Analytical modelling of chloride ingress in surface-treated concrete

A theoretical study is presented on the effect of surface treatments on chloride diffusion in surface-treated concrete. Analytical solutions are derived for chloride diffusion in both the two-layer model and single-layer model with a convective boundary condition. The former consists of the treated surface layer and the substrate layer of concrete; whereas the latter consists of only the substrate layer with the convective boundary representing the effect of the treated thin surface layer on the chloride diffusion in the substrate layer. The analytical solutions are validated using the numerical model and published experimental results. The results show that the effect of surface treatments on the chloride diffusion in the substrate layer of concrete can be represented by using the convective coefficient, expressed in terms of the diffusion coefficient of chlorides in the treated surface layer divided by the thickness of the treated surface layer.