Analytical solution and experimental validation for dual time-dependent chloride diffusion in concrete

An analytical solution for dual time-dependent chloride diffusion within concrete was developed by taking into account the time-dependent behaviour of both surface chloride concentration and chloride diffusion coefficient. Firstly, the time-varying chloride diffusion coefficient was transformed into a constant one by introducing the equivalent diffusion time. Then an analytical solution for dual time-dependent chloride diffusion within concrete was presented based on the Duhamel's theorem. Finally, the accuracy and applicability of the proposed analytical solution were validated by comparing with field data, existing approximate analytical solutions and numerical results from finite element analysis. Analysis results show that the influence of time-dependent behaviour of chloride diffusion coefficient on the chloride concentration distribution within concrete is much larger than that of surface chloride concentration. Furthermore, the proposed solution is applicable for various kinds of (such as square-root, exponential, logarithmic and power-law, etc.) time-varying models of surface chloride concentration with high accuracy.