Formulation and durability of metakaolin-based geopolymers

Abstract : The main objectives of this thesis were to assess the formulation and durability of metakaolin-based geopolymers as a binder for civil engineering materials. Geopolymers are alkali-activated materials; they are increasingly studied by the international community as they represent an alternative to traditional Portland cement. The first part of this study has been dedicated to the formulation of these materials, exclusively made from flash metakaolin and sodium silicate, which has shown performances comparable to a CEM I 52.5. A physicochemical characterization and a study of the porous network have highlighted differences between these two materials and allowed developing a database on the characteristics of the material. The achievement of concrete, up to precast plant, showed their ability to completely substitute known hydraulic binders, in terms of workability and compressive strength. Durability issues related to the high alkali content in this matrix were assessed by studies on alkali-silica reaction and carbonation. The results obtained have concluded that the alkali-silica reaction would not be detrimental in a matrix of metakaolin activated by sodium silicate, and that the very rapid reaction of the alkalis in the geopolymer pastes pore solution with atmospheric CO2 do not lead to a significant drop of the concrete pH, which could be detrimental in cement matrix, but could lead to the appearance of efflorescence on the surfaces of geopolymer.
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Raphaëlle Pouhet. Formulation and durability of metakaolin-based geopolymers. Civil Engineering. Université Paul Sabatier - Toulouse III, 2015. English. ⟨NNT : 2015TOU30085⟩. ⟨tel-01297848⟩

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