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Early C3A hydration in the presence of different kinds of calcium sulfate / S. Pourcheta in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 989–996 Titre : Early C3A hydration in the presence of different kinds of calcium sulfate Type de document : texte imprimé Auteurs : S. Pourcheta, Auteur ; L. Regnaud, Auteur ; J.P. Perez, Auteur Année de publication : 2010 Article en page(s) : pp. 989–996 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Hydration  ;  Ca3Al2O6  ;  Ettringite  ;  Kinetics Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Hydration reactions of C3A with various amounts of calcium sulfate hemihydrate, gypsum or a mixture of the two, were investigated by isothermal microcalorimetry, and a monitoring of the ionic concentrations of diluted suspensions. This study shows that sulfate type used modifies the early C3A–CaSO4 hydration products and the rate of this hydration. The fast initial AFm formation observed before ettringite precipitation in the C3A–gypsum system is avoided as soon as hemihydrate is present in the suspension. This was attributed to higher super saturation degrees and then higher nucleation frequency with regard to the ettringite obtained in the presence of hemihydrate. Moreover, replacement of gypsum by hemihydrate also leads to an increase of the ettringite formation rate during at least the five first hours under experimental conditions. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001793 [article] Early C3A hydration in the presence of different kinds of calcium sulfate [texte imprimé] / S. Pourcheta, Auteur ; L. Regnaud, Auteur ; J.P. Perez, Auteur . - 2010 . - pp. 989–996. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 989–996 Mots-clés : Hydration  ;  Ca3Al2O6  ;  Ettringite  ;  Kinetics Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Hydration reactions of C3A with various amounts of calcium sulfate hemihydrate, gypsum or a mixture of the two, were investigated by isothermal microcalorimetry, and a monitoring of the ionic concentrations of diluted suspensions. This study shows that sulfate type used modifies the early C3A–CaSO4 hydration products and the rate of this hydration. The fast initial AFm formation observed before ettringite precipitation in the C3A–gypsum system is avoided as soon as hemihydrate is present in the suspension. This was attributed to higher super saturation degrees and then higher nucleation frequency with regard to the ettringite obtained in the presence of hemihydrate. Moreover, replacement of gypsum by hemihydrate also leads to an increase of the ettringite formation rate during at least the five first hours under experimental conditions. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001793