Factors Influencing Chloride Diffusion in Recycled Aggregate Concrete: Based on Three-Dimensional Polyhedral Aggregate Model

Abstract In saline soil and coastal environments, the recycled aggregate concrete (RAC) exhibits high sensitivity to chloride ion erosion, while the long-term erosion process is difficult to be reproduced by the experiment. For the simulation of the chloride ion diffusion, many contributions have been reported based on the two-dimensional aggregate model, which ignores the three-dimensional characteristics of the shape and distribution for the aggregates. In this study, a three-dimensional random polyhedral aggregate model is developed employing the Python programming language. And then, a polyhedral RAC model considering the chloride diffusion is established based on the Fick’s second law. The validity of the proposed model is verified by comparing the chloride concentration in RAC obtained by simulation and experiment. Finally, the effect mechanism of structural parameters on the chloride diffusion in RAC is revealed. The simulation results indicate that, compared to the other parameters, the diffusion coefficient of the new mortar has the greatest impact on the apparent diffusion coefficient of RAC. Furthermore, the external chloride ion concentration has the greatest impact on the chloride ion concentration of RAC. Specifically, when the RA content and the diffusion coefficient of the new mortar increased by 40%, the apparent diffusion coefficient of RAC increased by 23.9% and 41.47%, respectively. This study provides fundamental insights for modeling and predicting the long-term diffusion process of chloride in RAC.