Calculation of chloride diffusion coefficients in concrete from ionic migration measurements

Abstract

A critical review is offered on the Rapid Chloride Permeability Test standarized by AASHTO, pointing out its limitations and errors but recognizing its contribution to the developing of a simple and quick test for chloride migration. Then another review is made on the electrochemical fundaments of the processes developped in concrete when an electrical field is applied and on the basic equations of mass transport (Nernst-Plank and Nernst-Einstein) which can be applied to calculate ionic movements. The limitations and assumptions needed for a simplified resolution of these equations, are presented, as well as numerical examples of calculation of the Effective Diffusion Coefficient of chlorides, $D_{eff}$, in steady state condition. Finally, considerations on the possibility of calculation of $D_{eff}$ from simple resistivity measurements are also offered.