MICROSTRUCTURE-BASED PREDICTION MODEL FOR CHLORIDE ION DIFFUSIVITY IN HYDRATED CEMENT PASTE

In cement hydration, various hydration products and pores are produced to form a complex microstructure. The quantity of the hydration products and pores heavily influences the macroscopic properties of hydrated cement paste. The chloride ion diffusivity of cement paste is considered to have a close relation to durability. We propose a prediction model of the chloride ion diffusivity of cement paste using homogenization theory to find the relationship between the microstructure and the macroscopic properties. This model considers the percolation phenomenon and the tortuosity of the transport path in the hydrated cement paste microstructure. The chloride ion diffusion coefficient of the cement paste was tested via electricity-accelerated diffusion experiments on cement pastes prepared using three water-cement ratios (0.23, 0.35 and 0.53, respectively). The Jennings-Tennis model was used to calculate the quantity of hydration products in the hydrated cement paste microstructure. With different homogenization theories, the predicted results of the chloride ion diffusion coefficients agree well with the experimental data, which shows the reliability of the presented model.