为了研究氯离子在开裂混凝土中的扩散性能，考虑混凝土细观结构的非均质性，将含有裂纹的混凝土试件视为由砂浆基质、骨料、界面过渡区以及裂纹组成的四相复合材料，建立了带有单条裂纹的二维细观有限元模型。数值模型中，骨料不具有渗透能力，砂浆基质和界面中的氯离子扩散性能由水灰比确定，裂纹相中氯离子扩散系数与裂纹宽度的定量关系由文献中已有试验数据的拟合获得。研究了骨料分布形式对氯离子扩散行为的影响，分析并探讨了不同裂纹宽度下混凝土中的氯离子扩散行为。数值结果与试验数据的良好吻合说明了该方法的准确性。研究结果表明：骨料的随机分布形式基本不影响混凝土中氯离子的扩散行为；裂纹宽度小于50μm时，混凝土中氯离子的扩散行为基本不受裂纹的影响；裂纹宽度介于50~170μm时，氯离子的扩散随裂纹宽度增大而明显加剧；裂纹宽度大于170μm时，氯离子在裂纹附近的扩散趋于二维扩散形态。%In order to investigate chloride diffusivity in cracked concrete, considering the mesoscopic heterogeneity of concrete, the concrete was simulated as a four-phase composite, i. e. , aggregate particles, mortar, the interfacial transition zone ( ITZ ) and cracks. A random aggregate structure of concrete with a single crack was constructed, in which the cement paste matrix was considered as homogeneous. In the two-dimensional finite element model, the aggregate phase was set as impermeable, the diffusion properties of the cement paste and the ITZ were determined based on water/cement ratio, and the quantitative relationship between the diffusion coefficient of the crack phase and crack width was derived by fitting the available test data. The effect of aggregate distribution on chloride diffusivity was studied, and chloride diffusivities in concrete with different crack widths were investigated and discussed. The present numerical model was validated against the available test data. It is found that the influence of aggregate distribution on chloride diffusivity in concrete can be ignored. Moreover, for crack with a width less than 50μm, chloride diffusivities are not affected by cracks. The effect of crack width on chloride diffusivity is more pronounced when the crack width is higher than 50μm. However, when crack width exceeds 170μm, chloride diffusivity near the crack is almost similar to that from two-dimensional models and it doesn' t change with crack widths.
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