To illustrate the applicability of the Katz–Thompson model for concrete materials and determine the K–T constant in the Katz–Thompson equation, pore structure parameters closely related to transport properties were analysed. Pore structure parameters, such as porosity, pore size distribution, character aperture and tortuosity, were measured and interpreted by mercury intrusion porosimetry. Percolation porosity and hydraulic diameter, as pore structure parameters closely related to percolation property, were used in the Katz–Thompson equation for concrete materials. The gas permeability of 48 concrete specimens was determined and corrected using the Klinkenberg effect to obtain the intrinsic permeability experimentally. The K–T constant was calculated by comparing the permeability predicted using the Katz–Thompson equation and the permeability obtained through permeability tests. It was found that the Katz–Thompson model can be applied in concrete materials. The K–T constants were found not to be fixed for concrete materials but to be closely related to the water/binder ratio; a linear relation between K–T constant and water/binder ratio was proposed.