The lattice Boltzmann (LB) method is an efficient numerical approach which is widely utilized in the modeling of mass transport in porous media within a few decades because of the easy implementation of complex boundary conditions, inherent parallelism and high numerical stability of this approach. This paper presents the simulation of the effective ionic diffusivity of cement paste using the LB method. The entire simulation consists of three main steps. Firstly, the three-dimensional (3D) microstructure of hydrating cement paste is developed by the cement hydration model HYMOSTRUC3D. Cement paste is modeled as a composite material consisting of capillary pores, un-hydrated cement particles and hydration products (inner-, outer-, contact-). Secondly, the obtained 3D microstructure is digitized into a 3D array of voxels at a certain identical resolution (voxel size). Each voxel is assigned to be pore or solid depending on the position of its center. Finally, the diffusion process driven by the concentration difference between inlet and outlet is simulated using LB model. The operations such as collision and streaming are running until the steady-state diffusion condition is achieved. On the basis of the calculated steady-state molar flux across the whole domain, the effective ionic diffusivity can be estimated. Taking the diffusion of chloride ions for example, the simulated effective chloride diffusivities of cement paste are compared with the experimental results presented in literature. The simulation shows a good agreement with the experimental results. In addition, the influence of resolution on the simulated effective chloride diffusivity is studied.
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