Drying stages during the heating of high-alumina, ultra-low-cement refractory castables

The purpose of this work was to investigate the drying kinetics of high-alumina, ultra-low-cement refractory castables under continuous heating conditions. Three main drying stages were identified during the castable heat-up and were related to the phase change of free water and to the decomposition of hydrated products present in the body. A clear correlation was found between the actual heating profile inside the castable and the dewatering stages under various heating schedules. Thermal analysis was used to assess the drying temperature that represents the highest risk of steam pressure buildup and, thus, of explosive spalling.