This material having been perfected within recent years, has many important uses. It is supplied commercially in a very finely ground state, and, when mixed with water alone, or when mixed with water and definite proportions of sand, gravel, or broken stone, it can be moulded to any form desired and will gradually harden in air or under water in the form to which it is moulded. When used in this way it is popularly known as concrete or beton.