due to long-term exposure to neutron flux in nuclear power plants is negligible. High dose gamma radiation is well documented as a degradation mechanism that decreases concrete's compressive strength; however, the effects of low-dose gamma radiation on the initial curing phase of concrete, having never been studied before, proved its compressive strength increases. Using a 137 Cs source, concrete samples were subjected to gamma radiation during the initial curing phase for seven, 14, and 28 days. The compressive strength after seven days is improved for gamma cured concrete by 24% and after 14 days by 76%. Concrete shows no improvement in compressive strength after 28 days of exposure to gamma radiation, showing that there is a threshold effect. Scanning Electron Microscopy is used to examine the microstructure of low-dose gamma radiation where no damage to its microstructure is found, showing no difference between gamma cured and conventionally cured concrete. Molecular dynamics modeling based on the MOPAC package is used to study how gamma radiation during the curing stage improves compressive strength of concrete. The modeling shows that when radiolysis occurs in freshly mixed concrete, the reactivity between key molecules responsible for bonding between cement and aggregate is enhanced due to improved reactivity at the molecular level. A new method is developed that successfully controls a concrete chemistry at the atomistic level by assuring its long-term exposure to neutron flux in nuclear power plants will not activate the dome wall to the level of low-level radioactive waste. This methodology is established to detect and select the level of trace elemental composition in concrete based on a low-flux neutron activation analysis (NAA). By carefully selecting aggregates that do not contain certain elements that activate to high concentrations after decades of concrete exposure to neutron flux, the end of life for concrete is improved by declassifying it as low-level radioactive waste. Directly, it improves economy of commissioning nuclear power plants to be built in near future and reducing important quantities of waste to be disposed at high costs.

Evaluation of static resistance of deep foundation [project summary].

DOT National Transportation Integrated Search

2017-06-01

Various types of deep foundations were investigated including steel H-piles, pre-stressed concrete piles, open cylindrical steel and concrete piles with diameters greater than 36 inches, and drilled shafts with partial length permanent casing. : The ...

Strengthening method of concrete structure

NASA Astrophysics Data System (ADS)

Inge, Wewin; Audrey; Nugroho, Sofie; Njo, Helen

2018-03-01

Building extension in Indonesia is not favored, and not many people know the advantages of the method because architects and engineers tend to lack the knowledge and experience. The aim of this paper is to explain a method on how to strengthen a concrete building structure that people can use/learn as a better way to cut potential cost and save time. The strengthening method explained in this paper is steel jacketing, providing a case study of this method in the extension of a restaurant located in Medan, Indonesia. In this study, engineers calculated that the tensile stress of the existing RC column and beam is not strong enough to reinforce the building extension applied load. Therefore, the steel jacketing method can be applied to improve the column and beam strength and ductility. The result of the case study proves that this is one of the best methods for building extension applied in Indonesia.

A Systematic Study of Simple Combinatorial Configurations.

ERIC Educational Resources Information Center

Dubois, Jean-Guy

1984-01-01

A classification of the simple combinatorial configurations which correspond to various cases of distribution and ordering of objects into boxes is given (in French). Concrete descriptions, structured relations, translations, and formalizations are discussed. (MNS)

Embedded Distributed Optical Fiber Sensors in Reinforced Concrete Structures—A Case Study

PubMed Central

Villalba, Sergi

2018-01-01

When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading and reloading processes. With this in mind the authors have carried out an experiment where polyimide-coated DOFS were installed on two concrete beams, both embedded in the rebar elements and also bonded to the concrete surface. The specimens were subjected to a three-point load test where after cracking, they are unloaded and reloaded again to assess the capability of the sensor when applied to a real loading scenarios in concrete structures. Rayleigh Optical Frequency Domain Reflectometry (OFDR) was used as the most suitable technique for crack detection in reinforced concrete elements. To verify the reliability and accuracy of the DOFS measurements, additional strain gauges were also installed at three locations along the rebar. The results show the feasibility of using a thin coated polyimide DOFS directly bonded on the reinforcing bar without the need of indention or mechanization. A proposal for a Spectral Shift Quality (SSQ) threshold is also obtained and proposed for future works when using polyimide-coated DOFS bonded to rebars with cyanoacrylate adhesive. PMID:29587449

Embedded Distributed Optical Fiber Sensors in Reinforced Concrete Structures-A Case Study.

PubMed

Barrias, António; Casas, Joan R; Villalba, Sergi

2018-03-26

When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading and reloading processes. With this in mind the authors have carried out an experiment where polyimide-coated DOFS were installed on two concrete beams, both embedded in the rebar elements and also bonded to the concrete surface. The specimens were subjected to a three-point load test where after cracking, they are unloaded and reloaded again to assess the capability of the sensor when applied to a real loading scenarios in concrete structures. Rayleigh Optical Frequency Domain Reflectometry (OFDR) was used as the most suitable technique for crack detection in reinforced concrete elements. To verify the reliability and accuracy of the DOFS measurements, additional strain gauges were also installed at three locations along the rebar. The results show the feasibility of using a thin coated polyimide DOFS directly bonded on the reinforcing bar without the need of indention or mechanization. A proposal for a Spectral Shift Quality (SSQ) threshold is also obtained and proposed for future works when using polyimide-coated DOFS bonded to rebars with cyanoacrylate adhesive.

The Greenhouse Gas Emission from Portland Cement Concrete Pavement Construction in China

PubMed Central

Ma, Feng; Sha, Aimin; Yang, Panpan; Huang, Yue

2016-01-01

This study proposes an inventory analysis method to evaluate the greenhouse gas (GHG) emissions from Portland cement concrete pavement construction, based on a case project in the west of China. The concrete pavement construction process was divided into three phases, namely raw material production, concrete manufacture and pavement onsite construction. The GHG emissions of the three phases are analyzed by a life cycle inventory method. The CO2e is used to indicate the GHG emissions. The results show that for 1 km Portland cement concrete pavement construction, the total CO2e is 8215.31 tons. Based on the evaluation results, the CO2e of the raw material production phase is 7617.27 tons, accounting for 92.7% of the total GHG emissions; the CO2e of the concrete manufacture phase is 598,033.10 kg, accounting for 7.2% of the total GHG emissions. Lastly, the CO2e of the pavement onsite construction phase is 8396.59 kg, accounting for only 0.1% of the total GHG emissions. The main greenhouse gas is CO2 in each phase, which accounts for more than 98% of total emissions. N2O and CH4 emissions are relatively insignificant. PMID:27347987

International Intervention in Intra-State Conflicts: The Case in Sri Lanka

DTIC Science & Technology

2013-03-01

it comes to practice, this model is very simplistic. Most interveners do not follow this concrete sequence, and there is no definite criterion to...there was a significant and unavoidable concern. The second section addresses the first concrete foundation of India’s domestic setting for...was fueled primarily by domestic interests. The third section addresses the second concrete foundation laid by Sri Lankans for Indian intervention

Research notes : non-destructive evaluation of FRP-strengthened reinforced concrete.

DOT National Transportation Integrated Search

2005-04-01

Many reinforced concrete structures across the country are being strengthened with fiber reinforced polymer (FRP) composites to increase the load capacity. In many cases, composites provide the most cost effective strengthening option, and they do no...

Implementing HPC on the Sunshine Bridge project

DOT National Transportation Integrated Search

2007-11-01

This report presents the research work from a pilot program regarding the feasibility of implementing high performance concrete on Arizona bridge decks, using the Sunshine Bridge in Holbrook, Arizona as a test case. An existing concrete slab was remo...

Implementing HPC on the Sunshine Bridge Project

DOT National Transportation Integrated Search

2007-11-16

This report presents the research work from a pilot program regarding the feasibility of implementing high performance concrete on Arizona bridge decks, using the Sunshine Bridge in Holbrook, Arizona as a test case. An existing concrete slab was remo...

Dynamic Fracture of Concrete. Part 1

DTIC Science & Technology

1990-02-14

unnotched) by Mindess and the Charpy type impact tests by Shah. In both cases, dynamic finite element modeling with the adjusted constitutive equavm for the...Mindess and the Charpy type impact tests by Shah. In both cases, dynamic finite element modeling with the adjusted constitutive equations for the...Modeling Shah’s Charpy Impact Tests ................ 190 Figure 7.20 Specimen Configuration and Finite Element Model for Concrete and Mortar Beam Impact

Construal level as a moderator of the role of affective and cognitive attitudes in the prediction of health-risk behavioural intentions.

PubMed

Carrera, Pilar; Caballero, Amparo; Muñoz, Dolores; González-Iraizoz, Marta; Fernández, Itziar

2014-12-01

In two preliminary control checks it was shown that affective attitudes presented greater abstraction than cognitive attitudes. Three further studies explored how construal level moderated the role of affective and cognitive attitudes in predicting one health-promoting behaviour (exercising) and two risk behaviours (sleep debt and binge drinking). There was a stronger influence of affective attitudes both when participants were in abstract (vs. concrete) mindsets induced by a priming task in Studies 1a and 1b, and when behavioural intentions were formed for the distant (vs. near) future in Study 2. In the case of concrete mindsets, the results were inconclusive; the interaction between construal level and cognitive attitudes was only marginally significant in Study 1b. The present research supports the assertion that in abstract mindsets (vs. concrete mindsets) people use more affective attitudes to construe their behavioural intentions. Practical implications for health promotion are discussed in the framework of construal-level theory. © 2014 The British Psychological Society.

A new discrete-element approach for the assessment of the seismic resistance of composite reinforced concrete-masonry buildings

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

Calio, I.; Cannizzaro, F.; Marletta, M.

2008-07-08

In the present study a new discrete-element approach for the evaluation of the seismic resistance of composite reinforced concrete-masonry structures is presented. In the proposed model, unreinforced masonry panels are modelled by means of two-dimensional discrete-elements, conceived by the authors for modelling masonry structures, whereas the reinforced concrete elements are modelled by lumped plasticity elements interacting with the masonry panels through nonlinear interface elements. The proposed procedure was adopted for the assessment of the seismic response of a case study confined-masonry building which was conceived to be a typical representative of a wide class of residential buildings designed to themore » requirements of the 1909 issue of the Italian seismic code and widely adopted in the aftermath of the 1908 earthquake for the reconstruction of the cities of Messina and Reggio Calabria.« less

A new discrete-element approach for the assessment of the seismic resistance of composite reinforced concrete-masonry buildings

NASA Astrophysics Data System (ADS)

Caliò, I.; Cannizzaro, F.; D'Amore, E.; Marletta, M.; Pantò, B.

2008-07-01

In the present study a new discrete-element approach for the evaluation of the seismic resistance of composite reinforced concrete-masonry structures is presented. In the proposed model, unreinforced masonry panels are modelled by means of two-dimensional discrete-elements, conceived by the authors for modelling masonry structures, whereas the reinforced concrete elements are modelled by lumped plasticity elements interacting with the masonry panels through nonlinear interface elements. The proposed procedure was adopted for the assessment of the seismic response of a case study confined-masonry building which was conceived to be a typical representative of a wide class of residential buildings designed to the requirements of the 1909 issue of the Italian seismic code and widely adopted in the aftermath of the 1908 earthquake for the reconstruction of the cities of Messina and Reggio Calabria.

Bibliography on Cold Regions Science and Technology Volume 53, Part 2

DTIC Science & Technology

1999-12-01

A.T. Claud, C. 53-1504 Interaction of ice floes with ships on offshore structures Case study of antarctic mesolow [1995, eng] 53-329 Coffey, M.T. [1992...in a dry-snow Dethloff, K Biogeochemistry of antarctic sea ice: a case study on avalanche [1998, eng] 53-2018 Climate variability in a nonlinear...concrete with respect to Effect of the Endicott Causeway on the population of Ferguson, M.E. frost resistance: a case study [1998, eng] 53-952 broad

Assessment of Reinforced Concrete Surface Breaking Crack Using Rayleigh Wave Measurement.

PubMed

Lee, Foo Wei; Chai, Hwa Kian; Lim, Kok Sing

2016-03-05

An improved single sided Rayleigh wave (R-wave) measurement was suggested to characterize surface breaking crack in steel reinforced concrete structures. Numerical simulations were performed to clarify the behavior of R-waves interacting with surface breaking crack with different depths and degrees of inclinations. Through analysis of simulation results, correlations between R-wave parameters of interest and crack characteristics (depth and degree of inclination) were obtained, which were then validated by experimental measurement of concrete specimens instigated with vertical and inclined artificial cracks of different depths. Wave parameters including velocity and amplitude attenuation for each case were studied. The correlations allowed us to estimate the depth and inclination of cracks measured experimentally with acceptable discrepancies, particularly for cracks which are relatively shallow and when the crack depth is smaller than the wavelength.

Repair, Evaluation, Maintenance, and Rehabilitation Research Program: Case Histories of Corps Breakwater and Jetty Structures. Report 5. North Atlantic Division

DTIC Science & Technology

1988-11-01

TERMS (Continue on reverse if necessary and identify by block number) FIELD GROUP SUB-GROUP Breakwater REMR (Repair, Evaluation, Concrete armor units...Maintenance, and Rehabilitation) Jetty Rubble-mound structures 19. ABSTRACT (Continue on reverse if necessary and identify by block number) :-This...have been repaired since construction. Other construction materials that have been used include steel, dolosse, concrete cap, concrete block , and

The Influence of Visual Word Form in Reading: Single Case Study of an Arabic Patient with Deep Dyslexia

ERIC Educational Resources Information Center

Boumaraf, Assia; Macoir, Joël

2016-01-01

Deep dyslexia is a written language disorder characterized by poor reading of non-words, and advantage for concrete over abstract words with production of semantic, visual and morphological errors. In this single case study of an Arabic patient with input deep dyslexia, we investigated the impact of graphic features of Arabic on manifestations of…

Infrared spectroscopy of the mineralogy of coprolites from Brean Down: evidence of past human activities and animal husbandry

NASA Astrophysics Data System (ADS)

Allen, Samantha D. M.; Almond, Matthew J.; Bell, Martin G.; Hollins, Peter; Marks, Sonja; Mortimore, Joanne L.

2002-03-01

The mineralogy of 11 concretions from the Bronze Age settlement horizons at Brean Down near Weston-super-Mare, Somerset, UK, has been examined by infrared spectroscopy. The concretions are found to contain calcite and apatite and, in some cases, quartz. Four further concretions from the later Iron Age Meare Village, soil samples from Brean Down and mineralised samples of known faecal origin from a cesspit within the Tudor Merchant's house in Tenby have been similarly examined. It is found that all samples contain calcite, but only the concretions and the Tenby cesspit samples contain apatite. None of the soil samples contain apatite, although these are relatively high in quartz. This suggests that the concretions are coprolites and that the apatite has a biological origin in small bone fragments. The infrared study is backed up by scanning electron microscopy which confirms the presence of phosphorus in the coprolite samples and shows a morphology suggestive of the presence of bone fragments; it is likely, therefore, that the coprolites result from a carnivore—most probably from dogs. The findings show the usefulness of infrared spectroscopy for the rapid identification of mineralised coprolitic material from archaeological sites.

Environmental evaluation of green concretes versus conventional concrete by means of LCA.

PubMed

Turk, Janez; Cotič, Zvonko; Mladenovič, Ana; Šajna, Aljoša

2015-11-01

A number of green concrete mixes having similar basic properties were evaluated from the environmental point of view by means of the Life Cycle Assessment method, and compared with a corresponding conventional concrete mix. The investigated green concrete mixes were prepared from three different types of industrial by-products, i.e. (1) foundry sand, and (2) steel slag, both of which were used as manufactured aggregates, and (3) fly ash, which was used as a mineral admixture. Some green concrete mixes were also prepared from a recycled aggregate, which was obtained from reinforced concrete waste. In some of the green concrete mixes the recycled aggregate was used in combination with the above-mentioned types of manufactured aggregate and fly ash. All of these materials are able, to some extent, to replace natural aggregate or Portland cement in concrete mixes, thus providing an environmental benefit from the point of view of the saving of natural resources. Taking into account consequential modelling, the credit related to the avoidance of the need to dispose of the waste materials is considered as a benefit. In case of the recycling of waste concrete into aggregate, credit is attributed to the recovery of scrap iron from the steel reinforcement. In the case of the use of steel slag, credit is attributed to the recovery of metals, which are extracted from the slag before being used as an alternative material. The disadvantage of using alternative materials and recycled aggregates can sometimes be their relatively long delivery distance. For this reason, a transport sensitivity analysis was carried out. The results indicate that the use of the discussed alternative and recycled materials is beneficial in the concrete production industry. Preference is given to the fly ash and foundry sand scenarios, and especially to those scenarios which are based on the combined use of recycled aggregate with these two alternative materials. It was found that longer delivery distances of the alternative materials do not necessarily affect the results significantly. However, variable delivery distances may have a greater effect when choosing between different alternative scenarios. Copyright © 2015 Elsevier Ltd. All rights reserved.

The (lack of) effect of dynamic visual noise on the concreteness effect in short-term memory.

PubMed

Castellà, Judit; Campoy, Guillermo

2018-05-17

It has been suggested that the concreteness effect in short-term memory (STM) is a consequence of concrete words having more distinctive and richer semantic representations. The generation and storage of visual codes in STM could also play a crucial role on the effect because concrete words are more imaginable than abstract words. If this were the case, the introduction of a visual interference task would be expected to disrupt recall of concrete words. A Dynamic Visual Noise (DVN) display, which has been proven to eliminate the concreteness effect on long-term memory (LTM), was presented along encoding of concrete and abstract words in a STM serial recall task. Results showed a main effect of word type, with more item errors in abstract words, a main effect of DVN, which impaired global performance due to more order errors, but no interaction, suggesting that DVN did not have any impact on the concreteness effect. These findings are discussed in terms of LTM participation through redintegration processes and in terms of the language-based models of verbal STM.

Technological parameters influence on the non-autoclaved foam concrete characteristics

NASA Astrophysics Data System (ADS)

Bartenjeva, Ekaterina; Mashkin, Nikolay

2017-01-01

Foam concretes are used as effective heat-insulating materials. The porous structure of foam concrete provides good insulating and strength properties that make them possible to be used as heat-insulating structural materials. Optimal structure of non-autoclaved foam concrete depends on both technological factors and properties of technical foam. In this connection, the possibility to manufacture heat-insulation structural foam concrete on a high-speed cavity plant with the usage of protein and synthetic foamers was estimated. This experiment was carried out using mathematical planning method, and in this case mathematical models were developed that demonstrated the dependence of operating performance of foam concrete on foaming and rotation speed of laboratory plant. The following material properties were selected for the investigation: average density, compressive strength, bending strength and thermal conductivity. The influence of laboratory equipment technological parameters on technical foam strength and foam stability coefficient in the cement paste was investigated, physical and mechanical properties of non-autoclaved foam concrete were defined based on investigated foam. As a result of investigation, foam concrete samples were developed with performance parameters ensuring their use in production. The mathematical data gathered demonstrated the dependence of foam concrete performance on the technological regime.

Leukemia in childhood and adolescence and exposure to ionizing radiation in homes built from uranium-containing alum shale concrete.

PubMed

Axelson, Olav; Fredrikson, Mats; Akerblom, Gustav; Hardell, Lennart

2002-03-01

Concerns in Sweden about indoor radon around 1980 prompted measurements of gamma-radiation from the facades of houses to identify those constructed of uranium-containing alum shale concrete, with potentially high radon concentrations. To evaluate any possible risk of acute lymphocytic leukemia from exposure to elevated gamma-radiation in these homes, we identified the acute lymphocytic leukemia cases less than 20 years of age in Sweden during 1980-1989 as well as eight controls per case from the population registry, matching on age, gender, and county. Using the existing measurements, exposure was assessable for 312 cases and 1,418 controls from 151 properly measured municipalities. A conditional logistic odds ratio of 1.4 (95% confidence interval = 1.0-1.9) was obtained for those ever having lived in alum shale concrete houses, with the average exposure exceeding 0.10 microsieverts per hour. Comparing those who ever lived in alum shale concrete houses (divided by higher and lower annual average exposure) with those who never lived in such houses, we found a weak dose-response relation. The results suggest some risk of acute lymphocytic leukemia from indoor ionizing radiation among children and young adults.

On metaheuristic "failure modes": a case study in Tabu search for job-shop scheduling.

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

Watson, Jean-Paul

2005-06-01

In this paper, we analyze the relationship between pool maintenance schemes, long-term memory mechanisms, and search space structure, with the goal of placing metaheuristic design on a more concrete foundation.

Embracing complexity: theory, cases and the future of bioethics.

PubMed

Wilson, James

2014-01-01

This paper reflects on the relationship between theory and practice in bioethics, by using various concepts drawn from debates on innovation in healthcare research--in particular debates around how best to connect up blue skies 'basic' research with practical innovations that can improve human lives. It argues that it is a mistake to assume that the most difficult and important questions in bioethics are the most abstract ones, and also a mistake to assume that getting clear about abstract cases will automatically be of much help in getting clear about more complex cases. It replaces this implicitly linear model with a more complex one that draws on the idea of translational research in healthcare. On the translational model, there is a continuum of cases from the most simple and abstract (thought experiments) to the most concrete and complex (real world cases). Insights need to travel in both directions along this continuum--from the more abstract to the more concrete and from the more concrete to the more abstract. The paper maps out some difficulties in moving from simpler to more complex cases, and in doing so makes recommendations about the future of bioethics.

Stress Wave Scattering: Friend or Enemy of Non Destructive Testing of Concrete?

NASA Astrophysics Data System (ADS)

Aggelis, Dimitrios G.; Shiotani, Tomoki; Philippidis, Theodore P.; Polyzos, Demosthenes

Cementitious materials are by definition inhomogeneous containing cement paste, sand, aggregates as well as air voids. Wave propagation in such a material is characterized by scattering phenomena. Damage in the form of micro or macro cracks certainly enhances scattering influence. Its most obvious manifestation is the velocity variation with frequency and excessive attenuation. The influence becomes stronger with increased mis-match of elastic properties of constituent materials and higher crack content. Therefore, in many cases of large concrete structures, field application of stress waves is hindered since attenuation makes the acquisition of reliable signals troublesome. However, measured wave parameters, combined with investigation with scattering theory can reveal much about the internal condition and supply information that cannot be obtained in any other way. The size and properties of the scatterers leave their signature on the dispersion and attenuation curves making thus the characterization more accurate in case of damage assessment, repair evaluation as well as composition inspection. In this paper, three indicative cases of scattering influence are presented. Namely, the interaction of actual distributed damage, as well as the repair material injected in an old concrete structure with the wave parameters. Other cases are the influence of light plastic inclusions in hardened mortar and the influence of sand and water content in the examination of fresh concrete. In all the above cases, scattering seems to complicate the propagation behavior but also offers the way for a more accurate characterization of the quality of the material.

Concrete Model Descriptions and Summary of Benchmark Studies for Blast Effects Simulations

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

Noble, C; Kokko, E; Darnell, I

2005-07-21

Concrete is perhaps one of the most widely used construction materials in the world. Engineers use it to build massive concrete dams, concrete waterways, highways, bridges, and even nuclear reactors. The advantages of using concrete is that it can be cast into any desired shape, it is durable, and very economical compared to structural steel. The disadvantages are its low tensile strength, low ductility, and low strength-to-weight ratio. Concrete is a composite material that consists of a coarse granular material, or aggregate, embedded in a hard matrix of material, or cement, which fills the gaps between the aggregates and bindsmore » them together. Concrete properties, however, vary widely. The properties depend on the choice of materials used and the proportions for a particular application, as well as differences in fabrication techniques. Table 1 provides a listing of typical engineering properties for structural concrete. Properties also depend on the level of concrete confinement, or hydrostatic pressure, the material is being subjected to. In general, concrete is rarely subjected to a single axial stress. The material may experience a combination of stresses all acting simultaneously. The behavior of concrete under these combined stresses are, however, extremely difficult to characterize. In addition to the type of loading, one must also consider the stress history of the material. Failure is determined not only by the ultimate stresses, but also by the rate of loading and the order in which these stresses were applied. The concrete model described herein accounts for this complex behavior of concrete. It was developed by Javier Malvar, Jim Wesevich, and John Crawford of Karagozian and Case, and Don Simon of Logicon RDA in support of the Defense Threat Reduction Agency's programs. The model is an enhanced version of the Concrete/Geological Material Model 16 in the Lagrangian finite element code DYNA3D. The modifications that were made to the original model ensured that the material response followed experimental observations for standard uniaxial, biaxial, and triaxial tests for both tension and compression type loading. A disadvantage of using this material model, however, is the overwhelming amount of input that is required from the user. Therefore, the goal of this report is to provide future users with the tools necessary for successfully using this model.« less

Magnetic anisotropy of Silurian organic-rich shale rocks and calcareous concretions from Northern Poland

NASA Astrophysics Data System (ADS)

Niezabitowska, Dominika; Szaniawski, Rafał

2017-04-01

The research has been performed on Wenlockian shales of Pelplin formation from the Pomerania region located in Northern Poland. These organic-rich marine shales were deposited on the western shelf of the Baltica paleo-continent and currently they constitute the cover of East European Platform. The studied shales lie almost completely flat without signs of tectonic deformations. Rock magnetic studies were carried out with the aim of recognizing ferro- and paramagnetic minerals in shales and thus fully understanding the origin of the magnetic anisotropy. The typical dark shales and spherical calcareous concretions from two boreholes were sampled. Based on deflection of shales beds bordered with a concretions, we deduce that such concretions were formed in the early stage of diagenesis, before the final compaction and lithification of surrounding shales. We obtained similar rockmagnetic results for both of rock types. The results of thermal variation of magnetic susceptibility and hysteresis loops show that the magnetic susceptibility is mainly controlled by paramagnetic minerals, due to domination of phyllosilicate minerals, with a smaller impact of ferromagnetic phase. The results of the hysteresis studies documented the domination of low coercivity ferromagnetic minerals, that is magnetite and pyrrhotite. The deposition alignment of flocculated phyllosilicates and further compaction determine distinct bedding parallel foliation of the AMS (Anisotropy of Magnetic Susceptibility) in the both drill cores. In one of the drill core the maximal AMS axes are almost randomly distributed in the bedding plane and show only a weak tendency for grouping. In the second drill core the magnetic lineation is better defined. In the case of concretions the bedding parallel magnetic foliation is also evident but it is much weaker than in shales. In turn, the magnetic lineation in the both drill cores is well developed and the maximal AMS axes are well grouped. In both of the cores the orientation of lineation from concretions complies with site mean lineation from shale rocks. To summarize, the results imply that the phyllosilicate minerals from shales are typically well aligned in the bedding plane by compaction processes. In the case of calcareous concretions the foliation is less developed due to their earlier cementation of flocculated phyllosicates in the calcareous matrix, which occurred before the end of sediments compaction. A good grouping of the maximal AMS axes within the early cemented concretions suggest that the magnetic lineation is rather sedimentary than tectonic in origin. We suggest that the magnetic lineation is probably related to the orientation of flocculated phyllosilicates due to transportation. This work has been funded by the Polish National Centre for Research and Development within the Blue Gas project (No BG2/SHALEMECH/14). Samples were provided by the PGNiG SA.

Effects of Interlocking and Supporting Conditions on Concrete Block Pavements

NASA Astrophysics Data System (ADS)

Mahapatra, Geetimukta; Kalita, Kuldeep

2018-02-01

Concrete Block Paving (CBP) is widely used as wearing course in flexible pavements, preferably under light and medium vehicular loadings. Construction of CBP at site is quick and easy in quality control. Usually, flexible pavement design philosophy is followed in CBP construction, though it is structurally different in terms of small block elements with high strength concrete and their interlocking aspects, frequent joints and discontinuity, restrained edge etc. Analytical solution for such group action of concrete blocks under loading in a three dimensional multilayer structure is complex and thus, the need of conducting experimental studies is necessitated for extensive understanding of the load—deformation characteristics and behavior of concrete blocks in pavement. The present paper focuses on the experimental studies for load transfer characteristics of CBP under different interlocking and supporting conditions. It is observed that both interlocking and supporting conditions affect significantly on the load transfer behavior in CBP structures. Coro-lock block exhibits better performance in terms of load carrying capacity and distortion behavior under static loads. Plate load tests are performed over subgrade, granular sub-base (GSB), CBP with and without GSB using different block shapes. For an example case, the comparison of CBP with conventional flexible pavement section is also presented and it is found that CBP provides considerable benefit in terms of construction cost of the road structure.

What happens with cow behavior when replacing concrete slatted floor by rubber coating: a case study.

PubMed

Platz, S; Ahrens, F; Bendel, J; Meyer, H H D; Erhard, M H

2008-03-01

An enhanced productive life cycle and improved animal welfare are aims pursued in dairy husbandry. This study assesses experimental observations on floor-associated behavior during the stepwise replacement of concrete slatted flooring by rubber mats. For this purpose, estrus (mounting) and hygiene behavior (licking while standing on 3 legs and caudal licking) within a herd of 50 loose-housed Brown Swiss dairy cows were analyzed by video observation before and after floor reconstruction. Still photographs and pedometers were used to asses step length and number of steps, representing walking behavior. Compared with the concrete floor surface, rubber coating led to an increase in step length (58 +/- 1 vs. 70 +/- 1 cm; n = 35) and in steps per day (4,226 +/- 450 vs. 5,611 +/- 495; mean +/- SEM; n = 9). Mounting was higher on the flooring covered with rubber mats (23 vs. 112). Collapsing or slipping during mounting only occurred on concrete slatted flooring (in 19 out of 23 mounting actions). Licking while standing on 3 legs and caudal licking increased up to 4-fold (105 vs. 511 observations). In conclusion, improvements were found in behavior when rubber-coated slatted floor surfaces were used in dairy cattle housing in transition from concrete flooring. Disorders in estrus and hygiene behavior were associated with the flooring of the barn and were relatively easy to investigate within the framework of farm welfare assessments.

Stiffness of reinforced concrete walls resisting in-place shear -- Tier 2: Aging and durability of concrete used in nuclear power plants. Final report

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

Monteiro, P.J.M.; Moehle, J.P.

1995-12-01

Reinforced concrete walls are commonly used in power-plant construction to resist earthquake effects. Determination of wall stiffness is of particular importance for establishing design forces on attached equipment. Available experimental data indicate differences between the measured and calculated stiffness of walls in cases where concrete mechanical properties are well defined. Additional data indicate that in-situ concrete mechanical properties may differ significantly from those specified in design. The work summarized in this report was undertaken to investigate the mechanical properties of concrete considering aging and deterioration. Existing data on mechanical properties of concrete are evaluated, and new tests are carried outmore » on concrete cylinders batched for nuclear power plants and stored under controlled conditions for up to twenty years. It is concluded that concretes batched for nuclear power plants commonly have 28-day strength that exceeds the design value by at least 1000 psi. Under curing conditions representative of those in the interior of thick concrete elements, strength gain with time can be estimated conservatively using the expression proposed by ACI Committee 209, with strengths at 25 years being approximately 1.3 times the 28-day strength. Young`s modulus can be estimated using the expression given by ACI Committee 318. Variabilities in mechanical properties are identified. A review of concrete durability identified the main causes and results of concrete deterioration that are relevant for the class of concretes and structures commonly used in nuclear power plants. Prospects for identifying the occurrence and predicting the extent of deterioration are discussed.« less

New Whole-House Case Study: William Ryan Homes, Tampa, Florida

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

none,

The builder worked with Consortium for Advanced Residential Buildings to design HERS-65 homes with energy-efficient heat pumps and programmable thermostats with humidity controls, foam-filled concrete block walls, draining house wrap, and airsealed kneewalls.

New Whole-House Solutions Case Study: Tindall Homes, Columbus, New Jersey

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

none,

The builder worked with IBACOS to build 20 HERS-58 homes with R-49 mixed attic insulation, poly-iso foam in advanced framed walls, precast concrete basement walls with rigid foam, tight airsealing, and HRV

Effects of Ambient Temperature and Relative Humidity on Subsurface Defect Detection in Concrete Structures by Active Thermal Imaging.

PubMed

Tran, Quang Huy; Han, Dongyeob; Kang, Choonghyun; Haldar, Achintya; Huh, Jungwon

2017-07-26

Active thermal imaging is an effective nondestructive technique in the structural health monitoring field, especially for concrete structures not exposed directly to the sun. However, the impact of meteorological factors on the testing results is considerable and should be studied in detail. In this study, the impulse thermography technique with halogen lamps heat sources is used to detect defects in concrete structural components that are not exposed directly to sunlight and not significantly affected by the wind, such as interior bridge box-girders and buildings. To consider the effect of environment, ambient temperature and relative humidity, these factors are investigated in twelve cases of testing on a concrete slab in the laboratory, to minimize the influence of wind. The results showed that the absolute contrast between the defective and sound areas becomes more apparent with an increase of ambient temperature, and it increases at a faster rate with large and shallow delaminations than small and deep delaminations. In addition, the absolute contrast of delamination near the surface might be greater under a highly humid atmosphere. This study indicated that the results obtained from the active thermography technique will be more apparent if the inspection is conducted on a day with high ambient temperature and humidity.

Policy Coherence towards East Asia: Development Challenges for OECD Countries. OECD Development Centre Policy Brief No. 26

ERIC Educational Resources Information Center

Fukasaku, K.; Kawai, M.; Plummer, M. G.; Trzeciak-Duval, A.

2005-01-01

Coherence issues drawn from specific country and regional cases can provide the most concrete information on the development implications of OECD-country policies. A first regional case study focused on East Asia, with financial support from the Policy Research Institute of the Japanese Ministry of Finance. The links between the region's…

Exploring Childhood Memories with Adult Survivors of Sexual Abuse: Concrete Reconstruction and Visualization Techniques.

ERIC Educational Resources Information Center

Roland, Catherine B.

1993-01-01

Describes two memory-enhancing techniques, visualization and concrete reconstruction, that have been successful in counseling adult survivors of sexual abuse. Includes suggested implementations, case examples, and implications for incorporating memory techniques into counseling process. Describes various risk factors involved in using these…

Secondary missile injury from lightning strike.

PubMed

Blumenthal, Ryan

2012-03-01

A 48-year-old-woman was struck dead by lightning on October 24, 2010, in Pretoria, South Africa. The cause of death was due to direct lightning strike. Examination showed secondary missile injury on her legs. This secondary missile (shrapnel) injury was caused by the lightning striking the concrete pavement next to her. Small pieces of concrete were located embedded within the shrapnel wounds. This case report represents the first documented case of secondary missile formation (shrapnel injury) due to lightning strike in the literature.

Experimental and Numerical Study on Tensile Strength of Concrete under Different Strain Rates

PubMed Central

Min, Fanlu; Yao, Zhanhu; Jiang, Teng

2014-01-01

The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10−7 s−1 to 10−4 s−1 in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates. PMID:24883355

Principles and Applications of Ultrasonic-Based Nondestructive Methods for Self-Healing in Cementitious Materials

PubMed Central

Ahn, Eunjong; Kim, Hyunjun; Sim, Sung-Han; Shin, Sung Woo; Shin, Myoungsu

2017-01-01

Recently, self-healing technologies have emerged as a promising approach to extend the service life of social infrastructure in the field of concrete construction. However, current evaluations of the self-healing technologies developed for cementitious materials are mostly limited to lab-scale experiments to inspect changes in surface crack width (by optical microscopy) and permeability. Furthermore, there is a universal lack of unified test methods to assess the effectiveness of self-healing technologies. Particularly, with respect to the self-healing of concrete applied in actual construction, nondestructive test methods are required to avoid interrupting the use of the structures under evaluation. This paper presents a review of all existing research on the principles of ultrasonic test methods and case studies pertaining to self-healing concrete. The main objective of the study is to examine the applicability and limitation of various ultrasonic test methods in assessing the self-healing performance. Finally, future directions on the development of reliable assessment methods for self-healing cementitious materials are suggested. PMID:28772640

Simulation Model for Scenario Optimization of the Ready-Mix Concrete Delivery Problem

NASA Astrophysics Data System (ADS)

Galić, Mario; Kraus, Ivan

2016-12-01

This paper introduces a discrete simulation model for solving routing and network material flow problems in construction projects. Before the description of the model a detailed literature review is provided. The model is verified using a case study of solving the ready-mix concrete network flow and routing problem in metropolitan area in Croatia. Within this study real-time input parameters were taken into account. Simulation model is structured in Enterprise Dynamics simulation software and Microsoft Excel linked with Google Maps. The model is dynamic, easily managed and adjustable, but also provides good estimation for minimization of costs and realization time in solving discrete routing and material network flow problems.

Studies of detailed biofilm characterization on fly ash concrete in comparison with normal and superplasticizer concrete in seawater environments.

PubMed

Vishwakarmaa, Vinita; George, R P; Ramachandran, D; Anandkumar, B; Mudalib, U Kamachi

2014-01-01

In cooling water systems, many concrete structures in the form of tanks, pillars and reservoirs that come in contact with aggressive seawater are being deteriorated by chemical and biological factors. The nuclear industry has decided to partially replace the Portland cement with appropriate pozzolans such as fly ash, which could densify the matrix and make the concrete impermeable. Three types of concrete mixes, viz., normal concrete (NC), concrete with fly ash and superplasticizer (FA) and concrete with only superplasticizer (SP) were fabricated for short- and long-term exposure studies and for screening out the better concrete in seawater environments. Biofilm characterization studies and microscopic studies showed excellent performance of FA concrete compared to the other two. Laboratory exposure studies in pure cultures of Thiobacillus thiooxidans and Fusarium oxysporum were demonstrated for the inhibition of microbial growth on fly ash. Epifluorescence and scanning electron microscopic studies supported the better performance of the FA specimen. Thus, the present study clearly showed that FA concrete is less prone to biofilm formation and biodeterioration.

Interactions between Obsessional Symptoms and Interpersonal Ambivalences in Psychodynamic Therapy: An Empirical Case Study

PubMed Central

Cornelis, Shana; Desmet, Mattias; Van Nieuwenhove, Kimberly L. H. D.; Meganck, Reitske; Willemsen, Jochem; Inslegers, Ruth; Feyaerts, Jasper

2017-01-01

The classical symptom specificity hypothesis (Blatt, 1974) particularly associates obsessional symptoms to interpersonal behavior directed at autonomy and separation from others. Cross-sectional group research, however, has yielded inconsistent findings on this predicted association, and a previous empirical case study (Cornelis et al., in press; see Chapter 2) documented obsessional pathology to be rooted in profound ambivalences between autonomous and dependent interpersonal dynamics. Therefore, in the present empirical case study, concrete operationalizations of the classical symptom specificity hypothesis are contrasted to alternative hypotheses based on the observed complexities in Chapter 2. Dynamic associations between obsessional symptoms and interpersonal functioning is further explored, aiming at further contribution to theory building (i.e., through suggestions for potential hypothesis-refinement; Stiles, 2009). Similar to the first empirical case study (Chapter 1), Consensual Qualitative Research for Case studies is used to quantitatively and qualitatively describe the longitudinal, clinical interplay between obsessional symptoms and interpersonal dynamics throughout the process of supportive-expressive psychodynamic therapy. In line with findings from Chapter 1, findings reveal close associations between obsessions and interpersonal dynamics, and therapist interventions focusing on interpersonal conflicts are documented as related to interpersonal and symptomatic alterations. Observations predominantly accord to the ambivalence-hypothesis rather than to the classical symptom specificity hypothesis. Yet, meaningful differences are observed in concrete manifestations of interpersonal ambivalences within significant relationships. Findings are again discussed in light of conceptual and methodological considerations; and limitations and future research indications are addressed. PMID:28649214

Nonlinear earthquake analysis of reinforced concrete frames with fiber and Bernoulli-Euler beam-column element.

PubMed

Karaton, Muhammet

2014-01-01

A beam-column element based on the Euler-Bernoulli beam theory is researched for nonlinear dynamic analysis of reinforced concrete (RC) structural element. Stiffness matrix of this element is obtained by using rigidity method. A solution technique that included nonlinear dynamic substructure procedure is developed for dynamic analyses of RC frames. A predicted-corrected form of the Bossak-α method is applied for dynamic integration scheme. A comparison of experimental data of a RC column element with numerical results, obtained from proposed solution technique, is studied for verification the numerical solutions. Furthermore, nonlinear cyclic analysis results of a portal reinforced concrete frame are achieved for comparing the proposed solution technique with Fibre element, based on flexibility method. However, seismic damage analyses of an 8-story RC frame structure with soft-story are investigated for cases of lumped/distributed mass and load. Damage region, propagation, and intensities according to both approaches are researched.

Shaft sealing issue in CO2 storage sites

NASA Astrophysics Data System (ADS)

Dieudonné, A.-C.; Charlier, R.; Collin, F.

2012-04-01

Carbon capture and storage is an innovating approach to tackle climate changes through the reduction of greenhouse gas emissions. Deep saline aquifers, depleted oil and gas reservoirs and unmineable coal seams are among the most studied reservoirs. However other types of reservoir, such as abandonned coal mines, could also be used for the storage of carbon dioxide. In this case, the problem of shaft sealing appears to be particularly critical regarding to the economic, ecologic and health aspects of geological storage. The purpose of the work is to study shaft sealing in the framework of CO2 storage projects in abandoned coal mines. The problem of gas transfers around a sealing system is studied numerically using the finite elements code LAGAMINE, which has been developped for 30 years at the University of Liege. A coupled hydro-mechanical model of unsaturated geomaterials is used for the analyses. The response of the two-phase flow model is first studied through a simple synthetic problem consisting in the injection of gas in a concrete-made column. It stands out of this first modeling that the advection of the gas phase represents the main transfer mechanism of CO2 in highly unsaturated materials. Furthermore the setting of a bentonite barrier seal limits considerably the gas influx into the biosphere. A 2D axisymetric hydromechanical modeling of the Anderlues natural gas storage site is then performed. The geological and hydrogeological contexts of the site are used to define the problem, for the initial and boundary conditions, as well as the material properties. In order to reproduce stress and water saturation states in the shale before CO2 injection in the mine, different phases corresponding to the shaft sinking, the mining and the set up of the sealing system are simulated. The system efficiency is then evaluated by simulating the CO2 injection with the imposed pressure at the shaft wall. According to the modeling, the low water saturation of concrete and its higher intrinsic permeability give the concrete a higher gas permeability than the one of the rock. Thus, the major part of CO2 fluxes flows through concrete elements. Moreover, the hydraulic seal of bentonite doesn't contribute to the reduction of CO2 fluxes to the atmosphere since it is in contact with the concrete shaft support. Indeed, in the present case, CO2 fluxes bypass the seal, going through the more permeable concrete. Consequently, the design of the shaft sealing system contributes significantly to a loss in performance and appears to be a significant parameter to evaluate the risks of CO2 leakage.

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.

78 FR 25958 - Takes of Marine Mammals Incidental to Specified Activities; Demolition and Construction...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-03

..., air compressor, electric screw guns, jackhammer, concrete saw, and chop saws) to be utilized on the... would be from a 980 Case backhoe, dump truck, air compressor, electric screw guns, jackhammer, concrete... behavioral effects related to project acoustic impacts, in the event of California sea lion and northern...

Some Guides to Discovery About Elm Trees, Owls, Cockroaches, Earthworms, Cement and Concrete.

ERIC Educational Resources Information Center

Busch, Phyllis S.

The introduction emphasizes the need for environmental and conservation education, and advocates an inquiry approach. Outdoor resources available to every school are listed. Detailed suggestions are made for investigating cement and concrete, cockroaches, earthworms, elm trees, and owls. In each case general background information and a list of…

The Usability of Rock-Like Materials for Numerical Studies on Rocks

NASA Astrophysics Data System (ADS)

Zengin, Enes; Abiddin Erguler, Zeynal

2017-04-01

The approaches of synthetic rock material and mass are widely used by many researchers for understanding the failure behavior of different rocks. In order to model the failure behavior of rock material, researchers take advantageous of different techniques and software. But, the majority of all these instruments are based on distinct element method (DEM). For modeling the failure behavior of rocks, and so to create a fundamental synthetic rock material model, it is required to perform related laboratory experiments for providing strength parameters. In modelling studies, model calibration processes are performed by using parameters of intact rocks such as porosity, grain size, modulus of elasticity and Poisson ratio. In some cases, it can be difficult or even impossible to acquire representative rock samples for laboratory experiments from heavily jointed rock masses and vuggy rocks. Considering this limitation, in this study, it was aimed to investigate the applicability of rock-like material (e.g. concrete) to understand and model the failure behavior of rock materials having complex inherent structures. For this purpose, concrete samples having a mixture of %65 cement dust and %35 water were utilized. Accordingly, intact concrete samples representing rocks were prepared in laboratory conditions and their physical properties such as porosity, pore size and density etc. were determined. In addition, to acquire the mechanical parameters of concrete samples, uniaxial compressive strength (UCS) tests were also performed by simultaneously measuring strain during testing. The measured physical and mechanical properties of these extracted concrete samples were used to create synthetic material and then uniaxial compressive tests were modeled and performed by using two dimensional discontinuum program known as Particle Flow Code (PFC2D). After modeling studies in PFC2D, approximately similar failure mechanism and testing results were achieved from both experimental and artificial simulations. The results obtained from these laboratory tests and modelling studies were compared with the other researcher's studies in respect to failure mechanism of different type of rocks. It can be concluded that there is similar failure mechanism between concrete and rock materials. Therefore, the results obtained from concrete samples that would be prepared at different porosity and pore sizes can be used in future studies in selection micro-mechanical and physical properties to constitute synthetic rock materials for understanding failure mechanism of rocks having complex inherent structures such as vuggy rocks or heavily jointed rock masses.

Study on Flexural Behaviour of Ternary Blended Reinforced Self Compacting Concrete Beam with Conventional RCC Beam

NASA Astrophysics Data System (ADS)

Marshaline Seles, M.; Suryanarayanan, R.; Vivek, S. S.; Dhinakaran, G.

2017-07-01

The conventional concrete when used for structures having dense congested reinforcement, the problems such as external compaction and vibration needs special attention. In such case, the self compacting concrete (SCC) which has the properties like flow ability, passing and filling ability would be an obvious answer. All those SCC flow behavior was governed by EFNARC specifications. In present study, the combination type of SCC was prepared by replacing cement with silica fume (SF) and metakaolin (MK) along with optimum dosages of chemical admixtures. From the fresh property test, cube compressive strength and cylinder split tensile strength, optimum ternary mix was obtained. In order to study the flexural behavior, the optimum ternary mix was taken in which beam specimens of size 1200 mm x 100 mm x 200 mm was designed as singly reinforced section according to IS: 456-2000, Limit state method. Finally the comparative experimental analysis was made between conventional RCC and SCC beams of same grade in terms of flexural strength namely yield load & ultimate load, load- deflection curve, crack size and pattern respectively.

Experimental Study on Impermeability of Recycled Concrete

NASA Astrophysics Data System (ADS)

Wang, Shao Zhen; Yang, Jian Gong; Wei, Lu

2018-06-01

Recycled concrete is a kind of concrete which is constructed by crushing and removing the building waste and concrete blocks and mixing them according to a certain proportion after grading. In this study, the applicability of recycled concrete is studied only in terms of impermeability.

Radiation-resistant composite for biological shield of personnel

NASA Astrophysics Data System (ADS)

Barabash, D. E.; Barabash, A. D.; Potapov, Yu B.; Panfilov, D. V.; Perekalskiy, O. E.

2017-10-01

This article presents the results of theoretical and practical justification for the use of polymer concrete based on nonisocyanate polyurethanes in biological shield structures. We have identified the impact of ratio: polymer - radiation-resistant filling compound on the durability and protection properties of polymer concrete. The article expounds regression dependence of the change of basic properties of the aforementioned polymer concrete on the absorbed radiation dose rate. Synergy effect in attenuation of radioactivity release in case of conjoint use of hydrogenous polymer base and radiation-resistant powder is also addressed herein.

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

Parametric estimation for reinforced concrete relief shelter for Aceh cases

NASA Astrophysics Data System (ADS)

Atthaillah; Saputra, Eri; Iqbal, Muhammad

2018-05-01

This paper was a work in progress (WIP) to discover a rapid parametric framework for post-disaster permanent shelter’s materials estimation. The intended shelters were reinforced concrete construction with bricks as its wall. Inevitably, in post-disaster cases, design variations were needed to help suited victims condition. It seemed impossible to satisfy a beneficiary with a satisfactory design utilizing the conventional method. This study offered a parametric framework to overcome slow construction-materials estimation issue against design variations. Further, this work integrated parametric tool, which was Grasshopper to establish algorithms that simultaneously model, visualize, calculate and write the calculated data to a spreadsheet in a real-time. Some customized Grasshopper components were created using GHPython scripting for a more optimized algorithm. The result from this study was a partial framework that successfully performed modeling, visualization, calculation and writing the calculated data simultaneously. It meant design alterations did not escalate time needed for modeling, visualization, and material estimation. Further, the future development of the parametric framework will be made open source.

Learning with Technology: Video Modeling with Concrete-Representational-Abstract Sequencing for Students with Autism Spectrum Disorder.

PubMed

Yakubova, Gulnoza; Hughes, Elizabeth M; Shinaberry, Megan

2016-07-01

The purpose of this study was to determine the effectiveness of a video modeling intervention with concrete-representational-abstract instructional sequence in teaching mathematics concepts to students with autism spectrum disorder (ASD). A multiple baseline across skills design of single-case experimental methodology was used to determine the effectiveness of the intervention on the acquisition and maintenance of addition, subtraction, and number comparison skills for four elementary school students with ASD. Findings supported the effectiveness of the intervention in improving skill acquisition and maintenance at a 3-week follow-up. Implications for practice and future research are discussed.

Recent trends in reinforcement corrosion assessment using piezo sensors via electro mechanical impedance technique

NASA Astrophysics Data System (ADS)

Visalakshi, Talakokula; Bhalla, Suresh; Gupta, Ashok; Bhattacharjee, Bishwajit

2014-03-01

Reinforced concrete (RC) is an economical, versatile and successful construction material as it can be moulded into a variety of shapes and finishes. In most cases, it is durable and strong, performing well throughout its service life. However, in some cases, it does not perform adequately due to various reasons, one of which is the corrosion of the embedded steel bars used as reinforcement. . Although the electro-mechanical impedance (EMI) technique is well established for damage detection and quantification of civil, mechanical and aerospace structures, only limited studies have been reported of its application for rebar corrosion detection in RC structures. This paper presents the recent trends in corrosion assessment based on the model derived from the equivalent structural parameters extracted from the impedance spectrum of concrete-rebar system using the lead zirconate titanate (PZT) sensors via EMI technique.

Construction Material-Based Methodology for Military Contingency Base Construction: Case Study of Maiduguri, Nigeria

DTIC Science & Technology

2016-09-01

NSDA Nigerian Steel Development Authority OPC ordinary Portland cement PDF population density factor RCC Reynolds Construction Company RHA rice...construction. Byproducts include blast furnace slag cement and gas. The increased use of steel scrap in production creates less dependence on the raw...The construction resources are gravel, cement , ready-mix concrete, lumber, steel , and brick. In some cases, there are multiple central areas in a

Developing Emotion-Based Case Formulations: A Research-Informed Method.

PubMed

Pascual-Leone, Antonio; Kramer, Ueli

2017-01-01

New research-informed methods for case conceptualization that cut across traditional therapy approaches are increasingly popular. This paper presents a trans-theoretical approach to case formulation based on the research observations of emotion. The sequential model of emotional processing (Pascual-Leone & Greenberg, 2007) is a process research model that provides concrete markers for therapists to observe the emerging emotional development of their clients. We illustrate how this model can be used by clinicians to track change and provides a 'clinical map,' by which therapist may orient themselves in-session and plan treatment interventions. Emotional processing offers as a trans-theoretical framework for therapists who wish to conduct emotion-based case formulations. First, we present criteria for why this research model translates well into practice. Second, two contrasting case studies are presented to demonstrate the method. The model bridges research with practice by using client emotion as an axis of integration. Key Practitioner Message Process research on emotion can offer a template for therapists to make case formulations while using a range of treatment approaches. The sequential model of emotional processing provides a 'process map' of concrete markers for therapists to (1) observe the emerging emotional development of their clients, and (2) help therapists develop a treatment plan. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

A case study of three methods used in detecting bridge deck deterioration associated with spalling.

DOT National Transportation Integrated Search

1973-01-01

The three most widely used current methods for detecting deterioration of concrete bridge decks associated with spalling were compared with a visual inspection of the reinforcing steel and to each other in order to determine the degree of agreement a...

Operational Art Requirements in the Korean War

DTIC Science & Technology

2012-05-17

Historical case studies can provide concrete examples to test the validity of theory and doctrine. A critical analysis of the examples provided by...war into a global conflagration .45 However, as early as 13 July 1950, MacArthur developed his plan to do more than reestablish the territorial

Evaluation of workability and strength of green concrete using waste steel scrap

NASA Astrophysics Data System (ADS)

Neeraja, D.; Arshad, Shaik Mohammed; Nawaz Nadaf, Alisha K.; Reddy, Mani Kumar

2017-11-01

This project works on the study of workability and mechanical properties of concrete using waste steel scrap from the lathe industry. Lathe industries produce waste steel scrap from the lathe machines. In this study, an attempt is made to use this waste in concrete, as accumulation of waste steel scrap cause disposal problem. Tests like compressive test, split tensile test, NDT test (UPV test) were conducted to determine the impact of steel scrap in concrete. The percentages of steel scrap considered in the study were 0%, 0.5%, 1%, 1.5%, and 2% respectively by volume of concrete, 7 day, 28 days test were conducted to find out strength of steel scrap concrete. It is observed that split tensile strength of steel scrap concrete is increased slightly. Split tensile strength of Steel scrap concrete is found to be maximum with volume fraction of 2.0% steel scrap. The steel scrap gives good result in split tensile strength of concrete. From the study concluded that steel scrap can be used in concrete to reduce brittleness of concrete to some extent.

Physical and mechanical properties of self-compacting concrete containing superplasticizer and metakaolin

NASA Astrophysics Data System (ADS)

Shahidan, Shahiron; Tayeh, Bassam A.; Jamaludin, A. A.; Bahari, N. A. A. S.; Mohd, S. S.; Zuki Ali, N.; Khalid, F. S.

2017-11-01

The development of concrete technology shows a variety of admixtures in concrete to produce special concrete. This includes the production of self-compacting concrete which is able to fill up all spaces, take formwork shapes and pass through congested reinforcement bars without vibrating or needing any external energy. In this study, the main objective is to compare the physical and mechanical properties of self-compacting concrete containing metakaolin with normal concrete. Four types of samples were produced to study the effect of metakaolin towards the physical and mechanical properties of self-compacting concrete where 0%, 5%, 10% and 15% of metakaolin were used as cement replacement. The physical properties were investigated using slump test for normal concrete and slump flow test for self-compacting concrete. The mechanical properties were tested for compressive strength and tensile strength. The findings of this study show that the inclusion of metakaolin as cement replacement can increase both compressive and tensile strength compared to normal concrete. The highest compressive strength was found in self-compacting concrete with 15% metakaolin replacement at 53.3 MPa while self-compacting concrete with 10% metakaolin replacement showed the highest tensile strength at 3.6 MPa. On top of that, the finishing or concrete surface of both cube and cylinder samples made of self-compacting concrete produced a smooth surface with the appearance of less honeycombs compared to normal concrete.

An Experimental Study on Shrinkage Strains of Normal-and High-Strength Concrete-Filled Frp Tubes

NASA Astrophysics Data System (ADS)

Vincent, Thomas; Ozbakkaloglu, Togay

2017-09-01

It is now well established that concrete-filled fiber reinforced polymer (FRP) tubes (CFFTs) are an attractive construction technique for new columns, however studies examining concrete shrinkage in CFFTs remain limited. Concrete shrinkage may pose a concern for CFFTs, as in these members the curing of concrete takes place inside the FRP tube. This paper reports the findings from an experimental study on concrete shrinkage strain measurements for CFFTs manufactured with normal- and high-strength concrete (NSC and HSC). A total of 6 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were manufactured, with 3 specimens each manufactured using NSC and HSC. The specimens were instrumented with surface and embedded strain gauges to monitor shrinkage development of exposed concrete and concrete sealed inside the CFFTs, respectively. All specimens were cylinders with a 152 mm diameter and 305 mm height, and their unconfined concrete strengths were 44.8 or 83.2 MPa. Analysis of the shrinkage measurements from concrete sealed inside the CFFTs revealed that embedment depth and concrete compressive strength only had minor influences on recorded shrinkage strains. However, an analysis of shrinkage measurements from the exposed concrete surface revealed that higher amounts of shrinkage can occur in HSC. Finally, it was observed that shrinkage strains are significantly higher for concrete exposed at the surface compared to concrete sealed inside the CFFTs.

Statistical and Detailed Analysis on Fiber Reinforced Self-Compacting Concrete Containing Admixtures- A State of Art of Review

NASA Astrophysics Data System (ADS)

Athiyamaan, V.; Mohan Ganesh, G.

2017-11-01

Self-Compacting Concrete is one of the special concretes that have ability to flow and consolidate on its own weight, completely fill the formwork even in the presence of dense reinforcement; whilst maintaining its homogeneity throughout the formwork without any requirement for vibration. Researchers all over the world are developing high performance concrete by adding various Fibers, admixtures in different proportions. Various different kinds Fibers like glass, steel, carbon, Poly propylene and aramid Fibers provide improvement in concrete properties like tensile strength, fatigue characteristic, durability, shrinkage, impact, erosion resistance and serviceability of concrete[6]. It includes fundamental study on fiber reinforced self-compacting concrete with admixtures; its rheological properties, mechanical properties and overview study on design methodology statistical approaches regarding optimizing the concrete performances. The study has been classified into seven basic chapters: introduction, phenomenal study on material properties review on self-compacting concrete, overview on fiber reinforced self-compacting concrete containing admixtures, review on design and analysis of experiment; a statistical approach, summary of existing works on FRSCC and statistical modeling, literature review and, conclusion. It is so eminent to know the resent studies that had been done on polymer based binder materials (fly ash, metakaolin, GGBS, etc.), fiber reinforced concrete and SCC; to do an effective research on fiber reinforced self-compacting concrete containing admixtures. The key aim of the study is to sort-out the research gap and to gain a complete knowledge on polymer based Self compacting fiber reinforced concrete.

Comparison of the quasi-static method and the dynamic method for simulating fracture processes in concrete

NASA Astrophysics Data System (ADS)

Liu, J. X.; Deng, S. C.; Liang, N. G.

2008-02-01

Concrete is heterogeneous and usually described as a three-phase material, where matrix, aggregate and interface are distinguished. To take this heterogeneity into consideration, the Generalized Beam (GB) lattice model is adopted. The GB lattice model is much more computationally efficient than the beam lattice model. Numerical procedures of both quasi-static method and dynamic method are developed to simulate fracture processes in uniaxial tensile tests conducted on a concrete panel. Cases of different loading rates are compared with the quasi-static case. It is found that the inertia effect due to load increasing becomes less important and can be ignored with the loading rate decreasing, but the inertia effect due to unstable crack propagation remains considerable no matter how low the loading rate is. Therefore, an unrealistic result will be obtained if a fracture process including unstable cracking is simulated by the quasi-static procedure.

Advance study of fiber-reinforced self-compacting concrete

NASA Astrophysics Data System (ADS)

Mironova, M.; Ivanova, M.; Naidenov, V.; Georgiev, I.; Stary, J.

2015-10-01

Incorporation in concrete composition of steel macro- and micro - fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.

Investigation on Flexure Test of Composite Beam of Repair Materials and Substrate Concrete for Durable Repair

NASA Astrophysics Data System (ADS)

Pattnaik, Rashmi R.; Rangaraju, Prasada Rao

2014-12-01

An experimental study was conducted on composite beam of repair materials and substrate concrete to investigate the failures of concrete repair due to differences in strength of repair materials and substrate concrete. In this investigation the flexural strength, load-deflection curves and failure patterns of the composite beam specimens are studied for the durability of the concrete repair. Flexure test was conducted to simulate tensile stress in the concrete repair material. Compressive strength and split tensile strength of the repair materials and substrate concrete are investigated to aid in the analysis of the concrete repair. It was observed that the repair materials of higher compressive strength than the substrate concrete are causing an incompatible failure in the concrete repair.

A Wireless Passive Sensing System for Displacement/Strain Measurement in Reinforced Concrete Members

PubMed Central

Ozbey, Burak; Erturk, Vakur B.; Demir, Hilmi Volkan; Altintas, Ayhan; Kurc, Ozgur

2016-01-01

In this study, we show a wireless passive sensing system embedded in a reinforced concrete member successfully being employed for the measurement of relative displacement and strain in a simply supported beam experiment. The system utilizes electromagnetic coupling between the transceiver antenna located outside the beam, and the sensing probes placed on the reinforcing bar (rebar) surface inside the beam. The probes were designed in the form of a nested split-ring resonator, a metamaterial-based structure chosen for its compact size and high sensitivity/resolution, which is at µm/microstrains level. Experiments were performed in both the elastic and plastic deformation cases of steel rebars, and the sensing system was demonstrated to acquire telemetric data in both cases. The wireless measurement results from multiple probes are compared with the data obtained from the strain gages, and an excellent agreement is observed. A discrete time measurement where the system records data at different force levels is also shown. Practical issues regarding the placement of the sensors and accurate recording of data are discussed. The proposed sensing technology is demonstrated to be a good candidate for wireless structural health monitoring (SHM) of reinforced concrete members by its high sensitivity and wide dynamic range. PMID:27070615

Modelling the influence of ionic and fluid transport on rebars corrosion in unsaturated cement systems

NASA Astrophysics Data System (ADS)

Dridi, W.; Dangla, P.; Foct, F.; Petre-Lazar, I.

2006-11-01

This paper deals with numerical modelling of rebar corrosion kinetics in unsaturated concrete structures. The corrosion kinetics is investigated in terms of mechanistic coupling between reaction rates at the steel surface and the ionic transport processes in the concrete pore system. The ionic and mass transport model consists of time-dependent equations for the concentration of dissolved species, the liquid pressure and the electrical potential. The complete set of nonlinear equations is solved using the finite-volume method. The nonlinear boundary conditions dealing with corrosion are introduced at the steel-concrete interface where they are implicitly coupled with the mass transport model in the concrete structure. Both the case of free corrosion and potentiostatic polarisation are discussed in a one dimensional model.

Treatment of fly ash for use in concrete

DOEpatents

Boxley, Chett [Park City, UT; Akash, Akash [Salt lake City, UT; Zhao, Qiang [Natick, MA

2012-05-08

A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with an activator solution sufficient to initiate a geopolymerization reaction and for a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 35% of the foam index of the untreated fly ash, and in some cases less than 10% of the foam index of the untreated fly ash. The activator solution may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.

Treatment of fly ash for use in concrete

DOEpatents

Boxley, Chett; Akash, Akash; Zhao, Qiang

2013-01-08

A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with an activator solution sufficient to initiate a geopolymerization reaction and for a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 35% of the foam index of the untreated fly ash, and in some cases less than 10% of the foam index of the untreated fly ash. The activator solution may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.

Portland cement concrete air content study.

DOT National Transportation Integrated Search

1987-04-20

This study took the analysis of Portland cement concrete air content. Based on the information gathered, this study hold the results were : 1) air-entrained concrete was more durable than non-air entrained concrete all other factors being equal; 2) A...

An Epistemological Approach to Modeling: Cases Studies and Implications for Science Teaching

ERIC Educational Resources Information Center

Sensevy, Gerard; Tiberghien, Andree; Santini, Jerome; Laube, Sylvain; Griggs, Peter

2008-01-01

Models and modeling are a major issue in science studies and in science education. In addressing such an issue, we first propose an epistemological discussion based on the works of Cartwright (1983, 1999), Fleck (1935/1979), and Hacking (1983). This leads us to emphasize the transitions between the abstract and the concrete in the modeling…

Chromate and amine contact allergies in workers manufacturing precast concrete elements.

PubMed

Mowitz, Martin; Zimerson, Erik; Hauksson, Inese; Pontén, Ann

2016-12-01

Five workers from a plant manufacturing concrete wall panels and beams were referred to our department because of suspected occupational dermatitis. When patch tested, 3 workers reacted to potassium dichromate. Four workers reacted to ethylenediamine dihydrochloride, without any obvious exposure. Owing to the high proportion of workers with recent-onset skin disease, an investigation of all workers at the plant was initiated. To investigate the prevalence of occupational dermatitis and contact allergy in the workers at the plant. All 24 workers at the plant underwent a clinical investigation and were patch tested. Four cases of allergic occupational contact dermatitis and 3 cases of irritant occupational contact dermatitis were diagnosed. Contact allergy to potassium dichromate was found in 4 workers. All 4 also reacted to ethylenediamine dihydrochloride and/or amines that were present as additives in the cement. Chromate contact allergy can still be found in concrete workers, despite the legislation regulating the amount of hexavalent chromium (chromate) in cement. Occupational contact allergy to amines can be found in workers exposed to cement and concrete, so amines should be tested in these workers. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Durability of lightweight concrete : Phase I : concrete temperature study.

DOT National Transportation Integrated Search

1968-08-01

This report describes a study conducted to determine the temperature gradient throughout the depth of a six inch concrete bridge deck. The bridge deck selected for study was constructed using lightweight concrete for the center spans and sand and gra...

The Influence of Framing on Clinicians’ Judgments of the Biological Basis of Behaviors

PubMed Central

Kim, Nancy S.; Ahn, Woo-kyoung; Johnson, Samuel G. B.; Knobe, Joshua

2015-01-01

Practicing clinicians frequently think about behaviors both abstractly (i.e., in terms of symptoms, as in the DSM-5; APA, 2013) and concretely (i.e., in terms of individual clients, as in DSM-5 Clinical Cases; Barnhill, 2013). Does abstract/concrete framing influence clinical judgments about behaviors? Seventy-four practicing mental health clinicians were presented with hallmark symptoms of six disorders framed abstractly versus concretely, and provided ratings of their biological and psychological bases (Experiment 1) and the likely efficacy of medication and psychotherapy in alleviating them (Experiment 2). Clinicians perceived behavioral symptoms in the abstract to be more biologically and less psychologically based than when concretely described, and medication was viewed as more effective for abstractly than concretely described symptoms. These findings suggest one possible basis for miscommunication and misalignment of views between primarily research-oriented and primarily practice-oriented clinicians; furthermore, clinicians may accept new neuroscience research more strongly in the abstract than for individual clients. PMID:26651348

Reliability assessment of slender concrete columns at the stability failure

NASA Astrophysics Data System (ADS)

Valašík, Adrián; Benko, Vladimír; Strauss, Alfred; Täubling, Benjamin

2018-01-01

The European Standard for designing concrete columns within the use of non-linear methods shows deficiencies in terms of global reliability, in case that the concrete columns fail by the loss of stability. The buckling failure is a brittle failure which occurs without warning and the probability of its formation depends on the columns slenderness. Experiments with slender concrete columns were carried out in cooperation with STRABAG Bratislava LTD in Central Laboratory of Faculty of Civil Engineering SUT in Bratislava. The following article aims to compare the global reliability of slender concrete columns with slenderness of 90 and higher. The columns were designed according to methods offered by EN 1992-1-1 [1]. The mentioned experiments were used as basis for deterministic nonlinear modelling of the columns and subsequent the probabilistic evaluation of structural response variability. Final results may be utilized as thresholds for loading of produced structural elements and they aim to present probabilistic design as less conservative compared to classic partial safety factor based design and alternative ECOV method.

Shear transfer in concrete reinforced with carbon fibers

NASA Astrophysics Data System (ADS)

El-Mokadem, Khaled Mounir

2001-10-01

Scope and method of study. The research started with preliminary tests and studies on the behavior and effect of carbon fibers in different water solutions and mortar/concrete mixes. The research work investigated the use of CF in the production of concrete pipes and prestressed concrete double-tee sections. The research then focused on studying the effect of using carbon fibers on the direct shear transfer of sand-lightweight reinforced concrete push-off specimens. Findings and conclusions. In general, adding carbon fibers to concrete improved its tensile characteristics but decreased its compressive strength. The decrease in compressive strength was due to the decrease in concrete density as fibers act as three-dimensional mesh that entrapped air. The decrease in compressive strength was also due to the increase in the total surface area of non-cementitious material in the concrete. Sand-lightweight reinforced concrete push-off specimens with carbon fibers had lower shear carrying capacity than those without carbon fibers for the same cement content in the concrete. Current building codes and specifications estimate the shear strength of concrete as a ratio of the compressive strength. If applying the same principals then the ratio of shear strength to compressive strength for concrete reinforced with carbon fibers is higher than that for concrete without carbon fibers.

Effects of cement alkalinity, exposure conditions and steel-concrete interface on the time-to-corrosion and chloride threshold for reinforcing steel in concrete

NASA Astrophysics Data System (ADS)

Nam, Jingak

Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH measurement of concrete pore water. Once specimens were fabricated and exposed to a corrosive chloride solution, various experimental techniques were employed to determine time-to-corrosion, chloride threshold, diffusion coefficient and void density along the rebar trace as well as pore water pH. Based upon the resultant data, several findings related to the above parameters have been obtained as summarized below. First, time for the corrosion initiation was longest for G109 concrete specimens with high alkalinity cement (HA). Also, chloride threshold increased with increasing time-to-corrosion and cement alkalinity. Consequently, the HA specimens exhibited the highest chloride threshold compared to low and normal alkalinity ones. Second, high temperature and temperature variations reduced time-to-corrosion of reinforcing steel in concrete since chloride diffusion was accelerated at higher temperature and possibly by temperature variations. The lowest chloride threshold values were found for outdoor exposed specimens suggesting that variation of RH or temperature (or both) facilitated rapid chloride diffusion. Third, an elevated time-to-corrosion and chloride threshold values were found for the wire brushed steel specimens compared to as-received ones. The higher ratio of [OH-]/[Fe n+] on the wire brushed steel surface compared to that of as-received case can be the possible cause because the higher ratio of this parameter enables the formation of a more protective passive film on the rebar. Fourth, voids at the steel-concrete interface facilitated passive film breakdown and onset of localized corrosion. This tendency for corrosion initiation increased in proportion to void size irrespective of specimen type. Also, [Cl -]th decreased with increasing void diameter. In addition, new ex-situ leaching method for determining concrete pore water alkalinity was developed.

Simulation analysis of temperature control on RCC arch dam of hydropower station

NASA Astrophysics Data System (ADS)

XIA, Shi-fa

2017-12-01

The temperature analysis of roller compacted concrete (RCC) dam plays an important role in their design and construction. Based on three-dimensional finite element method, in the computation of temperature field, many cases are included, such as air temperature, elevated temperature by cement hydration heat, concrete temperature during placing, the influence of water in the reservoir, and boundary temperature. According to the corresponding parameters of RCC arch dam, the analysis of temperature field and stress field during the period of construction and operation is performed. The study demonstrates that detailed thermal stress analysis should be performed for RCC dams to provide a basis to minimize and control the occurrence of thermal cracking.

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

Berke, N.S.; Dallaire, M.P.; Hicks, M.C.

Corrosion of steel in concrete is studied typically in uncracked concrete. In the field, however, concrete often has cracks that extend to the reinforcing steel. Electrochemical corrosion testing was performed in cracked concrete of two qualities. Results were compared to physical examination of the embedded reinforcement. Corrosion resistance improved significantly as the concrete properties and reinforcement cover approached that recommended in American Concrete Institute 318. Calcium nitrite additions to the concrete reduced corrosion significantly. Results indicated testing in cracked concrete should be performed in concrete representative of that specified in ACl 318.

Analysis of Solar Chimneys in Different Climate Zones - Case of Social Housing in Ecuador

NASA Astrophysics Data System (ADS)

Godoy-Vaca, Luis; Almaguer, Manuel; Martínez-Gómez, Javier; Lobato, Andrea; Palme, Massimo

2017-10-01

The aim of this research is to simulate the performance of a solar chimney located in different macro-zones in Ecuador. The proposed solar chimney model was simulated using a python script in order to predict the temperature distribution and the mass flow over time. The results obtained were firstly compared with experimental data for dry-warm climate. Then, the model was evaluated and tested in real weather conditions: dry-warm, moist-warm and rainy-cold. In addition, the assumed chimney dimensions were chosen according to the literature for the studied conditions. In spite of evaluating the best nightly ventilation, different chimney wall materials were tested: solid brick, common brick and reinforced concrete. The results showed that concrete in a dry-warm climate, a metallic layer on the gap with solid brick in a moist-warm climate and reinforced concrete in a rainy cold climate used for the absorbent wall improve the thermal inertia of the social housing.

Nonlinear Earthquake Analysis of Reinforced Concrete Frames with Fiber and Bernoulli-Euler Beam-Column Element

PubMed Central

Karaton, Muhammet

2014-01-01

A beam-column element based on the Euler-Bernoulli beam theory is researched for nonlinear dynamic analysis of reinforced concrete (RC) structural element. Stiffness matrix of this element is obtained by using rigidity method. A solution technique that included nonlinear dynamic substructure procedure is developed for dynamic analyses of RC frames. A predicted-corrected form of the Bossak-α method is applied for dynamic integration scheme. A comparison of experimental data of a RC column element with numerical results, obtained from proposed solution technique, is studied for verification the numerical solutions. Furthermore, nonlinear cyclic analysis results of a portal reinforced concrete frame are achieved for comparing the proposed solution technique with Fibre element, based on flexibility method. However, seismic damage analyses of an 8-story RC frame structure with soft-story are investigated for cases of lumped/distributed mass and load. Damage region, propagation, and intensities according to both approaches are researched. PMID:24578667

Shear Capacity of C-Shaped and L-Shaped Angle Shear Connectors

PubMed Central

Tahmasbi, Farzad; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.; Tahir, M. M.

2016-01-01

This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed. PMID:27478894

Shear Capacity of C-Shaped and L-Shaped Angle Shear Connectors.

PubMed

Tahmasbi, Farzad; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N H; Tahir, M M

2016-01-01

This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed.

DETAIL OF THE PROMENADE SHOWING (FROM RIGHT TO LEFT) THE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

DETAIL OF THE PROMENADE SHOWING (FROM RIGHT TO LEFT) THE STAIRWAY TO BASEMENT, A WOOD FRAMED POSTER CASE, DOORWAYS TO THE FOYER, AND SMALL RAISED CONCRETE SLAB FOR THE FORMER TICKET BOOTH. IN THE BACKGROUND ARE THE CAST CONCRETE LOUVERS OF THE OFFICE. VIEW FACING SOUTHEAST - U.S. Naval Base, Pearl Harbor, Theater, Hornet Avenue between Enterprise & Pokomoke Streets, Pearl City, Honolulu County, HI

Monitoring Strategies of Earth Dams by Ground-Based Radar Interferometry: How to Extract Useful Information for Seismic Risk Assessment.

PubMed

Di Pasquale, Andrea; Nico, Giovanni; Pitullo, Alfredo; Prezioso, Giuseppina

2018-01-16

The aim of this paper is to describe how ground-based radar interferometry can provide displacement measurements of earth dam surfaces and of vibration frequencies of its main concrete infrastructures. In many cases, dams were built many decades ago and, at that time, were not equipped with in situ sensors embedded in the structure when they were built. Earth dams have scattering properties similar to landslides for which the Ground-Based Synthetic Aperture Radar (GBSAR) technique has been so far extensively applied to study ground displacements. In this work, SAR and Real Aperture Radar (RAR) configurations are used for the measurement of earth dam surface displacements and vibration frequencies of concrete structures, respectively. A methodology for the acquisition of SAR data and the rendering of results is described. The geometrical correction factor, needed to transform the Line-of-Sight (LoS) displacement measurements of GBSAR into an estimate of the horizontal displacement vector of the dam surface, is derived. Furthermore, a methodology for the acquisition of RAR data and the representation of displacement temporal profiles and vibration frequency spectra of dam concrete structures is presented. For this study a Ku-band ground-based radar, equipped with horn antennas having different radiation patterns, has been used. Four case studies, using different radar acquisition strategies specifically developed for the monitoring of earth dams, are examined. The results of this work show the information that a Ku-band ground-based radar can provide to structural engineers for a non-destructive seismic assessment of earth dams.

Corrosion initiation and propagation behavior of corrosion resistant concrete reinforcing materials

NASA Astrophysics Data System (ADS)

Hurley, Michael F.

The life of a concrete structure exposed to deicing compounds or seawater is often limited by chloride induced corrosion of the steel reinforcement. In this study, the key material attributes that affect the corrosion initiation and propagation periods were studied. These included material composition, surface condition, ageing time, propagation behavior during active corrosion, morphology of attack, and type of corrosion products generated by each rebar material. The threshold chloride concentrations for solid 316LN stainless steel, 316L stainless steel clad over carbon steel, 2101 LDX, MMFX-2, and carbon steel rebar were investigated using electrochemical techniques in saturated calcium hydroxide solutions. Surface preparation, test method, duration of period exposed to a passivating condition prior to introduction of chloride, and presence of cladding defects all affected the threshold chloride concentration obtained. A model was implemented to predict the extension of time until corrosion initiation would be expected. 8 years was the predicted time to corrosion initiation for carbon steel. However, model results confirmed that use of 316LN may increase the time until onset of corrosion to 100 years or more. To assess the potential benefits afforded by new corrosion resistant rebar alloys from a corrosion resistance standpoint the corrosion propagation behavior and other factors that might affect the risk of corrosion-induced concrete cracking must also be considered. Radial pit growth was found to be ohmically controlled but repassivation occurred more readily at high potentials in the case of 316LN and 2101 stainless steels. The discovery of ohmically controlled propagation enabled transformation of propagation rates from simulated concrete pore solution to less conductive concrete by accounting for resistance changes in the surrounding medium. The corrosion propagation behavior as well as the morphology of attack directly affects the propensity for concrete cracking. Experimental results were used in conjunction with an existing model to predict the time until concrete cracking occurs for new rebar materials. The results suggest that corrosion resistant materials offer a significant extension to the corrosion propagation stage over carbon steel, even in very aggressive conditions because small, localized anodes develop when initiated.

Dynamic response of RC beams strengthened with near surface mounted Carbon-FRP rods subjected to damage

NASA Astrophysics Data System (ADS)

Capozucca, R.; Blasi, M. G.; Corina, V.

2015-07-01

Near surface mounted (NSM) technique with fiber reinforced polymer (FRP) is becoming a common method in the strengthening of concrete beams. The availability of NSM FRP technique depends on many factors linked to materials and geometry - dimensions of the rods used, type of FRP material employed, rods’ surface configuration, groove size - and to adhesion between concrete and FRP rods. In this paper detection of damage is investigated measuring the natural frequency values of beam in the case of free-free ends. Damage was due both to reduction of adhesion between concrete and carbon-FRP rectangular and circular rods and cracking of concrete under static bending tests on beams. Comparison between experimental and theoretical frequency values evaluating frequency changes due to damage permits to monitor actual behaviour of RC beams strengthened by NSM CFRP rods.

Evaluation of recycled concrete as aggregate in new concrete pavements.

DOT National Transportation Integrated Search

2014-04-01

This study evaluated the use of recycled concrete as coarse aggregate in new concrete pavements. : Recycled concrete aggregate (RCA) produced from demolished pavements in three geographically dispersed locations in Washington state were used to perfo...

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete

PubMed Central

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-01-01

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor (C) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results. PMID:28773402

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete.

PubMed

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-04-08

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor ( C ) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results.

Freeze-thaw durability of concrete: Ice formation process in pores

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

Cai, H.; Liu, X.

1998-09-01

Freeze-thaw durability of concrete is of great importance to hydraulic structures in cold areas. Study of ice formation process in concrete pores is necessary to evaluate the damages in concrete caused by freezing. In this paper, freezing of pore solution in concrete exposed to a freeze-thaw cycle is studied by following the change of concrete electrical conductivity with freezing temperatures. Concretes were subjected to freeze-thaw cycles with temperature varying between {minus}0 C and {minus}20 C. In the freezing process, the changing rate of concrete electrical conductivity obviously decreases at about {minus}10 C, indicating that more pore solution in concrete freezesmore » above {minus}10 C than below {minus}10C. According to Powers` static hydraulic pressure hypothesis, it is thought that frost damage mainly occurs between 0 C and {minus}100 C. To ordinary concrete, frost damages below {minus}10 C are negligible.« less

On Characterizing Particle Shape

NASA Technical Reports Server (NTRS)

Ennis, Bryan J.; Rickman, Douglas; Rollins, A. Brent; Ennis, Brandon

2014-01-01

It is well known that particle shape affects flow characteristics of granular materials, as well as a variety of other solids processing issues such as compaction, rheology, filtration and other two-phase flow problems. The impact of shape crosses many diverse and commercially important applications, including pharmaceuticals, civil engineering, metallurgy, health, and food processing. Two applications studied here include the dry solids flow of lunar simulants (e.g. JSC-1, NU-LHT-2M, OB-1), and the flow properties of wet concrete, including final compressive strength. A multi-dimensional generalized, engineering method to quantitatively characterize particle shapes has been developed, applicable to both single particle orientation and multi-particle assemblies. The two-dimension, three dimension inversion problem is also treated, and the application of these methods to DEM model particles will be discussed. In the case of lunar simulants, flow properties of six lunar simulants have been measured, and the impact of particle shape on flowability - as characterized by the shape method developed here -- is discussed, especially in the context of three simulants of similar size range. In the context of concrete processing, concrete construction is a major contributor to greenhouse gas production, of which the major contributor is cement binding loading. Any optimization in concrete rheology and packing that can reduce cement loading and improve strength loading can also reduce currently required construction safety factors. The characterization approach here is also demonstrated for the impact of rock aggregate shape on concrete slump rheology and dry compressive strength.

Molecular Survey of Concrete Biofilm Microbial Communities

EPA Science Inventory

Although several studies have shown that bacteria can deteriorate concrete structures, there is very little information on the composition of concrete microbial communities. To this end, we studied different microbial communities associated with concrete biofilms using 16S rRNA g...

Development of Vegetation-Pervious Concrete in Grid Beam System for Soil Slope Protection.

PubMed

Bao, Xiaohua; Liao, Wenyu; Dong, Zhijun; Wang, Shanyong; Tang, Waiching

2017-01-24

One of the most efficient and environmentally friendly methods for preventing a landslide on a slope is to vegetate it. Vegetation-pervious concretes have a promising potential for soil protection. In this study, the vegetation-pervious concrete with low alkalinity was developed and studied. Combined with a grid beam structure system, the stability and strength between the vegetation-pervious concrete and base soil are believed to be enhanced effectively. For improving plant adaptability, the alkalinity of concrete can be decreased innovatively by adding a self-designed admixture into the cement paste. The effects of the admixture content on alkalinity and compressive strength of the hardened pervious concrete were investigated using X-ray diffraction (XRD) and compression test, respectively. Meanwhile, the permeability of the vegetation-pervious concrete was studied as well. Through comparing with ordinary pervious concrete, the effect of low alkaline pervious concrete on vegetation growth was investigated in a small-scale field for ten weeks. The test results indicated that the alkalinity of the cement samples decreased with the increase of admixture content, and the vegetation grew successfully on previous concrete. By increasing the admixture content to approximately 3.6%, the compressive strength of pervious concrete was more than 25 MPa.

Recently learned foreign abstract and concrete nouns are represented in distinct cortical networks similar to the native language.

PubMed

Mayer, Katja M; Macedonia, Manuela; von Kriegstein, Katharina

2017-09-01

In the native language, abstract and concrete nouns are represented in distinct areas of the cerebral cortex. Currently, it is unknown whether this is also the case for abstract and concrete nouns of a foreign language. Here, we taught adult native speakers of German 45 abstract and 45 concrete nouns of a foreign language. After learning the nouns for 5 days, participants performed a vocabulary translation task during functional magnetic resonance imaging. Translating abstract nouns in contrast to concrete nouns elicited responses in regions that are also responsive to abstract nouns in the native language: the left inferior frontal gyrus and the left middle and superior temporal gyri. Concrete nouns elicited larger responses in the angular gyri bilaterally and the left parahippocampal gyrus than abstract nouns. The cluster in the left angular gyrus showed psychophysiological interaction (PPI) with the left lingual gyrus. The left parahippocampal gyrus showed PPI with the posterior cingulate cortex. Similar regions have been previously found for concrete nouns in the native language. The results reveal similarities in the cortical representation of foreign language nouns with the representation of native language nouns that already occur after 5 days of vocabulary learning. Furthermore, we showed that verbal and enriched learning methods were equally suitable to teach foreign abstract and concrete nouns. Hum Brain Mapp 38:4398-4412, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

The left inferior frontal gyrus: A neural crossroads between abstract and concrete knowledge.

PubMed

Della Rosa, Pasquale Anthony; Catricalà, Eleonora; Canini, Matteo; Vigliocco, Gabriella; Cappa, Stefano F

2018-07-15

Evidence from both neuropsychology and neuroimaging suggests that different types of information are necessary for representing and processing concrete and abstract word meanings. Both abstract and concrete concepts, however, conjointly rely on perceptual, verbal and contextual knowledge, with abstract concepts characterized by low values of imageability (IMG) (low sensory-motor grounding) and low context availability (CA) (more difficult to contextualize). Imaging studies supporting differences between abstract and concrete concepts show a greater recruitment of the left inferior frontal gyrus (LIFG) for abstract concepts, which has been attributed either to the representation of abstract-specific semantic knowledge or to the request for more executive control than in the case of concrete concepts. We conducted an fMRI study on 27 participants, using a lexical decision task involving both abstract and concrete words, whose IMG and CA values were explicitly modelled in separate parametric analyses. The LIFG was significantly more activated for abstract than for concrete words, and a conjunction analysis showed a common activation for words with low IMG or low CA only in the LIFG, in the same area reported for abstract words. A regional template map of brain activations was then traced for words with low IMG or low CA, and BOLD regional time-series were extracted and correlated with the specific LIFG neural activity elicited for abstract words. The regions associated to low IMG, which were functionally correlated with LIFG, were mainly in the left hemisphere, while those associated with low CA were in the right hemisphere. Finally, in order to reveal which LIFG-related network increased its connectivity with decreases of IMG or CA, we conducted generalized psychophysiological interaction analyses. The connectivity strength values extracted from each region connected with the LIFG were correlated with specific LIFG neural activity for abstract words, and a regression analysis was conducted to highlight which areas recruited by low IMG or low CA predicted the greater activation of the IFG for abstract concepts. Only the left middle temporal gyrus/angular gyrus, known to be involved in semantic processing, was a significant predictor of LIFG activity differentiating abstract from concrete words. The results show that the abstract conceptual processing requires the interplay of multiple brain regions, necessary for both the intrinsic and extrinsic properties of abstract knowledge. The LIFG can be thus identified as the neural crossroads between different types of information equally necessary for representing processing and differentiating abstract concepts from concrete ones. Copyright © 2018 Elsevier Inc. All rights reserved.

Bayesian Learning and the Psychology of Rule Induction

ERIC Educational Resources Information Center

Endress, Ansgar D.

2013-01-01

In recent years, Bayesian learning models have been applied to an increasing variety of domains. While such models have been criticized on theoretical grounds, the underlying assumptions and predictions are rarely made concrete and tested experimentally. Here, I use Frank and Tenenbaum's (2011) Bayesian model of rule-learning as a case study to…

Accreditation and Power: A Discourse Analysis of a New Regime of Governance in Higher Education

ERIC Educational Resources Information Center

Engebretsen, Eivind; Heggen, Kristin; Eilertsen, Heidi Annett

2012-01-01

This article studies discourses within the accreditation of Norwegian higher education conducted by the Norwegian Agency for Quality Assurance in Education (NOKUT), using one concrete case (the accreditation of bachelor programs in nursing). Analysis of policy documents and accreditation reports are influenced by two of Foucault's concepts of…

Passion into Action: Facilitating Teachers to Act Critically

ERIC Educational Resources Information Center

Daoud, Annette M.; Santamaria, Lorri J.

2010-01-01

This inquiry highlights K-12 teachers' commitment to turn their passion of providing equitable educational opportunities to all students into concrete actions. The inquiry uses a case study approach to investigate the process teachers undergo beginning in an MA course on multicultural education, and continuing through their MA program to define,…

Against BibliOblivion: How Modern Scribes Digitized an Old Book

ERIC Educational Resources Information Center

Delfino, Manuela

2011-01-01

In investigating how to best support the learning of digital competences at school, it is paramount to take into account the concrete reality (cultural, technological, and institutional) that teachers face in their daily struggle to prepare students for the information society. Hence case studies are needed to inform us on the complex relationship…

The Symmetry Group of the Permutahedron

ERIC Educational Resources Information Center

Crisman, Karl-Dieter

2011-01-01

Although it can be visualized fairly easily and its symmetry group is easy to calculate, the permutahedron is a somewhat neglected combinatorial object. We propose it as a useful case study in abstract algebra. It supplies concrete examples of group actions, the difference between right and left actions, and how geometry and algebra can work…

Treatment of Complicated Grief Using Virtual Reality: A Case Report

ERIC Educational Resources Information Center

Botella, C.; Osma, J.; Palacios, A. Garcia; Guillen, V.; Banos, R.

2008-01-01

This is the first work exploring the application of new technologies, concretely virtual reality, to facilitate emotional processing in the treatment of Complicated Grief. Our research team has designed a virtual reality environment (EMMA's World) to foster the expression and processing of emotions. In this study the authors present a description…

Institutional Assessment of Student Information Literacy Ability: A Case Study

ERIC Educational Resources Information Center

Chan, Christopher

2016-01-01

With increasing interest in the assessment of learning outcomes in higher education, stakeholders are demanding concrete evidence of student learning. This applies no less to information literacy outcomes, which have been adopted by many colleges and universities around the world. This article describes the experience of a university library in…

Design optimization of embedded ultrasonic transducers for concrete structures assessment.

PubMed

Dumoulin, Cédric; Deraemaeker, Arnaud

2017-08-01

In the last decades, the field of structural health monitoring and damage detection has been intensively explored. Active vibration techniques allow to excite structures at high frequency vibrations which are sensitive to small damage. Piezoelectric PZT transducers are perfect candidates for such testing due to their small size, low cost and large bandwidth. Current ultrasonic systems are based on external piezoelectric transducers which need to be placed on two faces of the concrete specimen. The limited accessibility of in-service structures makes such an arrangement often impractical. An alternative is to embed permanently low-cost transducers inside the structure. Such types of transducers have been applied successfully for the in-situ estimation of the P-wave velocity in fresh concrete, and for crack monitoring. Up to now, the design of such transducers was essentially based on trial and error, or in a few cases, on the limitation of the acoustic impedance mismatch between the PZT and concrete. In the present study, we explore the working principles of embedded piezoelectric transducers which are found to be significantly different from external transducers. One of the major challenges concerning embedded transducers is to produce very low cost transducers. We show that a practical way to achieve this imperative is to consider the radial mode of actuation of bulk PZT elements. This is done by developing a simple finite element model of a piezoelectric transducer embedded in an infinite medium. The model is coupled with a multi-objective genetic algorithm which is used to design specific ultrasonic embedded transducers both for hard and fresh concrete monitoring. The results show the efficiency of the approach and a few designs are proposed which are optimal for hard concrete, fresh concrete, or both, in a given frequency band of interest. Copyright © 2017 Elsevier B.V. All rights reserved.

FIELD STUDIES OF IMPREGNATED CONCRETE PIPE

EPA Science Inventory

The follow-on study (initiated in June 1980) continued to monitor performance of 1,400 ft of impregnated concrete pipe installed in several Texas cities. The performance of concrete pipe has been compared with that of sulfur-impregnated concrete pipe; hydrofluoric acid (HF)-treat...

Microsilica modified concrete for bridge deck overlays : construction report.

DOT National Transportation Integrated Search

1990-10-01

The study objective was to see if microsilica concrete (MC) is a viable alternative to the latex modified concrete (LMC) usually used on bridge deck overlays in Oregon. The study addresses MC overlays placed in 1989 on Portland cement concrete (PCC) ...

Usage of Crushed Concrete Fines in Decorative Concrete

NASA Astrophysics Data System (ADS)

Pilipenko, Anton; Bazhenova, Sofia

2017-10-01

The article is devoted to the questions of usage of crushed concrete fines from concrete scrap for the production of high-quality decorative composite materials based on mixed binder. The main problem in the application of crushed concrete in the manufacture of decorative concrete products is extremely low decorative properties of crushed concrete fines itself, as well as concrete products based on them. However, crushed concrete fines could have a positive impact on the structure of the concrete matrix and could improve the environmental and economic characteristics of the concrete products. Dust fraction of crushed concrete fines contains non-hydrated cement grains, which can be opened in screening process due to the low strength of the contact zone between the hydrated and non-hydrated cement. In addition, the screening process could increase activity of the crushed concrete fines, so it can be used as a fine aggregate and filler for concrete mixes. Previous studies have shown that the effect of the usage of the crushed concrete fines is small and does not allow to obtain concrete products with high strength. However, it is possible to improve the efficiency of the crushed concrete fines as a filler due to the complex of measures prior to mixing. Such measures may include a preliminary mechanochemical activation of the binder (cement binder, iron oxide pigment, silica fume and crushed concrete fines), as well as the usage of polycarboxylate superplasticizers. The development of specific surface area of activated crushed concrete fines ensures strong adhesion between grains of binder and filler during the formation of cement stone matrix. The particle size distribution of the crushed concrete fines could achieve the densest structure of cement stone matrix and improve its resistance to environmental effects. The authors examined the mechanisms of structure of concrete products with crushed concrete fines as a filler. The results of studies of the properties of the crushed concrete fines were provided. It is shown that the admixture of the crushed concrete fines has little effect on the colour characteristics of the decorative concrete products. The preferred options to improve the surfaces of decorative concrete are also proposed.

Molecular Survey of Concrete Sewer Biofilm Microbial Communities

EPA Science Inventory

Although bacteria are implicated in deteriorating concrete structures, there is very little information on the composition of concrete microbial communities. To this end, we studied different concrete biofilms by performing sequence analysis of 16S rDNA concrete clone libraries. ...

Forward problem studies of electrical resistance tomography system on concrete materials

NASA Astrophysics Data System (ADS)

Ang, Vernoon; Rahiman, M. H. F.; Rahim, R. A.; Aw, S. R.; Wahab, Y. A.; Thomas W. K., T.; Siow, L. T.

2017-03-01

Electrical resistance tomography (ERT) is well known as non-invasive imaging technique, inexpensive, radiation free, visualization measurements of the multiphase flows and frequently applied in geophysical, medical and Industrial Process Tomography (IPT) applications. Application of ERT in concrete is a new exploration field, which can be used in monitoring and detecting the health and condition of concrete without destroying it. In this paper, ERT model under the condition of concrete is studied in which the sensitivity field model is produced and simulated by using COMSOL software. The affects brought by different current injection values with different concrete conductivity are studied in detail. This study able to provide the important direction for the further study of inverse problem in ERT system. Besides, the results of this technique hopefully can open a new exploration in inspection method of concrete structures in order to maintain the health of the concrete structure for civilian safety.

Durability of styrene-butadiene latex modified concrete

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

Shaker, F.A.; El-Dieb, A.S.; Reda, M.M.

1997-05-01

The durability of reinforced concrete structures represents a major concern to many investigators. The use of latex modified concrete (LMC) in construction has urged researchers to review and investigate its different properties. This study is part of a comprehensive investigation carried on the use of polymers in concrete. The main objective of this study to investigate and evaluate the main durability aspects of Styrene-Butadiene latex modified concrete (LMC) compared to those of conventional concrete. Also, the main microstructural characteristics of LMC were studied using a Scanning Electron Microscope (SEM). The SEM investigation of the LMC showed major differences in itsmore » microstructure compared to that of the conventional concrete. The LMC proved to be superior in its durability compared to the durability of conventional concrete especially its water tightness (measured by water penetration, absorption, and sorptivity tests), abrasion, corrosion, and sulphate resistance.« less

Study of Interaction of Reinforcement with Concrete by Numerical Methods

NASA Astrophysics Data System (ADS)

Tikhomirov, V. M.; Samoshkin, A. S.

2018-01-01

This paper describes the study of deformation of reinforced concrete. A mathematical model for the interaction of reinforcement with concrete, based on the introduction of a contact layer, whose mechanical characteristics are determined from the experimental data, is developed. The limiting state of concrete is described using the Drucker-Prager theory and the fracture criterion with respect to maximum plastic deformations. A series of problems of the theory of reinforced concrete are solved: stretching of concrete from a central-reinforced prism and pre-stressing of concrete. It is shown that the results of the calculations are in good agreement with the experimental data.

Study on the Effect of Straw Fiber on the Performance of Volcanic Slag Concrete

NASA Astrophysics Data System (ADS)

Xiao, Li-guang; Liu, Xi-xu

2018-03-01

In this paper, the effects of straw fiber on the working performance, mechanical properties and frost resistance of volcanic slag lightweight aggregate concrete were studied. The experimental results show that the straw fiber is subjected to surface carbonization treatment and mixed into the volcanic slag light aggregate concrete. The flexural strength and fracture pressure ratio of volcanic slag lightweight aggregate concrete are improved obviously Improved volcanic slag lightweight aggregate concrete brittleness improves toughness. Carbonized straw fiber greatly improves the frost resistance of volcanic slag lightweight aggregate concrete. So that the volcanic slag light aggregate concrete freeze-thaw cycle can reach 300 times.

Comprehension of concrete and abstract words in semantic dementia

PubMed Central

Jefferies, Elizabeth; Patterson, Karalyn; Jones, Roy W.; Lambon Ralph, Matthew A.

2009-01-01

The vast majority of brain-injured patients with semantic impairment have better comprehension of concrete than abstract words. In contrast, several patients with semantic dementia (SD), who show circumscribed atrophy of the anterior temporal lobes bilaterally, have been reported to show reverse imageability effects, i.e., relative preservation of abstract knowledge. Although these reports largely concern individual patients, some researchers have recently proposed that superior comprehension of abstract concepts is a characteristic feature of SD. This would imply that the anterior temporal lobes are particularly crucial for processing sensory aspects of semantic knowledge, which are associated with concrete not abstract concepts. However, functional neuroimaging studies of healthy participants do not unequivocally predict reverse imageability effects in SD because the temporal poles sometimes show greater activation for more abstract concepts. We examined a case-series of eleven SD patients on a synonym judgement test that orthogonally varied the frequency and imageability of the items. All patients had higher success rates for more imageable as well as more frequent words, suggesting that (a) the anterior temporal lobes underpin semantic knowledge for both concrete and abstract concepts, (b) more imageable items – perhaps due to their richer multimodal representations – are typically more robust in the face of global semantic degradation and (c) reverse imageability effects are not a characteristic feature of SD. PMID:19586212

Flexural strength using Steel Plate, Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) on reinforced concrete beam in building technology

NASA Astrophysics Data System (ADS)

Tarigan, Johannes; Patra, Fadel Muhammad; Sitorus, Torang

2018-03-01

Reinforced concrete structures are very commonly used in buildings because they are cheaper than the steel structures. But in reality, many concrete structures are damaged, so there are several ways to overcome this problem, by providing reinforcement with Fiber Reinforced Polymer (FRP) and reinforcement with steel plates. Each type of reinforcements has its advantages and disadvantages. In this study, researchers discuss the comparison between flexural strength of reinforced concrete beam using steel plates and Fiber Reinforced Polymer (FRP). In this case, the researchers use Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) as external reinforcements. The dimension of the beams is 15 x 25 cm with the length of 320 cm. Based on the analytical results, the strength of the beam with CFRP is 1.991 times its initial, GFRP is 1.877 times while with the steel plate is 1.646 times. Based on test results, the strength of the beam with CFRP is 1.444 times its initial, GFRP is 1.333 times while the steel plate is 1.167 times. Based on these test results, the authors conclude that beam with CFRP is the best choice for external reinforcement in building technology than the others.

Experimental study on the strength parameter of Quarry Dust mixed Coconut Shell Concrete adding Coconut Fibre

NASA Astrophysics Data System (ADS)

Matangulu Shrestha, Victor; Anandh, S.; Sindhu Nachiar, S.

2017-07-01

Concrete is a heterogeneous mixture constitute of cement as the main ingredient with a different mix of fine and coarse aggregate. The massive use of conventional concrete has a shortfall in its key ingredients, natural sand and coarse aggregate, due to increased industrialisation and globalisation. To overcome the shortage of material, an alternate material with similar mechanical properties and composition has to be studied, as replacement of conventional concrete. Coconut shell concrete is a prime option as replacement of key ingredients of conventional concrete as coconut is produced in massive quantity in south East Asia. Coconut shell concrete is lightweight concrete and different research is still ongoing concerning about its mix design and composition in the construction industry. Concrete is weak in tension as compared to compression, hence the fibre is used to refrain the crack in the concrete. Coconut fibre is one of many fibres which can be used in concrete. The main aim of this project is to analyse the use of natural by-products in the construction industry, make light weight concrete and eco-friendly construction. This project concerns with the comparison of the mechanical properties of coconut shell concrete and conventional concrete, replacing fine aggregate with quarry dust using coconut fibre. M25 grade of concrete was adopted and testing of concrete was done at the age of 3, 7 and 28 days. In this concrete mix, sand was replaced completely in volumetric measurement by quarry dust. The result was analysed and compared with addition of coconut fibre at varying percentage of 1%, 2%, 3%, 4% and 5%. From the test conducted, coconut shell concrete with quarry dust has the maximum value at 4% of coconut fibre while conventional concrete showed the maximum value at 2% of coconut fibre.

Microsilica modified concrete for bridge deck overlays : first-year interim report.

DOT National Transportation Integrated Search

1991-11-01

The study objective was to see if microsilica concrete (MC) is a viable alternative to the latex modified concrete (LMC) usually used on bridge deck overlays in Oregon. The study addresses MC overlays placed in 1989 on 7 portland cement concrete (PCC...

Advance study of fiber-reinforced self-compacting concrete

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

Mironova, M., E-mail: mirona@imbm.bas.bg; Ivanova, M., E-mail: magdalena.ivanova@imbm.bas.bg; Naidenov, V., E-mail: valna53@mail.bg

2015-10-28

Incorporation in concrete composition of steel macro- and micro – fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural andmore » material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.« less

Physical and mechanical properties of carbon fiber reinforced smart porous concrete for planting

NASA Astrophysics Data System (ADS)

Park, Seung-Bum; Kim, Jung-Hwan; Seo, Dae-Seuk

2005-05-01

The reinforcement strength of porous concrete and its applicability as a recycled aggregate was measured. Changes in physical and mechanical properties, subsequent to the mixing of carbon fiber and silica fume, were examined, and the effect of recycled aggregate depending on their mixing rate was evaluated. The applicability of planting to concrete material was also assessed. The results showed that there were not any remarkable change in the porosity and strength characteristics although its proportion of recycled aggregate increased. Also, the mixture of 10% of silica was found to be most effective for strength enforcement. In case of carbon fiber, the highest flexural strength was obtained with its mixing rate being 3%. It was also noticed that PAN-derived carbon fiber was superior to Pitch-derived ones in view of strength. The evaluation of its use for vegetation proved that the growth of plants was directly affected by the existence of covering soil, in case of having the similar size of aggregate and void.

The 'relics of Joan of Arc': a forensic multidisciplinary analysis.

PubMed

Charlier, P; Poupon, J; Eb, A; De Mazancourt, P; Gilbert, T; Huynh-Charlier, I; Loublier, Y; Verhille, A M; Moulheirat, C; Patou-Mathis, M; Robbiola, L; Montagut, R; Masson, F; Etcheberry, A; Brun, L; Willerslev, E; de la Grandmaison, G Lorin; Durigon, M

2010-01-30

Archaeological remains can provide concrete cases, making it possible to develop, refine or validate medico-legal techniques. In the case of the so-called 'Joan of Arc's relics' (a group of bone and archaeological remains known as the 'Bottle of Chinon'), 14 specialists analysed the samples such as a cadaver X of carbonised aspect: forensic anthropologist, medical examiners, pathologists, geneticists, radiologist, biochemists, palynologists, zoologist and archaeologist. Materials, methods and results of this study are presented here. This study aims to offer an exploitable methodology for the modern medico-legal cases of small quantities of human bones of carbonised aspect. 2009 Elsevier Ireland Ltd. All rights reserved.

A Study on the Reuse of Plastic Concrete Using Extended Set-Retarding Admixtures.

PubMed

Lobo, Colin; Guthrie, William F; Kacker, Raghu

1995-01-01

The disposal of ready mixed concrete truck wash water and returned plastic concrete is a growing concern for the ready mixed concrete industry. Recently, extended set-retarding admixtures, or stabilizers, which slow or stop the hydration of portland cement have been introduced to the market. Treating truck wash-water or returned plastic concrete with stabilizing admixtures delays its setting and hardening, thereby facilitating the incorporation of these typically wasted materials in subsequent concrete batches. In a statistically designed experiment, the properties of blended concrete containing stabilized plastic concrete were evaluated. The variables in the study included (1) concrete age when stabilized, (2) stabilizer dosage, (3) holding period of the treated (stabilized) concrete prior to blending with fresh ingredients, and (4) amount of treated concrete in the blended batch. The setting time, strength, and drying shrinkage of the blended concretes were evaluated. For the conditions tested, batching 5 % treated concrete with fresh material did not have a significant effect on the setting time, strength, or drying shrinkage of the resulting blended concrete. Batching 50 % treated concrete with fresh materials had a significant effect on the setting characteristics of the blended cocnrete, which in turn affected the water demand to maintain slump. The data suggests that for a known set of conditions, the stabilizer dosage can be optimized within a relatively narrow range to produce desired setting characteristics. The strength and drying shrinkage of the blended concretes were essentially a function of the water content at different sampling ages and the relationship followed the general trend of control concrete.

A Study on the Reuse of Plastic Concrete Using Extended Set-Retarding Admixtures

PubMed Central

Lobo, Colin; Guthrie, William F.; Kacker, Raghu

1995-01-01

The disposal of ready mixed concrete truck wash water and returned plastic concrete is a growing concern for the ready mixed concrete industry. Recently, extended set-retarding admixtures, or stabilizers, which slow or stop the hydration of portland cement have been introduced to the market. Treating truck wash-water or returned plastic concrete with stabilizing admixtures delays its setting and hardening, thereby facilitating the incorporation of these typically wasted materials in subsequent concrete batches. In a statistically designed experiment, the properties of blended concrete containing stabilized plastic concrete were evaluated. The variables in the study included (1) concrete age when stabilized, (2) stabilizer dosage, (3) holding period of the treated (stabilized) concrete prior to blending with fresh ingredients, and (4) amount of treated concrete in the blended batch. The setting time, strength, and drying shrinkage of the blended concretes were evaluated. For the conditions tested, batching 5 % treated concrete with fresh material did not have a significant effect on the setting time, strength, or drying shrinkage of the resulting blended concrete. Batching 50 % treated concrete with fresh materials had a significant effect on the setting characteristics of the blended cocnrete, which in turn affected the water demand to maintain slump. The data suggests that for a known set of conditions, the stabilizer dosage can be optimized within a relatively narrow range to produce desired setting characteristics. The strength and drying shrinkage of the blended concretes were essentially a function of the water content at different sampling ages and the relationship followed the general trend of control concrete. PMID:29151762

Treatment of fly ash for use in concrete

DOEpatents

Boxley, Chett [Park City, UT

2012-05-15

A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with a quantity of spray dryer ash (SDA) and water to initiate a geopolymerization reaction and form a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 40%, and in some cases less than 20%, of the foam index of the untreated fly ash. An optional alkaline activator may be mixed with the fly ash and SDA to facilitate the geopolymerization reaction. The alkaline activator may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.

The use of nanomodified concrete in construction of high-rise buildings

NASA Astrophysics Data System (ADS)

Prokhorov, Sergei

2018-03-01

Construction is one of the leading economy sectors. Currently, concrete is the basis of most of the structural elements, without which it is impossible to imagine the construction of a single building or facility. Their strength, reinforcement and the period of concrete lifetime are determined at the design stage, taking into account long-term operation. However, in real life, the number of impacts that affects the structural strength is pretty high. In some cases, they are random and do not have standardized values. This is especially true in the construction and exploitation of high-rise buildings and structures. Unlike the multi-storey buildings, they experience significant loads already at the stage of erection, as they support load-lifting mechanisms, formwork systems, workers, etc. The purpose of the presented article is to develop a methodology for estimating the internal fatigue of concrete structures based on changes in their electrical conductivity.

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.

Development of Vegetation-Pervious Concrete in Grid Beam System for Soil Slope Protection

PubMed Central

Bao, Xiaohua; Liao, Wenyu; Dong, Zhijun; Wang, Shanyong; Tang, Waiching

2017-01-01

One of the most efficient and environmentally friendly methods for preventing a landslide on a slope is to vegetate it. Vegetation-pervious concretes have a promising potential for soil protection. In this study, the vegetation-pervious concrete with low alkalinity was developed and studied. Combined with a grid beam structure system, the stability and strength between the vegetation-pervious concrete and base soil are believed to be enhanced effectively. For improving plant adaptability, the alkalinity of concrete can be decreased innovatively by adding a self-designed admixture into the cement paste. The effects of the admixture content on alkalinity and compressive strength of the hardened pervious concrete were investigated using X-ray diffraction (XRD) and compression test, respectively. Meanwhile, the permeability of the vegetation-pervious concrete was studied as well. Through comparing with ordinary pervious concrete, the effect of low alkaline pervious concrete on vegetation growth was investigated in a small-scale field for ten weeks. The test results indicated that the alkalinity of the cement samples decreased with the increase of admixture content, and the vegetation grew successfully on previous concrete. By increasing the admixture content to approximately 3.6%, the compressive strength of pervious concrete was more than 25 MPa. PMID:28772454

Effect of mineral additives on structure and properties of concrete for pavements

NASA Astrophysics Data System (ADS)

Sobol, Khrystyna; Markiv, Taras; Hunyak, Oleksii

2017-12-01

Concrete pavements is an attractive alternative to asphalt pavements because of its lower cost and higher durability. Major contribution to sustainable development can be made by partial replacement of cement in concrete pavement with supplementary cementitious materials of different nature and origin. In this paper, the effect of natural zeolite and perlite additives in complex with chemical admixtures on the structure and properties of concrete for pavement was studied. Compressive and flexural strength test was used to study the mechanical behavior of designed concrete under load. Generally, the compressive strength of both control concrete and concrete containing mineral additives levels at the later ages of hardening. The microstructure analysis of concrete with mineral additives of different nature activity showed the formation of additional amount of hydration products such as tobermorite type calcium hydrosilicate which provide self-reinforcement of hardening concrete system.

Strength of masonry blocks made with recycled concrete aggregates

NASA Astrophysics Data System (ADS)

Matar, Pierre; Dalati, Rouba El

The idea of recycling concrete of demolished buildings aims at preserving the environment. Indeed, the reuse of concrete as aggregate in new concrete mixes helped to reduce the expenses related to construction and demolition (C&D) waste management and, especially, to protect the environment by reducing the development rate of new quarries. This paper presents the results of an experimental study conducted on masonry blocks containing aggregates resulting from concrete recycling. The purpose of this study is to investigate the effect of recycled aggregates on compressive strength of concrete blocks. Tests were performed on series of concrete blocks: five series each made of different proportions of recycled aggregates, and one series of reference blocks exclusively composed of natural aggregates. Tests showed that using recycled aggregates with addition of cement allows the production of concrete blocks with compressive strengths comparable to those obtained on concrete blocks made exclusively of natural aggregates.

The Study on the Durability of Submerged Structure Displacement due to Concrete Failure

NASA Astrophysics Data System (ADS)

Mohd, M.; Zainon, O.; Rasib, A. W.; Majid, Z.

2016-09-01

Concrete structures that exposed to marine environments are subjected to multiple deterioration mechanisms. An overview of the existing technology for submerged concrete, pressure resistant, concrete structures which related such as cracks, debonds, and delamination are discussed. Basic knowledge related to drowning durability such as submerged concrete structures in the maritime environment are the durability of a concrete and the ability to resist to weathering, chemical attack, abrasion or other deterioration processes. The measuring techniques and instrumentation for geometrical monitoring of submerged structural displacements have traditionally been categorized into two groups according to the two main groups, namely as geodetic surveying and geotechnical structural measurements of local displacements. This paper aims to study the durability of submerged concrete displacement and harmful effects of submerged concrete structures.

Passive monitoring using traffic noise recordings - case study on the Steinachtal Bridge

NASA Astrophysics Data System (ADS)

Salvermoser, Johannes; Stähler, Simon; Hadziioannou, Céline

2015-04-01

Civil structures age continuously. The early recognition of potentially critical damages is an important economical issue, but also one of public safety. Continuous tracking of small changes in the medium by using passive methods would offer an extension to established active non-destructive testing procedures at relatively low cost. Here we present a case study of structural monitoring using continuous recordings of traffic noise on a 200 meter long reinforced concrete highway bridge in Germany. Over two months of continuos geophone records are used in the frequency range of 2-8 Hz. Using passive image interferometry, evaluation of hourly cross-correlations between recordings at pairs of receivers yield velocity variations in the range of -1.5% to +2.1%. We were able to correlate our outcomes with temperature measurements of the same two month period. The measured velocity changes scale with the temperature variations with on average a dv/v of 0.064% per degree Celsius. This value is in accordance with other studies of concrete response to temperature, confirming that we are able to observe subtle changes with physical origin. It is shown that traffic noise is temporally homogenenous enough to fulfill the requirements of passive image interferometry.

Acoustic emission monitoring of concrete columns and beams strengthened with fiber reinforced polymer sheets

NASA Astrophysics Data System (ADS)

Ma, Gao; Li, Hui; Zhou, Wensong; Xian, Guijun

2012-04-01

Acoustic emission (AE) technique is an effective method in the nondestructive testing (NDT) field of civil engineering. During the last two decades, Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening concrete structures. The damage state of FRP strengthened concrete structures has become an important issue during the service period of the structure and it is a meaningful work to use AE technique as a nondestructive method to assess its damage state. The present study reports AE monitoring results of axial compression tests carried on basalt fiber reinforced polymer (BFRP) confined concrete columns and three-point-bending tests carried on BFRP reinforced concrete beams. AE parameters analysis was firstly utilized to give preliminary results of the concrete fracture process of these specimens. It was found that cumulative AE events can reflect the fracture development trend of both BFRP confined concrete columns and BFRP strengthened concrete beams and AE events had an abrupt increase at the point of BFRP breakage. Then the fracture process of BFRP confined concrete columns and BFRP strengthened concrete beams was studied through RA value-average frequency analysis. The RA value-average frequency tendencies of BFRP confined concrete were found different from that of BFRP strengthened concrete beams. The variation tendency of concrete crack patterns during the loading process was revealed.

Properties of concrete containing coconut shell powder (CSP) as a filler

NASA Astrophysics Data System (ADS)

Leman, A. S.; Shahidan, S.; Nasir, A. J.; Senin, M. S.; Zuki, S. S. Mohd; Ibrahim, M. H. Wan; Deraman, R.; Khalid, F. S.; Azhar, A. T. S.

2017-11-01

Coconut shellsare a type of agricultural waste which can be converted into useful material. Therefore,this study was conducted to investigate the properties of concrete which uses coconut shell powder (CSP) filler material and to define the optimum percentage of CSP which can be used asfiller material in concrete. Comparisons have been made between normal concrete mixes andconcrete containing CSP. In this study, CSP was added into concrete mixes invaryingpercentages (0%, 2%, 4%, 6%, 8% and 10%). The coconut shell was grounded into afine powder before use. Experimental tests which have been conducted in this study include theslump test, compressive test and splitting tensile strength test. CSP have the potential to be used as a concrete filler and thus the findings of this study may be applied to the construction industry. The use of CSP as a filler in concrete can help make the earth a more sustainable and greener place to live in.

Mathematical modeling of vibration processes in reinforced concrete structures for setting up crack initiation monitoring

NASA Astrophysics Data System (ADS)

Bykov, A. A.; Matveenko, B. P.; Serovaev, G. S.; Shardakov, I. N.; Shestakov, A. P.

2015-03-01

The contemporary construction industry is based on the use of reinforced concrete structures, but emergency situations resulting in fracture can arise in their exploitation. In a majority of cases, reinforced concrete fracture is realized as the process of crack formation and development. As a rule, the appearance of the first cracks does not lead to the complete loss of the carrying capacity but is a fracture precursor. One method for ensuring the safe operation of building structures is based on crack initiation monitoring. A vibration method for the monitoring of reinforced concrete structures is justified in this paper. An example of a reinforced concrete beam is used to consider all stages related to the analysis of the behavior of natural frequencies in the development of a crack-shaped defect and the use of the obtained numerical results for the vibration test method. The efficiency of the method is illustrated by the results of modeling of the physical part of the method related to the analysis of the natural frequency evolution as a response to the impact action in the crack development process.

Models of stochastic gene expression

NASA Astrophysics Data System (ADS)

Paulsson, Johan

2005-06-01

Gene expression is an inherently stochastic process: Genes are activated and inactivated by random association and dissociation events, transcription is typically rare, and many proteins are present in low numbers per cell. The last few years have seen an explosion in the stochastic modeling of these processes, predicting protein fluctuations in terms of the frequencies of the probabilistic events. Here I discuss commonalities between theoretical descriptions, focusing on a gene-mRNA-protein model that includes most published studies as special cases. I also show how expression bursts can be explained as simplistic time-averaging, and how generic approximations can allow for concrete interpretations without requiring concrete assumptions. Measures and nomenclature are discussed to some extent and the modeling literature is briefly reviewed.

Properties of Concrete partially replaced with Coconut Shell as Coarse aggregate and Steel fibres in addition to its Concrete volume

NASA Astrophysics Data System (ADS)

Kalyana Chakravarthy, P. R.; Janani, R.; Ilango, T.; Dharani, K.

2017-03-01

Cement is a binder material with various composition of Concrete but instantly it posses low tensile strength. The study deals with mechanical properties of that optimized fiber in comparison with conventional and coconut shell concrete. The accumulation of fibers arbitrarily dispersed in the composition increases the resistance to cracking, deflection and other serviceability conditions substantially. The steel fiber in extra is one of the revision in coconut shell concrete and the outcome of steel fiber in coconut shell concrete was to investigate and compare with the conventional concrete. For the given range of steel fibe from 0.5 to 2.0%, 12 beams and 36 cylindrical specimens were cast and tested to find the mechanical properties like flexural strength, split tensile, impact resistance and the modulus of elasticity of both conventional and coconut shell concrete has been studied and the test consequences are compared with the control concrete and coconut shell concrete for M25 Grade. It is fulfilled that, the steel fibers used in this venture has shown significant development in all the properties of conventional and coconut shell concrete while compared to controlled conventional and coconut shell concrete like, Flexural strength by 6.67 % for 1.0 % of steel fiber in conventional concrete and by 5.87 % for 1.5 % of steel fiber in coconut shell concrete.

Studies on residue-free decontaminants for chemical warfare agents.

PubMed

Wagner, George W

2015-03-17

Residue-free decontaminants based on hydrogen peroxide, which decomposes to water and oxygen in the environment, are examined as decontaminants for chemical warfare agents (CWA). For the apparent special case of CWA on concrete, H2O2 alone, without any additives, effectively decontaminates S-2-(diisopropylamino)ethyl O-ethyl methylphosphonothioate (VX), pinacolyl methylphosphorofluoridate (GD), and bis(2-choroethyl) sulfide (HD) in a process thought to involve H2O2 activation by surface-bound carbonates/bicarbonates (known H2O2 activators for CWA decontamination). A plethora of products are formed during the H2O2 decontamination of HD on concrete, and these are characterized by comparison to synthesized authentic compounds. As a potential residue-free decontaminant for surfaces other than concrete (or those lacking adsorbed carbonate/bicarbonate) H2O2 activation for CWA decontamination is feasible using residue-free NH3 and CO2 as demonstrated by reaction studies for VX, GD, and HD in homogeneous solution. Although H2O2/NH3/CO2 ("HPAC") decontaminants are active for CWA decontamination in solution, they require testing on actual surfaces of interest to assess their true efficacy for surface decontamination.

A Plasticity Model to Predict the Effects of Confinement on Concrete

NASA Astrophysics Data System (ADS)

Wolf, Julie

A plasticity model to predict the behavior of confined concrete is developed. The model is designed to implicitly account for the increase in strength and ductility due to confining a concrete member. The concrete model is implemented into a finite element (FE) model. By implicitly including the change in the strength and ductility in the material model, the confining material can be explicitly included in the FE model. Any confining material can be considered, and the effects on the concrete of failure in the confinement material can be modeled. Test data from a wide variety of different concretes utilizing different confinement methods are used to estimate the model parameters. This allows the FE model to capture the generalized behavior of concrete under multiaxial loading. The FE model is used to predict the results of tests on reinforced concrete members confined by steel hoops and fiber reinforced polymer (FRP) jackets. Loading includes pure axial load and axial load-moment combinations. Variability in the test data makes the model predictions difficult to compare but, overall, the FE model is able to capture the effects of confinement on concrete. Finally, the FE model is used to compare the performance of steel hoop to FRP confined sections, and of square to circular cross sections. As expected, circular sections are better able to engage the confining material, leading to higher strengths. However, higher strains are seen in the confining material for the circular sections. This leads to failure at lower axial strain levels in the case of the FRP confined sections. Significant differences are seen in the behavior of FRP confined members and steel hoop confined members. Failure in the FRP members is always determined by rupture in the composite jacket. As a result, the FRP members continue to take load up to failure. In contrast, the steel hoop confined sections exhibit extensive strain softening before failure. This comparison illustrates the usefulness of the concrete model as a tool for designers. Overall, the concrete model provides a flexible and powerful method to predict the performance of confined concrete.

Substratum type affects recruitment and development of marine assemblages over artificial substrata: A case study in the Alboran Sea

NASA Astrophysics Data System (ADS)

Sempere-Valverde, Juan; Ostalé-Valriberas, Enrique; Farfán, Gonzalo M.; Espinosa, Free

2018-05-01

There are more than 27,000 harbours along coasts worldwide and construction is expected to increase. The development and application of new ecological engineering ideas, for both old and new structures, is now imperative in order to reduce perturbation on marine coastal biota and to avoid the spread of non-native species. In this study, the early benthic assessment of subtidal and intertidal communities is tracked on five artificial substrata differing in origin, roughness, and chemical composition: Oyster Sandstone, Limestone, Gabbro, Slate and Concrete. Within substrata, Sandstone was the roughest on a 1-2 mm scale. Also, Sandstone and Limestone had predominantly calcareous composition while silicon was abundant in Concrete, Gabbro and Slate. In the intertidal zone, results showed that primary productivity and diatom abundance markedly increased with substratum roughness. In the subtidal zone, species richness and diversity over experimental substrata were lower than in adjacent rocky reefs. Nonetheless, during the first year of colonization communities varied within the experimental substrata. Coverage was higher on Sandstone than Concrete and Gabbro, and species richness was higher on Sandstone than Limestone. The differences are related to intrinsic substratum-type characteristics and showed Limestone, Gabbro and Concrete hold relatively poor ecological benefits in the first phases of ecological succession. The results may help to promote future research in this field and to test different substrata combinations and heterogeneities, for more environmentally sustainable surfaces in design of coastal structures.

Development of abstract mathematical reasoning: the case of algebra

PubMed Central

Susac, Ana; Bubic, Andreja; Vrbanc, Andrija; Planinic, Maja

2014-01-01

Algebra typically represents the students’ first encounter with abstract mathematical reasoning and it therefore causes significant difficulties for students who still reason concretely. The aim of the present study was to investigate the developmental trajectory of the students’ ability to solve simple algebraic equations. 311 participants between the ages of 13 and 17 were given a computerized test of equation rearrangement. Equations consisted of an unknown and two other elements (numbers or letters), and the operations of multiplication/division. The obtained results showed that younger participants are less accurate and slower in solving equations with letters (symbols) than those with numbers. This difference disappeared for older participants (16–17 years), suggesting that they had reached an abstract reasoning level, at least for this simple task. A corresponding conclusion arises from the analysis of their strategies which suggests that younger participants mostly used concrete strategies such as inserting numbers, while older participants typically used more abstract, rule-based strategies. These results indicate that the development of algebraic thinking is a process which unfolds over a long period of time. In agreement with previous research, we can conclude that, on average, children at the age of 15–16 transition from using concrete to abstract strategies while solving the algebra problems addressed within the present study. A better understanding of the timing and speed of students’ transition from concrete arithmetic reasoning to abstract algebraic reasoning might help in designing better curricula and teaching materials that would ease that transition. PMID:25228874

Development of abstract mathematical reasoning: the case of algebra.

PubMed

Susac, Ana; Bubic, Andreja; Vrbanc, Andrija; Planinic, Maja

2014-01-01

Algebra typically represents the students' first encounter with abstract mathematical reasoning and it therefore causes significant difficulties for students who still reason concretely. The aim of the present study was to investigate the developmental trajectory of the students' ability to solve simple algebraic equations. 311 participants between the ages of 13 and 17 were given a computerized test of equation rearrangement. Equations consisted of an unknown and two other elements (numbers or letters), and the operations of multiplication/division. The obtained results showed that younger participants are less accurate and slower in solving equations with letters (symbols) than those with numbers. This difference disappeared for older participants (16-17 years), suggesting that they had reached an abstract reasoning level, at least for this simple task. A corresponding conclusion arises from the analysis of their strategies which suggests that younger participants mostly used concrete strategies such as inserting numbers, while older participants typically used more abstract, rule-based strategies. These results indicate that the development of algebraic thinking is a process which unfolds over a long period of time. In agreement with previous research, we can conclude that, on average, children at the age of 15-16 transition from using concrete to abstract strategies while solving the algebra problems addressed within the present study. A better understanding of the timing and speed of students' transition from concrete arithmetic reasoning to abstract algebraic reasoning might help in designing better curricula and teaching materials that would ease that transition.

Connection Capacity of the Transition Zone in Steel-Concrete Hybrid Beam

NASA Astrophysics Data System (ADS)

Kozioł, Piotr; Kożuch, Maciej; Lorenc, Wojciech; Rowiński, Sławomir

2017-06-01

The problem of transition zone of structural steel element connected to concrete is discussed in the following paper. This zone may be located for instance in specific bridge composite girder. In such case the composite beam passes smoothly into concrete beam. Because of several dowels usage in the transition zone, the problem of uneven force distribution were discussed through analogy to bolted and welded connections. The authors present innovative solution of transition zone and discuss the results, with emphasis put on the transition zone structural response in term of bending capacity, failure model and force distribution on the connection length. The article wider the already executed experimental test and presents its newest results.

Computer-Aided Structural Engineering (CASE) Project. A Case Project Study of Finite Element Analysis of Concrete Flat Slabs.

DTIC Science & Technology

1987-01-01

CLASSIFICATION OF THIS PAGE rWhon Dot Entered) REPORT DOCUMENTATION PAGE READ INSTRUCTIONS BEFORE COMPLETING FORM I REPORT NUMBER 12. GOVT ACCESSION NO. 3...TO 383 a 4o0IFY 1 10 3 FROM 33 TO 30 TO 30 10 33 TO 30 TO 30 TO 30 TO 33 eEI 3 ELEA 19 351 8 FROM Ss7 33 105860 41 toD 368 41 TO ON 33 TO 347 30

Development of design parameters for mass concrete using finite element analysis : final report, February 2010.

DOT National Transportation Integrated Search

2010-02-01

A finite element model for analysis of mass concrete was developed in this study. To validate the developed model, large concrete blocks made with four different mixes of concrete, typical of use in mass concrete applications in Florida, were made an...

Material and Structural Performance Evaluations of Hwangtoh Admixtures and Recycled PET Fiber-Added Eco-Friendly Concrete for CO2 Emission Reduction

PubMed Central

Koo, Bon-Min; Kim, Jang-Ho Jay; Kim, Sung-Bae; Mun, Sungho

2014-01-01

In order to reduce carbon dioxide (CO2) emissions and produce an eco-friendly construction material, a type of concrete that uses a minimal amount of cement, yet still retains equivalent properties to ordinary cement concrete, has been developed and studied all over the world. Hwangtoh, a type of red clay broadly deposited around the world, has traditionally been considered an eco-friendly construction material, with bonus advantages of having health and cost benefits. Presently, Hwangtoh is not commonly used as a modern construction material due to properties such as low strength and high rates of shrinkage cracking. Recent studies, however, have shown that Hwangtoh can be used as a mineral admixture to improve the strength of concrete. In addition, polyethylene terephthalate (PET) fibers recycled from PET bottle waste can be used to control shrinkage cracks in Hwangtoh concrete. Therefore, in this study, performance verification is conducted on newly developed Hwangtoh concrete mixed with short recycled PET fibers. The results show that Hwangtoh concrete has compressive strength, elastic modulus, and pH properties that are similar to these features in ordinary cement concrete. The properties of carbonation depth and creep strain of Hwangtoh concrete, however, are larger and smaller, respectively, than in ordinary cement concrete. According to flexural tests, reinforced concrete (RC) specimens cast with Hwangtoh admixtures (with and without PET fibers) possess similar or better capacities than ordinary RC specimens. The addition of PET fibers significantly improves the structural ductility of RC specimens under normal environmental conditions. However, the implementations of the concrete in aggressive environment must be carefully considered, since a previous study result indicates degradation of its durability performance in aggressive environments, such as seawater [1]. The results of this study validate the possibility of using eco-friendly Hwangtoh concrete reinforced with recycled PET fibers as a structural material for modern construction. PMID:28788171

Material and Structural Performance Evaluations of Hwangtoh Admixtures and Recycled PET Fiber-Added Eco-Friendly Concrete for CO₂ Emission Reduction.

PubMed

Koo, Bon-Min; Kim, Jang-Ho Jay; Kim, Sung-Bae; Mun, Sungho

2014-08-19

In order to reduce carbon dioxide (CO₂) emissions and produce an eco-friendly construction material, a type of concrete that uses a minimal amount of cement, yet still retains equivalent properties to ordinary cement concrete, has been developed and studied all over the world. Hwangtoh, a type of red clay broadly deposited around the world, has traditionally been considered an eco-friendly construction material, with bonus advantages of having health and cost benefits. Presently, Hwangtoh is not commonly used as a modern construction material due to properties such as low strength and high rates of shrinkage cracking. Recent studies, however, have shown that Hwangtoh can be used as a mineral admixture to improve the strength of concrete. In addition, polyethylene terephthalate (PET) fibers recycled from PET bottle waste can be used to control shrinkage cracks in Hwangtoh concrete. Therefore, in this study, performance verification is conducted on newly developed Hwangtoh concrete mixed with short recycled PET fibers. The results show that Hwangtoh concrete has compressive strength, elastic modulus, and pH properties that are similar to these features in ordinary cement concrete. The properties of carbonation depth and creep strain of Hwangtoh concrete, however, are larger and smaller, respectively, than in ordinary cement concrete. According to flexural tests, reinforced concrete (RC) specimens cast with Hwangtoh admixtures (with and without PET fibers) possess similar or better capacities than ordinary RC specimens. The addition of PET fibers significantly improves the structural ductility of RC specimens under normal environmental conditions. However, the implementations of the concrete in aggressive environment must be carefully considered, since a previous study result indicates degradation of its durability performance in aggressive environments, such as seawater [1]. The results of this study validate the possibility of using eco-friendly Hwangtoh concrete reinforced with recycled PET fibers as a structural material for modern construction.

Study on the strength characteristics of High strength concrete with Micro steel fibers

NASA Astrophysics Data System (ADS)

Gowdham, K.; Sumathi, A.; Saravana Raja Mohan, K.

2017-07-01

The study of High Strength Concrete (HSC) has become interesting as concrete structures grow taller and larger. The usage of HSC in structures has been increased worldwide and has begun to make an impact in India. Ordinary cementitious materials are weak under tensile loads and fiber reinforced cementitious composites (FRCCs) have been developed to improve this weak point. High Strength concrete containing Alccofine as mineral admixture and reinforced with micro steel fibers were cast and tested to study the mechanical properties. The concrete were designed to have compressive strength of 60 MPa. Mixtures containing 0% and 10% replacement of cement by Alccofine and with 1%, 2% and 3% of micro steel fibers by weight of concrete were prepared. Mixtures incorporating Alccofine with fibers developed marginal increase in strength properties at all curing days when compared to control concrete.

Children's Construction of Mathematical Knowledge in Solving Novel Isomorphic Problems in Concrete and Written Form.

ERIC Educational Resources Information Center

English, Lyn D.

1996-01-01

Presents case study data of low- and high-achieving nine-year olds focusing on construction and analogical transfer of mathematical knowledge during novel problem solving, as reflected in strategies for dealing with isomorphic combinatorial problems presented in hands-on and written form. Results showed that achievement level does not predict…

Local Instruction Theory on Division in Mathematics GASING: The Case of Rural Area's Student in Indonesia

ERIC Educational Resources Information Center

Prahmana, Rully Charitas Indra; Suwasti, Petra

2014-01-01

Several studies on learning mathematics for rural area's student indicate that students have difficulty in understanding the concept of division operation. Students are more likely to be introduced by the use of the formula without involving the concept itself and learning division separate the concrete situation of learning process. This…

Habits of Mind: A Case Study of Three Teachers' Experiences with a Mindfulness-Based Intervention

ERIC Educational Resources Information Center

Dunn, Molly S.

2017-01-01

K-12 teachers encounter numerous occupational stressors as part of their profession, and these stressors place them at risk of job-related stress and burnout (Maslach & Jackson, 1981; Maslach, Schaufeli, & Leiter, 2001). Given the prevalence of stress and burnout among school personnel, concrete interventions designed to address the unique…

Contents or Ideology? A Case Study of Mathematical Teaching in North Korea

ERIC Educational Resources Information Center

Karp, Alexander; Lee, JungHang

2010-01-01

This article addresses mathematics education in one of the most closed countries in the world, North Korea. It is known that ideology permeates all aspects of life in North Korea, but how exactly do the ideological and substantive mathematical components interact in mathematics education there? What concrete form does this interaction take in…

Existing Whole-House Solutions Case Study: Habitat for Humanity South Sarasota County, Venice, Florida

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

none,

2011-11-01

PNNL and Calcs Plus helped the South Sarasota County Florida Habitat for Humanity retrofit a 1978 single-story home by stripping old drywall, air sealing concrete block walls, and installing rigid insulation, furring strips, and new drywall. The attic was sealed and insulated with spray foam to house a new heat pump.

Flexural strength of self compacting fiber reinforced concrete beams using polypropylene fiber: An experimental study

NASA Astrophysics Data System (ADS)

Lisantono, Ade; Praja, Baskoro Abdi; Hermawan, Billy Nouwen

2017-11-01

One of the methods to increase the tensile strength of concrete is adding a fiber material into the concrete. While to reduce a noise in a construction project, a self compacting concrete was a good choices in the project. This paper presents an experimental study of flexural behavior and strength of self compacting fiber reinforced concrete (RC) beams using polypropylene fiber. The micro monofilament polypropylene fibers with the proportion 0.9 kg/m3 of concrete weight were used in this study. Four beam specimens were cast and tested in this study. Two beams were cast of self compacting reinforced concrete without fiber, and two beams were cast of self compacting fiber reinforced concrete using polypropylene. The beams specimen had the section of (180×260) mm and the length was 2000 mm. The beams had simple supported with the span of 1800 mm. The longitudinal reinforcements were using diameter of 10 mm. Two reinforcements of Ø10 mm were put for compressive reinforcement and three reinforcements of Ø10 mm were put for tensile reinforcement. The shear reinforcement was using diameter of 8 mm. The shear reinforcements with spacing of 100 mm were put in the one fourth near to the support and the spacing of 150 mm were put in the middle span. Two points loading were used in the testing. The result shows that the load-carrying capacity of the self compacting reinforced concrete beam using polypropylene was a little bit higher than the self compacting reinforced concrete beam without polypropylene. The increment of load-carrying capacity of self compacting polypropylene fiber reinforced concrete was not so significant because the increment was only 2.80 % compare to self compacting non fiber reinforced concrete. And from the load-carrying capacity-deflection relationship curves show that both the self compacting polypropylene fiber reinforced concrete beam and the self compacting non fiber reinforced concrete beam were ductile beams.

Damage Detection in Railway Prestressed Concrete Sleepers using Acoustic Emission

NASA Astrophysics Data System (ADS)

Clark, A.; Kaewunruen, S.; Janeliukstis, R.; Papaelias, M.

2017-10-01

Prestressed concrete sleepers (or railroad ties) are safety-critical elements in railway tracks that distribute the wheel loads from the rails to the track support system. Over a period of time, the concrete sleepers age and deteriorate in addition to experiencing various types of static and dynamic loading conditions, which are attributable to train operations. In many cases, structural cracks can develop within the sleepers due to high intensity impact loads or due to poor track maintenance. Often, cracks of sleepers develop and present at the midspan due to excessive negative bending. These cracks can cause broken sleepers and sometimes called ‘center bound’ problem in railway lines. This paper is the world first to present an application of non-destructive acoustic emission technology for damage detection in railway concrete sleepers. It presents experimental investigations in order to detect center-bound cracks in railway prestressed concrete sleepers. Experimental laboratory testing involves three-point bending tests of four concrete sleepers. Three-point bending tests correspond to a real failure mode, when the loads are not transferred uniformly to the ballast support. It is observed that AE sensing provides an accurate means for detecting the location and magnitude of cracks in sleepers. Sensor location criticality is also highlighted in the paper to demonstrate the reliability-based damage detection of the sleepers.

USSR Report, Construction and Related Industries, No. 99

DTIC Science & Technology

1983-11-10

been created and is continuing to be developed in our republic. Many types of contruction materials and products have been delivered to us in large...grade wood with excess moisture content. Most of the window and door frames are delivered unpainted, without glass, and without installation of...reinforced concrete is placed with the aid of cranes, and about 80 percent of concrete work is done with the aid of wood casings. With such

Benchmark Design and Installation: A synthesis of Existing Information.

DTIC Science & Technology

1987-07-01

casings (15 ft deep) drilled to rock and filled with concrete. Disks - 1 . Set on vertically stable structures (e.g., dam monoliths). 2 . Set in rock ...Structural movement survey 1 . Rock outcrops (first choice) -- chiseled square on high point. 2 . Massive concrete structure (second choice) - cut square on...bolt marker (type 2 ). 58,. % %--"% %I 1 ± 4 -I,.- Table Cl. Recomnded benchmarks. Type of condition or terrain Type of markert Bedrock, rock outcrops

A review on carbonation study in concrete

NASA Astrophysics Data System (ADS)

Venkat Rao, N.; Meena, T.

2017-11-01

In this paper the authors have reviewed the carbonation studies which are a vital durability property of concrete. One of the major causes for deterioration and destruction of concrete is carbonation. The mechanism of carbonation involves the penetration carbon dioxide (CO2) into the concrete porous system to form an environment by reducing the pH around the reinforcement and initiation of the corrosion process. The paper also endeavours to focus and elucidate the gravity of importance, the process and chemistry of carbonate and how the various parameters like water/cement ratio, curing, depth of concrete cones, admixtures, grade of concrete, strength of concrete, porosity and permeability effect carbonation in concrete. The role of Supplementary Cementitious Materials (SCMs) like Ground granulated Blast Furnace Slag (GGBS) and Silica Fume (SF) has also been reviewed along with the influence of depth of carbonation.

Structural and mechanical study of concrete made from cementitious materials of low environmental impact

NASA Astrophysics Data System (ADS)

González, A. K.; Montaño, A. M.; González, C. P.; Santos, A.

2017-12-01

This work shows the results obtained by replacing Type I Portland®, by cementitious geopolymers materials, derived from minerals, in concrete mixtures. Synthesis of both geopolymers through alkaline activation of two alluminosilicates: Bentonite and Pumice with sodium silicate (Na2SiO3). XRD, SEM and XRDE are used to structural study of new geopolymers. Concrete mixtures with replacement of Portland have 10% and 30% of geopolymer. Finally, concrete mortars formed were mechanically analysed according to ICONTEC 220 at 7, 14, 28, 41, 90 and 120 days of cure. Results shows that compressive strength of concrete from Bentonite and Pumice are almost the same for the standard concrete at 28 days of cure. At 90 days of cure, compression resistance of concrete from Pumice at 10% is even higher than those that standard concrete shows.

Pervious concrete using fly ash aggregate as coarse aggregate-an experimental study

NASA Astrophysics Data System (ADS)

Dash, Subhakanta; Kar, Biswabandita; Mukherjee, Partha Sarathi

2018-05-01

The present study deals with the fabrication of pervious concrete from fly ash aggregates. The pervious concrete were obtained by the mixture of three different size fly ash aggregates (4.75 mm,9.5 mm,12.5 mm), Portland cement, water with little amount of sand or without sand. Admixtures like Silica fume(SF) and Super plasticizer are added to the mixture to enhance the strength of concrete. Trial being taken on preparation of Fly ash based pervious concrete (FPC) with different w/c ratio i.e. 0.30, 0.35 and 0.40 respectively. Tests such as porosity, permeability and compressive, strength are studied for this concrete material and the result concluded that the concrete when cured for 28 days its compressive strength falls in between 7.15 - 15.74 MPa and permeability 9.38 - 16.07 mm/s with porosity 27.59 - 34.05% and these are suited to be used as for use as an environment friendly concrete.

Effect of notch position on fracture energy for foamed concrete

NASA Astrophysics Data System (ADS)

Naqiuddin Zamri, Mohd; Rahman, Norashidah Abd; Jaini, Zainorizuan Mohd; Shamila Bahador, Nurul

2017-11-01

Foamed concrete is one of the lightweight concrete used to replace normal concrete. Foamed concrete has potential as a building construction material in Malaysia due to low density range. However, the behavior of fracture energy on foamed concrete still under investigation. Therefore, a study to determine the fracture energy of foamed concrete was conducted. In this study, foamed concrete fracture energy was obtained using the three-point bending test methods develop by RILEM and Hillerborg. A total of 12 beams with different types of notch and positions of notch were tested on the load-deflection condition. In addition, a total of 9 cube samples were cast to support the result of fracture energy by using model from Bazant and Becq-Giraudon and Comite Euro-International du Beton (CEB). Results showed the far the position of the notch from midpoint, the higher the value of fracture energy. In this study, the value of fracture energy ranges between 15 N/m and 40 N/m.

Evaluation of ilmenite serpentine concrete and ordinary concrete as nuclear reactor shielding

NASA Astrophysics Data System (ADS)

Abulfaraj, Waleed H.; Kamal, Salah M.

1994-07-01

The present study involves adapting a formal decision methodology to the selection of alternative nuclear reactor concretes shielding. Multiattribute utility theory is selected to accommodate decision makers' preferences. Multiattribute utility theory (MAU) is here employed to evaluate two appropriate nuclear reactor shielding concretes in terms of effectiveness to determine the optimal choice in order to meet the radiation protection regulations. These concretes are Ordinary concrete (O.C.) and Ilmenite Serpentile concrete (I.S.C.). These are normal weight concrete and heavy heat resistive concrete, respectively. The effectiveness objective of the nuclear reactor shielding is defined and structured into definite attributes and subattributes to evaluate the best alternative. Factors affecting the decision are dose received by reactor's workers, the material properties as well as cost of concrete shield. A computer program is employed to assist in performing utility analysis. Based upon data, the result shows the superiority of Ordinary concrete over Ilmenite Serpentine concrete.

Nonlinear micromechanics-based finite element analysis of the interfacial behaviour of FRP-strengthened reinforced concrete beams

NASA Astrophysics Data System (ADS)

Abd El Baky, Hussien

This research work is devoted to theoretical and numerical studies on the flexural behaviour of FRP-strengthened concrete beams. The objectives of this research are to extend and generalize the results of simple experiments, to recommend new design guidelines based on accurate numerical tools, and to enhance our comprehension of the bond performance of such beams. These numerical tools can be exploited to bridge the existing gaps in the development of analysis and modelling approaches that can predict the behaviour of FRP-strengthened concrete beams. The research effort here begins with the formulation of a concrete model and development of FRP/concrete interface constitutive laws, followed by finite element simulations for beams strengthened in flexure. Finally, a statistical analysis is carried out taking the advantage of the aforesaid numerical tools to propose design guidelines. In this dissertation, an alternative incremental formulation of the M4 microplane model is proposed to overcome the computational complexities associated with the original formulation. Through a number of numerical applications, this incremental formulation is shown to be equivalent to the original M4 model. To assess the computational efficiency of the incremental formulation, the "arc-length" numerical technique is also considered and implemented in the original Bazant et al. [2000] M4 formulation. Finally, the M4 microplane concrete model is coded in FORTRAN and implemented as a user-defined subroutine into the commercial software package ADINA, Version 8.4. Then this subroutine is used with the finite element package to analyze various applications involving FRP strengthening. In the first application a nonlinear micromechanics-based finite element analysis is performed to investigate the interfacial behaviour of FRP/concrete joints subjected to direct shear loadings. The intention of this part is to develop a reliable bond--slip model for the FRP/concrete interface. The bond--slip relation is developed considering the interaction between the interfacial normal and shear stress components along the bonded length. A new approach is proposed to describe the entire tau-s relationship based on three separate models. The first model captures the shear response of an orthotropic FRP laminate. The second model simulates the shear characteristics of an adhesive layer, while the third model represents the shear nonlinearity of a thin layer inside the concrete, referred to as the interfacial layer. The proposed bond--slip model reflects the geometrical and material characteristics of the FRP, concrete, and adhesive layers. Two-dimensional and three-dimensional nonlinear displacement-controlled finite element (FE) models are then developed to investigate the flexural and FRP/concrete interfacial responses of FRP-strengthened reinforced concrete beams. The three-dimensional finite element model is created to accommodate cases of beams having FRP anchorage systems. Discrete interface elements are proposed and used to simulate the FRP/concrete interfacial behaviour before and after cracking. The FE models are capable of simulating the various failure modes, including debonding of the FRP either at the plate end or at intermediate cracks. Particular attention is focused on the effect of crack initiation and propagation on the interfacial behaviour. This study leads to an accurate and refined interpretation of the plate-end and intermediate crack debonding failure mechanisms for FRP-strengthened beams with and without FRP anchorage systems. Finally, the FE models are used to conduct a parametric study to generalize the findings of the FE analysis. The variables under investigation include two material characteristics; namely, the concrete compressive strength and axial stiffness of the FRP laminates as well as three geometric properties; namely, the steel reinforcement ratio, the beam span length and the beam depth. The parametric study is followed by a statistical analysis for 43 strengthened beams involving the five aforementioned variables. The response surface methodology (RSM) technique is employed to optimize the accuracy of the statistical models while minimizing the numbers of finite element runs. In particular, a face-centred design (FCD) is applied to evaluate the influence of the critical variables on the debonding load and debonding strain limits in the FRP laminates. Based on these statistical models, a nonlinear statistical regression analysis is used to propose design guidelines for the FRP flexural strengthening of reinforced concrete beams. (Abstract shortened by UMI.)

A study on the performance of concrete containing recycled aggregates and ceramic as materials replacement

NASA Astrophysics Data System (ADS)

Azmi, N. B.; Khalid, F. S.; Irwan, J. M.; Anting, N.; Mazenan, P. N.

2017-11-01

Natural fine aggregate materials are commonly used in development and commercial construction in Malaysia. In fact, concrete production was increased as linear with the growing Malaysia economy. However, an issue was production of concrete was to locate adequate sources of natural fine aggregates. There lot of studies have been conducted in order to replace the fine aggregate in which natural fine aggregate replace with the waste material in concrete preparation. Therefore, this study aims to utilize the Recycled Concrete Aggregate (RCA) and ceramic waste which has great potential to replace the natural aggregate in concrete mix with different type of method, admixture, and parameters. This research were focused on compressive strength and water absorption test to determine the optimum mix ratio of concrete mix. The concrete aggregate was chosen due to improvement capillary bonding mechanisms and ceramic presented similar strength compared to the conventional concrete using natural aggregate. Percent of replacement have been used in this study was at 25%, 35% and 45% of the RCA and 5%, 10% and 15% for ceramic, respectively. Furthermore, this research was conduct to find the optimum percentage of aggregate replacement, using water-cement ratio of 0.55 with concrete grade 25/30. The best percentage of replacement was the RCA35% C15% with the compressive strength of 34.72 MPa and the water absorption was satisfied.

Thermal behavior of cylindrical buckling restrained braces at elevated temperatures.

PubMed

Talebi, Elnaz; Tahir, Mahmood Md; Zahmatkesh, Farshad; Yasreen, Airil; Mirza, Jahangir

2014-01-01

The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system.

An Exploratory Compressive Strength Of Concrete Containing Modified Artificial Polyethylene Aggregate (MAPEA)

NASA Astrophysics Data System (ADS)

Hadipramana, J.; Mokhatar, S. N.; Samad, A. A. A.; Hakim, N. F. A.

2016-11-01

Concrete is widely used in the world as building and construction material. However, the constituent materials used in concrete are high cost when associated with the global economic recession. This exploratory aspires to have an alternative source of replacing natural aggregate with plastic wastes. An investigation of the Modified Artificial Polyethylene Aggregate (MAPEA) as natural aggregate replacement in concrete through an experimental work was conducted in this study. The MAPEA was created to improve the bonding ability of Artificial Polyethylene Aggregate (APEA) with the cement paste. The concrete was mixed with 3%, 6%, 9%, and 12% of APEA and MAPEA for 14 and 28 curing days, respectively. Furthermore, the compressive strength test was conducted to find out the optimum composition of MAPEA in concrete and compared to the APEA concrete. Besides, this study observed the influence and behaviour of MAPEA in concrete. Therefore, the Scanning Electron Microscopy was applied to observe the microstructure of MAPEA and APEA concrete. The results showed the use of high composition of an artificial aggregate resulted inferior strength on the concrete and 3% MAPEA in the concrete mix was highest compressive strength than other content. The modification of APEA (MAPEA) concrete increased its strength due to its surface roughness. However, the interfacial zone cracking was still found and decreased the strength of MAPEA concrete especially when it was age 28 days.

Silica dust exposures during selected construction activities.

PubMed

Flanagan, Mary Ellen; Seixas, Noah; Majar, Maria; Camp, Janice; Morgan, Michael

2003-01-01

This study characterized exposure for dust-producing construction tasks. Eight common construction tasks were evaluated for quartz and respirable dust exposure by collecting 113 personal task period samples for cleanup; demolition with handheld tools; concrete cutting; concrete mixing; tuck-point grinding; surface grinding; sacking and patching concrete; and concrete floor sanding using both time-integrating filter samples and direct-reading respirable dust monitors. The geometric mean quartz concentration was 0.10 mg/m(3) (geometric standard deviation [GSD]=4.88) for all run time samples, with 71% exceeding the threshold limit value. Activities with the highest exposures were surface grinding, tuck-point grinding, and concrete demolition (GM[GSD] of 0.63[4.12], 0.22[1.94], and 0.10[2.60], respectively). Factors recorded each minute were task, tool, work area, respiratory protection and controls used, estimated cross draft, and whether anyone nearby was making dust. Factors important to exposure included tool used, work area configuration, controls employed, cross draft, and in some cases nearby dust. More protective respirators were employed as quartz concentration increased, although respiratory protection was found to be inadequate for 42% of exposures. Controls were employed for only 12% of samples. Exposures were reduced with three controls: box fan for surface grinding and floor sanding, and vacuum/shroud for surface grinding, with reductions of 57, 50, and 71%, respectively. Exposures were higher for sweeping compound, box fan for cleanup, ducted fan dilution, and wetted substrate. Construction masons and laborers are frequently overexposed to silica. The usual protection method, respirators, was not always adequate, and engineering control use was infrequent and often ineffective.

Design and evaluation of high-volume fly ash (HVFA) concrete mixes, report B : bond behavior of mild reinforcing steel in HVFA concrete.

DOT National Transportation Integrated Search

2012-10-01

The main objective of this study was to determine the effect on bond performance : of high-volume fly ash (HVFA) concrete. The HVFA concrete test program consisted of : comparing the bond performance of two concrete mix designs with 70% cement : repl...

High-performance concrete : applying life-cycle cost analysis and developing specifications.

DOT National Transportation Integrated Search

2016-12-01

Numerous studies and transportation agency experience across the nation have established that highperformance concrete (HPC) technology improves concrete quality and extends the service life of concrete structures at risk of chlorideinduced cor...

Life Cycle Cost Analysis of Ready Mix Concrete Plant

NASA Astrophysics Data System (ADS)

Topkar, V. M.; Duggar, A. R.; Kumar, A.; Bonde, P. P.; Girwalkar, R. S.; Gade, S. B.

2013-11-01

India, being a developing nation is experiencing major growth in its infrastructural sector. Concrete is the major component in construction. The requirement of good quality of concrete in large quantities can be fulfilled by ready mix concrete batching and mixing plants. The paper presents a technique of applying the value engineering tool life cycle cost analysis to a ready mix concrete plant. This will help an investor or an organization to take investment decisions regarding a ready mix concrete facility. No economic alternatives are compared in this study. A cost breakdown structure is prepared for the ready mix concrete plant. A market survey has been conducted to collect realistic costs for the ready mix concrete facility. The study establishes the cash flow for the ready mix concrete facility helpful in investment and capital generation related decisions. Transit mixers form an important component of the facility and are included in the calculations. A fleet size for transit mixers has been assumed for this purpose. The life cycle cost has been calculated for the system of the ready mix concrete plant and transit mixers.

An Experimental Study of High Strength-High Volume Fly Ash Concrete for Sustainable Construction Industry

NASA Astrophysics Data System (ADS)

Kate, Gunavant K.; Thakare, Sunil B., Dr.

2017-08-01

Concrete is the most widely used building material in the construction of infrastructures such as buildings, bridges, highways, dams, and many other facilities. This paper reports the development, the basic idea, the main properties of high strength-high volume fly ash with application in concrete associated with the development and implementation of Sustainable Properties of High Volume Fly Ash Concrete (HVFAC) Mixtures and Early Age Shrinkage and mechanical properties of concrete for 7,28,56 and 90days. Another alternative to make environment-friendly concrete is the development of high strength-high-volume fly ash concrete which is an synthesized from materials of geological origin or by-product materials such as fly ash which is rich in silicon and aluminum. In this paper 6 concrete mixtures were produced to evaluate the effect of key parameters on the mechanical properties of concrete and its behavior. The study key parameters are; binder material content, cement replacement ratios, and the steel fibers used to High Volume Fly Ash mixtures for increasing performance of concrete.

Reactive powder based concretes: Mechanical properties, durability and hybrid use with OPC

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

Cwirzen, A.; Penttala, V.; Vornanen, C.

2008-10-15

The basic mechanical properties, frost durability and the bond strength with normal strength concretes of the ultra high strength (UHS) mortars and concretes were studied. The produced mixes had plastic or fluid-like consistency. The 28-day compressive strength varied between 170 and 202 MPa for the heat-treated specimens and between 130 and 150 MPa for the non-heat-treated specimens. The shrinkage values were two times higher for the UHS mortars in comparison with the UHS concretes. After the initial shrinkage, swelling was noticed in the UHS mortars. The lowest creep values were measured for the non-heat-treated UHS concretes. The frost-deicing salts durabilitymore » of the UHS mortars and concretes appeared to be very good even despite the increased water uptake of the UHS concretes. The study of the hybrid concrete beams indicated the formation of low strength transition zone between the UHS mortar and normal strength concrete.« less

Shape Effect of Electrochemical Chloride Extraction in Structural Reinforced Concrete Elements Using a New Cement-Based Anodic System

PubMed Central

Carmona, Jesús; Climent, Miguel-Ángel; Antón, Carlos; de Vera, Guillem; Garcés, Pedro

2015-01-01

This article shows the research carried out by the authors focused on how the shape of structural reinforced concrete elements treated with electrochemical chloride extraction can affect the efficiency of this process. Assuming the current use of different anode systems, the present study considers the comparison of results between conventional anodes based on Ti-RuO2 wire mesh and a cement-based anodic system such as a paste of graphite-cement. Reinforced concrete elements of a meter length were molded to serve as laboratory specimens, to closely represent authentic structural supports, with circular and rectangular sections. Results confirm almost equal performances for both types of anode systems when electrochemical chloride extraction is applied to isotropic structural elements. In the case of anisotropic ones, such as rectangular sections with no uniformly distributed rebar, differences in electrical flow density were detected during the treatment. Those differences were more extreme for Ti-RuO2 mesh anode system. This particular shape effect is evidenced by obtaining the efficiencies of electrochemical chloride extraction in different points of specimens.

Acoustic emission of fire damaged fiber reinforced concrete

NASA Astrophysics Data System (ADS)

Mpalaskas, A. C.; Matikas, T. E.; Aggelis, D. G.

2016-04-01

The mechanical behavior of a fiber-reinforced concrete after extensive thermal damage is studied in this paper. Undulated steel fibers have been used for reinforcement. After being exposed to direct fire action at the temperature of 850°C, specimens were subjected to bending and compression in order to determine the loss of strength and stiffness in comparison to intact specimens and between the two types. The fire damage was assessed using nondestructive evaluation techniques, specifically ultrasonic pulse velocity (UPV) and acoustic emission (AE). Apart from the strong, well known, correlation of UPV to strength (both bending and compressive), AE parameters based mainly on the frequency and duration of the emitted signals after cracking events showed a similar or, in certain cases, better correlation with the mechanical parameters and temperature. This demonstrates the sensitivity of AE to the fracture incidents which eventually lead to failure of the material and it is encouraging for potential in-situ use of the technique, where it could provide indices with additional characterization capability concerning the mechanical performance of concrete after it subjected to fire.

Optimization of superplasticizer in portland pozzolana cement mortar and concrete

NASA Astrophysics Data System (ADS)

Sathyan, Dhanya; Anand, K. B.; Mini, K. M.; Aparna, S.

2018-02-01

Chemical Admixtures are added to concrete at the time of mixing of its constituents to impart workability. The requirement of right workability is the essence of good concrete. It has been found that the use of optimum use of admixtures is very important since low dosage may result in loss of fluidity and over dosage could lead to segregation, bleeding, excessive air entrainment etc in concrete. Hence it is essential to find optimum dosage of superplasticizer for getting good strength and workability. But large number of trial tests are required in the field to find the saturation dosage of superplasticizer in concrete which requires more materials and consume more time. The paper deals with developing a co-relation between the quantity requirements of superplasticiser in mortar to that of cement concrete to get good workability. In this work for preparing mortar and concrete 4 brands of locally available Portland pozzolana cement (PPC) and superplasticizer (SP) belonging to 4 different families namely Polycarboxylate Ether (PCE), Lignosulphate (LS), Sulfonated Naphthalene Formaldehyde (SNF) and Sulfonated Melamine Formaldehyde (SMF) are used. Two different brands of SP’s are taken from each family. Workability study on the superplasticized mortar with cement to sand ratio 1:1.5 and water cement ratio of 0.4 was performed using marsh cone and flow table test and workability study on the concrete with same cement/sand ratio and water cement ratio was done using slump cone and flow table test. Saturation dosage of superplasticizer in mortar and concrete determined experimentally was compared to study the correlation between two. Compressive strength study on concrete cubes were done on concrete mixes with a superplasticizer dosage corresponding to the saturation dosage and a comparative study were done to analyse the improvement in the compressive strength with addition of superplasticizer from different family.

Use of improved materials systems in marine piling : final report.

DOT National Transportation Integrated Search

1982-12-01

This report contains the results of a study to evaluate the feasibility of manufacturing precast, prestressed marine pile from polymer concrete, polymer impregnated concrete, internally sealed concrete and latex modified concrete. Included in the rep...

Attenuating mass concrete effects in drilled shafts.

DOT National Transportation Integrated Search

2009-09-01

Drilled shafts are large diameter cast in place concrete foundation elements that until recently were not viewed with the same scrutiny as other massive concrete elements when considering mass concrete aspects. This study addressed three aspects of t...

Study on Mechanical Properties of Hybrid Fiber Reinforced Concrete

NASA Astrophysics Data System (ADS)

He, Dongqing; Wu, Min; Jie, Pengyu

2017-12-01

Several common high elastic modulus fibers (steel fibers, basalt fibers, polyvinyl alcohol fibers) and low elastic modulus fibers (polypropylene fiber) are incorporated into the concrete, and its cube compressive strength, splitting tensile strength and flexural strength are studied. The test result and analysis demonstrate that single fiber and hybrid fiber will improve the integrity of the concrete at failure. The mechanical properties of hybrid steel fiber-polypropylene fiber reinforced concrete are excellent, and the cube compressive strength, splitting tensile strength and flexural strength respectively increase than plain concrete by 6.4%, 3.7%, 11.4%. Doped single basalt fiber or polypropylene fiber and basalt fibers hybrid has little effect on the mechanical properties of concrete. Polyvinyl alcohol fiber and polypropylene fiber hybrid exhibit ‘negative confounding effect’ on concrete, its splitting tensile and flexural strength respectively are reduced by 17.8% and 12.9% than the single-doped polyvinyl alcohol fiber concrete.

Research on curing behavior of concrete with anti-frost admixtures at subzero temperature

NASA Astrophysics Data System (ADS)

Ionov, Yulian; Kramar, Ludmila; Kirsanova, Alena; Kolegova, Irina

2017-01-01

The purpose of this paper is research on curing behavior of cold-weather concrete with anti-frost admixtures. During the study derivative thermal and X-ray phase analyses were performed and tests were carried out according to the standard GOST technique. The research results obtained reveal the peculiarities of cement hydration and concrete curing at subzero temperatures. The influence of subzero temperatures and anti-frost admixtures on hydrated phases of hardened cement paste and concrete strength formation was studied. It is found that cold-weather concrete does not cure at subzero temperatures, but when defrosting it attains 80 to 85% of its grade strength by the 28th day. Concrete achieves its grade strength when curing in normal conditions in 60 days only. Freezing concrete with anti-frost admixtures results in increase of calcium hydroxide content in hardened cement paste immediately when produced and has increased tendency of concrete to carbonation.

Properties of concrete containing foamed concrete block waste as fine aggregate replacement

NASA Astrophysics Data System (ADS)

Muthusamy, K.; Budiea, A. M. A.; Zaidan, A. L. F.; Rasid, M. H.; Hazimmah, D. S.

2017-11-01

Environmental degradation due to excessive sand mining dumping at certain places and disposal of foamed concrete block waste from lightweight concrete producing industry are issues that should be resolved for a better and cleaner environment of the community. Thus, the main intention of this study is to investigate the potential of foamed concrete block waste as partial sand replacement in concrete production. The foamed concrete waste (FCW) used in this research that were supplied by a local lightweight concrete producing industry. The workability and compressive strength of concrete containing various percentage of foamed concrete waste as partial sand replacement has been investigated. Prior to the use, the foamed concrete waste were crushed to produce finer particles. Six concrete mixes containing various content of crushed foamed concrete waste that are 0%, 10%, 20%, 30%, 40% and 50% were used in this experimental work. Then the prepared specimens were placed in water curing until the testing age. Compressive strength test and flexural strength tests were conducted at 7, 14 and 28 days. The result shows that integration of crushed foamed concrete waste as partial sand replacement in concrete reduces the mix workability. It is interesting to note that both compressive strength and flexural strength of concrete improves when 30% crushed foamed concrete waste is added as partial sand replacement.

Effect of Gum Arabic karroo as a Water-Reducing Admixture in Concrete

PubMed Central

Mbugua, Rose; Salim, Ramadhan; Ndambuki, Julius

2016-01-01

Concrete is one of the most popular construction materials in the world. Chemical admixtures are ingredients added to concrete to enhance its properties. However, most chemical admixtures on the market today are expensive, thereby making them out of reach for small consumers of concrete. In Africa, use of chemical admixtures is rare despite the harsh weather conditions. In the current study, Gum from Acacia karroo (GAK) was used as a water-reducing admixture in concrete. A slump test, density and compressive strength were studied using different dosages of GAK while neat concrete was the control. Results showed that slump increased by 200% at a 2% dosage of GAK. This enabled reduction of water-to-binder (w/b) ratio from 0.61 to 0.48 for samples with a 3% dosage. Reduction in w/b resulted in increased compressive strength of 37.03% above the control after 180 days of curing for a 3% dosage. XRD studies also showed a decreased rate of hydration in the presence of GAK in concrete. It was concluded that GAK can be used in concrete as a water-reducing admixture, which is environmentally-friendly, thus producing sustainable and greener concrete. PMID:28787879

Effect of Gum Arabic karroo as a Water-Reducing Admixture in Concrete.

PubMed

Mbugua, Rose; Salim, Ramadhan; Ndambuki, Julius

2016-01-28

Concrete is one of the most popular construction materials in the world. Chemical admixtures are ingredients added to concrete to enhance its properties. However, most chemical admixtures on the market today are expensive, thereby making them out of reach for small consumers of concrete. In Africa, use of chemical admixtures is rare despite the harsh weather conditions. In the current study, Gum from Acacia karroo (GAK) was used as a water-reducing admixture in concrete. A slump test, density and compressive strength were studied using different dosages of GAK while neat concrete was the control. Results showed that slump increased by 200% at a 2% dosage of GAK. This enabled reduction of water-to-binder (w/b) ratio from 0.61 to 0.48 for samples with a 3% dosage. Reduction in w/b resulted in increased compressive strength of 37.03% above the control after 180 days of curing for a 3% dosage. XRD studies also showed a decreased rate of hydration in the presence of GAK in concrete. It was concluded that GAK can be used in concrete as a water-reducing admixture, which is environmentally-friendly, thus producing sustainable and greener concrete.

Mechanical and Physical Performance of Concrete Including Waste Electrical Cable Rubber

NASA Astrophysics Data System (ADS)

Taner Yildirim, Salih; Pelin Duygun, Nur

2017-10-01

Solid wastes are important environmental problem all over the World. Consumption of the plastic solid waste covers big portion within the total solid waste. Although a numerous plastic material is subjected to the recycling process, it is not easy to be destroyed by nature. One of the recommended way to prevent is to utilize as an aggregate in cement-based material. There are many researches on use of recycling rubber in concrete. However, studies on recycling of waste electrical cable rubber (WECR) in concrete is insufficient although there are many research on waste tyre rubbers in concrete. In this study, fine aggregate was replaced with WECR which were 5%, 10%, and 15 % of the total aggregate volume in the concrete and researched workability, unit weight, water absorption, compressive strength, flexural strength, ultrasonic pulse velocity, modulus of elasticity, and abrasion resistance of concrete. As a result of experimental studies, increase of WECR amount in concrete increases workability due to lack of adherence between cement paste and WECR, and hydrophobic structure of WECR while it influences negatively mechanical properties of concrete. It is possible to use WECR in concrete taking into account the reduction in mechanical properties.

Enhancement of properties of recycled coarse aggregate concrete using bacteria

NASA Astrophysics Data System (ADS)

Sahoo; Arakha; Sarkar; P; Jha

2016-01-01

Due to rapid construction, necessity for raw materials of concrete, especially coarse aggregate, tends to increase the danger of early exhaustion of the natural resources. An alternative source of raw materials would perhaps delay the advent of this early exhaustion. Recycled coarse aggregate (RCA) plays a great role as an alternative raw material that can replace the natural coarse aggregate (NCA) for concrete. Previous studies show that the properties of RCA concrete are inferior in quality compared to NCA concrete. This article attempts to study the improvement of properties of RCA concrete with the addition of bacteria named as Bacillus subtilis. The experimental investigation was carried out to evaluate the improvement of the compressive strength, capillary water absorption, and drying shrinkage of RCA concrete incorporating bacteria. The compressive strength of RCA concrete is found to be increased by about 20% when the cell concentration of B. subtilis is 106 cells/ml. The capillary water absorption as well as drying shrinkage of RCA are reduced when bacteria is incorporated. The improvement of RCA concrete is confirmed to be due to the calcium carbonate precipitation as observed from the microstructure studies carried out on it such as EDX, SEM, and XRD.

Use of improved structural materials systems in marine piling : interim report.

DOT National Transportation Integrated Search

1982-09-01

This report contains the results of a study to evaluate the feasibility of manufacturing precast, prestressed marine pile from polymer concrete, polymer impregnated concrete, internally sealed concrete and latex modified concrete. Included in the rep...

Measurements of the thickness of in-place concrete with microwave reflection.

DOT National Transportation Integrated Search

1988-01-01

Previous microwave reflection measurements made on simple, unreinforced concrete blocks have shown that the transit time of a microwave through concrete is linearly related to its thickness. In this study measurements were conducted on concrete slabs...

Investigating causes and determine repair needs to mitigate falling concrete from bridge decks.

DOT National Transportation Integrated Search

2012-09-01

This study developed a procedure to identify concrete bridge decks that are exhibiting the characteristics associated : with falling concrete. Field exploratory work on reinforced concrete bridge decks was supported by analytical and : laboratory inv...

Recycled concrete aggregate in portland cement concrete.

DOT National Transportation Integrated Search

2013-01-01

Aggregates can be produced by crushing hydraulic cement concrete and are known as recycled concrete : aggregates (RCA). This report provides results from a New Jersey Department of Transportation study to identify : barriers to the use of RCA in new ...

Asphalt recycling technology: Literature review and research plan

NASA Astrophysics Data System (ADS)

Newcomb, D. E.; Epps, J. A.

1981-06-01

A review of current technology for the rehabilitation and maintenance of pavement surfaces by recycling was conducted. While the primary concern was asphalt concrete recycling, a brief review of portland cement concrete recycling is included. Reports of cases involving recycling technology and lessons learned are reviewed. Recommendations are presented outlining research required to advance the state-of-the-art in a manner that will permit the U.S. Air Force to fully attain the benefits of recycling technology.

Leakage of radioactive materials from particle accelerator facilities by non-radiation disasters like fire and flooding and its environmental impacts

NASA Astrophysics Data System (ADS)

Lee, A.; Jung, N. S.; Mokhtari Oranj, L.; Lee, H. S.

2018-06-01

The leakage of radioactive materials generated at particle accelerator facilities is one of the important issues in the view of radiation safety. In this study, fire and flooding at particle accelerator facilities were considered as the non-radiation disasters which result in the leakage of radioactive materials. To analyse the expected effects at each disaster, the case study on fired and flooded particle accelerator facilities was carried out with the property investigation of interesting materials presented in the accelerator tunnel and the activity estimation. Five major materials in the tunnel were investigated: dust, insulators, concrete, metals and paints. The activation levels on the concerned materials were calculated using several Monte Carlo codes (MCNPX 2.7+SP-FISPACT 2007, FLUKA 2011.4c and PHITS 2.64+DCHAIN-SP 2001). The impact weight to environment was estimated for the different beam particles (electron, proton, carbon and uranium) and the different beam energies (100, 430, 600 and 1000 MeV/nucleon). With the consideration of the leakage path of radioactive materials due to fire and flooding, the activation level of selected materials, and the impacts to the environment were evaluated. In the case of flooding, dust, concrete and metal were found as a considerable object. In the case of fire event, dust, insulator and paint were the major concerns. As expected, the influence of normal fire and flooding at electron accelerator facilities would be relatively low for both cases.

Guided wave propagation and spectral element method for debonding damage assessment in RC structures

NASA Astrophysics Data System (ADS)

Wang, Ying; Zhu, Xinqun; Hao, Hong; Ou, Jinping

2009-07-01

A concrete-steel interface spectral element is developed to study the guided wave propagation along the steel rebar in the concrete. Scalar damage parameters characterizing changes in the interface (debonding damage) are incorporated into the formulation of the spectral finite element that is used for damage detection of reinforced concrete structures. Experimental tests are carried out on a reinforced concrete beam with embedded piezoelectric elements to verify the performance of the proposed model and algorithm. Parametric studies are performed to evaluate the effect of different damage scenarios on wave propagation in the reinforced concrete structures. Numerical simulations and experimental results show that the method is effective to model wave propagation along the steel rebar in concrete and promising to detect damage in the concrete-steel interface.

Study on creep of fiber reinforced ultra-high strength concrete based on strength

NASA Astrophysics Data System (ADS)

Peng, Wenjun; Wang, Tao

2018-04-01

To complement the creep performance of ultra-high strength concrete, the long creep process of fiber reinforced concrete was studied in this paper. The long-term creep process and regularity of ultra-high strength concrete with 0.5% PVA fiber under the same axial compression were analyzed by using concrete strength (C80/C100/C120) as a variable. The results show that the creep coefficient of ultra-high strength concrete decreases with the increase of concrete strength. Compared with ACI209R (92), GL2000 models, it is found that the predicted value of ACI209R (92) are close to the experimental value, and the creep prediction model suitable for this experiment is proposed based on ACI209R (92).

Development of performance properties of ternary mixtures : laboratory study on concrete.

DOT National Transportation Integrated Search

2011-03-01

This research project is a comprehensive study of how supplementary cementitious materials (SCMs) can be used to : improve the performance of concrete mixtures. This report summarizes the findings of the Laboratory Study on Concrete : phase of this w...

The influence of concrete mixture’s rheological properties on the quality of formed concrete surfaces

NASA Astrophysics Data System (ADS)

Daukšys, M.; Klovas, A.; Venčkauskas, L.

2017-09-01

This study mainly lays emphasis on examining the influence of concrete mixture rheological properties on the quality of formed concrete surfaces. Mixture’s fine aggregate change was taken into the consideration. Over the course of concrete mixture preparation the inner ratio of fine aggregate (sand: fraction of 0/1 and 0/4) was changed. The idea was to increase the quantity of fine particles in the total aggregate’s volume therefore quantity of sand (fraction 0/1) was increased. Six different concrete mixture’s compositions were designed as well as three specimens (concrete piles of 1m2 surface area) were casted. Rheological properties of concrete mixtures were analytically obtained and the quality of formed concrete surfaces was evaluated using image analysis method “BetonGUY 2.0”. As can be obtained from the dependence between concrete mixture rheological properties and its formed surface quality, the increase of concrete mixture’s yield stress and plastic viscosity reduces the quantity of air pores on formed concrete surfaces.

Dissociations in mathematical knowledge: case studies in Down's syndrome and Williams syndrome.

PubMed

Robinson, Sally J; Temple, Christine M

2013-02-01

A study is reported of mathematical vocabulary and factual mathematical knowledge in PQ, a 22 year old with Down's syndrome (DS) who has a verbal mental age (MA) of 9 years 2 months and ST, a 15 year old with Williams syndrome (WS) who has a verbal MA of 9 years 6 months, matched to typically developing controls. The number of mathematical words contained within PQ's lexical stores was significantly reduced as reflected by performance on lexical decision. PQ was also impaired at both naming from descriptions and describing mathematical words. These results contrast with normal lexical decision and item descriptions for concrete words reported recently for PQ (Robinson and Temple, 2010). PQ's recall of mathematical facts was also impaired, whilst his recall of general knowledge facts was normal. This performance in DS indicates a deficit in both lexical representation and semantic knowledge for mathematical words and mathematical facts. In contrast, ST, the teenager with WS had good accuracy on lexical decision, naming and generating definitions for mathematical words. This contrasted with the atypical performance with concrete words recently reported for ST (Robinson and Temple, 2009). Knowledge of addition facts and general knowledge facts was also unimpaired for ST, though knowledge of multiplication facts was weak. Together the cases form a double dissociation and provide support for the distinct representation of mathematical and concrete items within the lexical-semantic system during development. The dissociations between mathematical and general factual knowledge also indicate that different types of factual knowledge may be selectively impaired during development. There is further support for a modular structure within which mathematical vocabulary and mathematical knowledge have distinct representations. This supports the case for the independent representation of factual and language-based knowledge within the semantic system during development. Copyright © 2011 Elsevier Ltd. All rights reserved.

Impact capacity reduction in railway prestressed concrete sleepers with vertical holes

NASA Astrophysics Data System (ADS)

Ngamkhanong, Chayut; Li, Dan; Kaewunruen, Sakdirat

2017-09-01

Railway prestressed concrete sleepers (or railroad ties) are principally designed in order to carry wheel loads from the rails to the ground as well as to secure rail gauge for dynamic safe movements of trains. In spite of the most common use of the prestressed concrete sleepers in railway tracks, the concrete sleepers are often modified on construction sites to fit in other systems such as cables, signalling gears, drainage pipes, etc. This is because those signalling, fibre optic, equipment cables are often damaged either by ballast corners or by tamping machine. It is thus necessary to modify concrete sleepers to cater cables internally so that the cables or drainage pipes would not experience detrimental or harsh environments. Accordingly, this study will extend from the previous study into the design criteria of holes and web openings. This paper will highlight structural capacity of concrete sleepers under dynamic transient loading. The modified compression field theory for ultimate strength design of concrete sleepers will be highlighted in this study. The outcome of this study will improve the understanding into dynamic behavior of prestressed concrete sleepers with vertical holes. The insight will enable predictive track maintenance regime in railway industry.

Study on Mechanical Properties of Concrete Using Plastic Waste as an Aggregate

NASA Astrophysics Data System (ADS)

Jaivignesh, B.; Sofi, A.

2017-07-01

Disposal of large quantity of plastic causes land, water and air pollution etc.., so a study is conducted to recycle the plastic in concrete. This work investigates about the replacement of natural aggregate with non-biodegradable plastic aggregate made up of mixed plastic waste in concrete. Several tests are conducted such as compressive strength of cube, split tensile strength of cylinder, flexural strength test of prism to identify the properties and behavior of concrete using plastic aggregate. Replacement of fine aggregate weight by 10%, 15%, 20% with Plastic fine (PF) aggregate and for each replacement of fine aggregate 15%, 20%, 25% of coarse aggregate replacement also conducted with Plastic Coarse(PC) aggregate. In literatures reported that the addition of plastic aggregate in concrete causes the reduction of strength in concrete due to poor bonding between concrete and plastic aggregate, so addition of 0.3% of steel fiber by weight of cement in concrete is done to improve the concrete strength. Totally 60 cubes, 60 cylinders and 40 prisms are casted to identify the compressive strength, split tensile strength and flexural strength respectively. Casted specimens are tested at 7 and 28 days. The identified results from concrete using plastic aggregate are compared with conventional concrete. Result shows that reduction in mechanical properties of plastic aggregate added concrete. This reduction in strength is mainly due to poor bond strength between cement and plastic aggregate.

Recycling of rubble from building demolition for low-shrinkage concretes.

PubMed

Corinaldesi, Valeria; Moriconi, Giacomo

2010-04-01

In this project concrete mixtures were prepared that were characterized by low ductility due to desiccation by using debris from building demolition, which after a suitable treatment was used as aggregate for partial replacement of natural aggregates. The recycled aggregate used came from a recycling plant, in which rubble from building demolition was selected, crushed, cleaned, sieved, and graded. Such aggregates are known to be more porous as indicated by the Saturated Surface Dry (SSD) moisture content. The recycled concrete used as aggregates were added to the concrete mixture in order to study their influence on the fresh and hardened concrete properties. They were added either after water pre-soaking or in dry condition, in order to evaluate the influence of moisture in aggregates on the performance of concrete containing recycled aggregate. In particular, the effect of internal curing, due to the use of such aggregates, was studied. Concrete behavior due to desiccation under dehydration was studied by means of both drying shrinkage test and German angle test, through which shrinkage under the restrained condition of early age concrete can be evaluated. Copyright 2009 Elsevier Ltd. All rights reserved.

Acoustic emission characterization of steel fibre reinforced concrete during bending

NASA Astrophysics Data System (ADS)

Aggelis, D. G.; Soulioti, D. V.; Sapouridis, N.; Barkoula, N. M.; Paipetis, A. S.; Matikas, T. E.

2010-04-01

The acoustic emission (AE) behaviour of steel fibre reinforced concrete is studied in this paper. The experiments were conducted in four-point bending with concurrent monitoring of AE signals. The sensors used, were of broadband response in order to capture a wide range of fracturing phenomena. The results indicate that AE parameters undergo significant changes much earlier than the final fracture of the specimens, even if the AE hit rate seems approximately constant. Specifically, the Ib-value which takes into account the amplitude distribution of the recent AE hits decreases when the load reaches about 60-70 % of its maximum value. Additionally, the average frequency of the signals decreases abruptly when a fracture incident occurs, indicating that matrix cracking events produce higher frequencies than fibre pull-out events. It is concluded that proper study of AE parameters enables the characterization of structural health of large structures in cases where remote monitoring is applied.

Characterising encapsulated nuclear waste using cosmic-ray muon tomography

NASA Astrophysics Data System (ADS)

Clarkson, A.; Hamilton, D. J.; Hoek, M.; Ireland, D. G.; Johnstone, J. R.; Kaiser, R.; Keri, T.; Lumsden, S.; Mahon, D. F.; McKinnon, B.; Murray, M.; Nutbeam-Tuffs, S.; Shearer, C.; Yang, G.; Zimmerman, C.

2015-03-01

Tomographic imaging techniques using the Coulomb scattering of cosmic-ray muons have been shown previously to successfully identify and characterise low- and high-Z materials within an air matrix using a prototype scintillating-fibre tracker system. Those studies were performed as the first in a series to assess the feasibility of this technology and image reconstruction techniques in characterising the potential high-Z contents of legacy nuclear waste containers for the U.K. Nuclear Industry. The present work continues the feasibility study and presents the first images reconstructed from experimental data collected using this small-scale prototype system of low- and high-Z materials encapsulated within a concrete-filled stainless-steel container. Clear discrimination is observed between the thick steel casing, the concrete matrix and the sample materials assayed. These reconstructed objects are presented and discussed in detail alongside the implications for future industrial scenarios.

Experimental Study on Voided Reinforced Concrete Beams with Polythene Balls

NASA Astrophysics Data System (ADS)

Sivaneshan, P.; Harishankar, S.

2017-07-01

The primary component in any structure is concrete, that exist in buildings and bridges. In present situation, a serious problems faced by construction industry is exhaustive use of raw materials. Recent times, various methods are being adopted to limit the use of concrete. In structural elements like beams, polythene balls can be induced to reduce the usage of concrete. A simply supported reinforced concrete beam has two zones, one above neutral axis and other below neutral axis. The region below neutral axis is in tension and above neutral axis is in compression. As concrete is weak in tension, steel reinforcements are provided in tension zone. The concrete below the neutral axis acts as a stress transfer medium between the compression zone and tension zone. The concrete above the neutral axis takes minimum stress so that we could partially replace the concrete above neutral axis by creating air voids using recycled polythene balls. Polythene balls of varying diameters of 75 mm, 65 mm and 35 mm were partially replaced in compression zone. Hence the usage of concrete in beams and self-weight of the beams got reduced considerably. The Load carrying capacity, Deflection of beams and crack patterns were studied and compared with conventional reinforced concrete beams.

Recycled materials in Portland cement concrete

DOT National Transportation Integrated Search

2000-06-01

This report pertains to a comprehensive study involving the use of recycled materials in Portland cement concrete. Three different materials were studied including crushed glass (CG), street sweepings (SS), and recycled concrete (RC). Blast furnace s...

Experimental Study on Permeability of Concrete

NASA Astrophysics Data System (ADS)

Yang, Honglu; Liu, Rentai; Zheng, Zhuo; Liu, Haojie; Gao, Yan; Liu, Yankai

2018-01-01

To study the influencing factors on permeability of pervious concrete, by adding inorganic organic composite materials obtained experimental results show that different aggregate size, aggregate cement ratio of different, different water cement ratio on the permeability performance. The permeability of the concrete was tested by using the self - made permeable device. The experimental results showed that the permeation coefficient of the experiment was obtained and the factors influencing the permeability of the concrete were compared and analyzed. At the same time, the porosity of pervious concrete was measured, the influence of various variables on porosity was studied, and the influence of various factors on the permeability of voids was found. Finally, through comprehensive analysis of a variety of factors, the optimal water cement ratio is 0.28. At this time, the pervious performance of concrete is optimal.

Model Checking Abstract PLEXIL Programs with SMART

NASA Technical Reports Server (NTRS)

Siminiceanu, Radu I.

2007-01-01

We describe a method to automatically generate discrete-state models of abstract Plan Execution Interchange Language (PLEXIL) programs that can be analyzed using model checking tools. Starting from a high-level description of a PLEXIL program or a family of programs with common characteristics, the generator lays the framework that models the principles of program execution. The concrete parts of the program are not automatically generated, but require the modeler to introduce them by hand. As a case study, we generate models to verify properties of the PLEXIL macro constructs that are introduced as shorthand notation. After an exhaustive analysis, we conclude that the macro definitions obey the intended semantics and behave as expected, but contingently on a few specific requirements on the timing semantics of micro-steps in the concrete executive implementation.

Technology Enhanced Learning: Virtual Realities; Concrete Results--Case Study on the Impact of TEL on Learning

ERIC Educational Resources Information Center

Al-Khatib, Hayat

2011-01-01

Technology Enhanced Learning is a feature of 21st century education. Innovations in ICT have provided unbound access to information in support of the learning process (APTEL, 2010; Allert et al, 2002; Baldry et al, 2006; Frustenberg et al, 2001; Sarkis, 2010). LMS has been extensively put to use in universities and educational institutions to…

Cooperation, College Knowledge, and Strong Parent Communities in the L.A. Concrete Jungle: The Case for Family-Centered Outreach

ERIC Educational Resources Information Center

Smith, Michael J.

2012-01-01

Urban African American teens are unprepared to compete for jobs in the global marketplace, but higher education professionals could partner with parents to reverse this trend. After reviewing parent involvement literature, this paper shares findings from a study of urban African American parents involved in their children's outreach programs. It…

Shaw High School A Case Study in Rural High School Improvement

ERIC Educational Resources Information Center

Williams, Doris Terry

2004-01-01

Shaw High School is one of two schools making up the Shaw School District. The school is located in an old and once majestic building whose large concrete pillars still stand at the entrance. A small white house across the street holds the district administrative office. Several buildings, detached from the main building, house the cafeteria,…

Beyond Description: Converting Web Site Usage Statistics into Concrete Site Improvement Ideas

ERIC Educational Resources Information Center

Arendt, Julie; Wagner, Cassie

2010-01-01

Web site usage statistics are a widely used tool for Web site development, but libraries are still learning how to use them successfully. This case study summarizes how Morris Library at Southern Illinois University Carbondale implemented Google Analytics on its Web site and used the reports to inform a site redesign. As the main campus library at…

Feeling and Thinking about Studio Practices: Exploring Dissonance in Semi-Structured Interviews with Students in Higher Education Music

ERIC Educational Resources Information Center

Burwell, Kim

2017-01-01

While studio-based instrumental and vocal learning is widely regarded as both important and effective in higher education music, research to date has offered little concrete information about studio practices that students have regarded as ineffective. Two recent case studies investigated what appear to be exceptional instances in which students…

Sensitivity study on durability variables of marine concrete structures

NASA Astrophysics Data System (ADS)

Zhou, Xin'gang; Li, Kefei

2013-06-01

In order to study the influence of parameters on durability of marine concrete structures, the parameter's sensitivity analysis was studied in this paper. With the Fick's 2nd law of diffusion and the deterministic sensitivity analysis method (DSA), the sensitivity factors of apparent surface chloride content, apparent chloride diffusion coefficient and its time dependent attenuation factor were analyzed. The results of the analysis show that the impact of design variables on concrete durability was different. The values of sensitivity factor of chloride diffusion coefficient and its time dependent attenuation factor were higher than others. Relative less error in chloride diffusion coefficient and its time dependent attenuation coefficient induces a bigger error in concrete durability design and life prediction. According to probability sensitivity analysis (PSA), the influence of mean value and variance of concrete durability design variables on the durability failure probability was studied. The results of the study provide quantitative measures of the importance of concrete durability design and life prediction variables. It was concluded that the chloride diffusion coefficient and its time dependent attenuation factor have more influence on the reliability of marine concrete structural durability. In durability design and life prediction of marine concrete structures, it was very important to reduce the measure and statistic error of durability design variables.

Improved design of special boundary elements for T-shaped reinforced concrete walls

NASA Astrophysics Data System (ADS)

Ji, Xiaodong; Liu, Dan; Qian, Jiaru

2017-01-01

This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements of T-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.

Experimental Study and Reactive Transport Modeling of Boric Acid Leaching of Concrete

NASA Astrophysics Data System (ADS)

Pabalan, R. T.; Chiang, K.-T. K.

2013-07-01

Borated water leakage through spent fuel pools (SFPs) at pressurized water reactors is a concern because it could cause corrosion of reinforcement steel in the concrete structure, compromise the integrity of the structure, or cause unmonitored releases of contaminated water to the environment. Experimental data indicate that pH is a critical parameter that determines the corrosion susceptibility of rebar in borated water and the degree of concrete degradation by boric acid leaching. In this study, reactive transport modeling of concrete leaching by borated water was performed to provide information on the solution pH in the concrete crack or matrix and the degree of concrete degradation at different locations of an SFP concrete structure exposed to borated water. Simulations up to 100 years were performed using different boric acid concentrations, crack apertures, and solution flow rates. Concrete cylinders were immersed in boric acid solutions for several months and the mineralogical changes and boric acid penetration in the concrete cylinder were evaluated as a function of time. The depths of concrete leaching by boric acid solution derived from the reactive transport simulations were compared with the measured boric acid penetration depth.

Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals.

PubMed

Kim, Junkyeong; Lee, Chaggil; Park, Seunghee

2017-06-07

Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process.

An Investigation into the Use of Manufactured Sand as a 100% Replacement for Fine Aggregate in Concrete.

PubMed

Pilegis, Martins; Gardner, Diane; Lark, Robert

2016-06-02

Manufactured sand differs from natural sea and river dredged sand in its physical and mineralogical properties. These can be both beneficial and detrimental to the fresh and hardened properties of concrete. This paper presents the results of a laboratory study in which manufactured sand produced in an industry sized crushing plant was characterised with respect to its physical and mineralogical properties. The influence of these characteristics on concrete workability and strength, when manufactured sand completely replaced natural sand in concrete, was investigated and modelled using artificial neural networks (ANN). The results show that the manufactured sand concrete made in this study generally requires a higher water/cement (w/c) ratio for workability equal to that of natural sand concrete due to the higher angularity of the manufactured sand particles. Water reducing admixtures can be used to compensate for this if the manufactured sand does not contain clay particles. At the same w/c ratio, the compressive and flexural strength of manufactured sand concrete exceeds that of natural sand concrete. ANN proved a valuable and reliable method of predicting concrete strength and workability based on the properties of the fine aggregate (FA) and the concrete mix composition.

An Investigation into the Use of Manufactured Sand as a 100% Replacement for Fine Aggregate in Concrete

PubMed Central

Pilegis, Martins; Gardner, Diane; Lark, Robert

2016-01-01

Manufactured sand differs from natural sea and river dredged sand in its physical and mineralogical properties. These can be both beneficial and detrimental to the fresh and hardened properties of concrete. This paper presents the results of a laboratory study in which manufactured sand produced in an industry sized crushing plant was characterised with respect to its physical and mineralogical properties. The influence of these characteristics on concrete workability and strength, when manufactured sand completely replaced natural sand in concrete, was investigated and modelled using artificial neural networks (ANN). The results show that the manufactured sand concrete made in this study generally requires a higher water/cement (w/c) ratio for workability equal to that of natural sand concrete due to the higher angularity of the manufactured sand particles. Water reducing admixtures can be used to compensate for this if the manufactured sand does not contain clay particles. At the same w/c ratio, the compressive and flexural strength of manufactured sand concrete exceeds that of natural sand concrete. ANN proved a valuable and reliable method of predicting concrete strength and workability based on the properties of the fine aggregate (FA) and the concrete mix composition. PMID:28773560

Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals

PubMed Central

Kim, Junkyeong; Lee, Chaggil; Park, Seunghee

2017-01-01

Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process. PMID:28590456

The optimum content of rubber ash in concrete: flexural strength

NASA Astrophysics Data System (ADS)

Senin, M. S.; Shahidan, S.; Shamsuddin, S. M.; Ariffin, S. F. A.; Othman, N. H.; Rahman, R.; Khalid, F. S.; Nazri, F. M.

2017-11-01

Discarded scrap tyres have become one of the major environmental problems nowadays. Several studies have been carried out to reuse waste tires as an additive or sand replacement in concrete with appropriate percentages of tire rubber, called as rubberized concrete to solve this problem. The main objectives of this study are to investigate the flexural strength performance of concrete when adding the rubber ash and also to analyse the optimum content of rubber ash in concrete prisms. The performance total of 30 number of concrete prisms in size of 100mm x 100mm x 500 mm were investigated, by partially replacement of rubber ash with percentage of 0%, 3%, 5%, 7% and 9% from the volume of the sand. The flexural strength is increased when percentage of rubber ash is added 3% from control concrete prism, RA 0 for both concrete prism age, 7 days and 28 days with value 1.21% and 0.976% respectively. However, for RA 5, RA 7 and RA 9, the flexural strength was decreased compared to the control for both age, 7 days and 28 days. In conclusion, 3% is the optimum content of rubber ash in concrete prism for both concrete age

Utilization of fly ash and ultrafine GGBS for higher strength foam concrete

NASA Astrophysics Data System (ADS)

Gowri, R.; Anand, K. B.

2018-02-01

Foam concrete is a widely accepted construction material, which is popular for diverse construction applications such as, thermal insulation in buildings, lightweight concrete blocks, ground stabilization, void filling etc. Currently, foam concrete is being used for structural applications with a density above 1800kg/m3. This study focuses on evolving mix proportions for foam concrete with a material density in the range of 1200 kg/m3 to 1600 kg/m3, so as to obtain strength ranges that will be sufficient to adopt it as a structural material. Foam concrete is made lighter by adding pre-formed foam of a particular density to the mortar mix. The foaming agent used in this study is Sodium Lauryl Sulphate and in order to densify the foam generated, Sodium hydroxide solution at a normality of one is also added. In this study efforts are made to make it a sustainable construction material by incorporating industrial waste products such as ultrafine GGBS as partial replacement of cement and fly ash for replacement of fine aggregate. The fresh state and hardened state properties of foam concrete at varying proportions of cement, sand, water and additives are evaluated. The proportion of ultrafine GGBS and fly ash in the foam concrete mix are varied aiming at higher compressive strength. Studies on air void-strength relationship of foam concrete are also included in this paper.

Study on evaluation of corrosion condition of reinforcing bar embedded concrete using infrared thermal imaging camera

NASA Astrophysics Data System (ADS)

Ruiko, Watanabe; Toshiaki, Mizobuchi

2017-04-01

Rapid aging of many concrete structures, which have been developed during rapid economic growth period in Japan, has become a serious problem for us these days. And thus, there is an urgent need to prolong their service life expectancies. For this purpose, the deterioration of reinforcing bars in the concrete structures should be detected quickly and correctly at the early stages. Nevertheless, conventional testing methods such as destructive and nondestructive testing have disadvantages: partial damages on concrete structures; difficulty with quantitative evaluation, etc. Many preceding studies have examined to estimate the deterioration of reinforcing bars based on the temperature of the concrete specimen surfaces. According to those papers, the differences in corrosion degree of reinforcing bars have a certain effect on the temperature of concrete specimen surfaces. In this study, firstly, the quantitative evaluation of the corrosion degree was conducted with 3D scanner which could measure the volume, coverage area and cross-sectional area. Secondly, the surface of the concrete specimen was cooled down with liquid nitrogen, and thirdly, thermographic change was observed up until the air temperature. Finally, the surface of the concrete specimen was detected clearly by the thermal images. As a result, this study shows that the corrosion thickness tends to get bigger, following the uprising temperature of the concrete specimen surfaces. The same kind of tendency can be observed by the thermal images, too.

Nouns, verbs, objects, actions, and abstractions: Local fMRI activity indexes semantics, not lexical categories

PubMed Central

Moseley, Rachel L.; Pulvermüller, Friedemann

2014-01-01

Noun/verb dissociations in the literature defy interpretation due to the confound between lexical category and semantic meaning; nouns and verbs typically describe concrete objects and actions. Abstract words, pertaining to neither, are a critical test case: dissociations along lexical-grammatical lines would support models purporting lexical category as the principle governing brain organisation, whilst semantic models predict dissociation between concrete words but not abstract items. During fMRI scanning, participants read orthogonalised word categories of nouns and verbs, with or without concrete, sensorimotor meaning. Analysis of inferior frontal/insula, precentral and central areas revealed an interaction between lexical class and semantic factors with clear category differences between concrete nouns and verbs but not abstract ones. Though the brain stores the combinatorial and lexical-grammatical properties of words, our data show that topographical differences in brain activation, especially in the motor system and inferior frontal cortex, are driven by semantics and not by lexical class. PMID:24727103

Nouns, verbs, objects, actions, and abstractions: local fMRI activity indexes semantics, not lexical categories.

PubMed

Moseley, Rachel L; Pulvermüller, Friedemann

2014-05-01

Noun/verb dissociations in the literature defy interpretation due to the confound between lexical category and semantic meaning; nouns and verbs typically describe concrete objects and actions. Abstract words, pertaining to neither, are a critical test case: dissociations along lexical-grammatical lines would support models purporting lexical category as the principle governing brain organisation, whilst semantic models predict dissociation between concrete words but not abstract items. During fMRI scanning, participants read orthogonalised word categories of nouns and verbs, with or without concrete, sensorimotor meaning. Analysis of inferior frontal/insula, precentral and central areas revealed an interaction between lexical class and semantic factors with clear category differences between concrete nouns and verbs but not abstract ones. Though the brain stores the combinatorial and lexical-grammatical properties of words, our data show that topographical differences in brain activation, especially in the motor system and inferior frontal cortex, are driven by semantics and not by lexical class. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Systems Study of Precast Concrete Tunnel Liners

DOT National Transportation Integrated Search

1975-03-01

The study addresses precast concrete lining systems. Existing precast concrete systems designed or constructed in Europe, Japan, and the United States are evaluated. With these as a point of departure, designs for lining systems applicable to the spe...

Concrete with onyx waste aggregate as aesthetically valued structural concrete

NASA Astrophysics Data System (ADS)

Setyowati E., W.; Soehardjono, A.; Wisnumurti

2017-09-01

The utillization of Tulungagung onyx stone waste as an aggregate of concrete mixture will improve the economic value of the concrete due to the brighter color and high aesthetic level of the products. We conducted the research of 75 samples as a test objects to measure the compression stress, splits tensile stress, flexural tensile stress, elasticity modulus, porosity modulus and also studied 15 test objects to identify the concrete micro structures using XRD test, EDAX test and SEM test. The test objects were made from mix designed concrete, having ratio cement : fine aggregate : coarse aggregate ratio = 1 : 1.5 : 2.1, and W/C ratio = 0.4. The 28 days examination results showed that the micro structure of Tulungagung onyx waste concrete is similar with normal concrete. Moreover, the mechanical test results proved that Tulungagung onyx waste concretes also have a qualified level of strength to be used as a structural concrete with higher aesthetic level.

Comparison of physical and mechanical properties of river sand concrete with quarry dust concrete

NASA Astrophysics Data System (ADS)

Opara, Hyginus E.; Eziefula, Uchechi G.; Eziefula, Bennett I.

2018-03-01

This study compared the physical and mechanical properties of river sand concrete with quarry dust concrete. The constituent materials were batched by weight. The water-cement ratio and mix ratio selected for the experimental investigation were 0.55 and 1:2:4, respectively. The specimens were cured for 7, 14, 21 and 28 days. Slump, density and compressive strength tests were carried out. The results showed that river sand concrete had greater density and compressive strength than quarry dust concrete for all curing ages. At 28 days of curing, river sand concrete exceeded the target compressive strength by 36%, whereas quarry dust concrete was less than the target compressive strength by 12%. Both river sand concrete and quarry dust concrete for the selected water/cement ratio and mix ratio are suitable for non-structural applications and lightly-loaded members where high strength is not a prerequisite.

Bond characteristics of reinforcing steel embedded in geopolymer concrete

NASA Astrophysics Data System (ADS)

Kathirvel, Parthiban; Thangavelu, Manju; Gopalan, Rashmi; Raja Mohan Kaliyaperumal, Saravana

2017-07-01

The force transferring between reinforcing steel and the surrounding concrete in reinforced concrete is influenced by several factors. Whereas, the study on bond behaviour of geopolymer concrete (GPC) is lagging. In this paper, an experimental attempt has been made to evaluate the geopolymer concrete bond with reinforcing steel of different diameter and embedded length using standard pull out test. The geopolymer concrete is made of ground granulated blast furnace slag (GGBFS) as geopolymer source material (GSM). The tests were conducted to evaluate the development of bond between steel and concrete of grade M40 and M50 with 12 and 16 mm diameter reinforcing steel for geopolymer and cement concrete mixes and to develop a relation between bond strength and compressive strength. From the experimental results, it has been observed that the bond strength of the geopolymer concrete mixes was more compared to the cement concrete mixes and increases with the reduction in the diameter of the bar.

Artificial lightweight aggregates as utilization for future ashes - A case study.

PubMed

Sarabèr, Angelo; Overhof, Robert; Green, Terry; Pels, Jan

2012-01-01

In the future, more electricity in the Netherlands will be produced using coal with co-combustion. Due to this, the generated annual ash volume will increase and the chemical composition will be influenced. One of the options for utilization if present markets are saturated and for use of fly ashes with different compositions, is as raw material for lightweight aggregates. This was selected as one of the best utilizations options regarding potential ash volume to be applied, environmental aspects and status of technology. Because of this, a study has been performed to assess the potential utilization of fly ash for the production of lightweight aggregate. Lightweight aggregate has been produced in a laboratory scale rotary kiln. The raw material consisted of class F fly ash with high free lime content. An addition of 8% clay was necessary to get green pellets with sufficient green strength. The basic properties of the produced lightweight aggregate and its behaviour in concrete have been investigated. The concrete has a good compressive strength and its leaching behaviour meets the most stringent requirements of Dutch environmental regulations. The carbon foot print of concrete will be negatively influenced if only the concrete itself is taken into account, but the reduction of the volume weight has advantages regarding design, transport emissions and isolation properties which may counteract this. In the Dutch situation the operational costs are higher than expected potential selling price for the LWA, which implies that the gate fee for the fly ash is negative. Copyright © 2011 Elsevier Ltd. All rights reserved.

Static and dynamic behaviours of railway prestressed concrete sleepers with longitudinal through hole

NASA Astrophysics Data System (ADS)

Ngamkhanong, C.; Kaewunruen, S.; Remennikov, A. M.

2017-10-01

As the crosstie beam in railway track systems, the prestressed concrete sleepers (or railroad ties) are principally designed in order to carry wheel loads from the rails to the ground. Their design takes into account static and dynamic loading conditions. It is evident that prestressed concrete has played a significant role as to maintain the high endurance of the sleepers under low to moderate repeated impact loads. In spite of the most common use of the prestressed concrete sleepers in railway tracks, there have always been many demands from rail engineers to improve serviceability and functionality of concrete sleepers. For example, signalling, fibre optic, equipment cables are often damaged either by ballast corners or by tamping machine. There has been a need to re-design concrete sleeper to cater cables internally so that they would not experience detrimental or harsh environments. Accordingly, this study will investigate the effects of through hole or longitudinal hole on static and dynamic behaviours of concrete sleepers under rail shock loading. The modified compression field theory for ultimate strength design of concrete sleepers will be highlighted in this study. The outcome of this study will enable the new design and calculation methods for prestressed concrete sleepers with holes and web opening that practically benefits civil, track and structural engineers in railway industry.

Use of steel fibres recovered from waste tyres as reinforcement in concrete: pull-out behaviour, compressive and flexural strength.

PubMed

Aiello, M A; Leuzzi, F; Centonze, G; Maffezzoli, A

2009-06-01

The increasing amount of waste tyres worldwide makes the disposition of tyres a relevant problem to be solved. In the last years over three million tons of waste tyres were generated in the EU states [ETRA, 2006. Tyre Technology International - Trends in Tyre Recycling. http://www.etra-eu.org]; most of them were disposed into landfills. Since the European Union Landfill Directive (EU Landfill, 1999) aims to significantly reduce the landfill disposal of waste tyres, the development of new markets for the tyres becomes fundamental. Recently some research has been devoted to the use of granulated rubber and steel fibres recovered from waste tyres in concrete. In particular, the concrete obtained by adding recycled steel fibres evidenced a satisfactory improvement of the fragile matrix, mostly in terms of toughness and post-cracking behaviour. As a consequence RSFRC (recycled steel fibres reinforced concrete) appears a promising candidate for both structural and non-structural applications. Within this context a research project was undertaken at the University of Salento (Italy) aiming to investigate the mechanical behaviour of concrete reinforced with RSF (recycled steel fibres) recovered from waste tyres by a mechanical process. In the present paper results obtained by the experimental work performed up to now are reported. In order to evaluate the concrete-fibres bond characteristics and to determine the critical fibre length, pull-out tests were initially carried out. Furthermore compressive strength of concrete was evaluated for different volume ratios of added RSF and flexural tests were performed to analyze the post-cracking behaviour of RSFRC. For comparison purposes, samples reinforced with industrial steel fibres (ISF) were also considered. Satisfactory results were obtained regarding the bond between recycled steel fibres and concrete; on the other hand compressive strength of concrete seems unaffected by the presence of fibres despite their irregular geometric properties. Finally, flexural tests furnished in some cases results comparable to those obtained when using ISF as concerns the post-cracking behaviour.

It's not all about moral reasoning: Understanding the content of Moral Case Deliberation.

PubMed

Svantesson, Mia; Silén, Marit; James, Inger

2018-03-01

Moral Case Deliberation is one form of clinical ethics support described as a facilitator-led collective moral reasoning by healthcare professionals on a concrete moral question connected to their practice. Evaluation research is needed, but, as human interaction is difficult to standardise, there is a need to capture the content beyond moral reasoning. This allows for a better understanding of Moral Case Deliberation, which may contribute to further development of valid outcome criteria and stimulate the normative discussion of what Moral Case Deliberation should contain. To explore and compare the content beyond moral reasoning in the dialogue in Moral Case Deliberation at Swedish workplaces. A mixed-methods approach was applied for analysing audio-recordings of 70 periodic Moral Case Deliberation meetings at 10 Swedish workplaces. Moral Case Deliberation facilitators and various healthcare professions participated, with registered nurses comprising the majority. Ethical considerations: No objection to the study was made by an Ethical Review Board. After oral and written information was provided, consent to be recorded was assumed by virtue of participation. Other than 'moral reasoning' (median (md): 45% of the spoken time), the Moral Case Deliberations consisted of 'reflections on the psychosocial work environment' to a varying extent (md: 29%). Additional content comprised 'assumptions about the patient's psychosocial situation' (md: 6%), 'facts about the patient's situation' (md: 5%), 'concrete problem-solving' (md: 6%) and 'process' (md: 3%). The findings suggest that a restorative function of staff's wellbeing in Moral Case Deliberation is needed, as this might contribute to good patient care. This supports outcome criteria of improved emotional support, which may include relief of moral distress. However, facilitators need a strategy for how to proceed from the participants' own emotional needs and to develop the use of their emotional knowing to focus on the ethically difficult patient situation.

Development of Mix Designs for RAP Concrete for Florida Concrete Test Road

DOT National Transportation Integrated Search

2017-12-01

The main objective of this study was to develop mix designs for concrete incorporating Reclaimed Asphalt Pavement (RAP) materials to be used in the Florida Concrete Test Road. Two different FDOT-approved RAP sources were selected and used in this stu...

Assessment of the Uretek process on continuously reinforced concrete pavement, jointed concrete pavement, and bridge approach slabs : technical assistance report.

DOT National Transportation Integrated Search

2004-12-01

This study evaluates the rehabilitation method utilizing the injection of Uretek (polyurethane) into the pavement structures on continuously reinforced concrete pavement (CRCP), jointed concrete pavement (JCP), and bridge approach slabs. The polyuret...

Laboratory comparison of several tests for evaluating the transport properties of concrete.

DOT National Transportation Integrated Search

2006-01-01

The transport properties of concrete are a primary element in determining the durability of concrete. In this study, several new test methods that directly measure aspects of fluid and ionic transport in concrete were examined. ASTM C 1543 and ASTM C...

Asphalt concrete overlays on CRCP : decision criteria, tack coat evaluation, and asphalt concrete mixture evaluation.

DOT National Transportation Integrated Search

2005-02-01

This report presents the research undertaken within two areas of study of thin asphalt concrete (AC) overlays to rehabilitate : continuously reinforced concrete pavements (CRCP). The first one is the development of a decision tree for the project : s...

Efforts to reduce reflective cracking of bituminous concrete overlays of Portland cement concrete pavements.

DOT National Transportation Integrated Search

1975-01-01

Studies of efforts in Virginia to reduce the incidence of reflection cracking when portland cement concrete pavements or bases are overlayed with asphaltic concrete are reported. The methods of reflection crack reduction discussed are: (1) The use of...

Lunar concrete for construction

NASA Technical Reports Server (NTRS)

Cullingford, Hatice S.; Keller, M. Dean

1992-01-01

Feasibility of using concrete for lunar base construction was discussed recently without relevant data for the effects of vacuum on concrete. Our experimental studies performed earlier at Los Alamos have shown that concrete is stable in vacuum with no deterioration of its quality as measured by the compressive strength. Various considerations of using concrete successfully on the Moon are provided in this paper, along with specific conclusions from the existing database.

Experimental study on durability improvement of fly ash concrete with durability improving admixture.

PubMed

Quan, Hong-zhu; Kasami, Hideo

2014-01-01

In order to improve the durability of fly ash concrete, a series of experimental studies are carried out, where durability improving admixture is used to reduce drying shrinkage and improve freezing-thawing resistance. The effects of durability improving admixture, air content, water-binder ratio, and fly ash replacement ratio on the performance of fly ash concrete are discussed in this paper. The results show that by using durability improving admixture in nonair-entraining fly ash concrete, the compressive strength of fly ash concrete can be improved by 10%-20%, and the drying shrinkage is reduced by 60%. Carbonation resistance of concrete is roughly proportional to water-cement ratio regardless of water-binder ratio and fly ash replacement ratio. For the specimens cured in air for 2 weeks, the freezing-thawing resistance is improved. In addition, by making use of durability improving admixture, it is easier to control the air content and make fly ash concrete into nonair-entraining one. The quality of fly ash concrete is thereby optimized.

Study on Effects of Different Replacement Rate on Bending Behavior of Big Recycled Aggregate Self Compacting Concrete

NASA Astrophysics Data System (ADS)

Li, Jing; Guo, Tiantian; Gao, Shuai; Jiang, Lin; Zhao, Zhijun; Wang, Yalin

2018-03-01

Big recycled aggregate self compacting concrete is a new type of recycled concrete, which has the advantages of low hydration heat and green environmental protection, but its bending behavior can be affected by different replacement rate. Therefor, in this paper, the research status of big Recycled aggregate self compacting concrete was systematically introduced, and the effect of different replacement rate of big recycled aggregate on failure mode, crack distribution and bending strength of the beam were studied through the bending behavior test of 4 big recycled aggregate self compacting concrete beams. The results show that: The crack distribution of the beam can be affected by the replacement rate; The failure modes of big recycled aggregate beams are the same as those of ordinary concrete; The plane section assumption is applicable to the big recycled aggregate self compacting concrete beam; The higher the replacement rate, the lower the bending strength of big recycled aggregate self compacting concrete beams.

Parametric Study of Fire Performance of Concrete Filled Hollow Steel Section Columns with Circular and Square Cross-Section

NASA Astrophysics Data System (ADS)

Nurfaidhi Rizalman, Ahmad; Tahir, Ng Seong Yap Mahmood Md; Mohammad, Shahrin

2018-03-01

Concrete filled hollow steel section column have been widely accepted by structural engineers and designers for high rise construction due to the benefits of combining steel and concrete. The advantages of concrete filled hollow steel section column include higher strength, ductility, energy absorption capacity, and good structural fire resistance. In this paper, comparison on the fire performance between circular and square concrete filled hollow steel section column is established. A three-dimensional finite element package, ABAQUS, was used to develop the numerical model to study the temperature development, critical temperature, and fire resistance time of the selected composite columns. Based on the analysis and comparison of typical parameters, the effect of equal cross-sectional size for both steel and concrete, concrete types, and thickness of external protection on temperature distribution and structural fire behaviour of the columns are discussed. The result showed that concrete filled hollow steel section column with circular cross-section generally has higher fire resistance than the square section.

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.

Spall Damage of Concrete Structures

DTIC Science & Technology

1988-06-01

structures prediction Structural response Cased charges Scabbing Tests Concrete walls--testing . emi -hardened Upgrading Conventional weapons Spall Weapon...recording devices in a trailer approximately 750 feet from the test pit. Up to 30 channels were recorded on a Sangamo Model III, 32-channel FM magnetic tape...6.7"’DEEP 23.6" N 21’.6" 0.114? 4000 0 73670636 RATx.000620 RAT%.000520 SHEILD WALL DESTROYED MAIM WALL 0.2611 4000 0.S9001025 RAT-.000S29 RATa.000S20

Alkali-Activated Natural Pozzolan/Slag Binder for Sustainable Concrete

NASA Astrophysics Data System (ADS)

Najimi, Meysam

This study aimed to fully replace Portland cement (PC) with environmentally friendly binders capable of improving longevity of concrete. The new binders consisted of different proportions of natural Pozzolan and slag which were alkaline-activated with various combinations of sodium hydroxide and sodium silicate. A step-by-step research program was designed to (1) develop alkali-activated natural Pozzolan/slag pastes with adequate fresh and strength properties, (2) produce alkali-activated natural Pozzolan/slag mortars to assess the effects of dominant variables on their plastic and hardened properties, and (3) finally produce and assess fresh, mechanical, dimensional, transport and durability properties of alkali-activated natural Pozzolan/slag concretes. The major variables included in this study were binder combination (natural Pozzolan/slag combinations of 70/30, 50/50 and 30/70), activator combination (sodium silicate/sodium hydroxide combinations of 20/80, 25/75 and 30/70), and sodium hydroxide concentration (1, 1.75 and 2.5M). The experimental program assessed performance of alkali-activated natural Pozzolan/slag mixtures including fresh properties (flow and setting times), unit weights (fresh, demolded and oven-dry), mechanical properties (compressive and tensile strengths, and modulus of elasticity), transport properties (absorption, rapid chloride penetration, and rapid chloride migration), durability (frost resistance, chloride induced corrosion, and resistance to sulfuric acid attack), and dimensional stability (drying shrinkage). This study also compared the performance of alkali-activated natural Pozzolan/slag concretes with that of an equivalent reference Portland cement concrete having a similar flow and strength characteristics. The results of this study revealed that it was doable to find optimum binder proportions, activator combinations and sodium hydroxide concentrations to achieve adequate plastic and hardened properties. Nearly for all studied alkali-activated concretes, workability and setting times were in the acceptable ranges. Overall, a 50/50 combination of natural Pozzolan and slag developed the highest strengths. Increasing slag content to 70%, however, was useful for mixtures with high NaOH concentrations (2.5M) and for acceleration of initial reactions. The strength of alkali-activated concretes improved with increases in sodium silicate portion of activator. Regarding effects of sodium hydroxide concentration on strength properties, there were optimum NaOH molarities which increased with an increase in slag portion of the binder. A 50/50 combination of natural Pozzolan and slag also proved to be the optimum combination for the results of absorption test. NaOH concentration and sodium silicate dosage had marginal effects on the absorption and volume of permeable voids. The chloride penetration depth reduced with decreases in natural Pozzolan portion of the binder (particularly from 70 to 50%), sodium silicate dosage, and NaOH concentration. A nearly similar trend was seen for the drying shrinkage of studied alkali-activated natural Pozzolan/slag concretes, as reduction of these variables also reduced the drying shrinkage. The mass loss of alkali-activated concretes subjected to acid attack increased with increases in slag content, sodium silicate dosage, and sodium hydroxide concentration. The failure time in corrosion test improved (increased) with increases in natural Pozzolan content, sodium silicate dosage, and sodium hydroxide concentration. The frost resistance of alkali-activated concretes improved as slag portion of the binder was increased. An increase in sodium silicate dosage was beneficial in improving frost resistance of concretes made with binders having 50 and 70% slag. An opposite trend was seen when slag portion of the binder was reduced to 30%. The mechanical properties (compressive strength, tensile strength and elastic modulus) of alkali-activated concretes made with activators having 20 and 25% sodium silicate were lower than those of the reference Portland cement concrete. As sodium silicate dosage of activator was increased to 30%, the compressive strengths of alkali-activated concretes were similar to those of the reference Portland cement concrete. Absorption of the studied alkali-activated natural Pozzolan/slag concretes was averagely 26% lower than that of the reference Portland cement concrete. Their chloride penetration depths were significantly lower (averagely about 80%) than that of the reference Portland cement concrete. The average drying shrinkage of alkali-activated natural Pozzolan/slag concretes was lower than that of reference PC concrete by nearly 26%. While the drying shrinkage of the worst performed alkali-activated natural Pozzolan/slag concrete was about 25% higher than that of the reference Portland cement concrete, there were several alkali-activated concretes that shrank considerably less than the reference Portland cement concrete. The corrosion and acid attack resistances of alkali-activated natural Pozzolan/slag concretes were significantly higher than that of the reference Portland cement concrete. The frost resistance of alkali-activated concretes having binders made with 50 and 70% slag was significantly higher than that of the reference Portland cement concrete. On the other hand, the frost resistance of concretes made with binders having 30% slag was similar to or less than (depending on sodium silicate content) that of the reference Portland cement concrete.

Model Checking Failed Conjectures in Theorem Proving: A Case Study

NASA Technical Reports Server (NTRS)

Pike, Lee; Miner, Paul; Torres-Pomales, Wilfredo

2004-01-01

Interactive mechanical theorem proving can provide high assurance of correct design, but it can also be a slow iterative process. Much time is spent determining why a proof of a conjecture is not forthcoming. In some cases, the conjecture is false and in others, the attempted proof is insufficient. In this case study, we use the SAL family of model checkers to generate a concrete counterexample to an unproven conjecture specified in the mechanical theorem prover, PVS. The focus of our case study is the ROBUS Interactive Consistency Protocol. We combine the use of a mechanical theorem prover and a model checker to expose a subtle flaw in the protocol that occurs under a particular scenario of faults and processor states. Uncovering the flaw allows us to mend the protocol and complete its general verification in PVS.

Mechanical properties of concrete containing a high volume of tire-rubber particles.

PubMed

Khaloo, Ali R; Dehestani, M; Rahmatabadi, P

2008-12-01

Due to the increasingly serious environmental problems presented by waste tires, the feasibility of using elastic and flexible tire-rubber particles as aggregate in concrete is investigated in this study. Tire-rubber particles composed of tire chips, crumb rubber, and a combination of tire chips and crumb rubber, were used to replace mineral aggregates in concrete. These particles were used to replace 12.5%, 25%, 37.5%, and 50% of the total mineral aggregate's volume in concrete. Cylindrical shape concrete specimens 15 cm in diameter and 30 cm in height were fabricated and cured. The fresh rubberized concrete exhibited lower unit weight and acceptable workability compared to plain concrete. The results of a uniaxial compressive strain control test conducted on hardened concrete specimens indicate large reductions in the strength and tangential modulus of elasticity. A significant decrease in the brittle behavior of concrete with increasing rubber content is also demonstrated using nonlinearity indices. The maximum toughness index, indicating the post failure strength of concrete, occurs in concretes with 25% rubber content. Unlike plain concrete, the failure state in rubberized concrete occurs gently and uniformly, and does not cause any separation in the specimen. Crack width and its propagation velocity in rubberized concrete are lower than those of plain concrete. Ultrasonic analysis reveals large reductions in the ultrasonic modulus and high sound absorption for tire-rubber concrete.

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.

Concrete deck material properties.

DOT National Transportation Integrated Search

2009-01-01

The two-fold focus of this study was (a) to develop an understanding of the mechanisms responsible for causing : cracking in the concrete; and (b) to study the influence of the local materials on the performance of NYSDOTs HP : concrete mixture. R...

Evaluation of various coarse aggregate concretes : final report.

DOT National Transportation Integrated Search

1983-10-01

This study was initiated to determine the properties of concrete using three types of coarse aggregate. The coarse aggregates evaluated in this study included silicious gravel, the standard aggregate for concrete in the state, with sandstone and lime...

Study on performance of concrete with over-burnt bricks aggregates and micro-silica admixture

NASA Astrophysics Data System (ADS)

Praveen, K.; Sathyan, Dhanya; Mini, K. M.

2016-09-01

Concrete is made by mixing cement, sand, aggregates and water in required proportion, where aggregates occupy the major volume. Addition of aggregates in concrete improves properties of concrete. With the natural resources depleting rapidly, limiting the use of natural resources and enhancing the use of waste materials is very important for sustainable development. Over-burnt bricks are a waste material which cannot be used in construction directly because of their irregular shape and dark colour. Use of over-burnt bricks helps to preserve natural aggregate source. The present study focuses on the effects of microsilica at various percentages as a partial cement replacement in concrete with over-burnt bricks as coarse aggregates. The mechanical properties of hardened concrete such as splitting tensile strength, flexural strength and compressive strength are studied and analyzed.

Retrieval of concrete words involves more contextual information than abstract words: multiple components for the concreteness effect.

PubMed

Xiao, Xin; Zhao, Di; Zhang, Qin; Guo, Chun-yan

2012-03-01

The current study used the directed forgetting paradigm in implicit and explicit memory to investigate the concreteness effect. Event-related potentials (ERPs) were recorded to explore the neural basis of this phenomenon. The behavioral results showed a clear concreteness effect in both implicit and explicit memory tests; participants responded significantly faster to concrete words than to abstract words. The ERP results revealed a concreteness effect (N400) in both the encoding and retrieval phases. In addition, behavioral and ERP results showed an interaction between word concreteness and memory instruction (to-be-forgotten vs. to-be-remembered) in the late epoch of the explicit retrieval phase, revealing a significant concreteness effect only under the to-be-remembered instruction condition. This concreteness effect was realized as an increased P600-like component in response to concrete words relative to abstract words, likely reflecting retrieval of contextual details. The time course of the concreteness effect suggests advantages of concrete words over abstract words due to greater contextual information. Copyright © 2011 Elsevier Inc. All rights reserved.

Mechanical Behavior of Recycled Aggregate Concrete-Filled Steel Tubular Columns before and after Fire.

PubMed

Liu, Wenchao; Cao, Wanlin; Zhang, Jianwei; Wang, Ruwei; Ren, Lele

2017-03-09

Recycled aggregate concrete (RAC) is an environmentally friendly building material. This paper investigates the mechanical behavior of recycled aggregate concrete filled steel tube (RACFST) columns exposed to fire. Two groups of 12 columns were designed and tested, under axial compression, before and after fire, to evaluate the degradation of bearing capacity due to fire exposure. Six specimens were subjected to axial compression tests at room temperature and the other six specimens were subjected to axial compression tests after a fire exposure. The main parameters of the specimens include the wall thickness of the steel tube (steel content) and the type of concrete materials. Several parameters as obtained from the experimental results were compared and analyzed, including the load-bearing capacity, deformation capacity, and failure characteristics of the specimens. Meanwhile, rate of loss of bearing capacity of specimens exposed to fire were calculated based on the standards EC4 and CECS28:90. The results show that concrete material has a large influence on the rate of loss of bearing capacity in the case of a relatively lower steel ratio. While steel content has little effect on the rate of loss of bearing capacity of concrete-filled steel tube (CFST) columns after fire, it has a relatively large influence on the loss rate of bearing capacity of the RACFST columns. The loss of bearing capacity of the specimens from the experiment is more serious than that from the calculation. As the calculated values are less conservative, particular attention should be given to the application of recycled aggregate concrete in actual structures.

Mechanical Behavior of Recycled Aggregate Concrete-Filled Steel Tubular Columns before and after Fire

PubMed Central

Liu, Wenchao; Cao, Wanlin; Zhang, Jianwei; Wang, Ruwei; Ren, Lele

2017-01-01

Recycled aggregate concrete (RAC) is an environmentally friendly building material. This paper investigates the mechanical behavior of recycled aggregate concrete filled steel tube (RACFST) columns exposed to fire. Two groups of 12 columns were designed and tested, under axial compression, before and after fire, to evaluate the degradation of bearing capacity due to fire exposure. Six specimens were subjected to axial compression tests at room temperature and the other six specimens were subjected to axial compression tests after a fire exposure. The main parameters of the specimens include the wall thickness of the steel tube (steel content) and the type of concrete materials. Several parameters as obtained from the experimental results were compared and analyzed, including the load-bearing capacity, deformation capacity, and failure characteristics of the specimens. Meanwhile, rate of loss of bearing capacity of specimens exposed to fire were calculated based on the standards EC4 and CECS28:90. The results show that concrete material has a large influence on the rate of loss of bearing capacity in the case of a relatively lower steel ratio. While steel content has little effect on the rate of loss of bearing capacity of concrete-filled steel tube (CFST) columns after fire, it has a relatively large influence on the loss rate of bearing capacity of the RACFST columns. The loss of bearing capacity of the specimens from the experiment is more serious than that from the calculation. As the calculated values are less conservative, particular attention should be given to the application of recycled aggregate concrete in actual structures. PMID:28772634

Development and mechanical properties of construction materials from lunar simulants

NASA Technical Reports Server (NTRS)

Desai, Chandra S.

1990-01-01

The development of construction materials such as concrete from lunar soils without the use of water requires a different methodology than that used for conventional terrestrial concrete. Currently, this research involves two aspects: (1) liquefaction of lunar simulants with various additives in a furnace so as to produce a construction material like an intermediate ceramic; and (2) cyclic loading of simulant with different initial vacuums and densities with respect to the theoretical maximum densities (TMD). In both cases, bending, triaxial compression, extension, and hydrostatic tests will be performed to define the stress-strain strength response of the resulting materials. In the case of the intermediate ceramic, bending and available multiaxial test devices will be used, while for the compacted case, tests will be performed directly in the new device. The tests will be performed by simulating in situ confining conditions. A preliminary review of high-purity metal is also conducted.

Production practices affecting worker task demands in concrete operations: A case study.

PubMed

Memarian, Babak; Mitropoulos, Panagiotis

2015-01-01

Construction work involves significant physical, mental, and temporal task demands. Excessive task demands can have negative consequences for safety, errors and production. This exploratory study investigates the magnitude and sources of task demands on a concrete operation, and examines the effect of the production practices on the workers' task demands. The NASA Task Load Index was used to measure the perceived task demands of two work crews. The operation involved the construction of a cast-in-place concrete building under high schedule pressures. Interviews with each crew member were used to identify the main sources of the perceived demands. Extensive field observations and interviews with the supervisors and crews identified the production practices. The workers perceived different level of task demands depending on their role. The production practices influenced the task demands in two ways: (1) practices related to work organization, task design, resource management, and crew management mitigated the task demands; and (2) other practices related to work planning and crew management increased the crew's ability to cope with and adapt to high task demands. The findings identify production practices that regulate the workers' task demands. The effect of task demands on performance is mitigated by the ability to cope with high demands.

Concretes and mortars with waste paper industry: Biomass ash and dregs.

PubMed

Martínez-Lage, Isabel; Velay-Lizancos, Miriam; Vázquez-Burgo, Pablo; Rivas-Fernández, Marcos; Vázquez-Herrero, Cristina; Ramírez-Rodríguez, Antonio; Martín-Cano, Miguel

2016-10-01

This article describes a study on the viability of using waste from the paper industry: biomass boiler ash and green liquor dregs to fabricate mortars and concretes. Both types of ash were characterized by obtaining their chemical and mineralogical composition, their organic matter content, granulometry, adsorption and other common tests for construction materials. Seven different mortars were fabricated, one for reference made up of cement, sand, and water, three in which 10, 20, or 30% of the cement was replaced by biomass ash, and three others in which 10, 20, or 30% of the cement was replaced with dregs. Test specimens were fabricated with these mortars to conduct flexural and compression tests. Flexural strength is reduced for all the mortars studied. Compressive strength increases for the mortars fabricated with biomass ash and decreases for the mortar with dregs. Finally, 5 concretes were made, one of them as a reference (neither biomass ash nor dregs added), two of them with replacements of 10 and 20% of biomass ash instead of cement and another two with replacements of 10 and 20% of dregs instead of cement. The compressive and tensile splitting strength increase when a 10% of ash is replaced and decrease in all the other cases. The modulus of elasticity always decreases. Copyright © 2016 Elsevier Ltd. All rights reserved.

A research for Class II defect Bored Pile’s Accept Criteria: A case of Penang Second Marine bridge

NASA Astrophysics Data System (ADS)

Huang, Kang

2018-03-01

The aim of this preliminary research is to study the accept criteria of class II bored pile with subtle defect. According to a detailed comparison of the existed different standards, Chinese ones are more applicable especially for the large diameter bored piles. Through the concrete coring at pile No P25-03 of this case and the comparison to the actual calculation, the Class II pile’s defects were very minor. Comparison was also made for the effects on pile structural capacities before and after repair of the defects. the feasible repair proposal may bring forward to more defects to the piles. The Class II piles don’t need any further repairation when piles have typical of similar character and sonic logging test result with P25-03‘s one. For other Class II piles with some differences in characters, verification is needed through further concrete coring on the pile. The recommendation of this research could be adopted for the similar huge marine structures which installed large diameter bored piles.

Effect of Micro-Teaching Practices with Concrete Models on Pre-Service Mathematics Teachers' Self-Efficacy Beliefs about Using Concrete Models

ERIC Educational Resources Information Center

Ünlü, Melihan

2018-01-01

The purpose of the current study was to investigate the effect of micro-teaching practices with concrete models on the pre-service teachers' self-efficacy beliefs about using concrete models and to determine the opinions of the pre-service teachers about this issue. In the current study, one of the mixed methods, the convergent design (embedded)…

Experiment on the concrete slab for floor vibration evaluation of deteriorated building

NASA Astrophysics Data System (ADS)

Hong, S. U.; Na, J. H.; Kim, S. H.; Lee, Y. T.

2014-08-01

Damages from noise and vibration are increasing every year, and most of which are noises between floors in deteriorated building caused by floor impact sound. In this study, the floor vibration of the deteriorated buildings constructed with the concrete slabs of thickness no more than 150 mm was evaluated by the vibration impact sound. This highly reliable study was conducted to assess floor vibration according with the serviceability evaluation standard of Reiher / Meister and Koch and vibration evaluation standard of ISO and AIJ. Designed pressure for the concrete slab sample of floor vibration assessment was 24MPa, and the sample was manufactured pursuant to KS F 2865 and JIS A 1440-2 with size of 3200 mm × 3200 mm × 140 mm. Tests were conducted twice with accelerometers, and Fast Fourier Transform was performed for comparative analysis by the vibration assessment criteria. The peak displacement from Test 1 was in the range of 0.00869 - 0.02540 mm; the value of peak frequency ranged from 18 to 27 Hz, and the average value was 22Hz. The peak acceleration value from Test 2 was in the range of 0.47 - 1.07 % g; the value of peak frequency was 18.5 - 22.57 Hz, and the average was 21Hz. The vibration was apparently recognizable in most cases according to the Reiher/Meister standard. In case of Koch graph for the damage assessment of the structure, the vibration was at the medium level and causes no damage to the building structure. The measured vibration results did not exceed the damage limit or serviceability limit of building according to the vibration assessment criteria of ISO and residential assessment guidelines provided by Architectural Institute of Japan (AIJ).

Experimental study on the performance of pervious concrete

NASA Astrophysics Data System (ADS)

Liu, Haojie; Liu, Rentai; Yang, Honglu; Ma, Chenyang; Zhou, Heng

2018-02-01

With the construction of sponge city, the pervious concrete material has been developed rapidly. A high-performance pervious concrete is developed by using cement, silica fume (SF) and superplasticizer (SP). The effects of SF, SP, aggregate size, water-cement ration and aggregate-cement ratio on the permeability coefficient, compressive strength and flexural strength are studied by controlling variables, and exploring the corrosion resistance and abrasion resistance of pervious concrete. The results show that using 0.5% SP, 5% SF and small aggregate can greatly improve the strength. There is an optimum value for water-cement ratio to make the strength and permeability coefficient maximum. Compared to ordinary pervious concrete, the corrosion resistance and abrasion resistance of this pervious concrete are very good.

Research on Durability of Big Recycled Aggregate Self-Compacting Concrete Beam

NASA Astrophysics Data System (ADS)

Gao, Shuai; Liu, Xuliang; Li, Jing; Li, Juan; Wang, Chang; Zheng, Jinkai

2018-03-01

Deflection and crack width are the most important durability indexes, which play a pivotal role in the popularization and application of the Big Recycled Aggregate Self-Compacting Concrete technology. In this research, comparative study on the Big Recycled Aggregate Self-Compacting Concrete Beam and ordinary concrete beam were conducted by measuring the deflection and crack width index. The results show that both kind of concrete beams have almost equal mid-span deflection value and are slightly different in the maximum crack width. It indicates that the Big Recycled Aggregate Self-Compacting Concrete Beam will be a good substitute for ordinary concrete beam in some less critical structure projects.

Use of rubber crumbs in cement concrete

NASA Astrophysics Data System (ADS)

Longvinenko, A. A.

2018-03-01

Rubber crumb obtained from worn out tires has been increasingly used over the last 15-20 years, especially in manufacture of asphalt and cement concrete mixtures. This review pays principal attention to application of the rubber crumb to cement concrete mixtures. Use of the rubber crumb in cement concrete is not as successful as in asphalt concrete mixtures, due to incompatibility problems linked to chemical composition and a significant difference in rigidity between the rubber crumb and concrete mixture aggregates. Different methods are proposed and studied to mitigate the adverse influence and increase the beneficial effects of the rubber crumb when added to cement concrete.

Reusing recycled aggregates in structural concrete

NASA Astrophysics Data System (ADS)

Kou, Shicong

The utilization of recycled aggregates in concrete can minimize environmental impact and reduce the consumption of natural resources in concrete applications. The aim of this thesis is to provide a scientific basis for the possible use of recycled aggregates in structure concrete by conducting a comprehensive programme of laboratory study to gain a better understanding of the mechanical, microstructure and durability properties of concrete produced with recycled aggregates. The study also explored possible techniques to of improve the properties of recycled aggregate concrete that is produced with high percentages (≧ 50%) of recycled aggregates. These techniques included: (a) using lower water-to-cement ratios in the concrete mix design; (b) using fly ash as a cement replacement or as an additional mineral admixture in the concrete mixes, and (c) precasting recycled aggregate concrete with steam curing regimes. The characteristics of the recycled aggregates produced both from laboratory and a commercially operated pilot construction and demolition (C&D) waste recycling plant were first studied. A mix proportioning procedure was then established to produce six series of concrete mixtures using different percentages of recycled coarse aggregates with and without the use of fly ash. The water-to-cement (binder) ratios of 0.55, 0.50, 0.45 and 0.40 were used. The fresh properties (including slump and bleeding) of recycled aggregate concrete (RAC) were then quantified. The effects of fly ash on the fresh and hardened properties of RAC were then studied and compared with those RAC prepared with no fly ash addition. Furthermore, the effects of steam curing on the hardened properties of RAC were investigated. For micro-structural properties, the interfacial transition zones of the aggregates and the mortar/cement paste were analyzed by SEM and EDX-mapping. Moreover, a detailed set of results on the fracture properties for RAC were obtained. Based on the experimental results, a number of recommendations were made on how to optimize the use of recycled aggregates for structural concrete production. The results demonstrate that one of the practical ways to utilize a higher percentage of recycled aggregates in concrete is "precasting" with the use of fly ash and an initial steam curing stage immediately after casting.

Concrete deck material properties : final report.

DOT National Transportation Integrated Search

2009-01-01

The two-fold focus of this study was (a) to develop an understanding of the mechanisms responsible for causing : cracking in the concrete; and (b) to study the influence of the local materials on the performance of NYSDOTs HP : concrete mixture. R...

Causes and prevention of splitting/bursting failure of concrete crossties: a computational study

DOT National Transportation Integrated Search

2017-09-17

Concrete splitting/bursting is a well-known failure mode of concrete crossties that can compromise the crosstie integrity and raise railroad maintenance and track safety concerns. This paper presents a computational study aimed at better understandin...

Study of strength kinetics of sand concrete system of accelerated hardening

NASA Astrophysics Data System (ADS)

Sharanova, A. V.; Lenkova, D. A.; Panfilova, A. D.

2018-04-01

Methods of calorimetric analysis are used to study the dynamics of the hydration processes of concretes with different accelerator contents. The efficiency of the isothermal calorimetry method is shown for study of strength kinetics of concrete mixtures of accelerated hardening, promising for additive technologies in civil engineering.

Research on the Influence of Size Effect for the mechanical Performance of GFRP tube concrete steel tube composite column under axial compression

NASA Astrophysics Data System (ADS)

Li, Wen; Wang, Tong; Na, Yu

2017-08-01

FRP tube-concrete-steel tube composite column (DSTC) was a new type of composite structures. The column consists of FRP outer tube and steel tube and concrete. Concrete was filled between FRP outer tube and steel tube. This column has the character of light and high strength and corrosion resistance. In this paper, properties of DSTC axial compression were studied in depth. The properties were studied by two groups DSTC short columns under axial compression performance experiment. The different size of DSTC short columns was importantly considered. According to results of the experiment, we can conclude that with the size of the column increases the ability of it to resist deformation drops. On the other hand, the size effect influences on properties of different concrete strength DSTC was different. The influence of size effect on high concrete strength was less than that of low concrete.

Determining the Environmental Benefits of Ultra High Performance Concrete as a Bridge Construction Material

NASA Astrophysics Data System (ADS)

Lande Larsen, Ingrid; Granseth Aasbakken, Ida; O'Born, Reyn; Vertes, Katalin; Terje Thorstensen, Rein

2017-10-01

Ultra High Performance Concrete (UHPC) is a material that is attracting attention in the construction industry due to the high mechanical strength and durability, leading to structures having low maintenance requirements. The production of UHPC, however, has generally higher environmental impact than normal strength concrete due to the increased demand of cement required in the concrete mix. What is still not sufficiently investigated, is if the longer lifetime, slimmer construction and lower maintenance requirements lead to a net environmental benefit compared to standard concrete bridge design. This study utilizes life cycle assessment (LCA) to determine the lifetime impacts of two comparable highway crossing footbridges spanning 40 meters, designed respectively with UHPC and normal strength concrete. The results of the study show that UHPC is an effective material for reducing lifetime emissions from construction and maintenance of long lasting infrastructure, as the UHPC design outperforms the normal strength concrete bridge in most impact categories.

Laterally Loaded Partially Prestressed Concrete Piles

DTIC Science & Technology

1989-09-01

of an extensive test program onl laterali y ioadeu. partially pr- estressed concrete fender piles. The study Included service load range as well ats...12,000-psi design strength). Configura- tion G utilized 14 r:- estress strand, in an unsymmetric pattern. To provide a uniform concrete prestress of 540...sudden loss in load carrying capacity directly related to the loss of concrete area. The compression concrete fractured longitudinally and along the

Lunar concrete for construction

NASA Technical Reports Server (NTRS)

Cullingford, Hatice S.; Keller, M. Dean

1988-01-01

Feasibility of using concrete for lunar-base construction has been discussed recently without relevant data for the effects of vacuum on concrete. Experimental studies performed earlier at Los Alamos have shown that concrete is stable in vacuum with no deterioration of its quality as measured by the compressive strength. Various considerations of using concrete successfully on the moon are provided in this paper along with specific conclusions from the existing data base.

A field investigation of a concrete overlay containing silica fume on Route 50 over Opequon Creek.

DOT National Transportation Integrated Search

1993-01-01

This study evaluated concretes containing silica fume for use in overlays as a suitable alternative to the widely used latex-modified concrete (LMC). A two-lane, four-span bridge deck was overlaid with concrete containing silica fume at 7 percent or ...

Design and evaluation of high-volume fly ash (HVFA) concrete mixes, report D : creep, shrinkage, and abrasion resistance of HVFA concrete.

DOT National Transportation Integrated Search

2012-10-01

The main objective of this study was to determine the effect on shrinkage, creep, : and abrasion resistance of high-volume fly ash (HVFA) concrete. The HVFA concrete : test program consisted of comparing the shrinkage, creep, and abrasion performance...

Estimating Durability of Reinforced Concrete

NASA Astrophysics Data System (ADS)

Varlamov, A. A.; Shapovalov, E. L.; Gavrilov, V. B.

2017-11-01

In this article we propose to use the methods of fracture mechanics to evaluate concrete durability. To evaluate concrete crack resistance characteristics of concrete directly in the structure in order to implement the methods of fracture mechanics, we have developed special methods. Various experimental studies have been carried out to determine the crack resistance characteristics and the concrete modulus of elasticity during its operating. A comparison was carried out for the results obtained with the use of the proposed methods and those obtained with the standard methods for determining the concrete crack resistance characteristics.

Precast concrete unit assessment through GPR survey and FDTD modelling

NASA Astrophysics Data System (ADS)

Campo, Davide

2017-04-01

Precast concrete elements are widely used within United Kingdom house building offering ease in assembly and added values as structural integrity, sound and thermal insulation; most common concrete components include walls, beams, floors, panels, lintels, stairs, etc. The lack of respect of the manufacturer instruction during assembling, however, may induce cracking and short/long term loss of bearing capacity. GPR is a well-established not destructive technique employed in the assessment of structural elements because of real-time imaging, quickness of data collecting and ability to discriminate finest structural details. In this work, GPR has been used to investigate two different precast elements: precast reinforced concrete planks constituting the roof slab of a school and precast wood-cement blocks with insulation material pre-fitted used to build a perimeter wall of a private building. Visible cracks affected both constructions. For the assessment surveys, a GSSI 2.0 GHz GPR antenna has been used because of the high resolution required and the small size of the antenna case (155 by 90 by 105mm) enabling scanning up to 45mm from any obstruction. Finite Difference Time Domain (FDTD) numerical modelling was also performed to build a scenario of the expected GPR signal response for a preliminary real-time interpretation and to help solve uncertainties due to complex reflection patterns: simulated radargrams were built using Reflex Software v. 8.2, reproducing the same GPR pulse used for the surveys in terms of wavelet, nominal frequency, sample frequency and time window. Model geometries were derived from the design projects available both for the planks and the blocks; the electromagnetic properties of the materials (concrete, reinforcing bars, air-filled void, insulation and wooden concrete) were inferred from both values reported in literature and a preliminary interpretation of radargrams where internal layer interfaces were clearly recognizable and univocally interpretable. Simulated and real radargrams comparison demonstrated that, in both cases, manufacturer instructions were not fully respected and confirmed GPR as a fast and effective structural assessment technique with the support of FDTD modelling as data interpretation validating method when complex reflection patterns are observed. GPR findings will be then used to address the intrusive coring necessary to evaluate the compressive strength of the concrete and, in synergy with the intrusive survey results, to plan properly corrective actions to ensure the stability of the structures and guarantee the usability.

Laboratory study of concrete properties to support implementation of the new AASHTO mechanistic-empirical pavement design guide.

DOT National Transportation Integrated Search

2012-09-01

Properties of concrete embodying materials typically used in Wisconsin paving projects were evaluated in support of future : implementation of the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG). The primary concrete : properties studied w...

Laboratory study of concrete properties to support implementation of the new AASHTO mechanistic empirical pavement design guide.

DOT National Transportation Integrated Search

2012-09-01

Properties of concrete embodying materials typically used in Wisconsin paving projects were evaluated in support of future : implementation of the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG). The primary concrete : properties studied w...

Study of the internal confinement of concrete reinforced (in civil engineering) with woven reinforcement

NASA Astrophysics Data System (ADS)

Dalal, M.; Goumairi, O.; El Malik, A.

2017-10-01

Concrete is generally the most used material in the field of construction. Despite its extensive use in structures, it represents some drawbacks related to its properties including its low tensile strength and low ductility. To solve this problem, the use of steel reinforcement in concrete structures is possible. Another possibility is the introduction of different types of continuous fibre / staple in the concrete, such as steel fibres or synthetic fibres, to obtain ″Concretes bundles″. Many types of fibre concrete, which have been developed and for many of them, the gain provided by the fibre was rather low and no significant improvement in tensile strength was really reaching. By cons, the ductility was higher than that of ordinary concrete. The objective of this study is to examine concrete reinforcement by inserting reinforcements woven polyester. These are either woven bidirectional (2D) or three-dimensional woven (3D). So we will report the properties of each type of reinforcement and the influence of the method of weaving on the strength reinforcements and on the strength of concrete in which they are incorporated. Such influence should contribute to improving the sustainability and enhancement of reinforcement

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

Lampropoulos, A. P.; Dritsos, S. E.

In this study, the technique of seismic strengthening existing reinforced concrete columns and beams using additional concrete layers and jackets is examined. The finite element method and the finite element program ATENA is used in this investigation. When a reinforced jacket or layer is being constructed around a column it is already preloaded due to existing service loads. This effect has been examined for different values of the axial load normalized to the strengthened column. The techniques of strengthening with a concrete jacket or a reinforced concrete layer on the compressive side of the column are examined. Another phenomenon thatmore » is examined in this study is the shrinkage of the new concrete of an additional layer used to strengthen an existing member. For this investigation, a simply supported beam with an additional reinforced concrete layer on the tensile side is examined. The results demonstrate that the effect of preloading is important when a reinforced concrete layer is being used with shear connectors between the old and the new reinforcement. It was also found that the shrinkage of the new concrete reduces the strength of the strengthened beam and induces an initial sliding between the old and the new concrete.« less

Bond-slip detection of concrete-encased composite structure using electro-mechanical impedance technique

NASA Astrophysics Data System (ADS)

Liang, Yabin; Li, Dongsheng; Parvasi, Seyed Mohammad; Kong, Qingzhao; Lim, Ing; Song, Gangbing

2016-09-01

Concrete-encased composite structure is a type of structure that takes the advantages of both steel and concrete materials, showing improved strength, ductility, and fire resistance compared to traditional reinforced concrete structures. The interface between concrete and steel profiles governs the interaction between these two materials under loading, however, debonding damage between these two materials may lead to severe degradation of the load transferring capacity which will affect the structural performance significantly. In this paper, the electro-mechanical impedance (EMI) technique using piezoceramic transducers was experimentally investigated to detect the bond-slip occurrence of the concrete-encased composite structure. The root-mean-square deviation is used to quantify the variations of the impedance signatures due to the presence of the bond-slip damage. In order to verify the validity of the proposed method, finite element model analysis was performed to simulate the behavior of concrete-steel debonding based on a 3D finite element concrete-steel bond model. The computed impedance signatures from the numerical results are compared with the results obtained from the experimental study, and both the numerical and experimental studies verify the proposed EMI method to detect bond slip of a concrete-encased composite structure.

Use of recycled plastics in concrete: A critical review.

PubMed

Gu, Lei; Ozbakkaloglu, Togay

2016-05-01

Plastics have become an essential part of our modern lifestyle, and the global plastic production has increased immensely during the past 50years. This has contributed greatly to the production of plastic-related waste. Reuse of waste and recycled plastic materials in concrete mix as an environmental friendly construction material has drawn attention of researchers in recent times, and a large number of studies reporting the behavior of concrete containing waste and recycled plastic materials have been published. This paper summarizes the current published literature until 2015, discussing the material properties and recycling methods of plastic and the influence of plastic materials on the properties of concrete. To provide a comprehensive review, a total of 84 studies were considered, and they were classified into sub categories based on whether they dealt with concrete containing plastic aggregates or plastic fibers. Furthermore, the morphology of concrete containing plastic materials is described in this paper to explain the influence of plastic aggregates and plastic fibers on the properties of concrete. The properties of concretes containing virgin plastic materials were also reviewed to establish their similarities and differences with concrete containing recycled plastics. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

How to Mutually Advance General Education and Major-Based Education: A Grounded Theory Study on the Course Level

ERIC Educational Resources Information Center

Fang, Hualiang

2018-01-01

The author employs grounded theory to investigate the teaching process of an interdisciplinary general education course at A University as a case. The author finds that under the condition of rather concrete relations between the subject of a major-based course and that of an elected general education course, if the major course is taught with a…

The Relationship between Item Context Characteristics and Student Performance: The Case of the 2006 and 2009 PISA Science Items

ERIC Educational Resources Information Center

Ruiz-Primo, Maria Araceli; Li, Min

2015-01-01

Background: A long-standing premise in test design is that contextualizing test items makes them concrete, less demanding, and more conducive to determining whether students can apply or transfer their knowledge. Purpose: We assert that despite decades of study and experience, much remains to be learned about how to construct effective and fair…

Concrete research

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

NONE

The papers in this volume deal with various facets of concrete technology. The first four papers discuss concrete performance from the perspectives of design, specifications, and testing. The following three papers address the use and management of by-products in cementitious systems. Kakodkar et al. present the results of a study to determine the influence of five different Class C fly ashes on inhibiting the expansion of concrete due to alkali-silica reaction. Ramakrishnan et al. present the results of an extensive study to determine the influence of natural possolans in reducing the deleterious expansion of concrete due to alkai-silica reaction. Themore » test results showed that all the natural pozzolans used in the study, except one, were very effective in reducing the expansions due to alkali-silica reaction. Johnston discusses a modified interpretation of the ASTM P214 test results for determining potential reactivity of sands used for concrete in South Dakota.« less

Studies for understanding effects of additions on the strength of cement concrete

NASA Astrophysics Data System (ADS)

Bucur, R. D.; Barbuta, M.; Konvalina, P.; Serbanoiu, A. A.; Bernas, J.

2017-09-01

The paper analyzes the effects of different types of additions introduced in concrete mix on the compressive strength. The current studies show that additions contribute to improve some characteristics of concrete and to reduce the cement dosage, so it can obtain concretes which are cheaper and friendlier with environment. In the experimental mixes were introduced: crushed natural aggregates, slag aggregates, silica fume, fly ash, chopped tire, polystyrene granule, glass fibers and metallic fibers. The experimental values of compressive strengths were compared for two concrete grades (C20/25 and C25/30). The study shown that near the well-known possibilities of improving mechanical strengths of cement concrete by increasing cement dosage and strength, by using crushed aggregates and by reducing the water/cement ratio, there are other methods in which less cement is used by replacing it with different wastes or by adding fiber.

A unified bond theory, probabilistic meso-scale modeling, and experimental validation of deformed steel rebar in normal strength concrete

NASA Astrophysics Data System (ADS)

Wu, Chenglin

Bond between deformed rebar and concrete is affected by rebar deformation pattern, concrete properties, concrete confinement, and rebar-concrete interfacial properties. Two distinct groups of bond models were traditionally developed based on the dominant effects of concrete splitting and near-interface shear-off failures. Their accuracy highly depended upon the test data sets selected in analysis and calibration. In this study, a unified bond model is proposed and developed based on an analogy to the indentation problem around the rib front of deformed rebar. This mechanics-based model can take into account the combined effect of concrete splitting and interface shear-off failures, resulting in average bond strengths for all practical scenarios. To understand the fracture process associated with bond failure, a probabilistic meso-scale model of concrete is proposed and its sensitivity to interface and confinement strengths are investigated. Both the mechanical and finite element models are validated with the available test data sets and are superior to existing models in prediction of average bond strength (< 6% error) and crack spacing (< 6% error). The validated bond model is applied to derive various interrelations among concrete crushing, concrete splitting, interfacial behavior, and the rib spacing-to-height ratio of deformed rebar. It can accurately predict the transition of failure modes from concrete splitting to rebar pullout and predict the effect of rebar surface characteristics as the rib spacing-to-height ratio increases. Based on the unified theory, a global bond model is proposed and developed by introducing bond-slip laws, and validated with testing of concrete beams with spliced reinforcement, achieving a load capacity prediction error of less than 26%. The optimal rebar parameters and concrete cover in structural designs can be derived from this study.

Thermal Behavior of Cylindrical Buckling Restrained Braces at Elevated Temperatures

PubMed Central

Talebi, Elnaz; Tahir, Mahmood Md.; Yasreen, Airil

2014-01-01

The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system. PMID:24526915

Binary effect of fly ash and palm oil fuel ash on heat of hydration aerated concrete.

PubMed

Mehmannavaz, Taha; Ismail, Mohammad; Radin Sumadi, Salihuddin; Rafique Bhutta, Muhammad Aamer; Samadi, Mostafa; Sajjadi, Seyed Mahdi

2014-01-01

The binary effect of pulverized fuel ash (PFA) and palm oil fuel ash (POFA) on heat of hydration of aerated concrete was studied. Three aerated concrete mixes were prepared, namely, concrete containing 100% ordinary Portland cement (control sample or Type I), binary concrete made from 50% POFA (Type II), and ternary concrete containing 30% POFA and 20% PFA (Type III). It is found that the temperature increases due to heat of hydration through all the concrete specimens especially in the control sample. However, the total temperature rises caused by the heat of hydration through both of the new binary and ternary concrete were significantly lower than the control sample. The obtained results reveal that the replacement of Portland cement with binary and ternary materials is beneficial, particularly for mass concrete where thermal cracking due to extreme heat rise is of great concern.

Binary Effect of Fly Ash and Palm Oil Fuel Ash on Heat of Hydration Aerated Concrete

PubMed Central

Mehmannavaz, Taha; Ismail, Mohammad; Radin Sumadi, Salihuddin; Rafique Bhutta, Muhammad Aamer; Samadi, Mostafa

2014-01-01

The binary effect of pulverized fuel ash (PFA) and palm oil fuel ash (POFA) on heat of hydration of aerated concrete was studied. Three aerated concrete mixes were prepared, namely, concrete containing 100% ordinary Portland cement (control sample or Type I), binary concrete made from 50% POFA (Type II), and ternary concrete containing 30% POFA and 20% PFA (Type III). It is found that the temperature increases due to heat of hydration through all the concrete specimens especially in the control sample. However, the total temperature rises caused by the heat of hydration through both of the new binary and ternary concrete were significantly lower than the control sample. The obtained results reveal that the replacement of Portland cement with binary and ternary materials is beneficial, particularly for mass concrete where thermal cracking due to extreme heat rise is of great concern. PMID:24696646

The durability of concrete containing recycled tyres as a partial replacement of fine aggregate

NASA Astrophysics Data System (ADS)

Syamir Senin, Mohamad; Shahidan, Shahiron; Syazani Leman, Alif; Othman, Nurulain; Shamsuddin, Shamrul-mar; Ibrahim, M. H. W.; Zuki, S. S. Mohd

2017-11-01

Nowadays, uncontrolled disposal of waste materials such as tyres can affect the environment. Therefore, careful management of waste disposal must be done in order to conserve the environment. Waste tyres can be use as a replacement for both fine aggregate and coarse aggregate in the production of concrete. This research was conducted to assess the durability of concrete containing recycled tyres which have been crushed into fine fragments to replace fine aggregate in the concrete mix. This study presents an overview of the use of waste rubber as a partial replacement of natural fine aggregate in a concrete mix. 36 concrete cubes measuring 100mm × 100mm × 100mm and 12 concrete cubes measuring 150mm × 150mm × 150mm were prepared and added with different percentages of rubber from recycled tyres (0%, 3%, 5% and 7%) as fine aggregate replacement. The results obtained show that the replacement of fine aggregate with 7% of rubber recorded a compressive strength of 43.7MPa while the addition of 3% of rubber in the concrete sample recorded a high compressive strength of 50.8MPa. This shows that there is a decrease in the strength and workability of concrete as the amount of rubber used a replacement for fine aggregate in concrete increases. On the other hand, the water absorption test indicated that concrete which contains rubber has better water absorption ability. In this study, 3% of rubber was found to be the optimal percentage as a partial replacement for fine aggregate in the production of concrete.

Performance of Microbial Concrete Developed Using Bacillus Subtilus JC3

NASA Astrophysics Data System (ADS)

Rao, M. V. Seshagiri; Reddy, V. Srinivasa; Sasikala, Ch.

2017-12-01

Concrete is vulnerable to deterioration, corrosion, and cracks, and the consequent damage and loss of strength requires immensely expensive remediation and repair. So need for special concrete that they would respond to crack formation with an autonomous self-healing action lead to research and development of microbial concrete. The microbial concrete works on the principle of calcite mineral precipitation by a specific group of alkali-resistant spore-forming bacteria related to the genus Bacillus called Bacillus subtilis JC3, this phenomenon is called biomineralization or Microbiologically Induced Calcite Crystal Precipitation. Bacillus subtilis JC3, a common soil bacterium, has inherent ability to precipitate calcite crystals continuously which enhances the strength and durability performance of concrete enormously. This microbial concrete can be called as a "Self healing Bacterial Concrete" because it can remediate its cracks by itself without any human intervention and would make the concrete more durable and sustainable. This paper discuss the incorporation of microorganism Bacillus subtilis JC3 (developed at JNTU, India) into concrete and presents the results of experimental investigations carried out to study the improved durability and sustainability characteristics of microbial concrete.

Physical-durable performance of concrete incorporating high loss on ignition-fly ash

NASA Astrophysics Data System (ADS)

Huynh, Trong-Phuoc; Ngo, Si-Huy; Hwang, Chao-Lung

2018-04-01

This study investigates the feasibility of using raw fly ash with a high loss on ignition in concrete. The fly ash-free concrete samples were prepared with different water-to-binder (w/b) ratios of 0.35, 0.40, and 0.45, whereas the fly ash concrete samples were prepared with a constant w/b of 0.40 and with various fly ash contents (10%, 20%, and 30%) as a cement substitution. The physical properties and durability performance of the concretes were evaluated through fresh concrete properties, compressive strength, strength efficiency of cement, ultrasonic pulse velocity, and resistance to sulfate attack. Test results show that the w/b ratio affected the concrete properties significantly. The incorporation of fly ash increased the workability and reduced the unit weight of fresh concrete. In addition, the fly ash concrete samples containing up to 20% fly ash exhibited an improved strength at long-term ages. Further, all of the fly ash concrete samples showed a good durability performance with ultrasonic pulse velocity value of greater than 4100 m/s and a comparable sulfate resistance to the no-fly ash concrete.

Influence of seawater mixing and curing on strength characteristics and porosity of ground granulated blast-furnace slag concrete

NASA Astrophysics Data System (ADS)

Adiwijaya; Hamada, H.; Sagawa, Y.; Yamamoto, D.

2017-11-01

Generally, in the concrete industry, several billion tons of fresh water are annually used for mixing water, curing water and cleaning water. Nevertheless, the utilization of seawater in the concrete industry is prohibited, because it increases the risk of corrosion of steel bars in concrete. This study presents strength characteristics and porosity of seawater mixed concrete and tap water mixed concrete incorporating Ground Granulated Blast-Furnace Slag (GGBS) with water-binder ratio (W/B) of 40%, 50% and 60%. The influence of seawater mixing, GGBS and curing conditions such as tap water curing (TC), seawater curing (SC) and air curing (AC) on the strength and porosity of concrete were evaluated. Based on investigation result, it was shown that there is no significant influence of seawater mixing in improving strength of GGBS concrete up to 365 days in TC and SC. Effectiveness of seawater-mixing on strength enhancement of GGBS concrete is larger in air curing than in water curing. Porosity of seawater-mixed concrete is decreased compared to tap water-mixed concrete in all curing conditions.

Smart Crack Control in Concrete through Use of Phase Change Materials (PCMs): A Review

PubMed Central

2018-01-01

Cracks in concrete structures present a threat to their durability. Therefore, numerous research studies have been devoted to reducing concrete cracking. In recent years, a new approach has been proposed for controlling temperature related cracking—utilization of phase change materials (PCMs) in concrete. Through their ability to capture heat, PCMs can offset temperature changes and reduce gradients in concrete structures. Nevertheless, they can also influence concrete properties. This paper presents a comprehensive overview of the literature devoted to using PCMs to control temperature related cracking in concrete. First, types of PCMs and ways of incorporation in concrete are discussed. Then, possible uses of PCMs in concrete technology are discussed. Further, the influences of PCMs on concrete properties (fresh, hardened, durability) are discussed in detail. This is followed by a discussion of modelling techniques for PCM-concrete composites and their performance. Finally, a summary and the possible research directions for future work are given. This overview aims to assure the researchers and asset owners of the potential of this maturing technology and bring it one step closer to practical application. PMID:29695076

Smart Crack Control in Concrete through Use of Phase Change Materials (PCMs): A Review.

PubMed

Šavija, Branko

2018-04-24

Cracks in concrete structures present a threat to their durability. Therefore, numerous research studies have been devoted to reducing concrete cracking. In recent years, a new approach has been proposed for controlling temperature related cracking—utilization of phase change materials (PCMs) in concrete. Through their ability to capture heat, PCMs can offset temperature changes and reduce gradients in concrete structures. Nevertheless, they can also influence concrete properties. This paper presents a comprehensive overview of the literature devoted to using PCMs to control temperature related cracking in concrete. First, types of PCMs and ways of incorporation in concrete are discussed. Then, possible uses of PCMs in concrete technology are discussed. Further, the influences of PCMs on concrete properties (fresh, hardened, durability) are discussed in detail. This is followed by a discussion of modelling techniques for PCM-concrete composites and their performance. Finally, a summary and the possible research directions for future work are given. This overview aims to assure the researchers and asset owners of the potential of this maturing technology and bring it one step closer to practical application.

Behaviour of Recycled Coarse Aggregate Concrete: Age and Successive Recycling

NASA Astrophysics Data System (ADS)

Sahoo, Kirtikanta; Pathappilly, Robin Davis; Sarkar, Pradip

2016-06-01

Recycled Coarse Aggregate (RCA) concrete construction technique can be called as `green concrete', as it minimizes the environmental hazard of the concrete waste disposal. Indian standard recommends target mean compressive strength of the conventional concrete in terms of water cement ratio ( w/ c). The present work is an attempt to study the behaviour of RCA concrete from two samples of parent concrete having different age group with regard to the relationship of compressive strength with water cement ratios. Number of recycling may influence the mechanical properties of RCA concrete. The influence of age and successive recycling on the properties such as capillary water absorption, drying shrinkage strain, air content, flexural strength and tensile splitting strength of the RCA concrete are examined. The relationship between compressive strength at different w/ c ratios obtained experimentally is investigated for the two parameters such as age of parent concrete and successive recycling. The recycled concrete using older recycled aggregate shows poor quality. While the compressive strength reduces with successive recycling gradually, the capillary water absorption increases abruptly, which leads to the conclusion that further recycling may not be advisable.

Effect of concrete strength gradation to the compressive strength of graded concrete, a numerical approach

NASA Astrophysics Data System (ADS)

Pratama, M. Mirza Abdillah; Aylie, Han; Gan, Buntara Sthenly; Umniati, B. Sri; Risdanareni, Puput; Fauziyah, Shifa

2017-09-01

Concrete casting, compacting method, and characteristic of the concrete material determine the performance of concrete as building element due to the material uniformity issue. Previous studies show that gradation in strength exists on building member by nature and negatively influence the load carrying capacity of the member. A pilot research had modeled the concrete gradation in strength with controllable variable and observed that the weakest material determines the strength of graded concrete through uniaxial compressive loading test. This research intends to confirm the recent finding by a numerical approach with extensive variables of strength disparity. The finite element analysis was conducted using the Strand7 nonlinear program. The results displayed that the increase of strength disparity in graded concrete models leads to the slight reduction of models strength. A substantial difference in displacement response is encountered on the models for the small disparity of concrete strength. However, the higher strength of concrete mix in the graded concrete models contributes to the rise of material stiffness that provides a beneficial purpose for serviceability of building members.

Utilization of sugarcane bagasse ash in concrete as partial replacement of cement

NASA Astrophysics Data System (ADS)

Mangi, Sajjad Ali; Jamaluddin, N.; Ibrahim, M. H. Wan; Halid Abdullah, Abd; Awal, A. S. M. Abdul; Sohu, Samiullah; Ali, Nizakat

2017-11-01

This research addresses the suitability of sugarcane bagasse ash (SCBA) in concrete used as partial cement replacement. Two grades of concrete M15 and M20 were used for the experimental analysis. The cement was partially replaced by SCBA at 0%, 5%, and 10%, by weight in normal strength concrete (NSC). The innovative part of this study is to consider two grades of concrete mixes to evaluate the performance of concrete while cement is replaced by sugarcane bagasse ash. The cylindrical specimens having size 150 mm × 300 mm were used and tested after curing period of 7, 14 and 28 days. It was observed through the experimental work that the compressive strength increases with incorporating SCBA in concrete. Results indicated that the use of SCBA in concrete (M20) at 5% increased the average amount of compressive strength by 12% as compared to the normal strength concrete. The outcome of this work indicates that maximum strength of concrete could be attained at 5% replacement of cement with SCBA. Furthermore, the SCBA also gives compatible slump values which increase the workability of concrete.

Utilisation of Waste Marble Dust as Fine Aggregate in Concrete

NASA Astrophysics Data System (ADS)

Vigneshpandian, G. V.; Aparna Shruthi, E.; Venkatasubramanian, C.; Muthu, D.

2017-07-01

Concrete is the important construction material and it is used in the construction industry due to its high compressive strength and its durability. Now a day’s various studies have been conducted to make concrete with waste material with the intention of reducing cost and unavailability of conventional materials. This paper investigates the strength properties of concrete specimens cast using waste marble dust as replacement of fine aggregate. The marble pieces are finely crushed to powdered and the gradation is compared with conventional fine aggregate. Concrete specimen were cast using wmd in the laboratory with different proportion (25%, 50% and 100%) by weight of cement and from the studies it reveals that addition of waste marble dust as a replacement of fine aggregate marginally improves compressive, tensile and flexural strength in concrete.

Foamed concrete containing rice husk ash as sand replacement: an experimental study on compressive strength

NASA Astrophysics Data System (ADS)

Rum, R. H. M.; Jaini, Z. M.; Boon, K. H.; Khairaddin, S. A. A.; Rahman, N. A.

2017-11-01

This study presents the utilization of rice husk ash (RHA) as sand replacement in foamed concrete. The study focuses on the effect of RHA on the compressive strength of foamed concrete. RHA contains high pozzolanic material that reacts with cementitious to enhance the strength and durability of foamed concrete. RHA also acts as filler causing the foamed concrete to become denser while retaining its unique low density. A total 243 cube specimens was prepared for the compression test. Two sets of mix design were employed at water-cement (W/C) ratio of 0.55, 0.60 and cement-sand ratio of 0.50, 0.33. The results revealed that the presence of RHA as sand replacement resulted in an increase in the compressive strength of foamed concrete. Moreover, 30% to 40% RHA was the optimum content level, contributing to the compressive strength of 18.1 MPa to 22.4 MPa. The W/C ratio and superplasticiser dosage play small roles in improving workability. In contrast, density governs the compressive strength of foamed concrete.

Are Pumpkins Better than Heaven? An ERP Investigation of Order Effects in the Concrete-Word Advantage

ERIC Educational Resources Information Center

Tolentino, Leida C.; Tokowicz, Natasha

2009-01-01

The present study investigated the cognitive and neural mechanisms underlying the processing of concrete and abstract words by recording event-related potentials (ERPs) while participants performed an English lexical decision task. Concrete and abstract words were presented in three stimulus-order conditions: abstract before concrete, concrete…

Strength of Perceptual Experience Predicts Word Processing Performance Better than Concreteness or Imageability

ERIC Educational Resources Information Center

Connell, Louise; Lynott, Dermot

2012-01-01

Abstract concepts are traditionally thought to differ from concrete concepts by their lack of perceptual information, which causes them to be processed more slowly and less accurately than perceptually-based concrete concepts. In two studies, we examined this assumption by comparing concreteness and imageability ratings to a set of perceptual…

Performance of Waterless Concrete

NASA Technical Reports Server (NTRS)

Toutanji, Houssam; Evans, Steve; Grugel, Richard N.

2010-01-01

The development of permanent lunar bases is constrained by performance of construction materials and availability of in-situ resources. Concrete seems a suitable construction material for the lunar environment, but water, one of its major components, is an extremely scarce resource on the Moon. This study explores an alternative to hydraulic concrete by replacing the binding mix of concrete (cement and water) with sulfur. Sulfur is a volatile element on the lunar surface that can be extracted from lunar soils by heating. Sulfur concrete mixes were prepared to investigate the effect of extreme environmental conditions on the properties of sulfur concrete. A hypervelocity impact test was conducted, having as its target a 5-cm cubic sample of sulfur concrete. This item consisted of JSC-1 lunar regolith simulant (65%) and sulfur (35%). The sample was placed in the MSFC Impact Test Facility s Micro Light Gas Gun target chamber, and was struck by a 1-mm diameter (1.4e-03 g) aluminum projectile at 5.85 km/s. In addition, HZTERN code, provided by NASA was used to study the effectiveness of sulfur concrete when subjected to space radiation.

Experimental Study on Durability Improvement of Fly Ash Concrete with Durability Improving Admixture

PubMed Central

Quan, Hong-zhu; Kasami, Hideo

2014-01-01

In order to improve the durability of fly ash concrete, a series of experimental studies are carried out, where durability improving admixture is used to reduce drying shrinkage and improve freezing-thawing resistance. The effects of durability improving admixture, air content, water-binder ratio, and fly ash replacement ratio on the performance of fly ash concrete are discussed in this paper. The results show that by using durability improving admixture in nonair-entraining fly ash concrete, the compressive strength of fly ash concrete can be improved by 10%–20%, and the drying shrinkage is reduced by 60%. Carbonation resistance of concrete is roughly proportional to water-cement ratio regardless of water-binder ratio and fly ash replacement ratio. For the specimens cured in air for 2 weeks, the freezing-thawing resistance is improved. In addition, by making use of durability improving admixture, it is easier to control the air content and make fly ash concrete into nonair-entraining one. The quality of fly ash concrete is thereby optimized. PMID:25013870

Investigation on dynamic performance of concrete column crumb rubber steel and fiber concrete

NASA Astrophysics Data System (ADS)

Siti Nurul Nureda, M. Z.; Mariyana, A. K.; Khiyon, M. Iqbal; Rahman, M. S. Abdul; Nurizaty, Z.

2017-11-01

In general the Normal Concrete (NC) are by quasi-brittle failure, where, the nearly complete loss of loading capacity, once failure is initiated especially under dynamic loadings. The significance of this study is to improve the damping properties of concrete structure by utilization of the recycled materials from waste tires to be used in concrete as structural materials that improve seismic performance. In this study, the concrete containing 10% of fine crumb rubber and 1 % volume fraction of steel fiber from waste tires is use to investigate the dynamic performance (natural frequency and damping ratio).A small scale column were fabricated from Treated Crumb Rubber and Steel Fiber Concrete (TCRSFC) and NC were cast and cured for 28 days to investigate the dynamic performance. Based on analysis, dynamic modulus, damping ratio and natural frequency of TCRSFC has improved considerably by 5.18%, 109% and 10.94% when compared with NC. The TCRSFC producing concrete with the desired properties as well as to introduce the huge potential as dynamic resistance structure from severe damage especially prevention on catastrophic failure.

Palm Oil Fuel Ash (POFA) and Eggshell Powder (ESP) as Partial Replacement for Cement in Concrete

NASA Astrophysics Data System (ADS)

Ezdiani Mohamad, Mazizah; Mahmood, Ali A.; Min, Alicia Yik Yee; Nur Nadhira A., R.

2018-03-01

This study is an attempt to partially replace Ordinary Portland cement (OPC) in concrete with palm oil fuel ash (POFA) and eggshell powder (ESP). The mix proportions of POFA and ESP were varied at 10% of cement replacement and compared with OPC concrete as control specimen. The fineness of POFA is characterized by passing through 300 μm sieve and ESP by passing through 75 μm sieve. Compressive strength testing was conducted on concrete specimens to determine the optimum mix proportion of POFA and ESP. Generally the compressive strength of OPC concrete is higher compared to POFA-ESP concrete. Based on the results of POFA-ESP concrete overall, it shows that the optimum mix proportion of concrete is 6%POFA:4% ESP achieved compressive strength of 38.60 N/mm2 at 28 days. The compressive strength of OPC concrete for the same period was 42.37 N/mm2. Higher water demand in concrete is needed due to low fineness of POFA that contributing to low compressive strength of POFA-ESP concrete. However, the compressive strength and workability of the POFA-ESP concrete were within the ranges typically encountered in regular concrete mixtures indicating the viability of this replacement procedure for structural and non-structural applications.

Experimental investigation of photocatalytic effects of concrete in air purification adopting entire concrete waste reuse model.

PubMed

Xu, Yidong; Chen, Wei; Jin, Ruoyu; Shen, Jiansheng; Smallbone, Kirsty; Yan, Chunyang; Hu, Lei

2018-07-05

This research investigated the capacities of recycled aggregate concrete adopting entire concrete waste reuse model in degrading NO 2. Two major issues within environmental sustainability were addressed: concrete waste reuse rate and mitigation of hazards substances in the polluted air. The study consisted of two stages: identification of proper replacement rates of recycled concrete wastes in new concrete mixture design, and the evaluation of photocatalytic performance of recycled aggregate concrete in degrading NO 2 . It was found that replacement rates up to 3%, 30%, and 50% for recycled power, recycled fine aggregate, and recycled coarse aggregate respectively could be applied in concrete mixture design without deteriorating concrete strength. Recycled aggregates contained both positive attributes ("internal curing") and negative effects (e.g., lower hardness) to concrete properties. It was found that 30%-50% of natural coarse aggregate replaced by recycled coarse aggregates coated with TiO 2 would significantly improve the photocatalytic performance of concrete measured by degradation rate of NO 2 . Micro-structures of recycled aggregates observed under microscope indicated that soaking recycled aggregates in TiO 2 solution resulted in whiskers that filled the porosity within recycled aggregates which enhanced concrete strength. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of Sand Bed Depth and Medium Age on Escherichia coli and Turbidity Removal in Biosand Filters.

PubMed

Napotnik, Julie A; Baker, Derek; Jellison, Kristen L

2017-03-21

The main objective of this study was to build several full-scale biosand filters (BSFs) and assess the long-term (9 month) efficacy for particulate and Escherichia coli removal under simulated real-world usage. Four replicates of three different filter designs were built: the traditional concrete BSF and two scaled-down versions that use a 5 or 2 gal bucket as the casing material. The smaller sand bed depths in the bucket-sized filters did not impact filter performance with respect to (i) turbidity and E. coli removal or (ii) effluent levels of turbidity and E. coli. All filters produced effluents with a mean turbidity of <0.6 nephelometric turbidity unit. In addition, 78, 74, and 72% of effluent samples for the concrete, 5 gal, and 2 gal filters, respectively, had E. coli concentrations of <1 colony-forming unit/100 mL. The bucket-sized filters were found to be a potential alternative to the concrete BSFs for the removal of E. coli and turbidity from drinking water. Because smaller BSFs must be filled more frequently than larger BSFs to produce comparable water volumes, the effect of shorter pause periods on BSF performance should be investigated.

An experimental evaluation of two effective medium theories for ultrasonic wave propagation in concrete.

PubMed

Chaix, Jean-François; Rossat, Mathieu; Garnier, Vincent; Corneloup, Gilles

2012-06-01

This study compares ultrasonic wave propagation modeling and experimental data in concrete. As a consequence of its composition and manufacturing process, this material has a high elastic scattering (sand and aggregates) and air (microcracks and porosities) content. The behavior of the "Waterman-Truell" and "Generalized Self Consistent Method" dynamic homogenization models are analyzed in the context of an application for strong heterogeneous solid materials, in which the scatterers are of various concentrations and types. The experimental validations of results predicted by the models are carried out by making use of the phase velocity and the attenuation of longitudinal waves, as measured by an immersed transmission setup. The test specimen material has a cement-like matrix containing spherical inclusions of air or glass, with radius close to the ultrasonic wavelength. The models are adapted to the case of materials presenting several types of scattering particle, and allow the propagation of longitudinal waves to be described at the scale of materials such as concrete. The validity limits for frequency and for particle volume ratio can be approached through a comparison with experimental data. The potential of these homogenization models for the prediction of phase velocity and attenuation in strongly heterogeneous solids is demonstrated.

Collaboration of polymer composite reinforcement and cement concrete

NASA Astrophysics Data System (ADS)

Khozin, V. G.; Gizdatullin, A. R.

2018-04-01

The results of experimental study of bond strength of cement concrete of different types with fiber reinforcing polymer (FRP) bars are reported. The reinforcing bars were manufactured of glass fibers and had a rebar with different types of the surface relief formed by winding a thin strip impregnated with a binder or by “sanding”. The pullout tests were carried out simultaneously for the steel reinforcing ribbed bars A400. The impact of friction, adhesion and mechanical bond on the strength of bonds between FRP and concrete was studied. The influence of the concrete strength and different operation factors on the bond strength of concrete was evaluated.

Influence of lithium slag from lepidolite on the durability of concrete

NASA Astrophysics Data System (ADS)

Qi, Luo; Shaowen, Huang; Yuxuan, Zhou; Jinyang, Li; Weiliang, Peng; Yufeng, Wen

2017-04-01

This paper mainly studies the effect of lithium slag from lepidolite on the property of concrete including dry shrinkage, anti-carbonation, wear resistance and chloride ion resistance. Concrete interface structure has been observed with SEM. The results show that adding lithium slag to concrete can improve concrete property including dry shrinkage, wear resistance and chloride ion resistance. However, the wear resistance tends to decrease when the amount of lithium slag reach 20%. Lithium slag also has negative effect on anti-carbonation property. With the increasing amount of lithium slag, anti-carbonation property of concrete decrease gradually.

In situ alkali-silica reaction observed by x-ray microscopy

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

Kurtis, K.E.; Monteiro, P.J.M.; Brown, J.T.

1997-04-01

In concrete, alkali metal ions and hydroxyl ions contributed by the cement and reactive silicates present in aggregate can participate in a destructive alkali-silica reaction (ASR). This reaction of the alkalis with the silicates produces a gel that tends to imbibe water found in the concrete pores, leading to swelling of the gel and eventual cracking of the affected concrete member. Over 104 cases of alkali-aggregate reaction in dams and spillways have been reported around the world. At present, no method exists to arrest the expansive chemical reaction which generates significant distress in the affected structures. Most existing techniques availablemore » for the examination of concrete microstructure, including ASR products, demand that samples be dried and exposed to high pressure during the observation period. These sample preparation requirements present a major disadvantage for the study of alkali-silica reaction. Given the nature of the reaction and the affect of water on its products, it is likely that the removal of water will affect the morphology, creating artifacts in the sample. The purpose of this research is to observe and characterize the alkali-silica reaction, including each of the specific reactions identified previously, in situ without introducing sample artifacts. For observation of unconditioned samples, x-ray microscopy offers an opportunity for such an examination of the alkali-silica reaction. Currently, this investigation is focusing on the effect of calcium ions on the alkali-silica reaction.« less

Photogrammetric analysis of concrete specimens and structures for condition assessment

NASA Astrophysics Data System (ADS)

D'Amico, Nicolas; Yu, Tzuyang

2016-04-01

Deterioration of civil infrastructure in America demands routine inspection and maintenance to avoid catastrophic failures from occurring. Among many other non-destructive evaluations (NDE), photogrammetry is an accessible and realistic approach used for non-destructive evaluation (NDE) of a civil infrastructure systems. The objective of this paper is to explore the capabilities of photogrammetry for locating, sizing, and analyzing the remaining capacity of a specimen or system using point cloud data. Geometric interpretations, composed from up to 70 photographs are analyzed as a mesh or point cloud models. In this case study, concrete, which exhibits a large amount of surface texture features, was thoroughly examined. These evaluative techniques discussed were applied to concrete cylinder models as well as portions of civil infrastructure including buildings, retaining walls, and bridge abutments. In this paper, the aim is to demonstrate the basic analytical functionality of photogrammetry, as well as its applicability to in-situ civil infrastructure systems. In concrete specimens defect length and location can be evaluated in a fully defined model (one with the maximum amount of correctly acquired photographs) with less than 2% error. Error was found to be inversely proportional to the number of acceptable photographs acquired, remaining significantly under 10% error for any model with enough data to render. Furthermore, volumetric stress evaluations were applied using a cross sectional evaluation technique to locate the critical area, and determine the severity of damages. Finally, findings and the accuracy of the results are discussed.

Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

PubMed Central

López-Uceda, Antonio; Ayuso, Jesús; Jiménez, José Ramón; Agrela, Francisco; Barbudo, Auxiliadora; De Brito, Jorge

2016-01-01

This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors’ knowledge, there have not been any upscaled applications of concrete with MRA and low cement content. PMID:28787892

Mechanical properties of bio self-healing concrete containing immobilized bacteria with iron oxide nanoparticles.

PubMed

Seifan, Mostafa; Sarmah, Ajit K; Samani, Ali Khajeh; Ebrahiminezhad, Alireza; Ghasemi, Younes; Berenjian, Aydin

2018-05-01

Concrete is arguably one of the most important and widely used materials in the world, responsible for the majority of the industrial revolution due to its unique properties. However, it is susceptible to cracking under internal and external stresses. The generated cracks result in a significant reduction in the concrete lifespan and an increase in maintenance and repair costs. In recent years, the implementation of bacterial-based healing agent in the concrete matrix has emerged as one of the most promising approaches to address the concrete cracking issue. However, the bacterial cells need to be protected from the high pH content of concrete as well as the exerted shear forces during preparation and hardening stages. To address these issues, we propose the magnetic immobilization of bacteria with iron oxide nanoparticles (IONs). In the present study, the effect of the designed bio-agent on mechanical properties of concrete (compressive strength and drying shrinkage) is investigated. The results indicate that the addition of immobilized Bacillus species with IONs in concrete matrix contributes to increasing the compressive strength. Moreover, the precipitates in the bio-concrete specimen were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The characterization studies confirm that the precipitated crystals in bio-concrete specimen were CaCO 3 , while no precipitation was observed in the control sample.

Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete.

PubMed

López-Uceda, Antonio; Ayuso, Jesús; Jiménez, José Ramón; Agrela, Francisco; Barbudo, Auxiliadora; De Brito, Jorge

2016-02-02

This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors' knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

Early age damage quantification of actively restrained concrete using inverse analysis

NASA Astrophysics Data System (ADS)

Albanna, Ali

Early-age cracking can be a significant problem in concrete pavements, floors, and bridge decks. Cracking occurs when the volumetric changes associated with drying, hydration, and temperature reduction are prevented. Good knowledge about the characteristics of early age concrete is necessary to achieve reliable crack control. Volumetric changes due to shrinkage depend on the type of concrete and its components. It has been found that light weight aggregates can work as internal reservoir to supply the concrete matrix with water that is needed during the early age; this process is called internal curing. Also fibers can give more ductility to the concrete and produce less shrinkage. There is a need to better understand the effects of early age uniaxial restraint on long term concrete mechanical performance. In this study, two types of concrete were studied (high performance fiber reinforced concrete and ordinary concrete) under actively restrained loading conditions to assess the effect on the long term fracture toughness and energy. Single edge notched specimens having dimensions of 250 mm x 150 mm x 75 mm and a notch to depth ratio of 0.33 were caste and used in both direct tension and three point bending. The direct tension tests were carried out on a direct tension loading frame constructed in house that was supplied with two mechanical jacks and load cell.

Composition and leaching of construction and demolition waste: inorganic elements and organic compounds.

PubMed

Butera, Stefania; Christensen, Thomas H; Astrup, Thomas F

2014-07-15

Thirty-three samples of construction and demolition waste collected at 11 recycling facilities in Denmark were characterised in terms of total content and leaching of inorganic elements and presence of the persistent organic pollutants PCBs and PAHs. Samples included (i) "clean" (i.e. unmixed) concrete waste, (ii) mixed masonry and concrete, (iii) asphalt and (iv) freshly cast concrete cores; both old and newly generated construction and demolition waste was included. PCBs and PAHs were detected in all samples, generally in non-critical concentrations. Overall, PAHs were comparable to background levels in urban environments. "Old" and "new" concrete samples indicated different PCB congener profiles and the presence of PCB even in new concrete suggested that background levels in raw materials may be an issue. Significant variability in total content of trace elements, even more pronounced for leaching, was observed indicating that the number of analysed samples may be critical in relation to decisions regarding management and utilisation of the materials. Higher leaching of chromium, sulphate and chloride were observed for masonry-containing and partly carbonated samples, indicating that source segregation and management practices may be important. Generally, leaching was in compliance with available leaching limits, except for selenium, and in some cases chromium, sulphate and antimony. Copyright © 2014 Elsevier B.V. All rights reserved.

Parameters of Concrete Modified with Glass Meal and Chalcedonite Dust

NASA Astrophysics Data System (ADS)

Kotwa, Anna

2017-10-01

Additives used for production of concrete mixtures affect the rheological properties and parameters of hardened concrete, including compressive strength, water resistance, durability and shrinkage of hardened concrete. By their application, the use of cement and production costs may be reduced. The scheduled program of laboratory tests included preparation of six batches of concrete mixtures with addition of glass meal and / or chalcedonite dust. Mineral dust is a waste product obtained from crushed aggregate mining, with grain size below 0,063μm. The main ingredient of chalcedonite dust is silica. Glass meal used in the study is a material with very fine grain size, less than 65μm. This particle size is present in 60% - 90% of the sample. Additives were used to replace cement in concrete mixes in an amount of 15% and 25%. The amount of aggregate was left unchanged. The study used Portland cement CEM I 42.5R. Concrete mixes were prepared with a constant rate w / s = 0.4. The aim of the study was to identify the effect of the addition of chalcedonite dust and / or glass meal on the parameters of hardened concrete, i.e. compressive strength, water absorption and capillarity. Additives used in the laboratory tests significantly affect the compressive strength. The largest decrease in compressive strength of concrete samples was recorded for samples with 50% substitutes of cement additives. This decrease is 34.35%. The smallest decrease in compressive strength was noted in concrete with the addition of 15% of chalcedonite dust or 15% glass meal, it amounts to an average of 15%. The study of absorption shows that all concrete with the addition of chalcedonite dust and glass meal gained a percentage weight increase between 2.7 ÷ 3.1% for the test batches. This is a very good result, which is probably due to grout sealing. In capillary action for the test batches, the percentage weight gains of samples ranges from 4.6% to 5.1%. However, the reference concrete obtained the lowest water absorption as compared to other batches.

Imaginal, semantic, and surface-level processing of concrete and abstract words: an electrophysiological investigation.

PubMed

West, W C; Holcomb, P J

2000-11-01

Words representing concrete concepts are processed more quickly and efficiently than words representing abstract concepts. Concreteness effects have also been observed in studies using event-related brain potentials (ERPs). The aim of this study was to examine concrete and abstract words using both reaction time (RT) and ERP measurements to determine (1) at what point in the stream of cognitive processing concreteness effects emerge and (2) how different types of cognitive operations influence these concreteness effects. Three groups of subjects performed a sentence verification task in which the final word of each sentence was concrete or abstract. For each group the truthfulness judgment required either (1) image generation, (2) semantic decision, or (3) evaluation of surface characteristics. Concrete and abstract words produced similar RTs and ERPs in the surface task, suggesting that postlexical semantic processing is necessary to elicit concreteness effects. In both the semantic and imagery tasks, RTs were shorter for concrete than for abstract words. This difference was greatest in the imagery task. Also, in both of these tasks concrete words elicited more negative ERPs than abstract words between 300 and 550 msec (N400). This effect was widespread across the scalp and may reflect activation in a linguistic semantic system common to both concrete and abstract words. ERPs were also more negative for concrete than abstract words between 550 and 800 msec. This effect was more frontally distributed and was most evident in the imagery task. We propose that this later anterior effect represents a distinct ERP component (N700) that is sensitive to the use of mental imagery. The N700 may reflect the a access of specific characteristics of the imaged item or activation in a working memory system specific to mental imagery. These results also support the extended dual-coding hypothesis that superior associative connections and the use of mental imagery both contribute to processing advantages for concrete words over abstract words.

Probabilistic design of fibre concrete structures

NASA Astrophysics Data System (ADS)

Pukl, R.; Novák, D.; Sajdlová, T.; Lehký, D.; Červenka, J.; Červenka, V.

2017-09-01

Advanced computer simulation is recently well-established methodology for evaluation of resistance of concrete engineering structures. The nonlinear finite element analysis enables to realistically predict structural damage, peak load, failure, post-peak response, development of cracks in concrete, yielding of reinforcement, concrete crushing or shear failure. The nonlinear material models can cover various types of concrete and reinforced concrete: ordinary concrete, plain or reinforced, without or with prestressing, fibre concrete, (ultra) high performance concrete, lightweight concrete, etc. Advanced material models taking into account fibre concrete properties such as shape of tensile softening branch, high toughness and ductility are described in the paper. Since the variability of the fibre concrete material properties is rather high, the probabilistic analysis seems to be the most appropriate format for structural design and evaluation of structural performance, reliability and safety. The presented combination of the nonlinear analysis with advanced probabilistic methods allows evaluation of structural safety characterized by failure probability or by reliability index respectively. Authors offer a methodology and computer tools for realistic safety assessment of concrete structures; the utilized approach is based on randomization of the nonlinear finite element analysis of the structural model. Uncertainty of the material properties or their randomness obtained from material tests are accounted in the random distribution. Furthermore, degradation of the reinforced concrete materials such as carbonation of concrete, corrosion of reinforcement, etc. can be accounted in order to analyze life-cycle structural performance and to enable prediction of the structural reliability and safety in time development. The results can serve as a rational basis for design of fibre concrete engineering structures based on advanced nonlinear computer analysis. The presented methodology is illustrated on results from two probabilistic studies with different types of concrete structures related to practical applications and made from various materials (with the parameters obtained from real material tests).

Separation and collection of coarse aggregate from waste concrete by electric pulsed power

NASA Astrophysics Data System (ADS)

Shigeishi, Mitsuhiro

2017-09-01

Waste concrete accounts for a substantial fraction of construction waste, and the recycling of waste concrete as concrete aggregate for construction is an important challenge associated with the rapid increase in the amount of waste concrete and the tight supply of natural aggregate. In this study, we propose a technique based on the use of high-voltage pulsed electric discharge into concrete underwater for separating and collecting aggregate from waste concrete with minimal deterioration of quality. By using this technique, the quality of the coarse aggregate separated and collected from concrete test specimens is comparable to that of coarse aggregate recycled by heating and grinding methods, thus satisfying the criteria in Japan Industrial Standard (JIS) A 5021 for the oven-dry density and the water absorption of coarse aggregate by advanced recycling.

Electrochemical Chloride Extraction : Influence of Concrete Surface on Treatment

DOT National Transportation Integrated Search

2002-09-01

One bridge restoration technique available for reducing corrosion-induced concrete deterioration, which removes chloride ions while simultaneously realkalizing the concrete adjacent to the steel, is electrochemical chloride extraction (ECE). Studies ...

Feasibility study of in-situ characterization of size distribution of air voids in concrete pavements.

DOT National Transportation Integrated Search

2013-06-01

This report concerns a feasibility study on the use of a non-destructive and non-invasive method to determine the size distribution of air voids in fresh concrete, which will be used for laying concrete pavement. A preliminary review of different tec...

Retrieval of Concrete Words Involves More Contextual Information than Abstract Words: Multiple Components for the Concreteness Effect

ERIC Educational Resources Information Center

Xiao, Xin; Zhao, Di; Zhang, Qin; Guo, Chun-yan

2012-01-01

The current study used the directed forgetting paradigm in implicit and explicit memory to investigate the concreteness effect. Event-related potentials (ERPs) were recorded to explore the neural basis of this phenomenon. The behavioral results showed a clear concreteness effect in both implicit and explicit memory tests; participants responded…

Accelerated testing for studying pavement design and performance (FY 2000) : effectiveness of fiber reinforced and plain, ultra-thin concrete overlays on Portland Cement Concrete Pavement (PCCP).

DOT National Transportation Integrated Search

2003-11-01

The objective of the research was to compare the performance of fiber reinforced and plain PCC concrete overlay when used as a thin non-dowelled overlay on top of a rubblized, distressed concrete pavement. The experiment was conducted at the Accelera...

Imagining the truth and the moon: an electrophysiological study of abstract and concrete word processing.

PubMed

Gullick, Margaret M; Mitra, Priya; Coch, Donna

2013-05-01

Previous event-related potential studies have indicated that both a widespread N400 and an anterior N700 index differential processing of concrete and abstract words, but the nature of these components in relation to concreteness and imagery has been unclear. Here, we separated the effects of word concreteness and task demands on the N400 and N700 in a single word processing paradigm with a within-subjects, between-tasks design and carefully controlled word stimuli. The N400 was larger to concrete words than to abstract words, and larger in the visualization task condition than in the surface task condition, with no interaction. A marked anterior N700 was elicited only by concrete words in the visualization task condition, suggesting that this component indexes imagery. These findings are consistent with a revised or extended dual coding theory according to which concrete words benefit from greater activation in both verbal and imagistic systems. Copyright © 2013 Society for Psychophysiological Research.

Influence of Silicon-Containing Additives on Concrete Waterproofness Property

NASA Astrophysics Data System (ADS)

Butakova, M. D.; Saribekyan, S. S.; Mikhaylov, A. V.

2017-11-01

The article studies the influence of silicon-containing additives on the property of the water resistance of concrete samples. It provides a review of the literature on common approaches and technologies improving concrete waterproofness and reinforced concrete structures. Normal hardening samples were obtained on the basis of concretes containing microsilica, aerosil or ash, or the combinations thereof. This research is aimed at the study of the complex modifier effect r on the basis of metakaolin, superplasticizer and silicon containing additives on the property of concrete water resistance. The need to use a superplasticizer to reduce the water-cement ratio and metakaolin as a hardening accelerator along with the set of strength is substantiated. This article describes a part of the results of the experiment conducted to find alternative options for colmatizing expensive additives used in the concreting foundations of private house-building. The implementation of the scientific work will not only clarify this area but will also broaden the knowledge of such additive as aerosol.

Strength development of pervious concrete containing engineered biomass aggregate

NASA Astrophysics Data System (ADS)

Sharif, A. A. M.; Shahidan, S.; Koh, H. B.; Kandash, A.; Zuki, S. S. Mohd

2017-11-01

Pervious concrete with high porosity has good permeability and low mechanical strengths are commonly used in controlling storm water management. It is different from normal concrete. It is only containing single size of coarse aggregate and has lower density compared with normal concrete. This study was focused on the effect of Engineered Biomass Aggregate (EBA) on the compressive strength, void ratio and water permeability of pervious concrete. EBA was prepared by coating the biomass aggregate with epoxy resin. EBA was used to replace natural coarse aggregate ranging from 0% to 25%. 150 mm cube specimens were prepared and used to study the compressive strength, void ratio and water permeability. Compressive strength was tested at 7, 14 and 28 days. Meanwhile, void ratio and permeability tests were carried out on 28 days. The experimental results showed that pervious concrete containing EBA gained lower compressive strength. The compressive strength was reduced gradually by increasing the percentage of EBA. Overall, Pervious concrete containing EBA achieved higher void ratio and permeability.

Reuse of ultrafine mineral wool production waste in the manufacture of refractory concrete.

PubMed

Stonys, R; Kuznetsov, D; Krasnikovs, A; Škamat, J; Baltakys, K; Antonovič, V; Černašėjus, O

2016-07-01

The paper deals with the mineral wool production waste (cupola dust - CD), presents CD characterization and aims to reuse CD in production of refractory concrete with calcium aluminate cement. The study of CD covers its chemical, phase and thermal analyses along with the morphological study and determination of particles size distribution. Zeta-potential, electrical conductivity and pH values of CD suspension are presented in the paper as well. Commercial microsilica additive in refractory concrete has been replaced with cupola dust. Compositions of refractory concrete have been prepared by incorporating 1%, 2% and 3% of CD. The bulk density, ultrasonic wave velocity, cold crushing strength and thermal shock resistance of the created refractory concrete have been determined. Based on experimental results, it has been found that cupola dust may be used for the production of refractory concrete. The environmental impact related to the CD reuse in refractory concrete production has been evaluated as well. Copyright © 2016 Elsevier Ltd. All rights reserved.

Analysis of Power Generating Speed Bumps Made of Concrete Foam Composite

NASA Astrophysics Data System (ADS)

Syam, B.; Muttaqin, M.; Hastrino, D.; Sebayang, A.; Basuki, W. S.; Sabri, M.; Abda, S.

2017-03-01

This paper discusses the analysis of speed bump made of concrete foam composite which is used to generate electrical power. Speed bumps are designed to decelerate the speed of vehicles before passing through toll gates, public areas, or any other safety purposes. In Indonesia a speed bump should be designed in the accordance with KM Menhub 3 year 1994. In this research, the speed bump was manufactured with dimensions and geometry comply to the regulation mentioned above. Concrete foam composite speed bumps were used due to its light weight and relatively strong to receive vertical forces from the tyres of vehicles passing over the bumps. The reinforcement materials are processed from empty fruit bunch of oil palm. The materials were subjected to various tests to obtain its physical and mechanical properties. To analyze the structure stability of the speed bumps some models were analyzed using a FEM-based numerical softwares. It was obtained that the speed bumps coupled with polymeric composite bar (3 inches in diameter) are significantly reduce the radial stresses. In addition, the speed bumps equipped with polymeric composite casing or steel casing are also suitable for use as part of system components in producing electrical energy.

From the abstract to the concrete - Implementation of an innovative tool in home care.

PubMed

Kajamaa, Anu; Schulz, Klaus-Peter

2018-02-01

Background The implementation of innovations in practice is a critical factor for change and development processes in health and home care. We therefore analyze how an innovative tool - a mobility agreement to maintain physical mobility of home care clients - was implemented in Finnish home care. Methods Our study involves ethnographic research of 13 home care visits, two years after the mobility agreement was implemented. We analyze the emergence of contradictions, the motives of the actors and the use of artifacts supporting or inhibiting the implementation. Two in-depth cases illustrate the implementation of the mobility agreement in home care visits. Findings Our findings show that, first, to achieve practice change and development, the innovation implementation requires the overcoming of contradictions in the implementation process. Second, it calls for the emergence of a shared motive between the actors to transform the abstract concept of an innovation into a concrete practice. Third, artifacts, customary to the clients are important in supporting the implementation process. Fourth, the implementation brings about a modification of the innovation and the adopting social system. Conclusions Innovation implementation should be seen as a transformation process of an abstract concept into a concrete practice, enabled by the actors involved. Concept design and implementation should be closely linked. In health/home care innovation management, the implementation of innovations needs to be understood as a complex collective learning process. Results can be far reaching - in our case leading to change of home care workers' professional understanding and elderly clients' mobility habits.

Creep and cracking of concrete hinges: insight from centric and eccentric compression experiments.

PubMed

Schlappal, Thomas; Schweigler, Michael; Gmainer, Susanne; Peyerl, Martin; Pichler, Bernhard

2017-01-01

Existing design guidelines for concrete hinges consider bending-induced tensile cracking, but the structural behavior is oversimplified to be time-independent. This is the motivation to study creep and bending-induced tensile cracking of initially monolithic concrete hinges systematically. Material tests on plain concrete specimens and structural tests on marginally reinforced concrete hinges are performed. The experiments characterize material and structural creep under centric compression as well as bending-induced tensile cracking and the interaction between creep and cracking of concrete hinges. As for the latter two aims, three nominally identical concrete hinges are subjected to short-term and to longer-term eccentric compression tests. Obtained material and structural creep functions referring to centric compression are found to be very similar. The structural creep activity under eccentric compression is significantly larger because of the interaction between creep and cracking, i.e. bending-induced cracks progressively open and propagate under sustained eccentric loading. As for concrete hinges in frame-like integral bridge construction, it is concluded (i) that realistic simulation of variable loads requires consideration of the here-studied time-dependent behavior and (ii) that permanent compressive normal forces shall be limited by 45% of the ultimate load carrying capacity, in order to avoid damage of concrete hinges under sustained loading.

Bio-reinforced self-healing concrete using magnetic iron oxide nanoparticles.

PubMed

Seifan, Mostafa; Sarmah, Ajit K; Ebrahiminezhad, Alireza; Ghasemi, Younes; Samani, Ali Khajeh; Berenjian, Aydin

2018-03-01

Immobilization has been reported as an efficient technique to address the bacterial vulnerability for application in bio self-healing concrete. In this study, for the first time, magnetic iron oxide nanoparticles (IONs) are being practically employed as the protective vehicle for bacteria to evaluate the self-healing performance in concrete environment. Magnetic IONs were successfully synthesized and characterized using different techniques. The scanning electron microscope (SEM) images show the efficient adsorption of nanoparticles to the Bacillus cells. Microscopic observation illustrates that the incorporation of the immobilized bacteria in the concrete matrix resulted in a significant crack healing behavior, while the control specimen had no healing characteristics. Analysis of bio-precipitates revealed that the induced minerals in the cracks were calcium carbonate. The effect of magnetic immobilized cells on the concrete water absorption showed that the concrete specimens supplemented with decorated bacteria with IONs had a higher resistance to water penetration. The initial and secondary water absorption rates in bio-concrete specimens were 26% and 22% lower than the control specimens. Due to the compatible behavior of IONs with the concrete compositions, the results of this study proved the potential application of IONs for developing a new generation of bio self-healing concrete.

Beneficial reuse of precast concrete industry sludge to produce alkaline stabilized biosolids.

PubMed

Gowda, C; Seth, R; Biswas, N

2008-01-01

The precast concrete industry generates waste called concrete sludge during routine mixer tank washing. It is highly alkaline and hazardous, and typically disposed of by landfilling. This study examined the stabilization of municipal sewage sludge using concrete sludge as an alkaline agent. Sewage sludge was amended with 10 to 40% of concrete sludge by wet weight, and 10 and 20% of lime by dry weight of the sludge mix. Mixes containing 30 and 40% of concrete sludge with 20% lime fulfilled the primary requirements of Category 1 and 2 (Canada) biosolids of maintaining a pH of 12 for at least 72 hours. The heavy metals were below Category 1 regulatory limits. The 40% concrete sludge mix was incubated at 52 degrees C for 12 of the 72 hours to achieve the Category 1 and 2 regulations of less than 1000 fecal coliform/g solids. The nutrient content of the biosolids was 8.2, 10 and 0.6 g/kg of nitrogen, phosphorus and potassium respectively. It can be used as a top soil or augmented with potassium for use as fertilizer. The study demonstrates that concrete sludge waste can be beneficially reused to produce biosolids, providing a long-term sustainable waste management solution for the concrete industry.

The Influence of Concreteness of Concepts on the Integration of Novel Words into the Semantic Network

PubMed Central

Ding, Jinfeng; Liu, Wenjuan; Yang, Yufang

2017-01-01

On the basis of previous studies revealing a processing advantage of concrete words over abstract words, the current study aimed to further explore the influence of concreteness on the integration of novel words into semantic memory with the event related potential (ERP) technique. In the experiment during the learning phase participants read two-sentence contexts and inferred the meaning of novel words. The novel words were two-character non-words in Chinese language. Their meaning was either a concrete or abstract known concept which could be inferred from the contexts. During the testing phase participants performed a lexical decision task in which the learned novel words served as primes for either their corresponding concepts, semantically related or unrelated targets. For the concrete novel words, the semantically related words belonged to the same semantic categories with their corresponding concepts. For the abstract novel words, the semantically related words were synonyms of their corresponding concepts. The unrelated targets were real words which were concrete or abstract for the concrete or abstract novel words respectively. The ERP results showed that the corresponding concepts and the semantically related words elicited smaller N400s than the unrelated words. The N400 effect was not modulated by the concreteness of the concepts. In addition, the concrete corresponding concepts elicited a smaller late positive component (LPC) than the concrete unrelated words. This LPC effect was absent for the abstract words. The results indicate that although both concrete and abstract novel words can be acquired and linked to their related words in the semantic network after a short learning phase, the concrete novel words are learned better. Our findings support the (extended) dual coding theory and broaden our understanding of adult word learning and changes in concept organization. PMID:29255440

The Influence of Concreteness of Concepts on the Integration of Novel Words into the Semantic Network.

PubMed

Ding, Jinfeng; Liu, Wenjuan; Yang, Yufang

2017-01-01

On the basis of previous studies revealing a processing advantage of concrete words over abstract words, the current study aimed to further explore the influence of concreteness on the integration of novel words into semantic memory with the event related potential (ERP) technique. In the experiment during the learning phase participants read two-sentence contexts and inferred the meaning of novel words. The novel words were two-character non-words in Chinese language. Their meaning was either a concrete or abstract known concept which could be inferred from the contexts. During the testing phase participants performed a lexical decision task in which the learned novel words served as primes for either their corresponding concepts, semantically related or unrelated targets. For the concrete novel words, the semantically related words belonged to the same semantic categories with their corresponding concepts. For the abstract novel words, the semantically related words were synonyms of their corresponding concepts. The unrelated targets were real words which were concrete or abstract for the concrete or abstract novel words respectively. The ERP results showed that the corresponding concepts and the semantically related words elicited smaller N400s than the unrelated words. The N400 effect was not modulated by the concreteness of the concepts. In addition, the concrete corresponding concepts elicited a smaller late positive component (LPC) than the concrete unrelated words. This LPC effect was absent for the abstract words. The results indicate that although both concrete and abstract novel words can be acquired and linked to their related words in the semantic network after a short learning phase, the concrete novel words are learned better. Our findings support the (extended) dual coding theory and broaden our understanding of adult word learning and changes in concept organization.

Concrete probe-strength study : final report.

DOT National Transportation Integrated Search

1969-12-01

The Windsor probe - test system was evaluated for determining compressive strength of concrete by comparing probe strengths against cylinder and core strengths from both laboratory and field-poured concrete. Advantages and disadvantages of this syste...

Influence of length-to-diameter ratio on shrinkage of basalt fiber concrete

NASA Astrophysics Data System (ADS)

Ruijie, MA; Yang, Jiansen; Liu, Yuan; Zheng, Xiaojun

2017-09-01

In order to study the shrinkage performance of basalt concrete, using the shrinkage rate as index, the work not only studied the influence of different length-to-diameter ratio (LDR) on plastic shrinkage and drying shrinkage of basalt fiber concrete, but also analyzed the action mechanism. The results show that when the fiber content is 0.1%, the LDR of 800 and 1200 take better effects on reducing plastic shrinkage, however the fiber content is 0.3%, that of LDR 600 is better. To improve drying shrinkage, the fiber of LDR 800 takes best effect. In the concrete structure, the adding basalt fibers form a uniform and chaotic supporting system, optimize the pore and the void structure of concrete, make the material further compacted, reduce the water loss, so as to decrease the shrinkage of concrete effectively.

Contrastive Numerical Investigations on Thermo-Structural Behaviors in Mass Concrete with Various Cements

PubMed Central

Zhou, Wei; Feng, Chuqiao; Liu, Xinghong; Liu, Shuhua; Zhang, Chao; Yuan, Wei

2016-01-01

This work is a contrastive investigation of numerical simulations to improve the comprehension of thermo-structural coupled phenomena of mass concrete structures during construction. The finite element (FE) analysis of thermo-structural behaviors is used to investigate the applicability of supersulfated cement (SSC) in mass concrete structures. A multi-scale framework based on a homogenization scheme is adopted in the parameter studies to describe the nonlinear concrete behaviors. Based on the experimental data of hydration heat evolution rate and quantity of SSC and fly ash Portland cement, the hydration properties of various cements are studied. Simulations are run on a concrete dam section with a conventional method and a chemo-thermo-mechanical coupled method. The results show that SSC is more suitable for mass concrete structures from the standpoint of temperature control and crack prevention. PMID:28773517

Contrastive Numerical Investigations on Thermo-Structural Behaviors in Mass Concrete with Various Cements.

PubMed

Zhou, Wei; Feng, Chuqiao; Liu, Xinghong; Liu, Shuhua; Zhang, Chao; Yuan, Wei

2016-05-20

This work is a contrastive investigation of numerical simulations to improve the comprehension of thermo-structural coupled phenomena of mass concrete structures during construction. The finite element (FE) analysis of thermo-structural behaviors is used to investigate the applicability of supersulfated cement (SSC) in mass concrete structures. A multi-scale framework based on a homogenization scheme is adopted in the parameter studies to describe the nonlinear concrete behaviors. Based on the experimental data of hydration heat evolution rate and quantity of SSC and fly ash Portland cement, the hydration properties of various cements are studied. Simulations are run on a concrete dam section with a conventional method and a chemo-thermo-mechanical coupled method. The results show that SSC is more suitable for mass concrete structures from the standpoint of temperature control and crack prevention.

Mechanical Properties of Steel Fiber Reinforced all Lightweight Aggregate Concrete

NASA Astrophysics Data System (ADS)

Yang, Y. M.; Li, J. Y.; Zhen, Y.; Nie, Y. N.; Dong, W. L.

2018-05-01

In order to study the basic mechanical properties and failure characteristics of all lightweight aggregate concrete with different volume of steel fiber (0%, 1%, 2%), shale ceramsite is used as light coarse aggregate. The shale sand is made of light fine aggregate and mixed with different volume of steel fiber, and the mix proportion design of all lightweight aggregate concrete is carried out. The cubic compressive strength, axial compressive strength, flexural strength, splitting strength and modulus of elasticity of steel fiber all lightweight aggregate concrete were studied. Test results show that the incorporation of steel fiber can restrict the cracking of concrete, improve crack resistance; at the same time, it shows good plastic deformation ability and failure morphology. It lays a theoretical foundation for further research on the application of all lightweight aggregate concrete in structural systems.

Preliminary study of neutron absorption by concrete with boron carbide addition

NASA Astrophysics Data System (ADS)

Abdullah, Yusof; Ariffin, Fatin Nabilah Tajul; Hamid, Roszilah; Yusof, Mohd Reusmaazran; Zali, Nurazila Mat; Ahmad, Megat Harun Al Rashid Megat; Yazid, Hafizal; Ahmad, Sahrim; Mohamed, Abdul Aziz

2014-02-01

Concrete has become a conventional material in construction of nuclear reactor due to its properties like safety and low cost. Boron carbide was added as additives in the concrete construction as it has a good neutron absorption property. The sample preparation for concrete was produced with different weight percent of boron carbide powder content. The neutron absorption rate of these samples was determined by using a fast neutron source of Americium-241/Be (Am-Be 241) and detection with a portable backscattering neutron detector. Concrete with 20 wt % of boron carbide shows the lowest count of neutron transmitted and this indicates the most neutrons have been absorbed by the concrete. Higher boron carbide content may affect the concrete strength and other properties.

Use of Residual Solids from Pulp and Paper Mills for Enhancing Strength and Durability of Ready-Mixed Concrete

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

Tarun R. Naik; Yoon-moon Chun; Rudolph N. Kraus

2003-09-18

This research was conducted to establish mixture proportioning and production technologies for ready-mixed concrete containing pulp and paper mill residual solids and to study technical, economical, and performance benefits of using the residual solids in the concrete. Fibrous residuals generated from pulp and paper mills were used, and concrete mixture proportions and productions technologies were first optimized under controlled laboratory conditions. Based on the mixture proportions established in the laboratory, prototype field concrete mixtures were manufactured at a ready-mixed concrete plant. Afterward, a field construction demonstration was held to demonstrate the production and placement of structural-grade cold-weather-resistant concrete containing residualmore » solids.« less

Numerical Simulation on the Dynamic Splitting Tensile Test of reinforced concrete

NASA Astrophysics Data System (ADS)

Zhao, Zhuan; Jia, Haokai; Jing, Lin

2018-03-01

The research for crack resistance was of RC was based on the split Hopkinson bar and numerical simulate software LS-DYNA3D. In the research, the difference of dynamic splitting failure modes between plane concrete and reinforced concrete were completed, and the change rule of tensile stress distribution with reinforcement ratio was studied; also the effect rule with the strain rate and the crack resistance was also discussed by the radial tensile stress time history curve of RC specimen under different loading speeds. The results shows that the reinforcement in the concrete can impede the crack extension, defer the failure time of concrete, increase the tension intensity of concrete; with strain rate of concrete increased, the crack resistance of RC increased.

Review of the Current State of Knowledge on the Effects of Radiation on Concrete

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

Rosseel, Thomas M.; Maruyama, Ippei; Le Pape, Yann

A review of the current state of knowledge on the effects of radiation on concrete in nuclear applications is presented. Emphasis is placed on the effects of radiation damage as reflected by changes in engineering properties of concrete in the evaluation of the long-term operation (LTO) and for Plant Life or Aging Management of nuclear power plants (NPPs) in Japan, Spain, and the United States. National issues and concerns are described for Japan and the US followed by a discussion of the fundamental understanding of the effects radiation on concrete. Specifically, the effects of temperature, moisture content, and irradiation onmore » ordinary Portland cement paste and the role of temperature and neutron energy spectra on radiation induced volumetric expansion (RIVE) of aggregate-forming minerals are described. This is followed by a discussion of the bounding conditions for extended operation, the significance of accelerated irradiation conditions, the role of temperature, creep, and how these issues are being incorporated into numerical and meso-scale models. From these insights on radiation damage, analyses of these effects on concrete structures are reviewed and the current status of work in Japan and the US are described. Also discussed is the recent formation of a new international scientific and technical organization, the International Committee on Irradiated Concrete (ICIC), to provide a forum for timely information exchanges among organizations pursuing the identification, quantification, and modeling of the effects of radiation on concrete in commercial nuclear applications. Lastly, the paper concludes with a discussion of research gaps including: 1) interpreting test-reactor data, 2) evaluating service-irradiated concrete for aging management and to inform radiation damage models with the Zorita NPP (Spain) serving as the first comprehensive test case, 3) irradiated-assisted alkali-silica reactions, and 4) RIVE under constrained conditions.« less

Review of the Current State of Knowledge on the Effects of Radiation on Concrete

DOE PAGES

Rosseel, Thomas M.; Maruyama, Ippei; Le Pape, Yann; ...

2016-07-01

A review of the current state of knowledge on the effects of radiation on concrete in nuclear applications is presented. Emphasis is placed on the effects of radiation damage as reflected by changes in engineering properties of concrete in the evaluation of the long-term operation (LTO) and for Plant Life or Aging Management of nuclear power plants (NPPs) in Japan, Spain, and the United States. National issues and concerns are described for Japan and the US followed by a discussion of the fundamental understanding of the effects radiation on concrete. Specifically, the effects of temperature, moisture content, and irradiation onmore » ordinary Portland cement paste and the role of temperature and neutron energy spectra on radiation induced volumetric expansion (RIVE) of aggregate-forming minerals are described. This is followed by a discussion of the bounding conditions for extended operation, the significance of accelerated irradiation conditions, the role of temperature, creep, and how these issues are being incorporated into numerical and meso-scale models. From these insights on radiation damage, analyses of these effects on concrete structures are reviewed and the current status of work in Japan and the US are described. Also discussed is the recent formation of a new international scientific and technical organization, the International Committee on Irradiated Concrete (ICIC), to provide a forum for timely information exchanges among organizations pursuing the identification, quantification, and modeling of the effects of radiation on concrete in commercial nuclear applications. Lastly, the paper concludes with a discussion of research gaps including: 1) interpreting test-reactor data, 2) evaluating service-irradiated concrete for aging management and to inform radiation damage models with the Zorita NPP (Spain) serving as the first comprehensive test case, 3) irradiated-assisted alkali-silica reactions, and 4) RIVE under constrained conditions.« less

Damage Model of Reinforced Concrete Members under Cyclic Loading

NASA Astrophysics Data System (ADS)

Wei, Bo Chen; Zhang, Jing Shu; Zhang, Yin Hua; Zhou, Jia Lai

2018-06-01

Based on the Kumar damage model, a new damage model for reinforced concrete members is established in this paper. According to the damage characteristics of reinforced concrete members subjected to cyclic loading, four judgment conditions for determining the rationality of damage models are put forward. An ideal damage index (D) is supposed to vary within a scale of zero (no damage) to one (collapse). D should be a monotone increasing function which tends to increase in the case of the same displacement amplitude. As for members under large displacement amplitude loading, the growth rate of D should be greater than that of D under small amplitude displacement loading. Subsequently, the Park-Ang damage model, the Niu-Ren damage model, the Lu-Wang damage model and the proposed damage model are analyzed for 30 experimental reinforced concrete members, including slabs, walls, beams and columns. The results show that current damage models do not fully matches the reasonable judgment conditions, but the proposed damage model does. Therefore, a conclusion can be drawn that the proposed damage model can be used for evaluating and predicting damage performance of RC members under cyclic loading.

Experimental Investigation of the Mechanical and Durability Properties of Crumb Rubber Concrete.

PubMed

Liu, Hanbing; Wang, Xianqiang; Jiao, Yubo; Sha, Tao

2016-03-07

Recycling waste tire rubber by incorporating it into concrete has become the preferred solution to dispose of waste tires. In this study, the effect of the volume content of crumb rubber and pretreatment methods on the performances of concrete was evaluated. Firstly, the fine aggregate and mixture were partly replaced by crumb rubber to produce crumb rubber concrete. Secondly, the mechanical and durability properties of crumb rubber concrete with different replacement forms and volume contents had been investigated. Finally, the crumb rubber after pretreatment by six modifiers was introduced into the concrete mixture. Corresponding tests were conducted to verify the effectiveness of pretreatment methods as compared to the concrete containing untreated crumb rubber. It was observed that the mechanical strength of crumb rubber concrete was reduced, while durability was improved with the increasing of crumb rubber content. 20% replacement of fine aggregate and 5% replacement of the total mixture exhibited acceptable properties for practical applications. In addition, the results indicated that the modifiers had a positive impact on the mechanical and durability properties of crumb rubber concrete. It avoided the disadvantage of crumb rubber concrete having lower strength and provides a reference for the production of modified crumb rubber concrete.

Experimental Investigation of the Mechanical and Durability Properties of Crumb Rubber Concrete

PubMed Central

Liu, Hanbing; Wang, Xianqiang; Jiao, Yubo; Sha, Tao

2016-01-01

Recycling waste tire rubber by incorporating it into concrete has become the preferred solution to dispose of waste tires. In this study, the effect of the volume content of crumb rubber and pretreatment methods on the performances of concrete was evaluated. Firstly, the fine aggregate and mixture were partly replaced by crumb rubber to produce crumb rubber concrete. Secondly, the mechanical and durability properties of crumb rubber concrete with different replacement forms and volume contents had been investigated. Finally, the crumb rubber after pretreatment by six modifiers was introduced into the concrete mixture. Corresponding tests were conducted to verify the effectiveness of pretreatment methods as compared to the concrete containing untreated crumb rubber. It was observed that the mechanical strength of crumb rubber concrete was reduced, while durability was improved with the increasing of crumb rubber content. 20% replacement of fine aggregate and 5% replacement of the total mixture exhibited acceptable properties for practical applications. In addition, the results indicated that the modifiers had a positive impact on the mechanical and durability properties of crumb rubber concrete. It avoided the disadvantage of crumb rubber concrete having lower strength and provides a reference for the production of modified crumb rubber concrete. PMID:28773298

A review of recent developments in parametric based acoustic emission techniques applied to concrete structures

NASA Astrophysics Data System (ADS)

Vidya Sagar, R.; Raghu Prasad, B. K.

2012-03-01

This article presents a review of recent developments in parametric based acoustic emission (AE) techniques applied to concrete structures. It recapitulates the significant milestones achieved by previous researchers including various methods and models developed in AE testing of concrete structures. The aim is to provide an overview of the specific features of parametric based AE techniques of concrete structures carried out over the years. Emphasis is given to traditional parameter-based AE techniques applied to concrete structures. A significant amount of research on AE techniques applied to concrete structures has already been published and considerable attention has been given to those publications. Some recent studies such as AE energy analysis and b-value analysis used to assess damage of concrete bridge beams have also been discussed. The formation of fracture process zone and the AE energy released during the fracture process in concrete beam specimens have been summarised. A large body of experimental data on AE characteristics of concrete has accumulated over the last three decades. This review of parametric based AE techniques applied to concrete structures may be helpful to the concerned researchers and engineers to better understand the failure mechanism of concrete and evolve more useful methods and approaches for diagnostic inspection of structural elements and failure prediction/prevention of concrete structures.

Assessment of concrete damage and strength degradation caused by reinforcement corrosion

NASA Astrophysics Data System (ADS)

Nepal, Jaya; Chen, Hua-Peng

2015-07-01

Structural performance deterioration of reinforced concrete structures has been extensively investigated, but very limited studies have been carried out to investigate the effect of reinforcement corrosion on time-dependent reliability with consideration of the influence of mechanical characteristics of the bond interface due to corrosion. This paper deals with how corrosion in reinforcement creates different types of defects in concrete structure and how they are responsible for the structural capacity deterioration of corrosion affected reinforced concrete structures during their service life. Cracking in cover concrete due to reinforcement corrosion is investigated by using rebar-concrete model and realistic concrete properties. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution due to reinforcement corrosion, which is examined by the experimental data available. The time-dependent reliability analysis is undertaken to calculate the life time structural reliability of corrosion damaged concrete structures by stochastic deterioration modelling of reinforced concrete. The results from the numerical example show that the proposed approach is capable of evaluating the damage caused by reinforcement corrosion and also predicting the structural reliability of concrete structures during their lifecycle.

Analysis of concrete targets with different kinds of reinforcements subjected to blast loading

NASA Astrophysics Data System (ADS)

Oña, M.; Morales-Alonso, G.; Gálvez, F.; Sánchez-Gálvez, V.; Cendón, D.

2016-05-01

In this paper we describe an experimental campaign carried out to study and analyse the behaviour of concrete slabs when subjected to blast loading. Four different types of concrete have been tested: normal strength concrete with steel rebar, normal strength concrete with steel rebar retrofitted with Kevlar coating, steel fibre reinforced concrete (SFRC) and polypropylene fibre reinforced concrete (PFRC). The major asset of the experimental setup used is that it allows to subject up to four specimens to the same blast load what, besides being cost effective, makes possible to have a measure of the experimental scatter. The results of SFRC and PFRC concretes have been analysed by using a previously developed material model for the numerical simulation of concrete elements subjected to blast. The experimental campaign and preliminary results of this numerical analysis show how the high strain rates, in spite of improving the mechanical properties of these kinds of fibre reinforced concretes, lead to an embrittlement of the material, which may be dangerous from the point of view of the structural behaviour.

The effect on slurry water as a fresh water replacement in concrete properties

NASA Astrophysics Data System (ADS)

Kadir, Aeslina Abdul; Shahidan, Shahiron; Hai Yee, Lau; Ikhmal Haqeem Hassan, Mohd; Bakri Abdullah, Mohd Mustafa Al

2016-06-01

Concrete is the most widely used engineering material in the world and one of the largest water consuming industries. Consequently, the concrete manufacturer, ready mixed concrete plant is increased dramatically due to high demand from urban development project. At the same time, slurry water was generated and leading to environmental problems. Thus, this paper is to investigate the effect of using slurry water on concrete properties in term of mechanical properties. The basic wastewater characterization was investigated according to USEPA (Method 150.1 & 300.0) while the mechanical property of concrete with slurry water was compared according to ASTM C1602 and BS EN 1008 standards. In this research, the compressive strength, modulus of elasticity and tensile strength were studied. The percentage of wastewater replaced in concrete mixing was ranging from 0% up to 50%. In addition, the resulted also suggested that the concrete with 20% replacement of slurry water was achieved the highest compressive strength and modulus of elasticity compared to other percentages. Moreover, the results also recommended that concrete with slurry water mix have better compressive strength compared to control mix concrete.

Flexural Behavior of GFRP Tubes Filled with Magnetically Driven Concrete

PubMed Central

Xie, Fang; Chen, Ju; Dong, Xinlong; Feng, Bing

2018-01-01

Experimental investigation of GFRP (glass fiber reinforced polymer) tubes that were filled with magnetically driven concrete was carried out to study the flexural behavior of specimens under bending. Specimens having different cross section and lengths were tested. The test specimens were fabricated by filling magnetically driven concrete into the GFRP tubes and the concrete was vibrated using magnetic force. Specimens vibrated using vibrating tube were also tested for comparison. In addition, specimens having steel reinforcing bars and GFRP bars were both tested to study the effect of reinforcing bars on the magnetically driven concrete. The load-displacement curves, load-strain curves, failure mode, and ultimate strengths of test specimens were obtained. Design methods for the flexural stiffness of test specimens were also discussed in this study. PMID:29316732

Flexural Behavior of GFRP Tubes Filled with Magnetically Driven Concrete.

PubMed

Xie, Fang; Chen, Ju; Dong, Xinlong; Feng, Bing

2018-01-08

Experimental investigation of GFRP (glass fiber reinforced polymer) tubes that were filled with magnetically driven concrete was carried out to study the flexural behavior of specimens under bending. Specimens having different cross section and lengths were tested. The test specimens were fabricated by filling magnetically driven concrete into the GFRP tubes and the concrete was vibrated using magnetic force. Specimens vibrated using vibrating tube were also tested for comparison. In addition, specimens having steel reinforcing bars and GFRP bars were both tested to study the effect of reinforcing bars on the magnetically driven concrete. The load-displacement curves, load-strain curves, failure mode, and ultimate strengths of test specimens were obtained. Design methods for the flexural stiffness of test specimens were also discussed in this study.

Different Types of Action Research to Promote Chemistry Teachers' Professional Development--A Joined Theoretical Reflection on Two Cases from Israel and Germany

ERIC Educational Resources Information Center

Mamlok-Naaman, Rachel; Eilks, Ingo

2012-01-01

Action research is defined as using research activities to develop concrete societal practices. Action research understands the change of practice as being already a central aim of the research process itself, and it also seeks to contribute to the professional development of all participants in the particular field of study. Even though (or maybe…

In Search of a New Paradigm for Higher Education: A Case Analysis of Faculty Experiences in the First Year of a New University.

ERIC Educational Resources Information Center

Gonzalez, Kenneth P.

This study examined the experiences of faculty members in the first year of a new university. Twelve faculty at the new institution were interviewed and observed during the 1995-96 academic year. The analysis presented in this paper is based on one particular interview. Overall, six concrete universals were found during the analysis: (1) the…

Feasibility study on cross-linked biopolymeric concrete encapsulating selenium glass wastes.

PubMed

Kim, Daeik; Park, Joon-Seok; Yen, Teh Fu

2012-08-01

Feasibility study was conducted to encapsulate the selenium (Se) contained in glass waste, using the biopolymer-modified concrete. Biopolymer has unique characteristics to provide the chemical sites to metals or toxic compounds through the three-dimensional cross-linked structure. Very minute amount of biopolymer enhanced the characteristics of cementitious material. The resulting biopolymeric composite with selenium glass waste showed 20% higher compressive strength than ordinary concrete and the lower leaching concentration than the equipment detection limit. For a qualitative measurement, X-ray diffraction (XRD; X-ray powder diffractogram) was used to characterize the biopolymeric concrete. The optimum waste content percentage with appropriate biopolymer concrete mixture ratio was identified for its possible commercial use.

Shielding properties of the ordinary concrete loaded with micro- and nano-particles against neutron and gamma radiations.

PubMed

Mesbahi, Asghar; Ghiasi, Hosein

2018-06-01

The shielding properties of ordinary concrete doped with some micro and nano scaled materials were studied in the current study. Narrow beam geometry was simulated using MCNPX Monte Carlo code and the mass attenuation coefficient of ordinary concrete doped with PbO 2 , Fe 2 O 3 , WO 3 and H 4 B (Boronium) in both nano and micro scales was calculated for photon and neutron beams. Mono-energetic beams of neutrons (100-3000 keV) and photons (142-1250 keV) were used for calculations. The concrete doped with nano-sized particles showed higher neutron removal cross section (7%) and photon attenuation coefficient (8%) relative to micro-particles. Application of nano-sized material in the composition of new concretes for dual protection against neutrons and photons are recommended. For further studies, the calculation of attenuation coefficients of these nano-concretes against higher energies of neutrons and photons and different particles are suggested. Copyright © 2018 Elsevier Ltd. All rights reserved.

Improved corrosion inspection procedures for reinforced concrete bridges : electrical resistivity of concrete.

DOT National Transportation Integrated Search

2015-07-01

The effects of steel reinforcement and chloride-induced corrosion initiation on the electrical resistivity measurements using the Wenner : probe technique were studied experimentally on custom-designed reinforced concrete slabs. Investigation paramet...

Concrete aggregate durability study.

DOT National Transportation Integrated Search

2009-06-01

There are many factors that affect the durability of Portland cement concrete (PCC), including the mix design and the : materials used, the quality of construction, and the environment. Durability is not an intrinsic property of the concrete, but : i...

Tests for early acceptance of concrete.

DOT National Transportation Integrated Search

1985-01-01

A literature survey and limited study of laboratory concretes were conducted to evaluate various methods for predicting concrete strengths at 28 days based on procedures for accelerated strength development or measurement of strength of normally cure...

A corrosion monitoring system for existing reinforced concrete structures.

DOT National Transportation Integrated Search

2015-05-01

This study evaluated a multi-parameter corrosion monitoring system for existing reinforced concrete structures in chloride-laden service environments. The system was fabricated based on a prototype concrete corrosion measurement system that : had bee...

Experimental investigation of FRCM/concrete interfacial debonding.

DOT National Transportation Integrated Search

2014-07-01

This report presents the results of an experimental study conducted to understand the stress-transfer mechanism of fiber reinforced concrete matrix (FRCM) composites externally bonded to a concrete substrate for strengthening applications. The FRCM c...

Microbiologically induced deterioration of concrete - A Review

PubMed Central

Wei, Shiping; Jiang, Zhenglong; Liu, Hao; Zhou, Dongsheng; Sanchez-Silva, Mauricio

2013-01-01

Microbiologically induced deterioration (MID) causes corrosion of concrete by producing acids (including organic and inorganic acids) that degrade concrete components and thus compromise the integrity of sewer pipelines and other structures, creating significant problems worldwide. Understanding of the fundamental corrosion process and the causal agents will help us develop an appropriate strategy to minimize the costs in repairs. This review presents how microorganisms induce the deterioration of concrete, including the organisms involved and their colonization and succession on concrete, the microbial deterioration mechanism, the approaches of studying MID and safeguards against concrete biodeterioration. In addition, the uninvestigated research area of MID is also proposed. PMID:24688488

Behavior of reinforcement SCC beams under elevated temperatures

NASA Astrophysics Data System (ADS)

Fathi, Hamoon; Farhang, Kianoosh

2015-09-01

This experimental study focuses on the behavior of heated reinforced concrete beams. Four types of concrete mixtures were used for the tested self-compacting concrete beams. A total of 72 reinforced concrete beams and 72 standard cylindrical specimens were tested. The compressive strength under uniaxial loading at 23 °C ranged from 30 to 45 MPa. The specimens were exposed to different temperatures. The test parameters of interest were the compressive strength and the temperature of the specimens. The effect of changes in the parameters was examined so as to control the behavior of the tested concrete and that of the reinforced concrete beam. The results indicated that flexibility and compressive strength of the reinforced concrete beams decreased at higher temperatures. Furthermore, heating beyond 400 °C produced greater variations in the structural behavior of the materials in both the cylindrical samples and the reinforced concrete beams.

An Investigation of Tendon Corrosion-Inhibitor Leakage into Concrete

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

Costello, J.F.; Naus, D.J.; Oland, C.B.

1999-07-05

During inspections performed at US nuclear power plants several years ago, some of the prestressed concrete containment had experienced leakage of the tendon sheathing filler. A study was conducted to indicate the extent of the leakage into the concrete and its potential effects on concrete properties. Concrete core samples were obtained from the Trojan Nuclear Plant. Examination and testing of the core samples indicated that the appearance of tendon sheathing filler on the surface was due to leakage of the filler from the conduits and its subsequent migration to the concrete surface through cracks that were present. Migration of themore » tendon sheathing filler was confined to the cracks with no perceptible movement into the concrete. Results of compressive strength tests indicated that the concrete quality was consistent in the containment and that the strength had increased relative to the strength at 28 days age.« less

Time-Dependent Topology of Railway Prestressed Concrete Sleepers

NASA Astrophysics Data System (ADS)

Li, Dan; Ngamkhanong, Chayut; Kaewunruen, Sakdirat

2017-10-01

The railway sleepers are very important component of railway track structure. The sleepers can be manufactured by using timber, concrete, steel or other engineered materials. Nowadays, prestressed concrete has become most commonly used type of sleepers. Prestressed concrete sleepers have longer life-cycle and lower maintenance cost than reinforced concrete sleepers. They are expected to withstand high dynamic loads and harsh environments. However, durability and long-term performance of prestressed concrete sleepers are largely dependent on creep and shrinkage responses. This study investigates the long-term behaviours of prestressed concrete sleepers and proposes the shortening and deflection diagrams. Comparison between design codes of Eurocode 2 and AS3600-2009 provides the insight into the time-dependent performance of prestressed concrete sleepers. The outcome of this paper will improve the rail maintenance and inspection criteria in order to establish appropriate sensible remote track condition monitor network in practice.

An Alternative Mechanism for Accelerated Carbon Sequestration in Concrete

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

Haselbach, Liv M.; Thomle, Jonathan N.

The increased rate of carbon dioxide sequestration (carbonation) is desired in many primary and secondary life applications of concrete in order to make the life cycle of concrete structures more carbon neutral. Most carbonation rate studies have focused on concrete exposed to air under various conditions. An alternative mechanism for accelerated carbon sequestration in concrete was investigated in this research based on the pH change of waters in contact with pervious concrete which have been submerged in carbonate laden waters. The results indicate that the concrete exposed to high levels of carbonate species in water may carbonate faster than whenmore » exposed to ambient air, and that the rate is higher with higher concentrations. Validation of increased carbon dioxide sequestration was also performed via thermogravimetric analysis (TGA). It is theorized that the proposed alternative mechanism reduces a limiting rate effect of carbon dioxide dissolution in water in the micro pores of the concrete.« less

Research on the Properties of the Waste Glass Concrete Composite Foundation

NASA Astrophysics Data System (ADS)

Jia, Shilong; Chen, Kaihui; Chen, Zhongliang

2018-02-01

The composite foundation of glass concrete can not only reuse the large number of waste glass, but also improve the bearing capacity of weak foundation and soil with special properties. In this paper, the engineering properties of glass concrete composite foundation are studied based on the development situation of glass concrete and the technology of composite foundation.

Effect of Elevated Temperature on the Residual Properties of Quartzite, Granite and Basalt Aggregate Concrete

NASA Astrophysics Data System (ADS)

Masood, A.; Shariq, M.; Alam, M. Masroor; Ahmad, T.; Beg, A.

2018-05-01

In the present study, experimental investigations have been carried out to determine the effect of elevated temperature on the residual properties of quartzite, granite and basalt aggregate concrete mixes. Ultrasonic pulse velocity and unstressed residual compressive strength tests on cube specimens have been conducted at ambient and after single heating-cooling cycle of elevated temperature ranging from 200 to 600 °C. The relationship between ultrasonic pulse velocity and residual compressive strength of all concrete mixes have been developed. Scanning electron microscopy was also carried out to study micro structure of quartzite, granite and basalt aggregate concrete subjected to single heating-cooling cycle of elevated temperature. The results show that the residual compressive strength of quartzite aggregate concrete has been found higher than granite and basalt aggregate concrete at ambient and at all temperatures. It has also been found that the loss of strength in concrete is due to the development of micro-cracks result in failure of cement matrix and coarse aggregate bond. Further, the basalt aggregate concrete has been observed lower strength due to low affinity with Portland cements ascribed to its ferro-magnesium rich mineral composition.

Exploring the Effects of Concreteness Fading across Grades in Elementary School Science Education

ERIC Educational Resources Information Center

Jaakkola, Tomi; Veermans, Koen

2018-01-01

The present study investigates the effects that concreteness fading has on learning and transfer across three grade levels (4-6) in elementary school science education in comparison to learning with constantly concrete representations. 127 9- to 12-years-old elementary school students studied electric circuits in a computer-based simulation…

Triaxial constitutive model for plain and reinforced concrete behavior

NASA Astrophysics Data System (ADS)

Kang, Hong Duk

Inelastic failure analysis of concrete structures has been one of the central issues in concrete mechanics. Especially, the effect of confinement has been of great importance to capture the transition from brittle to ductile fracture of concrete under triaxial loading scenarios. Moreover, it has been a difficult task to implement numerically material descriptions which are susceptible to loss of stability and localization. Consequently, it has been a challenge to develop comprehensive material formulations of concrete, which consider the full spectrum of loading histories which the material in a real structure is subjected to. A new triaxial constitutive model of concrete is presented that not only describes the hardening/softening behavior of concrete in tension and low confined compression, but also captures the transition from brittle to ductile failure under high confinement. The concrete model is based on a loading surface that is Csp1-continuous, and that closes smoothly in equitriaxial compression, while the deviatoric trace expands from a triangular to a circular shape with increasing confinement. The plastic potential has a different curvature from the plastic loading function for non-associativity in order to reduce excessive inelastic dilatancy. In the thesis, the results of deformation and localization analyses for various loading histories are presented in the constitutive study. In addition, studies of associativity and non-associativity, and two-invariant versus three-invariant formulations are performed. At the structural level the triaxial concrete model is used to predict the nonlinear response behavior of a reinforced concrete column subject to axial and lateral loadings.

Behaviour of fibre reinforced polymer confined reinforced concrete columns under fire condition

NASA Astrophysics Data System (ADS)

Chowdhury, Ershad Ullah

In recent years, fibre reinforced polymer (FRP) materials have demonstrated enormous potential as materials for repairing and retrofitting concrete bridges that have deteriorated from factors such as electro-chemical corrosion and increased load requirements. However, concerns associated with fire remain an obstacle to applications of FRP materials in buildings and parking garages due to FRP's sensitivity to high temperatures as compared with other structural materials and to limited knowledge on their thermal and mechanical behaviour in fire. This thesis presents results from an ongoing study on the fire performance of FRP materials, fire insulation materials and systems, and FRP wrapped reinforced concrete columns. The overall goal of the study is to understand the fire behaviour of FRP materials and FRP strengthened concrete columns and ultimately, provide rational fire safety design recommendations and guidelines for FRP strengthened concrete columns. A combined experimental and numerical investigation was conducted to achieve the goals of this research study. The experimental work consisted of both small-scale FRP material testing at elevated temperatures and full-scale fire tests on FRP strengthened columns. A numerical model was developed to simulate the behaviour of unwrapped reinforced concrete and FRP strengthened reinforced concrete square or rectangular columns in fire. After validating the numerical model against test data available in literature, it was determined that the numerical model can be used to analyze the behaviour of concrete axial compressive members in fire. Results from this study also demonstrated that although FRP materials experience considerable loss of their mechanical and bond properties at temperatures somewhat below the glass transition temperature of the resin matrix, externally-bonded FRP can be used in strengthening concrete structural members in buildings, if appropriate supplemental fire protection system is provided over the FRP strengthening system.

Enhancing Student Learning with Case-Based Teaching and Audience Response Systems in an Interdisciplinary Food Science Course

ERIC Educational Resources Information Center

Giacalone, Davide

2016-01-01

The purpose of this article is to discuss the implementation of case-based teaching and use of response technologies to graduate students in a food science course. The article focuses on teaching sensory science and sensometrics, presents several concrete examples used during the course, and discusses in each case some of the observed outcomes.…

Fine-grained semantic categorization across the abstract and concrete domains.

PubMed

Ghio, Marta; Vaghi, Matilde Maria Serena; Tettamanti, Marco

2013-01-01

A consolidated approach to the study of the mental representation of word meanings has consisted in contrasting different domains of knowledge, broadly reflecting the abstract-concrete dichotomy. More fine-grained semantic distinctions have emerged in neuropsychological and cognitive neuroscience work, reflecting semantic category specificity, but almost exclusively within the concrete domain. Theoretical advances, particularly within the area of embodied cognition, have more recently put forward the idea that distributed neural representations tied to the kinds of experience maintained with the concepts' referents might distinguish conceptual meanings with a high degree of specificity, including those within the abstract domain. Here we report the results of two psycholinguistic rating studies incorporating such theoretical advances with two main objectives: first, to provide empirical evidence of fine-grained distinctions within both the abstract and the concrete semantic domains with respect to relevant psycholinguistic dimensions; second, to develop a carefully controlled linguistic stimulus set that may be used for auditory as well as visual neuroimaging studies focusing on the parametrization of the semantic space beyond the abstract-concrete dichotomy. Ninety-six participants rated a set of 210 sentences across pre-selected concrete (mouth, hand, or leg action-related) and abstract (mental state-, emotion-, mathematics-related) categories, with respect either to different semantic domain-related scales (rating study 1), or to concreteness, familiarity, and context availability (rating study 2). Inferential statistics and correspondence analyses highlighted distinguishing semantic and psycholinguistic traits for each of the pre-selected categories, indicating that a simple abstract-concrete dichotomy is not sufficient to account for the entire semantic variability within either domains.

Fine-Grained Semantic Categorization across the Abstract and Concrete Domains

PubMed Central

Tettamanti, Marco

2013-01-01

A consolidated approach to the study of the mental representation of word meanings has consisted in contrasting different domains of knowledge, broadly reflecting the abstract-concrete dichotomy. More fine-grained semantic distinctions have emerged in neuropsychological and cognitive neuroscience work, reflecting semantic category specificity, but almost exclusively within the concrete domain. Theoretical advances, particularly within the area of embodied cognition, have more recently put forward the idea that distributed neural representations tied to the kinds of experience maintained with the concepts' referents might distinguish conceptual meanings with a high degree of specificity, including those within the abstract domain. Here we report the results of two psycholinguistic rating studies incorporating such theoretical advances with two main objectives: first, to provide empirical evidence of fine-grained distinctions within both the abstract and the concrete semantic domains with respect to relevant psycholinguistic dimensions; second, to develop a carefully controlled linguistic stimulus set that may be used for auditory as well as visual neuroimaging studies focusing on the parametrization of the semantic space beyond the abstract-concrete dichotomy. Ninety-six participants rated a set of 210 sentences across pre-selected concrete (mouth, hand, or leg action-related) and abstract (mental state-, emotion-, mathematics-related) categories, with respect either to different semantic domain-related scales (rating study 1), or to concreteness, familiarity, and context availability (rating study 2). Inferential statistics and correspondence analyses highlighted distinguishing semantic and psycholinguistic traits for each of the pre-selected categories, indicating that a simple abstract-concrete dichotomy is not sufficient to account for the entire semantic variability within either domains. PMID:23825625

Promoting Interoperability: The Case for Discipline-Specific PSAPS

DTIC Science & Technology

2014-12-01

incidents for two reasons: first, numerous steel and concrete floors that affected signal penetration; and second, so many different companies were...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited PROMOTING...INTEROPERABILITY: THE CASE FOR DISCIPLINE-SPECIFIC PSAPS by Thomas Michael Walsh December 2014 Thesis Advisor: Fathali Moghaddam Second Reader

77 FR 45589 - Initiation of Five-Year (“Sunset”) Review and Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-01

...) and 70 FR 62061 (October 28, 2005). Guidance on methodological or analytical issues relevant to the... Modification, 77 FR 8101 (February 14, 2012). Correction of Case Number From Previous Sunset Review Initiation... Department case number for the antidumping duty order on steel concrete reinforcing bars from Latvia. The...

A STUDY OF THE EFFECTS OF POST-COMBUSTION AMMONIA INJECTION ON FLY ASH QUALITY: CHARACTERIZATION OF AMMONIA RELEASE FROM CONCRETE AND MORTARS CONTAINING FLY ASH AS A POZZOLANIC ADMIXTURE

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

Robert F. Rathbone; Thomas L. Robl

2002-10-30

The Clean Air Act Amendments of 1990 require large reductions in emissions of NO{sub x} from coal-fired electric utility boilers. This will necessitate the use of ammonia injection, such as in selective catalytic reduction (SCR), in many power plants, resulting in the deposition of ammonia on the fly ash. The presence of ammonia could create a major barrier to fly ash utilization in concrete because of odor concerns. Although there have been limited studies of ammonia emission from concrete, little is known about the quantity of ammonia emitted during mixing and curing, and the kinetics of ammonia release. This ismore » manifested as widely varying opinions within the concrete and ash marketing industry regarding the maximum acceptable levels of ammonia in fly ash. Therefore, practical guidelines for using ammoniated fly ash are needed in advance of the installation of many more SCR systems. The goal of this project was to develop practical guidelines for the handling and utilization of ammoniated fly ash in concrete, in order to prevent a decrease in the use of fly ash for this application. The objective was to determine the amount of ammonia that is released, over the short- and long-term, from concrete that contains ammoniated fly ash. The technical approach in this project was to measure the release of ammonia from mortar and concrete during mixing, placement, and curing. Work initially focused on laboratory mortar experiments to develop fundamental data on ammonia diffusion characteristics. Larger-scale laboratory experiments were then conducted to study the emission of ammonia from concrete containing ammoniated fly ash. The final phase comprised monitoring ammonia emissions from large concrete slabs. The data indicated that, on average, 15% of the initial ammonia was lost from concrete during 40 minutes of mixing, depending on the mix proportions and batch size. Long-term experiments indicated that ammonia diffusion from concrete was relatively slow, with greater than 50% of the initial ammonia content remaining in an 11cm thick concrete slab after 1 month. When placing concrete in an enclosed space, with negligible ventilation, it is recommended that the ammonia concentration in the concrete mix water should not exceed 110 mg NH{sub 3}/L, if the NIOSH exposure limit of 25 ppm in the air is not to be exceeded. If even a modicum of ventilation is present, then the ammonia concentration in the concrete water should be less than 170 mg/L. The maximum level of ammonia in the fly ash can then be calculated using these limits if the concrete mix proportions are known. In general, during the mixing and placement of ammonia-laden concrete, no safety concerns were encountered. The only location where the ammonia concentration attained high levels (i.e. > 25 ppm in the air) was within the concrete mixing drum.« less

Behavior of Tilted Angle Shear Connectors

PubMed Central

Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.

2015-01-01

According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type. PMID:26642193

Seismic performance evaluation of an historical concrete deck arch bridge using survey and drawing of the damages, in situ tests, dynamic identification and pushover analysis

NASA Astrophysics Data System (ADS)

Bergamo, Otello; Russo, Eleonora; Lodolo, Fabio

2017-07-01

The paper describes the performance evaluation of a retrofit historical multi-span (RC) deck arch bridge analyzed with in situ tests, dynamic identification and FEM analysis. The peculiarity of this case study lies in the structural typology of "San Felice" bridge, an historical concrete arch bridge built in the early 20th century, a quite uncommon feature in Italy. The preservation and retrofit of historic cultural heritage and infrastructures has been carefully analyzed in the international codes governing seismic response. A complete survey of the bridge was carried out prior to sketching a drawing of the existing bridge. Subsequently, the study consists in four steps: material investigation and dynamic vibration tests, FEM analysis and calibration, retrofit assessment, pushover analysis. The aim is to define an innovative approach to calibrate the FEM analysis through modern experimental investigations capable of taking structural deterioration into account, and to offer an appropriate and cost-effective retrofitting strategy.

Behavior of Tilted Angle Shear Connectors.

PubMed

Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N H

2015-01-01

According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type.

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

Mittermayr, Florian, E-mail: f.mittermayr@tugraz.at; Baldermann, Andre; Kurta, Christoph

Understanding the mechanisms leading to chemical attack on concrete is crucial in order to prevent damage of concrete structures. To date, most studies on sulfate attack and thaumasite formation are based on empirical approaches, as the identification of associated reaction mechanisms and paths is known to be highly complex. In this study, sulfate damaged concrete from Austrian tunnels was investigated by mineralogical, chemical and isotope methods to identify the reactions which caused intense concrete alteration. Major, minor and trace elemental contents as well as isotope ratios of local ground water (GW), drainage water (DW) and interstitial solutions (IS), extracted frommore » damaged concrete material, were analyzed. Locally occurring GW contained 3 to 545 mg L{sup −1} of SO{sub 4} and is thus regarded as slightly aggressive to concrete in accordance to standard specifications (e.g. DIN EN 206-1). The concrete linings and drainage systems of the studied tunnels, however, have partly suffered from intensive sulfate attack. Heavily damaged concrete consisted mainly of thaumasite, secondary calcite, gypsum, and relicts of aggregates. Surprisingly, the concentrations of dissolved ions were extremely enriched in the IS with up to 30,000 and 12,000 mg L{sup −1} of SO{sub 4} and Cl, respectively. Analyses of aqueous ions with a highly conservative behavior, e.g. K, Rb and Li, as well as {sup 2}H/H and {sup 18}O/{sup 16}O isotope ratios of H{sub 2}O of the IS showed an intensive accumulation of ions and discrimination of the light isotopes vs. the GW. These isotope signals of the IS clearly revealed evaporation at distinct relative humidities. From ion accumulation and isotope fractionation individual total and current evaporation degrees were estimated. Our combined elemental and isotopic approach verified wetting–drying cycles within a highly dynamic concrete-solution-atmosphere system. Based on these boundary conditions, key factors controlling thaumasite formation are discussed regarding the development of more sulfate-resistant concrete and concrete structures.« less

Dominance of debonding defect of CFST on PZT sensor response considering the meso-scale structure of concrete with multi-scale simulation

NASA Astrophysics Data System (ADS)

Xu, Bin; Chen, Hongbing; Mo, Y.-L.; Zhou, Tianmin

2018-07-01

Piezoelectric-lead-zirconate-titanate(PZT)-based interface debonding defects detection for concrete filled steel tubulars (CFSTs) has been proposed and validated through experiments, and numerical study on its mechanism has been carried out recently by assuming that concrete material is homogenous. However, concrete is composed of coarse and fine aggregates, mortar and interface transition zones (ITZs) and even initial defects and is a typical nonhomogeneous material and its mesoscale structure might affect the wave propagation in the concrete core of CFST members. Therefore, it is significantly important to further investigate the influence of mesoscale structure of concrete on the stress wave propagation and the response of embedded PZT sensor for the interface debonding detection. In this study, multi-physical numerical simulation on the wave propagation and embedded PZT sensor response of rectangular CFST members with numerical concrete core considering the randomness in circular aggregate distribution, and coupled with surface-mounted PZT actuator and embedded PZT sensor is carried out. The effect of randomness in the circular aggregates distribution and the existence of ITZs are discussed. Both a local stress wave propagation behavior including transmission, reflection, and diffraction at the interface between concrete core and steel tube under a pulse signal excitation and a global wave field in the cross-section of the rectangular CFST models without and with interface debonding defects under sweep frequency excitation are simulated. The sensitivity of an evaluation index based on wavelet packet analysis on the embedded PZT sensor response on the variation of mesoscale parameters of concrete core without and with different interface debonding defects under sweep frequency voltage signal is investigated in details. The results show that the effect of the interface debondings on the embedded PZT measurement is dominant when compared to the meso-scale structures of concrete core. This study verified the feasibility of the PZT based debonding detection for rectangular CFST members even the meso-scale structure of concrete core is considered.

Surface Chloride Levels in Colorado Structural Concrete

DOT National Transportation Integrated Search

2018-01-01

This project focused on the chloride-induced corrosion of reinforcing steel in structural concrete. The primary goal of this project is to analyze the surface chloride concentration level of the concrete bridge decks throughout Colorado. The study in...

Influence of mixing procedure on robustness of self-consolidating concrete.

DOT National Transportation Integrated Search

2014-08-01

Self-Consolidating Concrete is, in the fresh state, more sensitive to small variations in the constituent elements and the mixing : procedure compared to Conventional Vibrated Concrete. Several studies have been performed recently to identify robustn...

Diagnostic evaluation and repair of deteriorated concrete bridges.

DOT National Transportation Integrated Search

2004-12-01

Concrete bridge deck degradation has been observed in several bridges located in north Mississippi. In this study a : survey was conducted to collect and document instances of deterioration in concrete bridges located throughout the State. The : main...

Rapid setting concrete patching study : final report.

DOT National Transportation Integrated Search

1975-03-01

This investigation was prompted by the increasing number of concrete roadway failures which have required corrective action. A more permanent solution than the placing of hot or cold mixed asphalt compounds into concrete voids was deemed necessary. t...

Preliminary study to develop standard acceptance tests for pervious concrete.

DOT National Transportation Integrated Search

2017-05-01

Pervious concrete pavements are permeable pavement systems that are desired for their role in stormwater management and runoff control. Increased popularity in pervious concrete pavement applications has raised the need for the development of quality...

Nondestructive Measurements Using Mechanical Waves in Reinforced Concrete Structures.

DOT National Transportation Integrated Search

2014-02-01

"This study evaluated various techniques that use mechanical waves for the evaluation of critical concrete properties, : such as proper consolidation of the concrete during placement and strength development; changes in modulus; and the detection : o...

Concrete debris assessment for road construction activities : summary.

DOT National Transportation Integrated Search

2016-09-01

University of Florida researchers studied the possible : impact of recycled concrete aggregate (RCA) used in : roadway base layers on the acid/base balance of the : subsurface environment. They also examined a related : issue: management of concrete ...

Concrete performance using low-degradation aggregates.

DOT National Transportation Integrated Search

2012-06-01

The durability of Portland cement concrete (PCC) has long been identified as a concern by transportation communities around the United States. In this study, the long-term performance of two batches of concrete incorporating either low-degradation (L...

Preliminary study of neutron absorption by concrete with boron carbide addition

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

Abdullah, Yusof, E-mail: yusofabd@nuclearmalaysia.gov.my; Yusof, Mohd Reusmaazran; Zali, Nurazila Mat

2014-02-12

Concrete has become a conventional material in construction of nuclear reactor due to its properties like safety and low cost. Boron carbide was added as additives in the concrete construction as it has a good neutron absorption property. The sample preparation for concrete was produced with different weight percent of boron carbide powder content. The neutron absorption rate of these samples was determined by using a fast neutron source of Americium-241/Be (Am-Be 241) and detection with a portable backscattering neutron detector. Concrete with 20 wt % of boron carbide shows the lowest count of neutron transmitted and this indicates themore » most neutrons have been absorbed by the concrete. Higher boron carbide content may affect the concrete strength and other properties.« less

Experimental research on durability of recycled aggregate concrete under freeze- thaw cycles

NASA Astrophysics Data System (ADS)

Cheng, Yanqiu; Shang, Xiaoyu; Zhang, Youjia

2017-07-01

The freeze-thaw durability of recycled aggregate concrete has significance for the concrete buildings in the cold region. In this paper, the rapid freezing and thawing cycles experience on recycle aggregate concrete was conducted to study on the effects of recycle aggregate amount, water-binder ratio and fly ash on freeze-thaw durability of recycle aggregate concrete. The results indicates that recycle aggregate amount makes the significant influence on the freeze-thaw durability. With the increase of recycled aggregates amount, the freeze-thaw resistance for recycled aggregate concrete decreases. Recycled aggregate concrete with lower water cement ratio demonstrates better performance of freeze-thaw durability. It is advised that the amount of fly ash is less than 30% for admixture of recycled aggregates in the cold region.

Structural-functional integrated concrete with macro-encapsulated inorganic PCM

NASA Astrophysics Data System (ADS)

Mohseni, Ehsan; Tang, Waiching; Wang, Zhiyu

2017-09-01

Over the last few years the application of thermal energy storage system incorporating phase change materials (PCMs) to foster productivity and efficiency of buildings energy has grown rapidly. In this study, a structural-functional integrated concrete was developed using macro-encapsulated PCM-lightweight aggregate (LWA) as partial replacement (25 and 50% by volume) of coarse aggregate in control concrete. The PCM-LWA was prepared by incorporation of an inorganic PCM into porous LWAs through vacuum impregnation. The mechanical and thermal performance of PCM-LWA concrete were studied. The test results revealed that though the compressive strength of concrete with PCM-LWA was lower than the control concrete, but ranged from 22.02 MPa to 42.88 MPa which above the minimum strength requirement for structural application. The thermal performance test indicated that macro-encapsulated PCM-LWA has underwent the phase change transition reducing the indoor temperature.

Properties of concrete containing scrap-tire rubber--an overview.

PubMed

Siddique, Rafat; Naik, Tarun R

2004-01-01

Solid waste management is one of the major environmental concerns in the United States. Over 5 billion tons of non-hazardous solid waste materials are generated in USA each year. Of these, more than 270 million scrap-tires (approximately 3.6 million tons) are generated each year. In addition to this, about 300 million scrap-tires have been stockpiled. Several studies have been carried out to reuse scrap-tires in a variety of rubber and plastic products, incineration for production of electricity, or as fuel for cement kilns, as well as in asphalt concrete. Studies show that workable rubberized concrete mixtures can be made with scrap-tire rubber. This paper presents an overview of some of the research published regarding the use of scrap-tires in portland cement concrete. The benefits of using magnesium oxychloride cement as a binder for rubberized concrete mixtures are also presented. The paper details the likely uses of rubberized concrete.

Critical factors in displacement ductility assessment of high-strength concrete columns

NASA Astrophysics Data System (ADS)

Taheri, Ali; Moghadam, Abdolreza S.; Tasnimi, Abass Ali

2017-12-01

Ductility of high-strength concrete (HSC) columns with rectangular sections was assessed in this study by reviewing experimental data from the available literature. Up to 112 normal weights concrete columns with strength in the range of 50-130 MPa were considered and presented as a database. The data included the results of column testes under axial and reversed lateral loading. Displacement ductility of HSC columns was evaluated in terms of their concrete and reinforcement strengths, bar arrangement, volumetric ratio of transverse reinforcement, and axial loading. The results indicated that the confinement requirements and displacement ductility in HSC columns are more sensitive than those in normal strength concrete columns. Moreover, ductility is descended by increasing concrete strength. However, it was possible to obtain ductile behavior in HSC columns through proper confinement. Furthermore, this study casts doubt about capability of P/ A g f c' ratio that being inversely proportional to displacement ductility of HSC columns.

Effect of High Temperature on the Tensile Behavior of CFRP and Cementitious Composites

NASA Technical Reports Server (NTRS)

Toutanji, Houssam A.

1999-01-01

Concrete and other composite manufacturing processes are continuing to evolve and become more and more suited for use in non-Earth settings such as the Moon and Mars. The fact that structures built in lunar environments would experience a range of effects from temperature extremes to bombardment by micrometeorites and that all the materials for concrete production exist on the Moon means that concrete appears to be the most feasible building material. it can provide adequate shelter from the harshness of the lunar environment and at the same time be a cost effective building material. With a return to the Moon planned by NASA to occur after the turn of the century, it will be necessary to include concrete manufacturing as one of the experiments to be conducted in one of the coming missions. Concrete's many possible uses and possibilities for manufacturing make it ideal for lunar construction. The objectives of this research are summarized as follows: i) study the possibility of concrete production on the Moon or other planets, ii) study the effect of high temperature on the tensile behavior of concrete, and iii) study the effect of high temperature on the tensile behavior of carbon fiber reinforced with inorganic polymer composites. Literature review indicates that production of concrete on the Moon or other planets is feasible using the indigenous materials. Results of this study has shown that both the tensile strength and static elastic modulus of concrete decreased with a rise in temperature from 200 to 500 C. The addition of silica fume to concrete showed higher resistance to high temperatures. Carbon fiber reinforced inorganic polymer (CFRIP) composites seemed to perform well up to 300 C. However, a significant reduction in strength was observed of about 40% at 400 C and up to 80% when the specimens were exposed to 700 C.

Investigation of rectangular concrete columns reinforced or prestressed with fiber reinforced polymer (FRP) bars or tendons

NASA Astrophysics Data System (ADS)

Choo, Ching Chiaw

Fiber reinforced polymer (FRP) composites have been increasingly used in concrete construction. This research focused on the behavior of concrete columns reinforced with FRP bars, or prestressed with FRP tendons. The methodology was based the ultimate strength approach where stress and strain compatibility conditions and material constitutive laws were applied. Axial strength-moment (P-M) interaction relations of reinforced or prestressed concrete columns with FRP, a linearly-elastic material, were examined. The analytical results identified the possibility of premature compression and/or brittle-tension failure occurring in FRP reinforced and prestressed concrete columns where sudden and explosive type failures were expected. These failures were related to the rupture of FRP rebars or tendons in compression and/or in tension prior to concrete reaching its ultimate strain and strength. The study also concluded that brittle-tension failure was more likely to occur due to the low ultimate tensile strain of FRP bars or tendons as compared to steel. In addition, the failures were more prevalent when long term effects such as creep and shrinkage of concrete, and creep rupture of FRP were considered. Barring FRP failure, concrete columns reinforced with FRP, in some instances, gained significant moment resistance. As expected the strength interaction of slender steel or FRP reinforced concrete columns were dependent more on column length rather than material differences between steel and FRP. Current ACI minimum reinforcement ratio for steel (rhomin) reinforced concrete columns may not be adequate for use in FRP reinforced concrete columns. Design aids were developed in this study to determine the minimum reinforcement ratio (rhof,min) required for rectangular reinforced concrete columns by averting brittle-tension failure to a failure controlled by concrete crushing which in nature was a less catastrophic and more gradual type failure. The proposed method using rhof,min enabled the analysis of FRP reinforced concrete columns to be carried out in a manner similar to steel reinforced concrete columns since similar provisions in ACI 318 were consistently used in developing these aids. The design aids produced accurate estimates of rhof,min. When creep and shrinkage effects of concrete were considered, conservative rhof,min values were obtained in order to preserve an adequate margin of safety due to their unpredictability.