Origin and Properties of Fireclays

One type of hydrated fireclay is called kaolinte. The formula for this clay is that of the last product of decomposition. Kaolinite has a structure of alternate layers of SiOt and Al(OH)6 . The SiO layer is made up of tetrahedra, and the Al(OH) layer is made up of octahedra. Interlayer bonding gives rise to the formation of H2O molecules. The charge balance is achieved by having common corners for the tetrahedra and octahedra. ions are located at these corners. 

Clays can get leached out of soluble matter by water flow. The resulting deposit is low in iron, alkalies, and alkaline earth and is called china clay. It is very pure, highly refractory, and fires white. The least pure clays are derived from basic rocks. They fire red and are useful as building bricks and for making drainage pipes. Between very pure and least pure clays are the intermediate pure ones. These include plastic ball clay, bond clay, flint fireclay, fireclay, and aluminous fireclay. 

Plashcify in a clay is equivalent to fluidity in a liquid. In liquids, flow occurs when pressure is applied. The velocity of this flow is given by Equation 23.1. 

---