Meso-scale Numerical Investigation on Chloride Diffusivity in Cracked Concrete

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 50 μm,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 50 μm. However,when crack widthexceeds 170 μm,chloride diffusivity near the crack is almost similar to that from two-dimensional models and it doesn't change with crack widths.