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Etude de la synthèse de composites liquides organiques/géopolymère en vue du conditionnement de déchets nucléaires

Abstract : This work is included in the management of radioactive organic liquids research field. The process is based on an emulsification of organic liquid in an alkali silicate solution allowing the synthesis of a geopolymer matrix. The first part of this work consists in carrying out a screening on different organic liquids. A model system representative of the various oils and a geopolymer reference formulation are then defined. The second part deals with the structuration of the organic liquid/geopolymer structuration, from the mixture of the reactants to the final material. It aims at determining the phenomena allowing the synthesis of a homogeneous composite. The last two parts aim at characterizing the composite by studying its structure (chemical structure, porosity of the geopolymer and dispersion of the oil) and its properties with respect to the application to the immobilization of radioactive waste. Unlike calcium silicate-based cementitious matrices, the structure of the geopolymer is not affected by the chemical nature of the organic liquids. Only acid oils inhibit or slow down the geopolymerization reaction. In order to obtain a homogeneous material, the presence of surfactant molecules is necessary. The emulsion stabilization mechanism at the base of the process is relying on a synergy between the surfactant molecules and the aluminosilicate particles present in the geopolymer paste. The kinetics (chemical and mechanical) of the geopolymerization are not impacted by the presence of oil or surfactants. Only an increase in the viscoelastic moduli and the elastic character of the pastes can be observed. This difference in rheological behavior is mainly due to the presence of surfactant. The structure of the matrix is identical to that of a pure geopolymer of the same formulation. The organic liquid is dispersed in spherical inclusions whose radius is between 5 and 15 μm. These droplets are separated from each other, and from the environment by the mesoporous network of the geopolymer. Mechanical and leaching properties were also evaluated.
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Vincent Cantarel. Etude de la synthèse de composites liquides organiques/géopolymère en vue du conditionnement de déchets nucléaires. Autre. Université Blaise Pascal - Clermont-Ferrand II, 2016. Français. ⟨NNT : 2016CLF22734⟩. ⟨tel-01511205⟩

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