Precast Materials and Methods of Manufacture

Abstract

Concrete has been a very versatile and durable material for replicating natural stone for over a century. The increasing scarcity of natural stone and the great expense of cutting and transporting it, has opened up a worldwide market for the production of reconstructed stone and precast concrete using cement as the binder. Fine dust matched to the colour and texture of natural stone is combined in a matrix of fine aggregates, cement and pigments and placed in moulds to form stone-like facing panels, slabs and decorative detailing. In the early years reconstructed or cast stone was processed by the moist-earth or dry cast method where the mix was made semi-dry with low water content and consolidated in timber moulds by ramming or tamping. Modern dry cast stone has a higher porosity than wet cast methods and lower strength, and this tends to limit production to relatively small unit sizes. This method is still used successfully today to replicate both simple and intricate details including ashlar walling, quoins, cornices, sills, string courses and columns on buildings.