Pore-scale modelling of relative permeability of cementitious materials using X-ray computed microtomography images

Permeability of cementitious materials is an important durability indicator. In practice, concrete is rarely saturated. Therefore, it is essential to study permeability of unsaturated cementitious materials. This paper presents an integrated modelling approach for estimating permeability of cementitious materials over the full range of saturation. An in-house code based on multiphase and single-phase lattice Boltzmann models is developed and used to simulate the moisture distribution and fluid flow in unsaturated cement paste with various curing ages, the 3D microstructures of which are obtained from X-ray micro-CT. The water permeability and gas permeability of partially saturated cement paste are then estimated. The results indicate with decreasing water saturation water permeability decreases while gas permeability increases. Additionally, the moisture distribution and permeability of unsaturated cement paste are strongly dependent on its microstructure. Moreover, there exists a unique relationship between permeability and effective porosity. The simulation results show good agreement with experimental data.