New equation for description of chloride ions diffusion in concrete under shallow immersion condition

A new equation describing chloride penetration into concrete under shallow immersion condition, based on modifications to the constant diffusivity solution of the Fick's second law, is developed in this study. When applied to real concrete material in a specific environment, the Fick's second law with constant diffusion coefficient assumption cannot provide a precise prediction of the chloride profile in concrete. The new equation, which considers the binding of chloride ions, the time-dependency of chloride diffusion coefficient due to hydration and the influence of calcium leaching on the diffusion process in its derivation, can predict the evolution of chloride profile with high accuracy. As shown in this study, both hydration of cement in concrete (expressed by the time-dependency factor) and calcium leaching (expressed by the leaching effect factor) can retard the ingress of chloride ions into concrete.