Modeling Chloride Diffusion and Corrosion Initiation

Abstract

The objective of this study is to develop a multi-species model for chloride diffusion in saturated cementitious materials, taking into account all ions present in the pore solution, as well as ion-ion and ion-solid interactions, including mineral dissolution and precipitation phenomena. The ionic flux is calculated using the Poisson–Nernst–Planck equation, which incorporates diffusion, ionic migration, and chemical activity mechanisms. The Langmuir model is employed to simulate the chemical binding of chlorides to the material (chloride isotherms). The initiation of steel reinforcement corrosion is also predicted based on the threshold chloride concentration at the steel–concrete interface.

The proposed model is applied to a reinforced mortar made with Portland cement, exposed to chlorides under laboratory conditions over a period of fifty years. To support the model in terms of input data, initial conditions, and boundary conditions, the chloride diffusion coefficient and porosity of the tested mortar were determined experimentally.