Computer simulation of the diffusivity of cement-based materials

Abstract

A digital image-based model of the microstructure of cement paste, coupled with exact transport algorithms, is used to study the diffusivity of Portland cement paste. The principal variables considered are water∶cement ratio, degree of cement hydration and capillary porosity. Computational methods are described and diffusivity results are presented, which are found to agree with the available experimental measurements within experimental error. Model cement pastes prepared with different water∶cement ratios, and having different degrees of hydration, are found to have diffusivities that lie on a single master curve when plotted as a function of capillary porosity. Concepts from percolation theory are used to explain quantitatively the dependence of diffusivity on capillary porosity. The effect of silica fume addition on diffusivity is also examined.