Mesoscale numerical investigation of chloride transport in recycled aggregate concrete considering calcium leaching: Multi-phase and multi-interface

Abstract

Chloride penetration and calcium leaching (C-L) combine to induce steel corrosion, which is the primary cause of the declining durability of recycled aggregate concrete (RAC). A multiphase numerical model was developed to investigate the diffusion behavior of chloride ions in RAC, considering C-L, the presence of multiple interfacial transition zones, and the time-varying diffusion coefficients of different components. The model was validated through chloride ion erosion experiments. Additionally, the relationship between chloride ion transport and the temporal-spatial distribution of porosity was explored. The results show that: 1) At a certain exposure depth, the chloride ion concentration is relatively high when considering C-L. After approximately three years of exposure, the failure thickness without considering C-L is approximately 4.71 mm less than with C-L. 2) Diffusion coefficient multipliers $H\left(t\right)$ and $H\left(\phi \right)$ were negatively and positively correlated with time, respectively. 3) As erosion time increased from 180 to 1080 days, the leaching extent increased from approximately 25 mm to 50 mm. Additionally, porosity showed an upward trend from the internal leach surface to the exposed surface due to the effect of C-L. This study can serve as a reference for further in- depth research on chloride ion transport in RAC.