Gas permeability of alumina–spinel refractory castables bonded with hydratable magnesium carboxylate

Abstract The high level of gas permeability can effectively reduce the explosive spalling risk of refractory castables. The hydratable magnesium carboxylate (HMC) is expected to improve the permeability of castables owing to the thermal decomposition of the HMC hydrates. This study compared the gas permeability and explosive spalling resistance of HMC bonded refractory castables (HMCC) with calcium aluminate cement bonded refractory castables (CACC). Thermal decomposition of (Mg 3 (C 6 H 5 O 7 ) 2 ∙11H 2 O) (hydrates of HMC), drying behavior, and the pores size distribution of castables were investigated. The level of gas permeability of HMCC is higher than that of CACC, which was confirmed by the higher values of Darcian k 1 and non‐Darcian k 2 . The degas temperatures of HMC hydrates (156°C) and HMCC (432°C) are lower than those of CAC hydrates (289°C) and CACC (536°C) at a heating rate of 20°C/min, respectively. The large‐size and more permeable pores in HMCC were obtained according to the mercury intrusion porosimeter (MIP) results, which formed the connected paths for gases (H 2 O, CO 2 , C 2 H 4 , CO, CH 4 ) released from the castables.