In this study, the pore structure and the charge passed of cement-based materials were measured with the mercury intrusion porosimetry (MIP) method and the rapid chloride permeability test (RUT), respectively. In order to investigate the effect of the water/cement (w/c) ratio on the pore structure and the charge passed of cement-based materials, specimens with eight different w/c ratios were made. ASTM Type I Portland cement with constant aggregates and no mineral additives was used for all mixes. Based on the porosity-electrical resistivity relationship, fits to the experimental data of the coarse capillary pore volume as a function of the charge passed were obtained. A good correlation between coarse capillary pore volume and charge passed has been determined. (c) 2005 Elsevier B.V. All rights reserved.