Basic Bricks

These bricks are used for basic lining of refractories, such as lining of Bessemer converter. Open hearth furnaces, and blast furnaces. The common types of basic refractory bricks are
i) Magnetite bricks
ii) Dolomite bricks and
iii) Bauxite bricks
At least 85 per cent of Magnetite bricks is composed of magnesia and the rest is calcium oxide and silica. The burning temperature of these bricks is as high as 1800 C. These bricks are available in crystalline form.
Dolomite refractory bricks are made by first grinding natural Dolomite rocks with clay and then tempering with water and finally moulding them to the required size and shape. After drying, they are brunt at high temperature.
Bauxite bricks contain 50% per cent or more of Alumina and Silica. It is mixed with 15 to 30 per cent of fire clay, tempered with water and then moulded. After burning at high temperature, they can be used as refractory bricks. These bricks have high shrinkage at higher temperatures and hence are not used commonly.