A castable refractory composition may include from 5% to 95% by weight of alumina, aluminosilicate, or mixtures thereof; from 0.5% to 1.5% by weight alkaline earth metal oxide and/or hydroxide, and 0.1% to 5% by weight of silica having a surface area of at least about 10 m2/g. The refractory composition may include no more than 0.5% by weight of cementitious binder. The refractory composition may release less than 25 cm3 of hydrogen gas per kilogram of castable refractory composition upon addition of water. The refractory compositions may set on addition of water.