Multi-scale modeling of the chloride diffusivity and the elasticity of Portland cement paste

International audienceThe multi-scale modeling of Portland cement paste is addressed to predict simultaneously its stiffness and its effective diffusion coefficient of chloride ions. The heterogeneity of cement paste is handled thanks to a hierarchy of Eshelby-based homogenization schemes within the framework of micromechanics. The same microstructure description is used for both mechanical and transport properties. In a first model, the porosity is partitioned at three scales into gel pores, small and large capillary pores. Two layers of hydration products around clinker grains are considered: an inner layer comprising high density C-S-H gel and nano-sized crystal hydrates; and an outer C-S-H layer containing low density C-S-H gel and small capillary pores. In a second model, only three phases are considered: clinker grains, hydrates and capillary pores. A comparison of models with experimental results shows that both transport and mechanical properties of cement paste, throughout hydration, are accurately reproduced