Hot bending strength and creep behaviour at 1000–1400 °C of high alumina refractory castables with spinel, periclase and dolomite additions

The modulus of rupture and creep behaviour of refractory castables at high temperature (1000–1400 °C) with additions of spinel, periclase and dolomite has been studied. Three processing routes for obtaining refractory concretes within the alumina-rich zone of the Al2O3–MgO–CaO ternary system were employed. To achieve high temperature mechanical properties special attention was paid to the processing route (synthetic spinel, periclase and dolomite additions), and the composition (effect of synthetic or self-forming spinel and CaO contents).The results demonstrate that these refractory castables show a highly viscoplasticity behaviour at temperatures >1100 °C and a hot bending strength depending on the loading rate. Refractory castables made with synthetic spinel have lower high temperature bending strength values than castables made with periclase additions owing to their less viscoplastic behaviour. In this work neither the amount of spinel nor processing route chosen were found to have any significant influence on the hot bending tests between 1100 and 1400 °C. The creep tests show that in the temperature range of 1100–1300 °C the main reaction governing deformation is the interaction between the alumina and the calcium aluminate cement phases. Above 1300 °C, castables made first with dolomite, then with periclase and finally with synthetic spinel are more prone to deformation in that order.