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Chemical reactions can lead to the expansion of the geomaterial because of the strong precipitation of minerals in the pores of the medium. The quantity and the variability of these reactions led to the development of several chemo-mechanical models. A generic chemo-poromechanical model is proposed to predict both the material degradation induced by various concrete pathologies and the environmental multi-factor impact on the macroscopic swelling. The model is based on the coupling between reactive transport (species diffusion and chemical reactions) and poromechanics. The mineralogy and the poromechanical properties are estimated by a hydration-micromechanics model which allows to consider the material effects. The main applications are dedicated to External Sulfate Attack and Delayed Ettringite Formation of cementitious material at mesoscale. The studies highlight the ability of the model to deal with complex and various phenomena such as coupling chemical reactions with calcium leaching, sulfate sorption and ettringite precipitation, and to consider their impact on the macroscopic expansion. Results also bring out the accuracy of the chemo-poromechanical model to simulate different swelling pathologies. The characteristic crack paths induced by differential strain, material impact, and swelling at the macroscopic scale, fit with experimental observations. [ABSTRACT FROM AUTHOR]

Durability of concrete exposed to an external sulfate attack is a great concern for the long-term reliability of nuclear waste containment. This paper presents experimental results obtained on cement paste subjected to a low concentration (30 ×10−3 mol/L) external sulfate attack. Samples were characterized with complementary methods (XRD, SEM-EDS, microtomography, microindentation, autoradiography) to follow the evolution of chemical, mineralogical, microstructural and mechanical properties during 8 months. Cement pastes of different C 3 A contents were used to boost either ettringite or gypsum formation during the sulfate attack to assess their respective impact on the degradation. Cracks parallel to the attacked surface occurred in the zone of gypsum formation and portlandite dissolution, which suggests that gypsum has a key effect on the expansion. Reactive transport modeling supported the discussion on the competition between hydrolysis, gypsum and ettringite precipitation as well as the analytical homogenization to estimate Young's moduli. • Multiple characterization tools were used including a synchrotron radiation CT. • Contributions of hydrolysis and sulfate attack on damage were discriminated. • Expansion occurred even for low C3A content and groundwater SO 4 concentration. • Cracking was initiated in the gypsum formation zone. • Ettringite formation was identified by microindentation and homogenization. [ABSTRACT FROM AUTHOR]