The Experts below are selected from a list of 1158 Experts worldwide ranked by ideXlab platform
Kookjae Shin - One of the best experts on this subject based on the ideXlab platform.
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frost attack resistance and steel bar corrosion of antiwashout Underwater Concrete containing mineral admixtures
Construction and Building Materials, 2007Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:Abstract This study aims to evaluate frost durability and steel-bar corrosion in antiwashout-Underwater Concrete, which has been neglected to date. To achieve this goal, repeated freezing and thawing and accelerated steel-bar corrosion tests have been performed for three types of antiwashout-Underwater Concrete specimens. The results of repeated freezing and thawing test reveal that adding mineral admixtures has little effects on frost durability because of the large and uneven entrapped-air imprisoned by the cellulose-type antiwashout-Underwater admixture. Slight improvement of frost durability was observed through the action of air-entrained (AE) agent in the case of SG50 which presented an air content of 6 ± 0.5%. Measurement results using the half-cell potential showed that, among the entire specimens, steel-bar in Control specimen manufactured under artificial seawater was the first one that exceeded the threshold value, −350 mV proposed by ASTM C 876, at 14 cycles, where the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm2 and 0.258%, respectively. For the other specimens, potential values became below −350 mV later than 18 cycles.
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Evaluation on steel bar corrosion embedded in antiwashout Underwater Concrete containing mineral admixtures
Cement and Concrete Research, 2006Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:Abstract This study aims the evaluation of the corrosion of steel bar embedded in antiwashout Underwater Concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed for three series of steel bar-reinforced antiwashout Underwater Concrete specimens manufactured with different admixtures and under different environments. The three series of antiwashout Underwater Concrete were: Concrete constituted exclusively by ordinary portland cement (OPC), Concrete composed by ordinary portland cement mixed with fly-ash in 20% ratio (FA20) and Concrete with ground granulated blast furnace slag is mixed in 50% ratio (BFS50). And, the three different environments were: manufacture in the air, in tap water, and in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC manufactured in artificial seawater was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below − 350 mV after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm 2 and 0.258%. On the other hand, for the other specimens that are FA20 and BFS50, potential values below − 350 mV were observed later at 18 and 20 cycles, respectively. Results confirmed the expectation that mineral admixtures may be more effective in delaying the development of steel bar corrosion in antiwashout Underwater Concrete.
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Freezing and Thawing Resistance and fundamental Properties of Antiwashout Underwater Concrete Containing Mineral Admixtures
Journal of The Korea Concrete Institute, 2005Co-Authors: Hanyoung Moon, Kookjae Shin, Yong-kyu SongAbstract:Today the application of antiwashout Underwater Concrete to the construction sites is increasing steadily, while its reliability is in issue. Particularly, antiwashout Underwater Concrete is known to have very weak durability on frost attack, and hence Japan society of civil engineers(JSCE) regulated that not to use of antiwashout Underwater Concrete where the freezing and thawing is suspected. This study aims the improvement of the freezing and thawing resistance for antiwashout Underwater Concrete. From the results of fundamental test, FA20 and SG50 showed good performance in fluidity and long term compressive strength than control Concrete. Meanwhile, MK10 marked the highest compressive strength through the whole curing age but a defect on fluidity was discovered. The results from the repeated freezing and thawing test show that the large volumes of air entrapped by cellulose based antiwashout Underwater admixture gave bad effects to frost durability and hence not much benefits were confirmed from the use of mineral admixtures. However there were some increasing effects on frost durability of MK10 and SG50 by securing of entraining air. In the meantime, there was a increasing tendency of frost durability by increasing blame's fineness of ground granulated blast furnace slag.
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evaluation on steel bar corrosion embedded in antiwashout Underwater Concrete
International Journal of Concrete Structures and Materials, 2005Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:This study aims the evaluation of the corrosion of steel bar embedded in antiwashout Underwater Concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed on three series of steel bar-reinforced antiwashout Underwater Concrete specimens manufactured with different admixtures. The three series of antiwashout Underwater Concrete were: Concrete constituted exclusively with ordinary portland cement (OPC), Concrete composed of ordinary portland cement mixed with fly-ash in ratio (FA20), and Concrete with ground granulated blast furnace slag mixed in ratio (BFS50). The environment of manufacture was in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below -350mv after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as and . On the other hand, for the other specimens that are FA20 and BFS50, potential values below -350mV were observed later at 18 and 20 cycles, respectively. Results confirmed the hypothesis that mineral admixtures may be more effective on delay the development of steel bar corrosion in antiwashout Underwater Concrete.
Hanyoung Moon - One of the best experts on this subject based on the ideXlab platform.
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frost attack resistance and steel bar corrosion of antiwashout Underwater Concrete containing mineral admixtures
Construction and Building Materials, 2007Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:Abstract This study aims to evaluate frost durability and steel-bar corrosion in antiwashout-Underwater Concrete, which has been neglected to date. To achieve this goal, repeated freezing and thawing and accelerated steel-bar corrosion tests have been performed for three types of antiwashout-Underwater Concrete specimens. The results of repeated freezing and thawing test reveal that adding mineral admixtures has little effects on frost durability because of the large and uneven entrapped-air imprisoned by the cellulose-type antiwashout-Underwater admixture. Slight improvement of frost durability was observed through the action of air-entrained (AE) agent in the case of SG50 which presented an air content of 6 ± 0.5%. Measurement results using the half-cell potential showed that, among the entire specimens, steel-bar in Control specimen manufactured under artificial seawater was the first one that exceeded the threshold value, −350 mV proposed by ASTM C 876, at 14 cycles, where the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm2 and 0.258%, respectively. For the other specimens, potential values became below −350 mV later than 18 cycles.
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Evaluation on steel bar corrosion embedded in antiwashout Underwater Concrete containing mineral admixtures
Cement and Concrete Research, 2006Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:Abstract This study aims the evaluation of the corrosion of steel bar embedded in antiwashout Underwater Concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed for three series of steel bar-reinforced antiwashout Underwater Concrete specimens manufactured with different admixtures and under different environments. The three series of antiwashout Underwater Concrete were: Concrete constituted exclusively by ordinary portland cement (OPC), Concrete composed by ordinary portland cement mixed with fly-ash in 20% ratio (FA20) and Concrete with ground granulated blast furnace slag is mixed in 50% ratio (BFS50). And, the three different environments were: manufacture in the air, in tap water, and in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC manufactured in artificial seawater was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below − 350 mV after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm 2 and 0.258%. On the other hand, for the other specimens that are FA20 and BFS50, potential values below − 350 mV were observed later at 18 and 20 cycles, respectively. Results confirmed the expectation that mineral admixtures may be more effective in delaying the development of steel bar corrosion in antiwashout Underwater Concrete.
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Freezing and Thawing Resistance and fundamental Properties of Antiwashout Underwater Concrete Containing Mineral Admixtures
Journal of The Korea Concrete Institute, 2005Co-Authors: Hanyoung Moon, Kookjae Shin, Yong-kyu SongAbstract:Today the application of antiwashout Underwater Concrete to the construction sites is increasing steadily, while its reliability is in issue. Particularly, antiwashout Underwater Concrete is known to have very weak durability on frost attack, and hence Japan society of civil engineers(JSCE) regulated that not to use of antiwashout Underwater Concrete where the freezing and thawing is suspected. This study aims the improvement of the freezing and thawing resistance for antiwashout Underwater Concrete. From the results of fundamental test, FA20 and SG50 showed good performance in fluidity and long term compressive strength than control Concrete. Meanwhile, MK10 marked the highest compressive strength through the whole curing age but a defect on fluidity was discovered. The results from the repeated freezing and thawing test show that the large volumes of air entrapped by cellulose based antiwashout Underwater admixture gave bad effects to frost durability and hence not much benefits were confirmed from the use of mineral admixtures. However there were some increasing effects on frost durability of MK10 and SG50 by securing of entraining air. In the meantime, there was a increasing tendency of frost durability by increasing blame's fineness of ground granulated blast furnace slag.
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evaluation on steel bar corrosion embedded in antiwashout Underwater Concrete
International Journal of Concrete Structures and Materials, 2005Co-Authors: Hanyoung Moon, Kookjae ShinAbstract:This study aims the evaluation of the corrosion of steel bar embedded in antiwashout Underwater Concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed on three series of steel bar-reinforced antiwashout Underwater Concrete specimens manufactured with different admixtures. The three series of antiwashout Underwater Concrete were: Concrete constituted exclusively with ordinary portland cement (OPC), Concrete composed of ordinary portland cement mixed with fly-ash in ratio (FA20), and Concrete with ground granulated blast furnace slag mixed in ratio (BFS50). The environment of manufacture was in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below -350mv after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as and . On the other hand, for the other specimens that are FA20 and BFS50, potential values below -350mV were observed later at 18 and 20 cycles, respectively. Results confirmed the hypothesis that mineral admixtures may be more effective on delay the development of steel bar corrosion in antiwashout Underwater Concrete.
Joseph J Assaad - One of the best experts on this subject based on the ideXlab platform.
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Bond of tension bars in Underwater Concrete: effect of bar diameter and cover
Materials and Structures, 2015Co-Authors: Camille A. Issa, Joseph J AssaadAbstract:This research project is undertaken to assess the effect of washout loss on the drop in bond properties of reinforcing steel bars embedded in Underwater Concrete (UWC). Special emphasis was placed to evaluate bond using the same Concrete mixtures that were subjected to washout. Testing was realized using the beam-end specimen method, and parameters evaluated included level of washout loss, bar diameter, and Concrete cover. Test results showed that bond between steel and UWC is affected by the level of washout loss, which in turn is directly influenced by the mixture composition. Similarly to bond in Concrete cast and consolidated above water, the ultimate UWC bond strength increases for smaller bar diameters and higher confinement reflected by increased Concrete covers. UWC mixtures with increased washout losses exhibited higher drops in compressive, tensile, and bond strengths, as compared to Concrete cast above water. Two boxes depending on the level of washout loss, i.e. from 4.2 to 6.9 % and from 8.8 to 10.8 %, have been proposed to predict the extent of bond decrease in UWC mixtures.
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Mechanisms of strength loss in Underwater Concrete
Materials and Structures, 2013Co-Authors: Joseph J Assaad, Camille A. IssaAbstract:In-situ hardened properties of Underwater Concrete (UWC) are affected by washout loss and water infiltration occurring during the casting and post-casting stages. This paper evaluates the suitability of the falling-head method determined using a permeameter cell to assess water infiltration or, permeability ( k ), in freshly mixed UWC. Correlations between k and washout loss determined using the CRD C61 test method are established. The paper also seeks to quantify the coupled effect of washout loss and water infiltration on the drop in UWC compressive strength. Test results showed that Darcy’s law is valid to evaluate water permeability in UWC. The k and washout loss values are found to be well correlated within each other. UWC mixtures subjected to washout or water infiltration exhibited lower compressive strengths, as compared to reference Concrete sampled in dry conditions. The drop in UWC strength was attributed to a combination of factors including washout loss of cementitious phase together with relative increases in aggregate concentration and specified water-to-cement ratio.
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effect of washout loss on bond behavior of steel embedded in Underwater Concrete
Aci Structural Journal, 2013Co-Authors: Joseph J Assaad, Camille A. IssaAbstract:Limited studies have been undertaken to investigate the bond properties of reinforcing steel bars embedded in Underwater Concrete (UWC). Approximately 60 pullout tests were carried out to evaluate the effect of washout loss (W) on residual compressive and bond strengths. Washout was determined using the CRD C61 test and by simulation using a newly developed air-pressurized tube. Reference mixtures sampled in dry conditions were also tested. Test results showed that bond between steel and UWC is affected by a combination of parameters that complement those documented in the literature for Concrete cast and consolidated above water. These include the level of W, degree of segregation, hydrostatic water head, and interfacial Concrete-water velocity. The bond-stress-versus-slip behavior of UWC is remarkably different from the one obtained using reference mixtures. Initially, the linear response is less stiff due to a coupled effect related to lower strength and increase in the relative coarse aggregate concentration. The slip at ultimate bond strength was found to decrease for UWC mixtures exhibiting higher levels of W.
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Bond strength of epoxy-coated bars in Underwater Concrete
Construction and Building Materials, 2012Co-Authors: Joseph J Assaad, Camille A. IssaAbstract:Abstract A comprehensive research project was carried out to assess the effect of washout loss on bond between Underwater Concrete (UWC) and epoxy-coated reinforcing steel. Washout loss of investigated mixtures was evaluated using the CRD C61 test method. The compressive and bond strengths of UWC were determined using the same Concrete samples that were used for washout loss measurement. Test results showed that the ultimate bond strengths of epoxy-coated bars embedded in UWC are affected by the level of washout loss. Compared to reference Concrete sampled in dry condition, a decrease in bond varying from 15% to 25% was measured for UWC possessing washout loss in the range of 8% ± 3%. The bond stress vs. slip behavior of epoxy-coated bars is remarkably different than the one obtained using reference Concrete. Mixtures subjected to some washout exhibited less stiffness together with a decrease in the ultimate bond strength and shifting of the slip towards lower values.
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use of cem approach to develop and optimize high performance Underwater Concrete
Journal of Materials in Civil Engineering, 2011Co-Authors: Joseph J Assaad, Yehia Daou, Jacques HarbAbstract:The development and optimization of Underwater Concrete (UWC) characteristics (i.e., washout loss, threshold water head prior to Concrete deterioration, and residual compressive strength) require considerable time, effort, and energy for testing. This paper seeks to propose a new testing method developed on the basis of the Concrete-equivalent-mortar (CEM) approach to optimize and simplify evaluating the effect of mixture composition on washout characteristics of UWC cast under different conditions. Washout of CEM was determined using an adapted version of the commonly used CRD C61 test method as well as by simulation using an air-pressurized tube measuring 300 mm in height. Test results showed that CEM mixtures proportioned without coarse aggregates can adequately be used to predict washout characteristics of UWC. Statistical regression models were developed to enable direct estimation of washout loss and threshold water head of CEM and UWC mixtures.
Kamal H. Khayat - One of the best experts on this subject based on the ideXlab platform.
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simulation of water pressure on washout of Underwater Concrete repair
Aci Materials Journal, 2009Co-Authors: Joseph J Assaad, Yehia Daou, Kamal H. KhayatAbstract:A comprehensive research project was undertaken to evaluate the effect of hydrostatic pressure and interfacial Concrete/water velocity on the performance of Underwater Concrete (UWC) designated for repair applications. Washout loss was determined on 33 optimized mixtures using the CRD C61 test method, as well as a newly developed device enabling the simulation of Concrete washout placed at various depths down to 140 m (460 ft) below water surface level. Test results showed that washout loss of UWC increases with the increase in water head. Depending on the mixture composition, a critical threshold water depth can be found, beyond which significant washout loss could take place. The effect of decreasing the interfacial Concrete/water velocity from 2.5 to 0.5 m/s (8.2 to 1.6 ft/s) was found to reduce washout loss for a given depth of casting or enable the casting in deeper water for a given washout resistance. Good correlations were obtained between washout loss determined as per the CRD C61 test method and the washout loss derived from estimates given a certain interfacial Concrete/water velocity and water depth.
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PERFORMANCE OF Underwater Concrete CAST IN STILL AND FLOWING WATER
2003Co-Authors: Mohammed Sonebi, Kamal H. KhayatAbstract:The use of Underwater Concrete in the construction of the Confederation Bridge in Canada, the repair of the stilling basin of the Red Rock Dam in Iowa, USA and the rehabilitation of velocity caps of an intake structure of a power plant in the ocean surf zone are described. A study by the Universite de Sherbrooke in Canada investigating the effects of water velocity and mixture composition and flow properties on the in situ performance of Concrete cast under water is outlined. The study demonstrated the importance of protecting Concrete from flowing water during casting. A second study investigating the effects of mixture composition on the washout resistance of highly flowable Underwater Concrete is reported. For a constant slump flow, the increase in water/cementitious materials ratio reduced the relative strength of the Concrete.
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Effect of Mixture Composition on Relative Strength of Highly Flowable Underwater Concrete
Aci Materials Journal, 2001Co-Authors: Mohamed Sonebi, Kamal H. KhayatAbstract:Concrete used for Underwater repair is often proportioned to spread readily into place and self-consolidate, and to develop high resistance to segregation and water dilution. A study was conducted to determine the effect of the dosage of antiwashout admixture, water-cementitious materials ratio (w/cm), and binder composition on the relative residual strength of highly flowable Underwater Concrete. Two types of antiwashout admixtures and 4 binder compositions were used. Results indicate that for a given washout mass loss and slump flow consistency, greater relative residual strength can be secured when the dosage of antiwashout admixture is increased, the w/cm reduced, and a binary binder with 10% silica fume substitution or the ternary binder are employed.
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Applications of Statistical Models for Proportioning Underwater Concrete
Aci Materials Journal, 1999Co-Authors: Kamal H. Khayat, Ammar Yahia, Mohammed SonebiAbstract:A factorial design was carried out to model mathematically the influence of five key parameters on slump consistency, washout mass loss, and compressive strength that are important for the successful development of Underwater Concrete. The parameters considered were the content of cementitious materials, water-to-cementitious material ratio, sand-to-total aggregate ratio, and concentrations of antiwashout admixture and high-range water reducer. The derived statistical models are valid for a wide range of mixture proportioning and reveal the order of influence of each parameter on the modeled responses. The utility of such models to optimize Concrete mixtures to achieve good balance between slump consistency, washout resistance, compressive strength, and cost is discussed. Examples highlighting the usefulness of the models are presented using contour diagrams to demonstrate single and coupled effects of mixture parameters on consistency and washout resistance. Cost analysis is carried out to show trade-offs between material cost and specified consistency and washout resistance levels that can be used to identify economic mixtures. This paper establishes the usefulness of the mathematical models as a tool to facilitate the test protocol required to optimize high-performance Concrete for Underwater applications.
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Assessment of washout resistance of Underwater Concrete: a comparison between CRD C61 and new MC-1 tests
Materials and Structures, 1999Co-Authors: Mohammed Sonebi, P. Bartos, Kamal H. KhayatAbstract:An investigation was carried out to compare the performance and, in particular the repeatability and sensitivity of assessment of workability and washout resistance of Underwater Concrete using two test methods based on different principles. The first method is the plunge test (CRD C61), used in North America, and the second is the new spray test (MC-1), developed at the University of Paisley. The sensitivity of the test results to variation of dosage of the anti-washout admixture and of superplasticizer, was investigated.
Camille A. Issa - One of the best experts on this subject based on the ideXlab platform.
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Bond of tension bars in Underwater Concrete: effect of bar diameter and cover
Materials and Structures, 2015Co-Authors: Camille A. Issa, Joseph J AssaadAbstract:This research project is undertaken to assess the effect of washout loss on the drop in bond properties of reinforcing steel bars embedded in Underwater Concrete (UWC). Special emphasis was placed to evaluate bond using the same Concrete mixtures that were subjected to washout. Testing was realized using the beam-end specimen method, and parameters evaluated included level of washout loss, bar diameter, and Concrete cover. Test results showed that bond between steel and UWC is affected by the level of washout loss, which in turn is directly influenced by the mixture composition. Similarly to bond in Concrete cast and consolidated above water, the ultimate UWC bond strength increases for smaller bar diameters and higher confinement reflected by increased Concrete covers. UWC mixtures with increased washout losses exhibited higher drops in compressive, tensile, and bond strengths, as compared to Concrete cast above water. Two boxes depending on the level of washout loss, i.e. from 4.2 to 6.9 % and from 8.8 to 10.8 %, have been proposed to predict the extent of bond decrease in UWC mixtures.
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Mechanisms of strength loss in Underwater Concrete
Materials and Structures, 2013Co-Authors: Joseph J Assaad, Camille A. IssaAbstract:In-situ hardened properties of Underwater Concrete (UWC) are affected by washout loss and water infiltration occurring during the casting and post-casting stages. This paper evaluates the suitability of the falling-head method determined using a permeameter cell to assess water infiltration or, permeability ( k ), in freshly mixed UWC. Correlations between k and washout loss determined using the CRD C61 test method are established. The paper also seeks to quantify the coupled effect of washout loss and water infiltration on the drop in UWC compressive strength. Test results showed that Darcy’s law is valid to evaluate water permeability in UWC. The k and washout loss values are found to be well correlated within each other. UWC mixtures subjected to washout or water infiltration exhibited lower compressive strengths, as compared to reference Concrete sampled in dry conditions. The drop in UWC strength was attributed to a combination of factors including washout loss of cementitious phase together with relative increases in aggregate concentration and specified water-to-cement ratio.
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effect of washout loss on bond behavior of steel embedded in Underwater Concrete
Aci Structural Journal, 2013Co-Authors: Joseph J Assaad, Camille A. IssaAbstract:Limited studies have been undertaken to investigate the bond properties of reinforcing steel bars embedded in Underwater Concrete (UWC). Approximately 60 pullout tests were carried out to evaluate the effect of washout loss (W) on residual compressive and bond strengths. Washout was determined using the CRD C61 test and by simulation using a newly developed air-pressurized tube. Reference mixtures sampled in dry conditions were also tested. Test results showed that bond between steel and UWC is affected by a combination of parameters that complement those documented in the literature for Concrete cast and consolidated above water. These include the level of W, degree of segregation, hydrostatic water head, and interfacial Concrete-water velocity. The bond-stress-versus-slip behavior of UWC is remarkably different from the one obtained using reference mixtures. Initially, the linear response is less stiff due to a coupled effect related to lower strength and increase in the relative coarse aggregate concentration. The slip at ultimate bond strength was found to decrease for UWC mixtures exhibiting higher levels of W.
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Bond strength of epoxy-coated bars in Underwater Concrete
Construction and Building Materials, 2012Co-Authors: Joseph J Assaad, Camille A. IssaAbstract:Abstract A comprehensive research project was carried out to assess the effect of washout loss on bond between Underwater Concrete (UWC) and epoxy-coated reinforcing steel. Washout loss of investigated mixtures was evaluated using the CRD C61 test method. The compressive and bond strengths of UWC were determined using the same Concrete samples that were used for washout loss measurement. Test results showed that the ultimate bond strengths of epoxy-coated bars embedded in UWC are affected by the level of washout loss. Compared to reference Concrete sampled in dry condition, a decrease in bond varying from 15% to 25% was measured for UWC possessing washout loss in the range of 8% ± 3%. The bond stress vs. slip behavior of epoxy-coated bars is remarkably different than the one obtained using reference Concrete. Mixtures subjected to some washout exhibited less stiffness together with a decrease in the ultimate bond strength and shifting of the slip towards lower values.
