Heat-assisted grinding of a mixture of AI(OH)(3) and Ca(OH)(2) was conducted at different temperatures ranging from room temperature (about 293 K) to 773 K using a tumbling ball mill. The grinding of the mixture for up to 100 h at 373 K enabled us to synthesize hydrated calcium aluminate directly. This compound was not formed by grinding at room temperature nor at a temperature higher than 473 K. All the mixture ground for 100 h at any temperature was transformed into excess hydrated calcium aluminate by the addition of water but the unground mixture remained unchanged.