Chamotte is high alumina calcined clay, used primarily for the production of ceramics and refractories.
Chamotte—also known as ‘grog’, ‘firesand’ or “fireclay” —is calcined clay containing a high proportion of alumina. It is produced by firing selected fire clays in a rotary kiln to temperatures between 1,400°C and 1,600°C, before grinding and screening to specific particle sizes.
For ceramics, typical chamotte contains 40% minimum alumina, 30% minimum silica, 4% maximum iron oxide, and up to 2% calcium oxide and magnesium oxide combined. The particle size distribution is generally coarser in size than the other raw materials used to prepare sanitaryware bodies for instance.
For refractories, chamotte contains from 38% to 48% alumina in general. Iron is generally limited to 2.5% and alkalies must be also limited in amount to preserve refractoriness and thermal stability at temperatures up to 1400°C.
Highly resistant to extreme temperatures, harsh operating conditions, mechanical failure and corrosion, chamotte is a crucial ingredient in the production of ceramics—in particular sanitaryware—and refractories.
Chamotte grains have been treated at very high temperature, which means that they will be stable when fired at slightly lower temperature. They are used to make up the rigid skeleton of ceramics and refractories at high temperature, limiting shrinkage due to sintering.
Imerys produces chamotte in the Bordeaux area (France), in Georgia(USA) and in Ukraine.
In the production of sanitaryware pieces, Imerys chamottes are used to produce fine fire-clays which act like a skeleton, enabling the production of large, complex pieces such as baths and shower trays with enhanced mechanical properties. Fine fire-clays are more suited to the production of large, more sophisticated designs than vitreous ceramics.
The tile industry also uses chamottes, particularly for extruded tiles.
For refractory applications, high-duty and super-duty, high-alumina chamottes are used as aggregates and for the matrix component for refractory brick and monolithics products,
Imerys also proposes unique cordierite-chamotte materials used in the composition of some kiln furniture or refractory bodies to produce outstanding thermal shock resistance and thermal stability. These materials are made in Clerac (France) by combining selected raw materials which are calcined in kilns.
Shower tray produced with fine fire-clay using chamotte.
Imerys will continue to deliver chamottes for improved performance and greater productivity with the ultimate aim of helping our customers achieve ever higher yields and design possibilities.