This article reports on an experimental investigation of the dewatering process of cement-free high-alumina refractory castables. Simultaneous fluid dynamic, thermal, and mass loss effects were investigated during the removal of physically absorbed water at temperatures of 250 to 700 degreesC. The release of steam was decisively affected by the castable's permeability level and the heating rate applied. The analysis of fluid dynamics revealed that at 1 degreesC/min, the main bulk of physical water was released as steam under saturated conditions at 100 degreesC. However, at 5 degreesC/min, steam was trapped within the pores, and water loss was chaotically released and shifted to higher temperatures. Thermal analysis showed that the endothermic boiling of water may result in a critical thermal shock in the castable's structure. Both steam entrapment and thermal shock were more severe with the reduction in the castable's permeability level.