Diffusivity in cement-silica fume based materials Experimental and computer modeling studies

International audience; Concrete durability continues to be a subject of considerable interest since the use of cementitious materials in the construction of several structures. In particular, cement based materials are largely used in the nuclear industry for the building of nuclear power plants and the infrastructures dedicated to the storage of the radioactive waste. Concrete durability is mainly explained by the resistance of concrete to the penetration of aggressive agents principally by diffusion. The latter is closely related to the mineral composition and the porosity of the material. Therefore, the knowledge of the relationship between microstructure and transport properties is a point of major importance. This work proposes the study of cement pastes and mortars containing Ordinary Portland Cement and Silica fume. Based on a hydration modeling of cement-silica fume pastes, and using a multi scale homogenization approach implemented in a numerical platform, the mineral composition and the effective diffusion coefficient of cement pastes can be estimated. For mortars, and to evaluate the effective diffusion coefficient, finite element simulations with mixed boundary conditions were performed on 3D structures of mortar at different inclusion volume fractions. On another side, mortars were prepared with sand volume fractions ranging from 0 to 60%, a silica fume replacement of 10% by weight and were tested by tritiated water diffusion. The numerical results are confronted with the experimental data and analyzed.