养护条件与暴露环境对氯离子传输的耦合作用

Chloride penetrating under co-effects of initial curing and exposure conditions

为研究早期养护条件和后期暴露环境作用对混凝土抗氯离子扩散性能的耦合作用效应,选取不同的早期养护条件和海洋暴露环境对混凝土试件进行暴露试验.设定5种环境干湿状况及养护龄期用以模拟施工中出现的不同养护条件,并选取具备不同干湿循环比例的海洋环境对混凝土试件进行6个月的暴露.暴露结束后,通过酸溶法氯离子浓度分布测定及稳态电迁移试验讨论氯离子在混凝土中的传输特性影响.同时还对氯离子在非饱和混凝土中的传输进行数值模拟研究.结果表明,早期的不充分养护和后期的干湿交替环境使得混凝土浅表层的毛细吸附行为和氯离子在浅表层的富集变得十分显著.服役环境的供水能力强,则氯离子在混凝土内部的扩散效应显著;反之,氯离子的扩散效应被弱化.因此提出,在海洋环境中服役的钢筋混凝土结构进行耐久性设计时,必须重视并且考虑早期养护条件和后期暴露环境的干湿循环比例的耦合作用.

The co-effects of initial curing conditions and the following exposure environments were discussed in this study.Concrete cylinders were cured in five conditions characterized with different humidity and curing duration and were moved into three kinds of marine environments for half a year＇s exposure.The apparent diffusion coefficient and the effective diffusion coefficient of the chloride ions were obtained.The chloride transportation model in unstructured concrete was adopted to simulate the testing.The results indicate that inadequate water curing in the very beginning few days and the environmental wetting-drying cycles have a marked negative influence on chloride capillary suction and accumulation in the skin concrete.With the increasing of environmental wetting-drying ratio,diffusion dominates the moving of chloride ions in core concrete.Conventionally,by the decreasing of wetting-drying ratio,diffusion effect fakes out.Based on the results,the co-effect of initial curing conditions and the wet-dry interval ratios of the environments is suggested to be concerned during the durability design of the concrete.