Thermal Shock Resistance of Silica-Free Alumina-Spinel Castables

To improve the thermal shock resistance of ladle lining castable, silicafree alumina-spinel castables with an extensive range of calcium aluminate cement content (2-10 wt%) were prepared and the properties were investigated. The results showed that the card-house structures formed by the hexagonal flake calcium hexaluminate grains and the appropriate density of microcracks caused by the expansive reflection of calcium hexaluminate formation after firing at 1550 degrees C, which were beneficial to strengthen the aggregate-matrix combination and alleviate thermal stress. Consequently, the performance of the castables, including the retained moduli values and hot modulus of rupture, reached to the optimal values after 3 thermal cycles while 5-8 wt% cement was added. But while further increasing the cement content, these performances of the castables were degraded by the excessive volume expansion and density matrix due to the formation of calcium hexaluminate and the space occupation of calcium dialuminate respectively.