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A comparative structural study of wet and dried ettringite / G. Renaudin in Cement and concrete research, Vol. 40 N° 3 (Mars 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 3 (Mars 2010) . - pp. 370–375 Titre : A comparative structural study of wet and dried ettringite Type de document : texte imprimé Auteurs : G. Renaudin, Auteur ; Y. Filinchuk, Auteur Année de publication : 2012 Article en page(s) : pp. 370–375 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Ettringite  ;  Crystal  structure  ;  X-ray  diffraction  ;  Raman  spectroscopy  ;  Hydration Résumé : Two different techniques were used to compare structural characteristics of “wet” ettringite (stored in the synthesis mother liquid) and “dried” ettringite (dried to 35% relative humidity over saturated CaCl2 solution). Lattice parameters and the water content in the channel region of the structure (site occupancy factor of the water molecule not bonded to cations) as well as microstructure parameters (size and strain) were determined from a Rietveld refinement on synchrotron powder diffraction data. Local environment of sulphate anions and of the hydrogen bonding network was characterized by Raman spectroscopy. Both techniques led to the same conclusion: the “wet” ettringite sample immersed in the mother solution from the synthesis presents similar structural features as ettringite dried to 35% relative humidity. An increase of the a lattice parameter combined with a decrease of the c lattice parameter occurs on drying. The amount of structural water, the point symmetry of sulphate and the hydrogen bond network are unchanged when passing from the wet to the dried ettringite powder. Ettringite does not form a high-hydrate polymorph in equilibrium with alkaline solution, in contrast to the AFm phases that lose water molecules on drying. According to these results we conclude that ettringite precipitated in aqueous solution at the early hydration stages is of the same chemical composition as ettringite present in the hardening concrete. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003172 [article] A comparative structural study of wet and dried ettringite [texte imprimé] / G. Renaudin, Auteur ; Y. Filinchuk, Auteur . - 2012 . - pp. 370–375. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 3 (Mars 2010) . - pp. 370–375 Mots-clés : Ettringite  ;  Crystal  structure  ;  X-ray  diffraction  ;  Raman  spectroscopy  ;  Hydration Résumé : Two different techniques were used to compare structural characteristics of “wet” ettringite (stored in the synthesis mother liquid) and “dried” ettringite (dried to 35% relative humidity over saturated CaCl2 solution). Lattice parameters and the water content in the channel region of the structure (site occupancy factor of the water molecule not bonded to cations) as well as microstructure parameters (size and strain) were determined from a Rietveld refinement on synchrotron powder diffraction data. Local environment of sulphate anions and of the hydrogen bonding network was characterized by Raman spectroscopy. Both techniques led to the same conclusion: the “wet” ettringite sample immersed in the mother solution from the synthesis presents similar structural features as ettringite dried to 35% relative humidity. An increase of the a lattice parameter combined with a decrease of the c lattice parameter occurs on drying. The amount of structural water, the point symmetry of sulphate and the hydrogen bond network are unchanged when passing from the wet to the dried ettringite powder. Ettringite does not form a high-hydrate polymorph in equilibrium with alkaline solution, in contrast to the AFm phases that lose water molecules on drying. According to these results we conclude that ettringite precipitated in aqueous solution at the early hydration stages is of the same chemical composition as ettringite present in the hardening concrete. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003172