Let’s discuss the definition of fire clay:
Fire clay is a range of refractory clays used in the manufacture of ceramics, especially for fire brick.
The United States Environmental Protection Agency defines fire clay as a “Mineral aggregate composed of hydrous silicates of aluminum (Al2O3.SiO2.2H2O) with or without silica.”
Properties of fire clay:
- Natural water content – 12%
- Moisture absorption – 6.8%
- Minus No.200 sieve size – 87%
- Loss of ignition – 10.6%
- Specific gravity – 2.66
- Loss of ignition – 7.4%
- Liquid limit – 35%
- Plastic limit – 19%
- Plasticity index – 16%
- Drawing shrinkage – 4.8%
- Fired shrinkage – 16.2%
- Maximum dry density – 1.83 Mg/m cube.
- Optimum moisture content – 12.3%
- Shear strength – 180 KN per metre square
- The angle of internal friction – 29.6 degree
- Ultrasonic pulse velocity – 2.1 km/s
- Uniaxial compressive strength – 22 MPa
Significance of fire clay :
- Fire clay has attractive qualities as refractory raw material.
- It is more abundant and cheap material
- Extensively used in all places like glass melting furnaces, boiler furnaces, Chimney linings, pottery kilns, blast furnaces and reheating furnace.
- The refractoriness and other qualities of the clay as a refractory raw material can be improved by the addition of Bauxite a common practice in industries.
- The rhythmically changing properties of the coalfield cyclothem can pose some foundation problems arising from inter bedding of soft and hard layers.