New spinel-containing refractory cements

Use of spinel-containing high alumina refractory concretes has increased significantly over the last few years. Currently the high cost of sintered or electrofused spinels limits their applications. This paper describes new and inexpensive new spinel-containing refractory cements obtained by a reaction-sintering process between dolomite and alumina. The reaction-sintering process occurs in two well defined steps: (a) reaction and (b) sintering. The reaction also happened in two successive stages: (a) dolomite decomposition in the range 700–900 °C, and (b) reaction of lime and magnesia with alumina, in the range from 900 to 1250 °C. A selected composition containing: 43±5 wt.% CaAl2O4, 15±3 wt.% CaAl4O7 and 42±2 wt.% MgAl2O4, showed a hydration and dehydration behaviour similar to that of commercial calcium aluminate cements. The evolution of the hydrated pure CaAl2O4 cement up to 1500 °C has also been studied.