A multiphase numerical simulation of chloride ions diffusion in concrete using electron microprobe analysis for characterizing properties of ITZ

In order to demonstrate the chlorides ions diffusion in concrete, a multi-phase numerical model was established at mesoscale. The thickness of interfacial transition zone (ITZ) surrounding aggregate was measured based on an element analysis using electron probe technique. And the diffusivities of ITZ and mortar matrix were deduced through a one-dimensional transmission test. By introducing the experiment parameters into the two-dimensional numerical model, the chloride ions diffusion in concrete was simulated and verified through the electron probe technique accordingly. A sensitivity analysis on the parameters was conducted to furtherly assess the influence ITZ on the chloride ions diffusion in concrete. This study indicates that the size of coarse aggregate has no influence on the thickness of ITZ which follows a normal distribution. The properties of ITZ, including its the thickness and diffusivity, have significant affections on the diffusion of chlorides ions in concrete. And for the concrete employed in this research, the diffusivity affects the diffusion more severely than thickness of ITZ.