Numerical Method for Predicting Chloride Diffusivity of Mature Cement Paste

Abstract

This paper develops a highly efficient numerical method for estimating the chloride diffusivity of mature cement paste. In the method, the two-dimensional microstructure of cement paste is reconstructed through computer simulation. Each unhydrated cement core and the surrounding inner and outer hydration products are incorporated into an equivalent hydration cement particle (EHCP), and the chloride diffusivity is derived analytically. Based on the first-passage-time equation, an efficient two-dimensional random walk simulation is conducted to estimate the chloride diffusivity of cement paste. It is found from the numerical results that the degree of cement hydration, the capillary porosity, and the chloride diffusivity evaluated from two-dimensional simulation are in excellent agreement with those evaluated from a three-dimensional one but at tremendously reduced computational time, which makes it possible for the method to be implemented on a regular computer. It is also found from the numerical results that, with the proposed EHCP model, the computational time for two-dimensional simulation is further reduced by a factor of about 2. Finally, through comparison with the experimental results obtained in this paper and collected from the literature, the validity of the numerical method is verified.