In this study, the total chloride contents at different penetration depth were measured after the 90-day ponding test, and the Fick's second law of diffusion was fitted to the data to determine the diffusion coefficient of concrete. The porosity and the continuous pore diameter of the same mortar in concrete were examined with the mercury intrusion porosimetry (MIP) method. The continuous pore diameter was used to assess the connectivity of cement-based materials. The diffusion coefficients obtained from ponding test were compared and correlated with the capillary porosity (pore diameter between 30 and 10000 nm) and the continuous pore diameter from the MIP testing. A good correlation between the capillary porosity and the diffusion coefficient of concrete has been determined. The continuous pore diameter is linearly related to the diffusion coefficient of concrete. (c) 2006 Published by Elsevier B.V.