Fundamental approach to compute gas and water permeability of concrete is suggested. For several compositions of cement pastes, the permeability coefficients were calculated with the analytical formulation, followed by a microstructure-based model. As the result of calculation of permeabilities for concrete, hydration leaded to the significant reduction of the coefficients. Meanwhile, the relationship between gas permeability and water permeability has a linear function for cement paste based on Klinkenberg effect, however, which is not effective for concrete.

Gas permeability is a substantial parameter for understanding the durability performance of concrete and its micro‐structural densification. Nevertheless, it is very rate to deal with the effect of carbonation on the parameter. In this paper, it is introduced to define transport coefficient of carbonated concrete such as gas permeability coefficient Kg. These are expressed as time function considering hydration evolution of hardened cement paste. The definition of the material parameters is a prerequisite to simulate the deterioration of concrete as time elapsed