The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Kyong-ku Yun - One of the best experts on this subject based on the ideXlab platform.
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Effect of fine fly ash and calcium hydroxide on air void structure in very-early-strength Latex-Modified Concrete
Canadian Journal of Civil Engineering, 2015Co-Authors: Pangil Choi, Sung Il Jeon, Kyong-ku YunAbstract:Very-early-strength Latex-Modified Concrete (VES-LMC) was developed for rapid repairs of distresses in Concrete bridge decks and pavements, with the emphasis on early-age strength gain so that the repaired bridges and pavements can be opened to traffic within the time frame required in the specifications. However, there are two main concerns in the use of VES-LMC — early-age cracking and poor air void structure. The main objective of this study was to further improve VES-LMC to minimize early-age cracking and improve freeze–thaw durability, which included the use of fine fly ash (FFA) and calcium hydroxide (CH). Laboratory experiments were conducted on VES-LMC materials with cement replaced with FFA as well as CH, and various tests performed. Early-age drying shrinkages of VES-LMC containing both FFA and CH in the amounts evaluated in this study were smaller than that of VES-LMC with no replacements. It is expected that the use of FFA and CH in the range evaluated in this study will reduce the cracking potential of VES-LMC. Overall, the replacement of cement with FFA and CH improved the characteristics of entrained air void system, which will enhance the durability of VES-LMC against freeze–thaw damage. Scanning electron microscope and energy dispersive spectroscopy analysis indicate the primary mechanism of the generation of small sized air voids in Concretes containing adequate amount of FFA and CH is the gas formation reaction between citric acid solutions and CH during Concrete mixing. It is expected that the inclusion of adequate amounts of FFA and CH in VES-LMC will improve the performance of repaired bridge decks and pavements in terms of reduced cracking and improved freeze-thaw durability.
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Experimental analysis of latex-solid content effect on early-age and autogenous shrinkage of very-early strength Latex-Modified Concrete
Construction and Building Materials, 2014Co-Authors: Pangil Choi, Kyong-ku YunAbstract:Abstract Very-early strength Latex-Modified Concrete (VES-LMC) was developed for the purpose of creating a fast-track overlay of a Concrete bridge deck, concentrating on the workability and strength gain so that the bridge can be opened to traffic within hours of placement. The mixture of VES-LMC might accompany very high heat of hydration at early-age because of its inherent rapid hardening property, and could be susceptible to autogenous shrinkage because of its relatively low water to cement ratio. From the field survey, some transverse and map cracking due to Concrete material and construction issues were investigated in the bridge deck repaired with VES-LMC. This research focused on the effect due to material issue during early age. This study evaluated the effect of the latex-solid contents of both the constant and variable slumps on the hydration heat and early-age shrinkages of VES-LMC by carrying out a simple heat of hydration test and early-age shrinkage experiment. The results are as follows: The overall trends of hydration temperature were similar regardless of latex-solid contents within this study, although the initial setting by the latex-solid content varied a little. Total and autogenous shrinkage increased with the increase in latex-solid content. The total shrinkage occurs very quickly, with up to 80% of the maximum shrinkage during the first six hours after Concrete placement, and the remaining 20% of shrinkage occurring during the next 18 h. It is, therefore, highly recommended to maintain the minimum six hours of wet curing of Concrete in order to minimize early-age shrinkage and shrinkage cracking.
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Nonlinear Flexural Analysis of RC Beam Rehabilitated by Very-Early Strength Latex-Modified Concrete
Journal of the Korea Academia-Industrial cooperation Society, 2010Co-Authors: Sung-yong Choi, Kyong-ku Yun, Yong-bin Kim, Mun-sik KangAbstract:Abstract Latex modification of Concrete provides the material with higher flexural strength, as well as high bond strength and reduced water permeability. One of the most advantages of the very early-strength Latex-Modified Concrete (VES-LMC) could be the similar contraction and expansion behaviour to normal Concrete substrate, which enable to ensure long-term performance. The purpose of this study was to parametric nonlinear flexural nonlinear analysis of RC beam rehabilitated by VES-LMC. The results were as follows; The flexural nonlinear analysis model of RC beam overlaid by VES-LMC in ABAQUS was proposed to predict the load-deflection response, interfacial stress, and ultimate strength. The proposed FE analysis model was verified by comparison of an experimental data and the FE analysis results. The FE analysis results showed that yield point as well as flexural stiffness increased as the depth increased; the stiffness of beam overall increased as the bond stiffness became larger; the bond strength between two different materials is a key factor in composite beam. A parametric study showed that an overlay thickness was a main influencing factor to the behavior of RC beam overlaid by VES-LMC. Key Words : VES-LMC, ABAQUS, Nonlinear, FE analysis, Rehabilitation
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Autogenous Shrinkage of Very-Early Strength Latex-Modified Concrete with Latex Contents
Journal of the Korea Academia-Industrial cooperation Society, 2010Co-Authors: Won-il Park, Kyong-ku Yun, Pangil Choi, Bong-hak LeeAbstract:Very-early strength Latex-Modified Concrete (VES-LMC) was developed for the purpose of fast-track overlay of a Concrete bridge deck under heavy traffic, concentrated on the workability, durability, and strength gain so that it can be opened to the traffic only three hours after its placement. The mixture of VES-LMC might accompany very high heat of hydration at early-age because of its inherent rapid hardening property and could have susceptibility to autogenous shrinkage because of its relatively low water-cement ratio. This study evaluated the effect of the latex-cement ratio(L/C) both of the constant and variable slumps on the autogenous shrinkage of VES-LMC by carrying out simple temperature rise test and early-age shrinkage experiment. Test results are as follows: The latex contributes on the enhancement of the Concrete durability but has little effect on its hydration and the accompanied heat of hydration in VES-LMC. Autogenous shrinkage increased with the increase in latex-cement ratio at variable slumps and its pattern followed regularly a logarithmic increase. However, the influence of water-cement ratio and latex-cement ratios for the test specimens at constant slump on early-age autogenous shrinkage property was found to be minor due to the simultaneous effect of the two experimental variables.
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Autogenous Shrinkage of Very-Early Strength Latex-Modified Concrete with Retarder Contents
2009Co-Authors: Pangil Choi, Kyong-ku Yun, Bong-hak LeeAbstract:The autogenous shrinkage of high-performance Concrete, including very-early strength Latex-Modified Concrete(VES-LMC), is generally bigger than that of normal strength Concrete because of the low water/cement ratio, high binder contents, and usage of superplasticizer. Mix. proportion of VES-LMC has low water/cement ratio(0.38), high cement content(390kg/m), and aid of latex(15% of cement weight). Thus, these factors of VES-LMC, rapid water self-dissipation and evaporation within 3 hours of Concrete placement would increase the autogenous shrinkage. The purpose of this study was to evaluate the early-age shrinkage, thermal deformation and autogenous shrinkages of VES-LMC with retarder contents(retarder solids-cement ratio, by weight) using to secure working time in field. The experimental results showed that retarder contents do not affect of the maximum hydration temperature. Early-age expansion of VES-LMC was mostly caused by thermal expansion and partly by autogenous expansion. The autogenous shrinkage is decreased by increasing the retarder contents within this study. On the other hand, the usage of retarder should be decided carefully considering the field conditions because an excessive usage of retarder can cause handful early-age expansion.
Michael M Sprinkel - One of the best experts on this subject based on the ideXlab platform.
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Sampling and Testing Latex-Modified Concrete for Permeability to Chloride Ion
Transportation Research Record, 2009Co-Authors: Michael M SprinkelAbstract:The overall experience with Latex-Modified Concrete (LMC) overlays constructed with Types I-II, III, and K cements and rapid set cement continues to be good. The most frequent problem with LMC since the late 1990s has been the high incidence of LMC samples failing the permeability test (AASHTO T277) when done at an early age. Approximately one-third of the field-prepared specimens fail because they have permeability values > 1,500 coulombs. Research was done to determine the cause and significance of the failing early-age LMC permeability test results and to recommend changes in practice. The approach included testing of specimens prepared in the laboratory, specimens prepared in the field, and cores from three bridge overlays that had failing early-age test results for field-prepared specimens. Results indicate that the permeability of LMC decreases as the Concrete ages. LMC that meets the specification with the exception of early-age permeability should have a very low permeability at later age regardle...
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Latex--Modified Concrete Overlay Containing Type K Cement Performance
2006Co-Authors: Michael M SprinkelAbstract:This paper describes how shrinkage of the Concrete is the most common cause of cracking in hydraulic cement Concrete overlays placed on bridge decks. The use of type K (expansive) cement should increase the probability that Concrete overlays will be constructed with minimal cracks. This paper describes the Virginia Department of Transportation’s (VDOT) first experience with the use of type K cement for the construction of a Latex-Modified Concrete overlay. One lane was constructed with traditional Type I/II cement and the other lane was constructed with Type K cement. With the exception of the cement, the requirements for the overlays were the same. The evaluation of the overlays included measurements for slump, temperature, air content, compressive strength, permeability to chloride ion, shrinkage, and bond strength. As expected the shrinkage of the Concrete containing Type K cement was much less than that of the Concrete containing Type I/II cement. Other properties were similar. The use of the Type K cement is estimated to increase the cost of the Concrete approximately 2.6 per cent or about $1 dollar per square yard for a 1.5-in thick overlay. This is much less than the cost of about $10 per sq. yard to seal the shrinkage cracks in an overlay. Greater savings can come from the longer service life of a crack free overlay as compared to one that is cracked.
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Shrinkage of Latex-Modified and microsilica Concrete overlays
Transportation Research Record, 2003Co-Authors: Patricia M. Buchanan, David W Mokarem, Richard E. Weyers, Michael M SprinkelAbstract:Shrinkage performance was examined of Virginia Department of Transportation-approved Latex-Modified and microsilica Concrete overlay mixtures. Research was conducted on both field-sampled and laboratory-fabricated restrained and unrestrained specimens. From crack and delamination surveys of sampled bridge decks and laboratory test results, a shrinkage performance-based specification for the Virginia Department of Transportation was developed. There was no significant difference between the unrestrained shrinkage values of Latex-Modified and microsilica Concrete overlay mixtures for the specified time periods. Restrained microsilica Concrete specimens generally cracked earlier and more frequently than restrained Latex-Modified Concrete specimens. However, the bridge deck crack and delamination surveys show that conditions and quality of construction and type and frequency of traffic may have a greater effect on cracking than the overlay material.
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Very-Early-Strength Latex-Modified Concrete Overlay:
Transportation Research Record, 1999Co-Authors: Michael M SprinkelAbstract:The installation and condition of the first two very-early-strength latexmodified Concrete (LMC-VE) overlays constructed for the Virginia Department of Transportation are described. The overlays were prepared with a special blended cement rather than with the Type I/II cement used in the conventional Latex-Modified Concrete (LMC) overlay. LMC-VE mixture proportions, installation equipment, and procedures are similar to those used for conventional LMC overlays. However, when working with LMC-VE, the contractor must work faster because the Concrete loses slump rapidly and the curing period is approximately 3 rather than 72 hours. Tests of the compressive strength of the LMC-VE overlay performed during the early hours after installation indicated that traffic could be placed on the overlay within 3 hours rather than within the 4 to 7 days required for the conventional LMC overlay. Tests of bond strength and permeability to chloride ion indicated that the overlays are performing satisfactorily and can be used...
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Twenty-Year Performance of Latex-Modified Concrete Overlays
Polymer-Modified Hydraulic-Cement Mixtures, 1Co-Authors: Michael M SprinkelAbstract:Fourteen bridge decks with Latex-Modified Concrete (LMC) overlays ranging in age from 2 to 20 years and two overlays without latex were studied, and their general condition was found to be good. The half-cell and chloride data indicate that the overlays are performing satisfactorily. Rate-of-corrosion data indicate that the overlays can be used to extend the life of decks suffering from chloride-induced corrosion of the top mat of the rebar even though corrosion continues under the overlay. The permeability to chloride ions was an average of 630 coulombs (very low) for a 1.25-in.-thick LMC overlay and 5,274 coulombs (high) for the base Concretes. The 2-in.-thick overlays with and without latex had permeabilities of 101 and 1,305 coulombs, respectively. Adequate shear and tensile rupture strength at the bond interface was obtained and maintained. The data indicate that LMC overlays placed on decks with less than 2 lb/cu yd of chloride ion at the rebar can be expected to have a service life of more than 20 years. The study provided the opportunity to evaluate two overlays with latex and two without latex that were installed as part of two bridges constructed in 1974. When data from these bridges were obtained in 1990 and compared with data obtained from earlier evaluations, the high quality portland cement Concrete overlays without latex showed greater negative increases in half-cell potentials, greater increases in chloride content, and a higher percentage of higher rates of corrosion than the LMC overlays. Also, for these two bridges, higher shear and tensile rupture strengths were obtained at the bond interface with LMC than with Concrete without latex. Higher rupture strengths were not obtained on the other bridges because of the low strength of the scarified surface of the base Concrete.
M.m. Reda - One of the best experts on this subject based on the ideXlab platform.
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Durability of Styrene-Butadiene latex modified Concrete
Cement and Concrete Research, 1997Co-Authors: F.a. Shaker, Amr S. El-dieb, M.m. RedaAbstract: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 its 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.
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Evaluation of the corrosion resistance of latex modified Concrete (LMC)
Cement and Concrete Research, 1997Co-Authors: S.h. Okba, Amr S. El-dieb, M.m. RedaAbstract:In recent years, various reinforced Concrete structures worldwide have suffered rapid deterioration. Therefore, durability of Concrete structures especially those exposed to aggressive environments is of great concern. Many deterioration causes and factors have been investigated. Corrosion of steel reinforcement was found to be one of the major deterioration problems. Penetration of chloride ions is one of the main causes which induces corrosion. The objective of this study is to evaluate the corrosion resistance of latex modified Concrete (LMC) compared to conventional Concrete using an accelerated corrosion cell. The corrosion cell proved to be a good and simple method to evaluate the durability of Concretes especially with respect to chloride ion penetration, and the protection of reinforcement against corrosion. The LMC proved to be superior in its corrosion resistance compared to conventional Concrete, which recommends its use in structures exposed to severe aggressive environments.
Pangil Choi - One of the best experts on this subject based on the ideXlab platform.
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Effect of fine fly ash and calcium hydroxide on air void structure in very-early-strength Latex-Modified Concrete
Canadian Journal of Civil Engineering, 2015Co-Authors: Pangil Choi, Sung Il Jeon, Kyong-ku YunAbstract:Very-early-strength Latex-Modified Concrete (VES-LMC) was developed for rapid repairs of distresses in Concrete bridge decks and pavements, with the emphasis on early-age strength gain so that the repaired bridges and pavements can be opened to traffic within the time frame required in the specifications. However, there are two main concerns in the use of VES-LMC — early-age cracking and poor air void structure. The main objective of this study was to further improve VES-LMC to minimize early-age cracking and improve freeze–thaw durability, which included the use of fine fly ash (FFA) and calcium hydroxide (CH). Laboratory experiments were conducted on VES-LMC materials with cement replaced with FFA as well as CH, and various tests performed. Early-age drying shrinkages of VES-LMC containing both FFA and CH in the amounts evaluated in this study were smaller than that of VES-LMC with no replacements. It is expected that the use of FFA and CH in the range evaluated in this study will reduce the cracking potential of VES-LMC. Overall, the replacement of cement with FFA and CH improved the characteristics of entrained air void system, which will enhance the durability of VES-LMC against freeze–thaw damage. Scanning electron microscope and energy dispersive spectroscopy analysis indicate the primary mechanism of the generation of small sized air voids in Concretes containing adequate amount of FFA and CH is the gas formation reaction between citric acid solutions and CH during Concrete mixing. It is expected that the inclusion of adequate amounts of FFA and CH in VES-LMC will improve the performance of repaired bridge decks and pavements in terms of reduced cracking and improved freeze-thaw durability.
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Experimental analysis of latex-solid content effect on early-age and autogenous shrinkage of very-early strength Latex-Modified Concrete
Construction and Building Materials, 2014Co-Authors: Pangil Choi, Kyong-ku YunAbstract:Abstract Very-early strength Latex-Modified Concrete (VES-LMC) was developed for the purpose of creating a fast-track overlay of a Concrete bridge deck, concentrating on the workability and strength gain so that the bridge can be opened to traffic within hours of placement. The mixture of VES-LMC might accompany very high heat of hydration at early-age because of its inherent rapid hardening property, and could be susceptible to autogenous shrinkage because of its relatively low water to cement ratio. From the field survey, some transverse and map cracking due to Concrete material and construction issues were investigated in the bridge deck repaired with VES-LMC. This research focused on the effect due to material issue during early age. This study evaluated the effect of the latex-solid contents of both the constant and variable slumps on the hydration heat and early-age shrinkages of VES-LMC by carrying out a simple heat of hydration test and early-age shrinkage experiment. The results are as follows: The overall trends of hydration temperature were similar regardless of latex-solid contents within this study, although the initial setting by the latex-solid content varied a little. Total and autogenous shrinkage increased with the increase in latex-solid content. The total shrinkage occurs very quickly, with up to 80% of the maximum shrinkage during the first six hours after Concrete placement, and the remaining 20% of shrinkage occurring during the next 18 h. It is, therefore, highly recommended to maintain the minimum six hours of wet curing of Concrete in order to minimize early-age shrinkage and shrinkage cracking.
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Autogenous Shrinkage of Very-Early Strength Latex-Modified Concrete with Latex Contents
Journal of the Korea Academia-Industrial cooperation Society, 2010Co-Authors: Won-il Park, Kyong-ku Yun, Pangil Choi, Bong-hak LeeAbstract:Very-early strength Latex-Modified Concrete (VES-LMC) was developed for the purpose of fast-track overlay of a Concrete bridge deck under heavy traffic, concentrated on the workability, durability, and strength gain so that it can be opened to the traffic only three hours after its placement. The mixture of VES-LMC might accompany very high heat of hydration at early-age because of its inherent rapid hardening property and could have susceptibility to autogenous shrinkage because of its relatively low water-cement ratio. This study evaluated the effect of the latex-cement ratio(L/C) both of the constant and variable slumps on the autogenous shrinkage of VES-LMC by carrying out simple temperature rise test and early-age shrinkage experiment. Test results are as follows: The latex contributes on the enhancement of the Concrete durability but has little effect on its hydration and the accompanied heat of hydration in VES-LMC. Autogenous shrinkage increased with the increase in latex-cement ratio at variable slumps and its pattern followed regularly a logarithmic increase. However, the influence of water-cement ratio and latex-cement ratios for the test specimens at constant slump on early-age autogenous shrinkage property was found to be minor due to the simultaneous effect of the two experimental variables.
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Autogenous Shrinkage of Very-Early Strength Latex-Modified Concrete with Retarder Contents
2009Co-Authors: Pangil Choi, Kyong-ku Yun, Bong-hak LeeAbstract:The autogenous shrinkage of high-performance Concrete, including very-early strength Latex-Modified Concrete(VES-LMC), is generally bigger than that of normal strength Concrete because of the low water/cement ratio, high binder contents, and usage of superplasticizer. Mix. proportion of VES-LMC has low water/cement ratio(0.38), high cement content(390kg/m), and aid of latex(15% of cement weight). Thus, these factors of VES-LMC, rapid water self-dissipation and evaporation within 3 hours of Concrete placement would increase the autogenous shrinkage. The purpose of this study was to evaluate the early-age shrinkage, thermal deformation and autogenous shrinkages of VES-LMC with retarder contents(retarder solids-cement ratio, by weight) using to secure working time in field. The experimental results showed that retarder contents do not affect of the maximum hydration temperature. Early-age expansion of VES-LMC was mostly caused by thermal expansion and partly by autogenous expansion. The autogenous shrinkage is decreased by increasing the retarder contents within this study. On the other hand, the usage of retarder should be decided carefully considering the field conditions because an excessive usage of retarder can cause handful early-age expansion.
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Thermal and Autogenous Shrinkages of Very Early Strength Latex-Modified Concrete
Transportation Research Record, 2007Co-Authors: Kyong-ku Yun, Pangil Choi, Sung-yong Choi, Ki-heun KimAbstract:A study evaluated the factors influencing thermal and autogenous shrinkages of very early strength Latex-Modified Concrete (VES-LMC) with respect to latex content (latex solids-cement ratio, by weight); water-cement ratio; retarder content (retarder solids-cement ratio, by weight); and antifoamer content (antifoamer-latex solids ratio, by weight). Examined were three levels of latex content (0%, 5%, 15%) at a constant slump, three levels of water-cement ratio (0.34, 0.38, 0.42) at a constant latex content of 15%, three levels of retarder content (0.0%, 0.3%, 0.6%), and three levels of antifoamer content (0.0%, 0.5% and 1.0%) at a constant latex content and water-cement ratio. Results were that total shrinkage was governed by thermal deformation at very early age because of the high heat of hydration of VES cement. After 5 h, total shrinkage was governed by the autogenous shrinkage process. The absolute magnitude of thermal expansion was 130 micro strains while the autogenous shrinkage was 120 micro strain...
Mohamed A. Elgawady - One of the best experts on this subject based on the ideXlab platform.
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Latex-Modified Concrete overlays using waste paint
Construction and Building Materials, 2016Co-Authors: Aly M. Said, Oscar Quiroz, D. W. Hatchett, Mohamed A. ElgawadyAbstract:Abstract The U.S. generates over 35 million gallons of waste latex paint annually, which is difficult to recycle as it contains volatile organic compounds. However, waste latex paint can be used to produce an economic Latex-Modified Concrete used for whitetopping, wearing surfaces in parking garages, and overlays, instead of commercial products resulting in significant cost savings. This study compares the use of waste latex paint to commercially available styrene-butadiene rubber latex in Concrete for overlays, and evaluates Concrete fresh and hardened properties as well as transport properties. Waste latex paint added to Concrete results in characteristics comparable to polymer-modified Concrete made with commercial latex products.
