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Cohesion and expansion in polycrystalline solids formed by hydration reactions — The case of gypsum plasters / Ellis M. Gartner in Cement and concrete research, Vol. 39 N° 4 (Avril 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 4 (Avril 2009) . - pp. 289–295 Titre : Cohesion and expansion in polycrystalline solids formed by hydration reactions — The case of gypsum plasters Type de document : texte imprimé Auteurs : Ellis M. Gartner, Auteur Année de publication : 2009 Article en page(s) : pp. 289–295 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Hydration;  Microstructure;  Expansion;  Mechanical  properties Résumé : When powdered plaster (CaSO4·1/2H2O) is mixed with sufficient water to give a plastic paste, hydration occurs rapidly, forming a hardened mass of gypsum (CaSO4·2H2O), usually with slight bulk expansion. The addition of certain compounds can greatly increase the expansion, which may lead to destructive pressures. Here I show that this effect increases with the size of the alkyl group in an homologous series of simple water-soluble calcium carboxylate salts: Ca(HCOO)2; Ca(CH3COO)2; Ca(CH3CH2COO)2. The latter two, when used at aqueous concentrations of 10% or more, cause large expansions. The results can be explained by a delicate balance between crystal growth pressures and cohesive interactions at the interfaces between crystallites, on the assumption that only two principal classes of interface exist in the hardened structure: “bridging” and “non-bridging.” This hypothesis allows us to make some useful conjectures about the performance of mineral-based hydraulic binders in general, with potential implications for their durability. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000234 [article] Cohesion and expansion in polycrystalline solids formed by hydration reactions — The case of gypsum plasters [texte imprimé] / Ellis M. Gartner, Auteur . - 2009 . - pp. 289–295. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 4 (Avril 2009) . - pp. 289–295 Mots-clés : Hydration;  Microstructure;  Expansion;  Mechanical  properties Résumé : When powdered plaster (CaSO4·1/2H2O) is mixed with sufficient water to give a plastic paste, hydration occurs rapidly, forming a hardened mass of gypsum (CaSO4·2H2O), usually with slight bulk expansion. The addition of certain compounds can greatly increase the expansion, which may lead to destructive pressures. Here I show that this effect increases with the size of the alkyl group in an homologous series of simple water-soluble calcium carboxylate salts: Ca(HCOO)2; Ca(CH3COO)2; Ca(CH3CH2COO)2. The latter two, when used at aqueous concentrations of 10% or more, cause large expansions. The results can be explained by a delicate balance between crystal growth pressures and cohesive interactions at the interfaces between crystallites, on the assumption that only two principal classes of interface exist in the hardened structure: “bridging” and “non-bridging.” This hypothesis allows us to make some useful conjectures about the performance of mineral-based hydraulic binders in general, with potential implications for their durability. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000234