Silicate industry

The industry processing the natural compounds of silicon is called the silicate industry. It embraces the pro­duction of cement, glass, and ceramics.

The production of ceramic goods is based on the prop­erty of clay when mixed with water to form a putty from which various articles can easily be moulded. When these articles are dried and then baked, that is, ignited at a high temperature, they become hard and retain their shape, no longer being softened by water.

In this way clay mixed with water and sand is moulded into bricks, which are then dried and baked. The materials used to make silicate bricks are white sand and slaked lime.

Cement Production. Cement is made from limestone and clay, or from their natural mixture, marls. The materials roasted in cylindrical rotary kilns are charged into a slowly rotating kiln at its upper end and travel, mixing continuously, towards the lower end, while a current of hot gases, the products of the burning of fuel, flows in the opposite direction. During the period of their movement through the kiln the clay and the limestone react chemically, and the material emerging from the kiln in lumps of a caked, mass is cement, which is then ground.

When cement is mixed with water, it forms mortar, which hardens, binding various objects, such as bricks or stones, very firmly. It is for this reason that cement is used widely as a binding material in large-scale construction, including underwater construction.

Cement is often mixed with sand or gravel, in which case we get concrete. Concrete has roughly the same coefficient of thermal expansion as iron.