The effect of particle size of MgO and Al(2)O(3) on the spinel formation associated with permanent linear change on reheating (PLCR) and microstructure of Al(2)O(3)-MgAl(2)O(4)-C refractory is investigated as a function of heating cycle at 1600 degrees C with 2 h holding at each cycle. It was found that rate of spinet formation and associated volume expansion is very much dependent on the reactivity and particle size of the reactant. When the reactants are very fine and reactive there is considerable amount of spinet formation, whereas coarser reactants with lower reactivity show negligible formation of spinel phase and associated expansion. Magnesia and alumina with moderate reactivity develops optimum PLCR of the refractory. It continuously increases with the number of heating cycles. The SEM photomicrographs show that in Al(2)O(3)-MgAl(2)O(4)-C refractory the spinel phase is formed in between the calcined bauxite grain and the EDX analysis indicates that the spinel phase formed is stoichiometric in nature. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved