Coupling PhreeqC with electro-diffusion tests for an accurate determination of the diffusion properties on cementitious materials

Abstract

An improved numerical method as regard with the widely used analytical approximation is presented for determining the transport properties from electro-diffusion tests. Based on the geochemical software PhreeqC, this study aims to better understand and quantify the part of each phenomenon in the diffusion process: (i) the geometrical material properties (as porosity and tortuosity); (ii) the chemical reactions between chloride ions and the cement solid phase; (iii) electro-capillarity effects (such as electrical double layer effects). Tests have been performed on CEM I hydrated cement pastes of different W/C ratio (0.35; 0.42 and 0.50) with different chloride concentrations (500 and 50 mol/m3). The results revealed a good accuracy on the chloride diffusion coefficients DE, Cl− given by the numerical model while having a weak set of main adjustable parameters. The large amount of experimental data collected during the tests increases the robustness of the model.