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

Abstract:

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 to compute 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.

• Periodical: Key Engineering Materials (Volume 711)
• Pages: 1098-1104
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.711.1098
• Online since: September 2016
• Authors: Z. Bajja*, W. Dridi, A. Darquennes, R. Bennacer
• Keywords: Cement Paste, Diffusion, Microstructure, Modelling, Mortars, Silica Fume

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