Abstract
In an attempt to improve the quality of refractory concrete containing 20 wt% high alumina cement and 80 wt% MgO-spinel aggregate, different amounts of cement (0.0, 5, 10 and 15 wt%) were substituted by microsilica. The hydrated concrete samples, at 20 C, as well as those fired at different firing temperatures up to 1500 C, were investigated through their mineralogical compositions by X-ray analysis. The microstructure of some selected samples was also investigated. Sintering parameters and refractory properties were tested at different firing temperatures according to standard specifications. The mix containing 5 wt% microsilica was chosen as optimum as it shows a compromise between good sintering and high refractory properties at room temperature (20 C) as well as after firing at high temperatures. 18 refs.