That is not the fundamental issue as far as HARDENING is concerned. The water creates an exothermic chemical reaction called "hydration" in which the finely powdered active materials in the cement change to different compounds which form a hard crystalline form in which the hard crystals grow in size as the mortar / concrete dries out. The hardened crystals fill the spaces between the inactive aggregate (sharp sand and gravel in the case of concrete, or builder's sand in the case of mortar).
It doesn't need it to *harden*, it needs it to turn it from a dry powder to a thick paste.
hardening of cement is a chemical process in which water is necessarie