In order to examine the effect of load-induced transverse cracks on the chloride penetration in flexural concrete beams, two different concretes, Portland cement concrete(PCC) and fly ash concrete(FAC), were tested wi...In order to examine the effect of load-induced transverse cracks on the chloride penetration in flexural concrete beams, two different concretes, Portland cement concrete(PCC) and fly ash concrete(FAC), were tested with various crack widths. Total 14 reinforced concrete(RC) beams, ten of which were self-anchored in a three-point bending mode, were immersed into a 5% NaCl solution with the condition of dry-wet cycles. Then, the free chloride ion contents were determined by rapid chloride testing(RCT) method. Based on the proposed analytical models of chloride penetration in sound and cracked concrete subjected to dry-wet cycles, the apparent chloride diffusion coefficient and chloride diffusivity of concrete were discussed. It can be found that the performance of chloride diffusivity in both concretes will be improved with the increase of crack width, and that the influence of convection action will also be augmented. Based on the two samples obtained in sound concrete after 15 and 30 cycles, the time-exponent, m, for chloride diffusion coefficient was determined to be 0.58, 0.42, 0.62 and 0.77 for PCC1, PCC2, FAC1 and FAC2 specimens, respectively. Finally, two influencing factors of fly ash content and crack width on chloride diffusivity were obtained by regression analysis of test data, and it can be seen that factors kf and kw can be expressed with quadratic polynomial functions of fly ash content, f, and crack width, w, respectively.展开更多
Reinforcement inside the concrete is protected from corrosion and its damages until several years after the construction. After corrosion initiation, the cross section of reinforcement begins to reduce and often load ...Reinforcement inside the concrete is protected from corrosion and its damages until several years after the construction. After corrosion initiation, the cross section of reinforcement begins to reduce and often load bearing of the reinforced concrete structure will be reduced significantly. Corrosion of reinforcements in concrete in polluted and contaminated areas can occur in two ways: chloride and carbonation. In this work, meta-heuristic approach of charged system search(CSS) is used to calculate corrosion occurrence probability due to chloride ions penetration. The model efficiency is verified by comparing the available examples in technical literature and results of Monte Carlo analysis. According to the analyses performed, using different probabilistic distributions regardless of probabilistic moments based on real distribution leads to diverse results. In addition, influence of each effective parameter in corrosion occurrence varies by changing other parameters.展开更多
New-old concrete composite system usually exists in concrete repairing structure.In the present work,series of experiments were carried out to investigate permeability and ion diffusion properties of new-old concrete ...New-old concrete composite system usually exists in concrete repairing structure.In the present work,series of experiments were carried out to investigate permeability and ion diffusion properties of new-old concrete composite by measuring 6-hour coulomb charge and chloride diffusivity.The interrelation among transport properties of new-old composites,new,and old concretes was also discussed.Results indicate that the permeability and chloride diffusivity of new-old concrete composite system closely interrelate to the corresponding new concrete and old concrete.The interfacial transition zone between new concrete and old concrete greatly influences the transport property of new-old concrete system.Compared with the corresponding new concrete and old concrete lower permeability and diffusivity values for the new-old concrete composites can be achieved by choosing suitable new concrete.It is possible to design the tailor-made new-old concrete composite system for repair given the transport property.展开更多
基金Projects(50908103,51278230,51378241)supported by the National Natural Science Foundation of ChinaProject(2012M511215)supported by China Postdoctoral Science Foundation+2 种基金Project(11JDG132)supported by the High-grade Talent Program of Jiangsu University,ChinaProject(2011CEM010)supported by State Key Laboratory Foundation of High Performance Civil Engineering Material,ChinaProject(20123227110006)supported by Doctoral Foundation of Ministry of Education of China
文摘In order to examine the effect of load-induced transverse cracks on the chloride penetration in flexural concrete beams, two different concretes, Portland cement concrete(PCC) and fly ash concrete(FAC), were tested with various crack widths. Total 14 reinforced concrete(RC) beams, ten of which were self-anchored in a three-point bending mode, were immersed into a 5% NaCl solution with the condition of dry-wet cycles. Then, the free chloride ion contents were determined by rapid chloride testing(RCT) method. Based on the proposed analytical models of chloride penetration in sound and cracked concrete subjected to dry-wet cycles, the apparent chloride diffusion coefficient and chloride diffusivity of concrete were discussed. It can be found that the performance of chloride diffusivity in both concretes will be improved with the increase of crack width, and that the influence of convection action will also be augmented. Based on the two samples obtained in sound concrete after 15 and 30 cycles, the time-exponent, m, for chloride diffusion coefficient was determined to be 0.58, 0.42, 0.62 and 0.77 for PCC1, PCC2, FAC1 and FAC2 specimens, respectively. Finally, two influencing factors of fly ash content and crack width on chloride diffusivity were obtained by regression analysis of test data, and it can be seen that factors kf and kw can be expressed with quadratic polynomial functions of fly ash content, f, and crack width, w, respectively.
文摘Reinforcement inside the concrete is protected from corrosion and its damages until several years after the construction. After corrosion initiation, the cross section of reinforcement begins to reduce and often load bearing of the reinforced concrete structure will be reduced significantly. Corrosion of reinforcements in concrete in polluted and contaminated areas can occur in two ways: chloride and carbonation. In this work, meta-heuristic approach of charged system search(CSS) is used to calculate corrosion occurrence probability due to chloride ions penetration. The model efficiency is verified by comparing the available examples in technical literature and results of Monte Carlo analysis. According to the analyses performed, using different probabilistic distributions regardless of probabilistic moments based on real distribution leads to diverse results. In addition, influence of each effective parameter in corrosion occurrence varies by changing other parameters.
基金Project(2013CB036201)supported by the National Basic Research Program of ChinaProject(51178467)supported by National Natural Science Foundation of ChinaProject(NCET-10-0839)supported by Program for New Century Excellent Talents in University,China
文摘New-old concrete composite system usually exists in concrete repairing structure.In the present work,series of experiments were carried out to investigate permeability and ion diffusion properties of new-old concrete composite by measuring 6-hour coulomb charge and chloride diffusivity.The interrelation among transport properties of new-old composites,new,and old concretes was also discussed.Results indicate that the permeability and chloride diffusivity of new-old concrete composite system closely interrelate to the corresponding new concrete and old concrete.The interfacial transition zone between new concrete and old concrete greatly influences the transport property of new-old concrete system.Compared with the corresponding new concrete and old concrete lower permeability and diffusivity values for the new-old concrete composites can be achieved by choosing suitable new concrete.It is possible to design the tailor-made new-old concrete composite system for repair given the transport property.
