混凝土内修正的氯离子运移模型及耐久性分析

Modified migration model for chloride ions in concrete and durability analysis of concrete

基于Fick第二定律,建立了混凝土内综合考虑扩散、电场迁移与结合作用的氯离子运移耦合模型,并通过已有试验数据对模型进行验证。以南通盐渍土环境为例,运用Comsol Multiphysics软件分析盐渍土内混凝土中氯离子的运移机制以及混凝土内氯离子随时间和空间的分布,研究不同强度等级的普通硅酸盐水泥混凝土和粉煤灰混凝土抗氯盐侵蚀的能力。结果表明:盐渍土腐蚀环境下,普通硅酸盐水泥混凝土结构仅靠提高混凝土强度和保护层厚度不能满足高耐久性要求,采用粉煤灰混凝土能延长结构使用年限;在保证使用年限为100 a的前提下,建议南通盐渍土环境中的钢筋混凝土结构采用粉煤灰混凝土,强度等级为C30、C40、C50和C60的混凝土结构保护层厚度分别为55 mm、50 mm、45 mm和40 mm。

In consideration of the diffusion,electric field migration,and binding,a coupling chloride ion migration model was established based on Fick＇s second law. The model was verified with experimental data. Using the saline soil environment in Nantong City as an example,Comsol Multiphysics software was used to analyze the migration mechanisms of chloride ions in concrete,to simulate the temporal and spatial distributions of chloride ions in concrete,and to examine the chloride resistance of ordinary Portland cement（ OPC） concrete and fly ash concrete with different strength grades. The results show that,in the saline soil environment,the OPC concrete structure cannot meet the durability requirements by only improving the concrete strength grade and protective cover thickness. Fly ash concrete can improve the service life of the concrete structure. In the saline soil environment in Nantong City,a reinforced concrete structure should adopt fly ash concrete,and the protective cover thickness of fly ash concrete with strength grades of C30,C40,C50,and C60 should be 55 mm,50 mm,45 mm,and 40 mm,respectively,for a service life of 100 years.