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Analyse multi-echelle des déformations différées dans les matériaux cimentaires sous dessiccation ou réaction sulfatique interne

Abstract : Today, the operating life of some concrete structures is likely to be extended, in parallel, structures show early signs of damage due sometimes to poor consideration of environmental conditions. Ensuring the sustainability of structures also means ensuring their safe, economical and ecological operation. Our objective is first to understand the phenomena and mechanisms at play, as well as their potential couplings; then, in a second step, to create reliable predictive models of these behaviours.The work presented is particularly interested in nuclear structures, which, in addition to having a major stake in our societies, present risks with regard to desiccation and thermo-activated pathologies such as the delayed ettringite formation (DEF). More precisely, the objective of this thesis is to understand the participation of aggregates in the degradation mechanisms of the material under these two respective stresses, and then their coupling.To this end, a multi-scale experimental approach is being conducted. It takes interest in the evolution of delayed deformations as well as the mechanical and transfer properties of cementitious materials subjected to either desiccation or DEF. In both cases, the influential parameters of the aggregates in the mechanisms were identified and a parametric study was carried out to clearly identify the influence of these parameters.First, the desiccation study is based on the monitoring and characterization of seven model formulations; i.e. granular skeletons were controlled and selected according to the size and volume fraction of the aggregates in the material; over 200 days. The tests revealed the influence of these parameters in the phenomenon of aggregate restraint.In parallel, the experimental study of DEF aims at characterizing the influence of the mineralogical nature of aggregates on the formation and progression of the pathology. We are interested in the influence of this parameter on the reaction kinetics and rate, but also on the evolution of the material properties, in order to identify all the physico-chemical mechanisms at stake. Finally, a final study is interested in the coupling between RSI and desiccation. Here, the aggregate parameters were set, and samples reactive to DEF were subjected to drying and soaking cycles.
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Marie Malbois. Analyse multi-echelle des déformations différées dans les matériaux cimentaires sous dessiccation ou réaction sulfatique interne. Génie civil. Université Paris-Saclay, 2019. Français. ⟨NNT : 2019SACLN025⟩. ⟨tel-02328736⟩

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