Significance of water/solid ratio and temperature on the physico-mechanical characteristics of hydrating 4CaO.Al2O3.Fe2O3

Tetracalcium alumino-ferrite in paste form, at water/solid ( W/S) ratios of 0.3, 0.4, 0.5 and 1.0, and in pressed form at effective water/solid ratios of 0.13 and 0.08 has been hydrated for up to 45 days at temperatures of 23 and 80 degrees C. Some prehydrated samples have also been subjected to autoclave treatment at 216 degrees C. Of all the samples studied, that hydrated at a W/S=0.13 at 80 degrees C indicated the highest ratio of cubic phase to hexagonal phase; that hydrated at a W/S=0.08 at 23 degrees C showed the lowest. Thermograms gave evidence of the formation of hexagonal phases, although X-ray diffraction patterns did not. The specific surface area values depended on the degree of hydration and the nature of the product, autoclaved samples giving the lowest values. During the four days of hydration the specimen hydrated at 80 degrees C expanded more than that hydrated at 23 degrees C, but after that time the rates of expansion were reversed; that of the sample hydrated at 80 degrees C was much lower than that of the sample hydrated at 23 degrees C. Microstructural examination of the material formed at higher temperatures and lower water/solid ratios indicated a closely welded, continuous network of cubic phase. Such a structure yields a product of higher strength than that of a loose structure formed at higher water/solid ratios. A reasonably linear relation was found between porosity and logarithm of microhardness.Des \ue9chantillons d'alumino-ferrite de t\ue9tracalcium, sous forme de p\ue2te (rapport eau/solide de 0,3; 0,4; 0,5 et 1,0) ou sous une forme comprim\ue9e, sont hydrat\ue9s jusqu'\ue0 45 jours \ue0 des temp\ue9ratures de 23 degr\ue9s C et 80 degr\ue9s C. Le sp\ue9cimen hydrat\ue9 \ue0 un rapport eau/solide de 0,13 produit le rapport phase cubique/phase hexagonale le plus \ue9lev\ue9. Les sp\ue9cimens trait\ue9s \ue0 l'autoclave donnent l'aire de surface sp\ue9cifique la plus faible. L'expansion de l'\ue9chantillon hydrat\ue9 \ue0 80 degr\ue9s C est moins marqu\ue9e que celle de l'\ue9chantillon hydrat\ue9 \ue0 23 degr\ue9s C. Le produit form\ue9 \ue0 une temp\ue9rature plus \ue9lev\ue9e comporte un r\ue9seau de liens \ue9troits pour la phase cubique et une plus grande r\ue9sistance.Peer reviewed: YesNRC publication: Ye