Mass Transfer Analysis of Calcium in Concrete Using the Lattice Kinetic Scheme for a Binary Miscible Fluid Mixture

Abstract

The lattice kinetic scheme (LKS) for a binary miscible fluid mixture is a applied to mass transfer analysis of Calcium in concrete. In general, cement paste that is a major component of concrete is a porous medium with three-dimensional complicated geometries. The present concrete structure is determined on the basis of experimental data previously obtained by high-intensity X-Ray Computed Tomography (X-Ray-CT). As for the numerical method, the LKS, which is an improved scheme of the original lattice Boltzmann method (LBM), is employed to save computation memory and to maintain numerical stability. First, an unsteady convection-diffusion problem is calculated and the accuracy of the method and error norms with different lattice resolutions are investigated. Next, the mass transfer problem of Calcium in concrete is simulated. Pressure drops in the concrete are calculated for different Reynolds numbers and compared with the empirical equation based on experimental data. Also, velocity fields and concentration profiles are obtained at a pore scale in the structure with heterogeneous mass diffusivity. These simulations indicate that the present method can be useful for prediction of Calcium leaching in concrete from the microscopic point of view.