Fireclay

fireclay

[′fīr ‚klā]

(geology)

A clay that can resist high temperatures without becoming glassy.

Soft, embedded, white or gray clay rich in hydrated aluminum silicates or silica and deficient in alkalies and iron.

Fireclay

 

refractory clay or kaolinite, which when roasted loses plasticity, the chemically bound water is removed, and a certain degree of sintering occurs. The Russian term for “fireclay”—shamot—is also applied sometimes to certain other initial materials used in the production of refractories, roasted to obtain pelletized powders (often in a clay mixture) and to stabilize the properties of the material (high-alumina, corundum, and zircon fireclays).

Fireclay is obtained by roasting—in rotary, shaft, or other furnaces at temperatures of, for the most part, 1300°-1500°C—the raw material, which is in the form of natural pieces or briquettes prepared in belt, roller, and other presses. The degree of sintering of fireclay is characterized by water absorption, which is usually between 2–3 and 8–10 percent, but can be as high as 20–25 percent for “low-roasted” fireclay. After fragmentation and grinding, fireclay is used as a component (to reduce plasticity and shrinkage during drying and roasting) of bulk fireclays in molding articles (or correspondingly, high-alumina and other refractory materials). It is also used in the production of mortars and bulk gunite and as an aggregate in refractory concrete. In the mid-20th century, fireclay came to be used in sculpture, primarily for small statuettes.

REFERENCE

Khimicheskaia tekhnologiia keramiki i ogneuporov. Moscow, 1972.