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The French "Institut de Radioprotection et de Sûreté Nucléaire" (IRSN) conducts researches on the impact of internal swellings reactions on concrete, such as Sulfate Reactions. Such reactions are characterized by the precipitation of ettringite which induces swellings and cracks by differential strain. These cracks are preferential location for ions diffusion and further ettringite precipitations.

The aim of the study is to model the degradation of a mature material by ettringite pressure at the aggregate scale. A chemo-mechanical model based on a coupling between reactive transport (species diffusion and chemical reactions) and mechanics in cracked porous medium is developed and is solved with a generic staggered approach. The initial microstructure and poro-mechanical and diffusion parameters are estimated by hydration computing and analytical homogenization. The coupled chemo-mechanical model is validated and then applied to Sulfate External and Internal Attack. The impact of the concrete composition and the chemical environments on the swelling kinetics and crack path is taken into account. Furthermore, our simulations highlight the influences of inclusions and cracks on the inhomogeneous spatial distribution of precipitation areas of ettringite and associated swelling stress.