Transport properties evolution of cement model system under degradation - Incorporation of a pore-scale approach into reactive transport modelling

International audience; This paper describes a multi-scale approach for the modelling of the degradation of model cement pastesusing reactive transport. It specifically aims at incorporating chemistry-transport feedback results from apore-scale approach into a continuum description. Starting from a numerical representative elementaryvolume of the model cement paste, which was built according to extensive experimental dedicatedchacarterizations, this paper provides three separate descriptions of two different degradations: leachingand carbonation. First, 2D pore-scale simulations are performed and predict degradation depths in verygood agreement with experiments. Second, 3D pore scale descriptions of how the microstructre evolvesprovides accurate description of the evolution of transport properties through degradation. Finally, thoselatter results are incorporated as a feedback law between porosity and effective diffusion coefficient intoa 1D continuum approach of reactive transport. This paper provides pore-scale explanations of whyreactive transport modelling has encountered mitigated success when applied to cementitious materials,especially during carbonation or degradations consisting of precipitation reactions. In addition to that,different degradation modellings are in very good agreement with experimental observations.