INFLUENCE OF HEAT TREATMENT MODES ON THE PROCESS OF SYNTHESIS OF CALCIUM-ALUMINATE PHASES IN THE TECHNOLOGY OF SPECIAL HIGH PURITY ALUMINUM CEMENT

The results of experimental studies on the phase formation CaAl2O4 (CA) and CaAl4O7 (CA2) from CaCO3-Al2O3 powder mixtures in temperature range 1250 - 1450 ° C ate presented. In order to calculate content raw materials charge, criterion obtaining high-alumina clinker with Al2O3 71 72 wt. % CaO 27 28 wt.% is proceeded. This mass ratio system state diagram suggests presence two calcium-aluminate phases CA CA2. projected composition 64 mol. 36 (CA2). As precursors chalk grade M-90 technical alumina G-0 are used. initial charge heat-treated at temperatures 1250, 1300, 1350, 1450°C isothermal stage times 1 2 hours. It supposed that synthesis target CA2 preceded by followed degradation calcium-enriched metastable C12A7. assumption confirmed thermogravimetric X-ray analyses scanning electron microscopy. process products dispersed powders aluminum oxide calcium carbonate increasing time exposure determined mainly diffusion more mobile Ca2+ cations released C12A7 area high concentrations oxide.