Multi-scale strategy to estimate the mechanical and diffusive properties of cementitious materials prepared with CEM II/CM

A procedure to estimate the mechanical and diffusive properties of cement pastes, mortars and concretes made with a novel CEM II/C-M (S-LL) binder that has been developed within the European EnDurCrete project, is presented in this paper. The objective is to set up a strategy able to determine the materials composition at different scales and in various configurations, and to provide reliable estimates of the properties. The phase assemblages of the cement pastes upon hydration, and further exposed to carbonation, leaching with water or chloride containing solutions, are first simulated using thermodynamic modeling. Different homogenization schemes are then applied, to estimate the mechanical and diffusive properties of the hydrated and degraded materials at different scales. The interfacial transition zone (ITZ) in mortar and concrete is accounted for by means of specific hypotheses regarding its thickness and the respective volume fraction of hydrates and capillary pores. The application of the differential scheme (DIF) at the cement paste scale, and at higher scales of the generalized self-consistent scheme (GSCS) or a procedure accounting for ITZ modeled as an interface combined with the DIF scheme, show a good consistency with the measured Young's modulus. In parallel, simulations are performed on 3D specimens composed of spherical particles surrounded by an ITZ layer to provide additional data for comparison. Numerical results and analytical estimations are found to be in excellent agreement. Finally, a specific study focusing on the effects of the ITZ on both mechanical and diffusive properties shows a significant impact of its thickness and its composition.