Troisiéme Conférence Européenne sur les Matériaux et les Procédés Avancés
J. Phys. IV France 03 (1993) C7-1403-C7-1406
Low-shrinkage refractories bonded with high-alumina cement mixed with colloidal silicaN. RICHARD, N. LEQUEUX and P. BOCH
Laboratoire Céramiques et Matériaux Minéraux, UA-CNRS, Matériaux Inorganiques, ESPCI, 10 rue Vauquelin, 75005 Paris, France
Low-shrinkage refractories were prepared by bonding ceramic grains with high-alumina cement mixed with colloidal silica. The phases formed during hydration or heat treatment were studied by XRD and IR-spectroscopy.The main hydrated phases were CaO-Al2O3-10H2O (hydration at 20°C) and 3CaO-Al2O3-6H2O plus 2CaO-Al2O3-SiO2-8H2O (hydration at 50°C). 12CaO-7Al2O3 was the first phase that crystallised during thermal treatments. At [MATH], 12CaO-7Al2O3 reacts with silica to form anorthite (CaO-Al2O3-2SiO2) and gehlenite (2CaO-Al2O3-SiO2). Part of colloidal silica combines with calcium and aluminum to form cristobalite, which is stabilised in its [MATH]-form. Shrinkage was measured by dilatometry. The crystallisation phenomena are beneficial to reduce firing shrinkage. The stabilisation of [MATH]-cristobalite eliminates the dilatometric anomaly usually induced by the [MATH] transformation at [MATH] 200°C.
© EDP Sciences 1993