Aluminous cements containing magnesium aluminate spinel from Egyptian dolomite

Three mixes of calcium aluminate cements containing MA spinel were prepared using appropriate mixtures of Egyptian dolomite (MgO, 20.16% and CaO, 31.32%) with active alumina (99.50% A)¹. The cement mixes were prepared at 1600°C using the sintering method. The products were finely ground and their chemical and mineralogical compositions were investigated using the appropriate techniques. Also, their physicomechanical and refractory properties had been determined. The results indicated that their mineralogical compositions were refractory MA spinel, in addition to CA and/or CA₂ phases depending on the composition of the starting materials. The prepared cements exhibited a compromise between considerable strength and higher refractoriness. When 10% of such cements were added to refractory grade magnesia aggregate, in the presence of 0.1% Li₂CO₃ as a strength modifier, refractory castable bodies with improved hot-strength and thermal shock resistance had been achieved.