Correlating the Chloride Diffusion Coefficient and Pore Structure of Cement-Based Materials Using Modified Noncontact Electrical Resistivity Measurement

Abstract

The electrical resistivity of hardened cement-based materials was measured in this work by a modified noncontact electrical resistivity measurement (MN-CM). The resistivity was further processed to compute the chloride diffusion coefficient (Dρ) using the Nernst-Einstein equation. Also, the rapid chloride migration test (RCM) was carried out to obtain the chloride migration coefficient (DRCM), and the relationship between Dρ and DRCM has been established. The obtained Dρ was further correlated to the pore structure parameters characterized by low-field nuclear magnetic resonance (NMR) spectroscopy. The results show that the DRCM is more sensitive to the change of pore connectivity, while Dρ is more sensitive to the change of porosity. The Dρ is smaller than DRCM since it strictly follows the Nernst-Einstein equation while RCM neglects the other driving forces such as capillary sorption and concentration gradient. It is concluded that the proposed MN-CM can obtain the chloride diffusion coefficient of saturated cement-based materials in a quick, stable, and reliable manner.