Refractory fire brick or chamotte brick is a ceramic block with refractory (refractaire) properties. These bricks are used in construction of furnaces, cupola, stoves and hotbeds. This type of brick is mainly used to resist to high temperatures, with a low thermal conductivity to save energy. Usually, refractory bricks (brique refractaire) are used in applications where there are high temperatures, mechanical friction, chemical corrosion and so on, such as inside an oven or furnace. They are also recommended for the construction of fireplaces as they store heat and keep it for a longer period.
Insulating refractory fire bricks (brique refractaire) or lightweight bricks are widely used in insulating refractory linings. These products have a total porosity of over 30% and they are generally made of kaolin, clays, silica-alumina lightweight chamotte, with or without fuel or foam additives. Using these types of bricks leads to major benefits due to the reduction of thermal energy consumption. Regarding formats and dimensions, they are available in a wide range of standard and non-standard sizes. Depending on customers’ requirements, refractory bricks can be achieved in other special formats, based on technical drawings.
The main components of refractory fire bricks are aluminium oxide, titanium oxide and silica oxide. The specified characteristics are kept up to temperatures of maximum 1850ºC. They have a mechanical, thermal and chemical remarkable stability, operating at all temperatures specified. Their features are: low thermal conductivity, low thermal capacity, high compressive strength; very good chemical stability; resistance to thermal shock.
The characteristic of refractoriness means the property of a product to withstand high temperatures. The resistance of products to high temperatures depends on refractoriness and it is linked to the chemical and mineralogical composition of the products. Refractoriness does not indicate the operating temperature of refractory products (refractaire); it is higher than this temperature: from 30-80ºC in silica products, to 200-300ºC for silica-alumina products.
Resistance to compression is the physical property that is defined by the maximum value of tension that can be supported by a refractory product without deforming or being destroyed. Based on the resistance to compression, certain conclusions can be drawn regarding: the product’s behaviour at high temperatures, its resistance to thermal shock, its resistance to mechanical shock, its resistance to abrasion, its resistance to chemical corrosion.
Refractory products, by their nature, are more or less porous; the pores are larger or smaller, and they either communicate by capillaries, or are closed. There are two types of porosity: apparent or open porosity and total porosity. Apparent porosity is the ratio between the volume of open pores and the apparent volume of a product expressed in volume percentage. Total porosity is the ratio between the total pore volume (closed and open) and the apparent volume of a product, expressed in percentage of volume.
All types of refractory materials (refractaire), including refractory fire brick (brique refractaire) are special construction materials which require special knowledge and procedures. Their producers must follow certain rules and regulations in order to provide their customers with products of the highest quality that could resist to different conditions.