Studi chimico-fisici del 3CaO.Al[2]O[3], del 4CaO.Al[2]O[ 3].Fe[2]O[3] e del CaO.Al[2]O[3] idratati con bassi rapporti acqua: solido = Physico-chemical studies of 3CaO. Al[2]O[3], 4CaO.Al[2]O[3].Fe[2]O[3] and CaO.Al[2]O[3] hydrated at low water: solid ratios

Tricalcium aluminate (C3A) and tetracalcium alluminoferrite (C4AF) together, comprising 12-25% of Port/ant cement, influence its early hydration, setting and other long term characteristics [1]. Tricalcium aluminate, on hydration forms a mixture of metastable hexagonal hydration products C2AH8 and C4AH19 that convert to the stable cubic hydrate C3AH6. Similarly tetracalcium aluminoferrite forms metastable hexagonal and stable cubic hydrates in which iron substitutes for aluminum. Both C3A and C4AF pastes yield lower strengths than do the silicate phases under normal conditions of hydration. It is generally believed that C3A and C4 AF develop low strengths owing to the formation of the cubic hydrate phase. Monocalcium aluminate, CA, is the main component of the high alumina cement. The hydration products of CA consist of CAH10, C2AHs, C3AH6 and AH3 (gel or crystalline). At lower temperatures the products of CA comprise CAH10, C2AH8 and AH3 gel while at higher temperatures C3AH6 and gibbsite predominate. The\uab Conversion \ubb or \uab Inversion \ubb that occurs as a consequence of the transformation of the hexagonal phases CAH10 and C2AH8 into the cubic phase C3AH6 is accompanied by a loss in strength of the hardened high alumina cement.L?aluminate tricalcique (C3A) et l?aluminoferrite t\ue9tracalcique (C4AF), formant ensemble de 12 \ue0 25 % du ciment Portland, influent sur son hydratation aux jeunes \ue2ges, sa prise et d?autres caract\ue9ristiques \ue0 plus long terme. Le C3A, au moment de l?hydratation, forme un m\ue9lange des produits d?hydratation hexagonaux m\ue9tastables C2AH8 et C4AH19 qui se convertissent en hydrate cubique stable C3AH6. Dans le m\ueame ordre d?id\ue9es, le C4AF forme des hydrates cubiques stables et hexagonaux m\ue9tastables dans lesquels le fer remplace l?aluminium. Les p\ue2tes de C3A et de C4AF donnent toutes deux des r\ue9sistances inf\ue9rieures \ue0 celles des phases de silicate en conditions normales d?hydratation. On croit g\ue9n\ue9ralement que le C3A et le C4AF d\ue9veloppent des r\ue9sistances plus faibles en raison de la formation de la phase d?hydrate cubique. L?aluminate monocalcique (CA) est le principal constituant du ciment alumineux (\ue0 haute teneur en alumine). Les produits d?hydratation du CA sont CAH10, C2AHs, C3AH6 et AH3 (gel ou cristallin). \uc0 des temp\ue9ratures plus basses, les produits du CA comportent CAH10, C2AH8 et AH3 comme gel, tandis qu?\ue0 des temp\ue9ratures plus \ue9lev\ue9es, le C3AH6 et la gibbsite pr\ue9dominent. La \uab conversion \ubb ou l?\uab inversion \ubb qui se produit en cons\ue9quence de la transformation des phases hexagonales de CAH10 et de C2AH8 en phase cubique C3AH6 s?accompagne d?une perte dans la r\ue9sistance du ciment alumineux durci.Peer reviewed: YesNRC publication: Ye