| INORGANIC MATERIALS AND CERAMIC MATRIX COMPOSITES |
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| A Two-scale Chloride Diffusion Coefficient Model in Cement Pastes Based on General Effective Medium Theory |
| TIAN Zhuang, XIAO Guanyan, XIA Jin, JIN Weiliang*
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| College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China |
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Abstract Pores are the basic channels for ion transport in cementitious materials. As hydration proceeds, the relevant parameters of the pore structure will change, which needs to be quantitatively calculated in terms of the values of the parameters at different water-cement ratios and curing ages. The effects of different pores on the diffusion coefficient of chloride ions were studied by NEL (Nernst-Einstein lab) test and NMR(Nuclear magnetic resonance) experiment. The general effective medium (GEM) theory was used to fit the key parameter of chloride diffusion coefficient model at the scale of cement paste and hydration products. The results show that the pore structure of the cement paste changes significantly under different conditions. At the scale of the cement paste, ions are more inclined to diffuse into the capillary pores. The diffusion coefficient is strongly correlated with the capillary porosity, and the diffusion coefficient of the hydration product phase decreases with the increase of the water-cement ratio, and increases with the extension of the age. At the scale of the hydration product, the effect of the gel pores on the diffusion of ions is non-negligible, the diffusion coefficient and the gel porosity are strongly correlated with each other. The critical porosity is approximately 0.122 to 0.172, and the percolation index of gel pores is approximately 1.880 to 2.241. The model can calculate the chloride diffusion coefficients based on different types of porosities, and accurately assign the parameter values, which is of significance for the durability design of engineering structures.
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Published: 25 November 2025
Online: 2025-11-14
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