Effects of steel bar and bi-directional erosion on chloride diffusion in reinforced concrete: A 3D mesoscale study

This work proposes a novel numerical framework to investigate 3D chloride diffusion behavior in reinforced concrete (RC). An efficient dynamic modeling approach is developed to generate the RC models with real-shaped aggregates at mesoscale. A semi-closed form solution of Fick's second law is established to account for the time -varying chloride diffusion coefficient and surface chloride concentration through a genetic algorithm. Moreover, the effects of aggregate distribution and morphology on chloride diffusion are examined. The validated results demonstrate that the random distribution of aggregates leads to varied chloride concentration, and anisotropic aggregate morphology increases hindrance to chloride diffusion. Steel bar also affects chloride diffusion, causing an increase in chloride concentration on the steel surface. This hinder effect intensifies as the steel diameter increases and the protective layer thickness decreases. Additionally, bi-directional diffusion elevates chloride concentration on the corner steel surface, while smaller steel diameter and thicker protective layer render the corner steel bar more susceptible to bi-directional diffusion. The proposed framework has incorporated various influencing factors with comprehensive parametric analyses and holds potential for engineering design of RC structures considering durability, safety, and sustainability.