Diffusivity in Cement-Silica Fume Based Materials: Experimental and Computer Modeling Results on Mortars

摘要

Silica fume cement (SFC) based materials are largely used as a containment barrier for nuclear waste management. The safety of this storage mode depends on the knowledge of the effective diffusion coefficients of such materials.This work proposes a combination of computer models able to estimate the diffusion coefficients of SFC pastes and mortars, from a single investigation of the microstructure by nitrogen adsorption. The approach used consists firstly in manufacturing SFC mortars by varying sand volume fraction from 30 to 65% while silica fume replacement and water to binder ratio were respectively set at 10% and 0.4. Nitrogen adsorption tests were then performed and collected data on C-S-H nature are introduced into a SFC pastes hydration model. The latter provides the mineral composition which is an input parameter in the multilayer transport model that estimates the effective diffusion coefficient (D_e) of cement pastes. For mortars, a 3D biphasic model (sand and cement matrix) was used tocompute the (D_e) of mortars at different inclusion volume fractions.The numerical results were approved by comparison to experimental data obtained from tritiated water (HTO) diffusion tests performed on manufactured mortars.