Prediction of Chloride Ingress in Saturated Concrete Using Formation Factor and Chloride Binding Isotherm

This article describes an approach to predict chloride ingress in saturated concrete using the formation factor and chloride binding isotherm. The formation factor is calculated as the ratio of the measured electrical resistivity of concrete and the electrical resistivity of the pore solution. The chloride binding isotherms are determined experimentally by placing ground concrete powder in sodium chloride (NaCl) solutions of varying concentrations and using titration to quantify the bound chloride contents. The Nernst-Plank equation is used to predict the chloride ingress with the ionic diffusion coefficients (calculated from the formation factor) and the fitted (Freundlich) chloride binding isotherm. The simulation results correspond well with experimentally obtained chloride profiles of saturated concrete after being ponded in NaCl solution. It is found that 70 % of simulated values for total chloride contents have a relative error of less than 30 % when compared to the experimental data. The approach presented in this article can be considered as an alternative for mixture qualification and quality control, though further work is needed to benchmark this against existing procedures.