Abstract: To investigate the shortest effective curing time of hydratable alumina-bonded castables, the effect of curing duration (4, 6, 12, 18, 24, 48 and 72 h) on the demoulding and drying strengths of the castables at 20 ℃ and 40% was studied. The results show that, during the early curing stage (4-18 h), the hydration degree of hydratable alumina increases. The amount of interlaced network-like hydration products boehmite (β-AlOOH) and bayerite (β-Al(OH)₃) also increases significantly. As a result, the demoulding strength rises continuously, meeting the industrial demoulding strength requirement after 18 h.When the curing time is prolonged from 18 h to 72 h, the newly formed hydration products gradually create a dense covering layer on the surfaces of hydratable alumina particles. This reduces the contact area between hydratable alumina and water, thereby inhibiting further hydration reaction. Therefore, additional curing time contributes little to promoting the hydration process. The morphology of the hydration products remains unchanged, and their amount increases only slightly. Thus, the demoulding strength of castables changes little. After different curing time, the castables were dried at 110 ℃ for 24 h. During drying, the unhydrated hydratable alumina from the curing stage undergoes further hydration. Moreover, the hydratable alumina with lower hydration degree undergoes greater rehydration during drying, maximizing the hydration degree after drying. The amounts of hydration products show little difference. Their micro-morphologies are also identical. Therefore, the drying strength of castables cured for different time changes little.Hence, after curing for 18 h to reach the demoulding strength, hydratable alumina-bonded castables can be directly transferred to the drying process to improve production efficiency.