Four types of refractory aggregates (three sintered mullites using different starting materials and one tabular alumina) were synthesized by reaction sintering process and their properties evaluated. The microstructures of the aggregates have been studied by Scanning Electron Microscopy and correlated with the properties of the corresponding aggregates. The performance of these aggregates was also studied at high temperatures by using it in ca. © 1999 Taylor and Francis Group, LLC.