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Approche multi-technique et multi-échelle d'étude des propriétés structurales des matériaux hétérogènes : Application à un granulat siliceux naturel

Abstract : A multi-technique and multi-scale approach was developed in order to study the structural properties of heterogeneous materials. Different techniques were used among which we can quote: Environmental Scanning Electron Microscopy, X-Ray Diffraction, X-ray absorption spectroscopy (EXAFS and XANES) and Nuclear Magnetic Resonance. Correlations between the results obtained at different scales (long, medium and short range order) enabled us to advance in the comprehension of the mechanisms of the structural deterioration of an aggregate SiO2 submitted to the Alkali-Silica Reaction. At the long-range order the structural changes appear towards the reduction of the size of the grains and the formation of an amorphous phase followed by an increase of the crystallinity of the crystallized phase. Those phenomena show that the attack proceeds preferentially in the amorphous and/or badly crystallized zones. According to the NMR the amorphous phase formed during the reaction consists of a mixture of silanols and amorphous silica. This product that have a random composition along the reaction process could be likely to cause formation of expansive product in the aggregate. At the short-range order the first coordination shell around silicon atoms shows an increase in the order within tetrahedra. That phenomenon could be due to the relaxation of the Si-O bonds. This result is in agreement with the presence of amorphous silica and it could be accentuated by the presence of silanols. The second coordination shell around silicon atoms remains unchanged. Those results make it essential to start again the study of the initiation process of the reaction.
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https://tel.archives-ouvertes.fr/tel-00010494
Contributor : Johan Verstraete <>
Submitted on : Wednesday, November 23, 2005 - 3:42:33 PM
Last modification on : Friday, October 23, 2020 - 4:38:42 PM
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Johan Verstraete. Approche multi-technique et multi-échelle d'étude des propriétés structurales des matériaux hétérogènes : Application à un granulat siliceux naturel. Autre. Université de Haute Alsace - Mulhouse, 2005. Français. ⟨tel-00010494v2⟩

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