A process for producing a hard material from a cementitious mixture, the process including the steps of blending together a cement constituent and a filler constituent whilst in a dry condition to provide a compactable homogeneous mixture containing a predetermined volume of voids defined between filler particles up to a predetermined size, laying the dry mixture onto a substrate, sparingly applying water to the surface of the mixture to dampen the surface layer of the mixture for causing setting of the cement in said surface layer and subsequently applying more water for causing setting and hardening of the remainder of the cement.