Analytical solution for chloride diffusion in concrete with the consideration of nonlinear chloride binding

Abstract

An analytical study is presented on the diffusion of chloride in concrete coupled with the effect of nonlinear chloride binding. A double-segment piecewise linear chloride binding isotherm (the DS-PWL isotherm) is proposed that can fit well quite a number of experimentally measured chloride binding isotherms which were reported by many published works. The proposal of the DS-PWL isotherm makes feasible the development of analytical solutions for chloride diffusion in concrete that accommodate nonlinear chloride binding, which is not feasible at present. Based on the proposed isotherm, an analytical solution is obtained for one-dimensional diffusion of chloride in a semi-infinite concrete medium in the context of nonlinear chloride binding. The obtained solution is successfully validated against numerical solution for mathematical correctness while the proposed analytical model is shown to be in tolerably good agreements with a reported chloride diffusion experiment. Moreover, the proposed model is also shown to be in good agreements with the Freundlich-based model, exhibiting a desirable applicability. Parametric study is conducted using the proposed solution to examine the influence of each of the three DS-PWL characterizing parameters on chloride diffusion. Finally, the proposed solution is applied to investigating the influence of nanomaterial addition (the dosage of addition and the type of the nanomaterial added) on the service life of an RC structure member subjected to chloride ingress.