Chamotte - general information
What is it clay slate?
It is a layered clay stone - sedimentary rock formed by weathering of igneous rocks (granites, tuffs). The dominant component is the clay mineral kaolinite.
The sedimentation of kaolinite occur in all geological periods, the diagenetical reinforcement, however, only in the Palaeozoic and Mesozoic. It is also related to its occurrence near coal layer.
It is a layered pelitic material (grain size below 0.002 mm). Its strength is different from clays and at the same time with less compactness than that of clay shale.
Chemically is clay slate aluminosilicates containing Al2O3 up to 43 % and SiO2 content of around 55 % (in the annealed state), with different degrees of contamination of coloring metal oxides and organic matter.
Refractoriness, typical for this ceramic material, is the result of a high content of Al2O3 and at the same time low content of low-melting additives.
The firing process creates very stable material called ceramic grog. The materials are characterized by their thermal stability (refractoriness, coefficient of thermal expansion). Followed crushing and sorting bring grog with specific refractory and grain size parameters.
Grog, thanks to its angularity fills maximally up space in shaping operations and forms an excellent framework for subsequent processing of ceramic products (drying, firing). The thermal and mechanical properties depend on the content of the grog in the final product. Low porosity of the material is reached due to quality firing. This, together with an appropriate grain structure help to low need of plastic components in the production of ceramic products, respectively foundry molds.
- are of Carboniferous origin
- content of Al2O3 at intervals from 33 % to 43 %
- content of Fe2O3 at intervals from 1 % to 3 %
- firing in a rotary kiln at a temperature of about 1,350 °C
- have low loss on ignition
- have high bulk density
- have low water absorption
Application: in a wide range of industries such as:
- production of refractory bricks, blocks and tiles
- production of castables
- production of foundry moulds
- production of sanitary ceramics
- addition to ceramics mixtures
- production of electroporcelain and porcelain
- finely milled for the production of glazes