Modeling the three-dimensional unsaturated water transport in concrete at the mesoscale

Understanding water transport in partially saturated concrete is of great significance for the durability assessment and service life prediction in engineering practice. In this paper, the three-dimensional (3D) unsaturated transport in concrete under capillary suction, hydraulic pressure and gravity force is simulated by the finite element method (FEM). A three-phase mesoscale model containing mortar matrix, coarse aggregates and interfacial transition zone (ITZ) is utilized, in which the zero-thickness interface element is employed for simulating thin ITZ structure. As the most important parameters for unsaturated mass transport analysis, the hydraulic diffusivity and unsaturated permeability are rationally estimated from the physical experiments. The cumulative mass of water penetration, as well as the penetration depth, obtained from the numerical modeling shows reasonable accordance with the experimental results. Moreover, main characteristics of the unsaturated transport (e.g., pore water pressure development, flow velocity distribution and the dynamic movement of wetting front and phreatic surface) are well captured by the simulation.