Alumina–spinel castables were prepared using tabular alumina and coarse spinel as aggregates, calcium aluminate cement, fused alumina fines, spinel fines and ultrafine alumina as matrixes. Effect of microsilica and dispersant on the properties of alumina–spinel castables were investigated in this paper. The results show that with the same content of microsilica addition, the values of permanent linear change and apparent porosity of samples with different additives fired at 1500°C and 1600°C are noticeably increased. The maximum expansion value is 2.01%, 1.47% and 2.59%, respectively, for Sample B (additive: FS 10), Sample E (additive: sodium tripolyphosphate) and Sample F (additive: sodium tripolyphosphate +H3BO3). There is a decrease in the final expansion value with the soaking time increases, which is associated to the sintering shrinkage of the castables in this temperature range under a compression load of 0.2 MPa, Expansion behavior of alumina–spinel castables is much different with different additive addition due to abrupt CA6 crystal growth.
