Thermo-mechanical behaviour of low cement castables derived from mullite aggregates synthesised from beach sand sillimanite

Mullite aggregates were synthesised from beach sand sillimanite, a by-product generated during rare earth extraction, by reaction sintering with calcined alumina. The aggregates were characterised in terms of chemical composition, mineral phases, microstructure and important thermo-mechanical properties critical for refractory applications. To evaluate its suitability in castable refractories, low cement castables were prepared using the aggregates with commercial high alumina cement. The physical and thermo-mechanical properties such as bulk density, apparent porosity, cold crushing strength, hot modulus of rupture and compressive creep was studied in relation to temperature. The castables exhibited good modulus of rupture and excellent creep resistance at 1400 °C. Attempts were made to correlate these properties with corresponding microstructure and phases.