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氯离子是钢筋混凝土结构中钢筋锈蚀主要原因。现今研究者大多利用Fick第二定律及其数学模型的解析解对暴露于氯离子环境下的混凝土材料和构件进行一维分析。本文研究建立了氯离子在混凝土中扩散的二维有限元数值模型,提出了混凝土多边形骨料生成算法,生成了骨料、砂浆和界面的三相复合数值模型。分析了混凝土材料中氯离子的迁移规律。将计算结果与试验结果进行了比较。结果表明,使用二维有限元数值模型可以较好的预测混凝土中不同时间、位置变化的氯离子集聚和扩散情况。分析了混凝土中骨料体积率对混凝土渗透系数的影响。研究结果表明:骨料体积率和混凝土的氯离子渗透系数基本呈线性关系,体积率越大,渗透系数越小。
Chloride ion is the main reason for corrosion of steel bars in reinforced concrete structures. Nowadays, most researchers use Fick’s second law and analytical solution of the mathematical model to conduct one-dimensional analysis of concrete materials and structures exposed to chloride ions. In this paper, a two-dimensional finite element numerical model of chloride ion diffusion in concrete was established. The algorithm of polygonal aggregate generation was proposed and a three-phase composite numerical model of aggregate, mortar and interface was generated. The chloride ion migration rule in concrete was analyzed. The calculated results are compared with the experimental results. The results show that the two-dimensional finite element numerical model can be used to predict the concentration and diffusion of chloride ions in concrete at different time and location. The effect of aggregate volume fraction on concrete permeability coefficient was analyzed. The results show that the volume fraction of aggregates has a linear relationship with the chloride ion permeability coefficient of concrete. The larger the volume fraction is, the smaller the permeability coefficient is.