Microstructure-based 3D modelling of diffusivity in sound and cracked cement paste

Exposing reinforced concrete (RC) structures to aggressive environmental conditions is one of the main reasons that may limit their service life. Diffusion of chloride ions through concrete cover is one of the most damaging environmental actions, since it may cause corrosion of steel reinforcement. Therefore, modelling this phenomenon allows supporting a better durability assessment of RC structures. In the present study, a modelling strategy considering a 3D cement paste microstructure, which is obtained using HYMOSTRUC3D software, is adopted to compute the diffusion process in saturated sound and cracked cement pastes. The diffusion process is calculated as a statistical result of random walkers (representing ionic species) through the porosity of the cement paste microstructure. The simulation is implemented using a random walk algorithm (RWA), which is compatible to be used in sound and cracked cement paste microstructures. Additionally, the proposed modelling strategy aims to establish a relation between the diffusion coefficient of cement paste and the level of tensile damage in the microstructure, which is obtained by considering the microcrack development in the cement paste. A lattice fracture model is employed to simulate the microcracks. The primary results of the proposed model are presented and discussed in the present paper.