Clay Brick Composition

Building bricks tend to be a mixture of clay and sand which is mixed with water to create the desired consistency. Sometimes the bricks also have lime added, ash or organic matter which speeds up the firing of the brick. The clay mixture is then formed into moulds to the desired specification ready to be dried then fired in the kiln.
Clay: The properties and quality of bricks depend on the type of clay being used. The most common form of clay used for everyday bricks, has a sandy consistency of silicate or alumina, which usually contains small quantities of lime or iron oxide. Silica, when added to pure clay in the form of sand, tends to prevent cracking, shrinking and warping of the brick. If there is a large proportion of sand used in the mixture the brick will be more textured and shapely. An excess of sand, however, renders the bricks far too brittle and destroys their cohesion. A quarter of silica is said to be advantageous. Iron oxide in the clay enables the silica and alumina to fuse together and adds considerably to the hardness and strength of the finished bricks. The iron content of the brick is evident in the colour of the brick and can be used to add the familiar red colour to the bricks.

However a clay which is fired to a red colour will provide a stronger brick than clay which is fired to a white or yellow brick. The lime content in a brick has two different effects. It stops the raw brick from shrinking and drying out, and it also acts as a flux during burning which causes the silica to melt and creates the bond which binds all the components of the brick together. However, too much lime can cause the brick to melt and loose its shape. Any amount of quicklime within a brick degrades its quality and can cause the brick to split into pieces. For the best qualities of pressed brick the clay is carefully selected both for colour and composition. Clay from different sources or geographical locations is also mixed together to create the desired mixture.

Zhengtai Machiney Factory of Gongyi is specialized in the field of full set machinery of automatic brick making machine. After 20 years' development, our factory has a contingent of an advanced manufacturing technology, perfect detection means, and a complete quality assurance system according to the inferior soil, coal gangue, shale, fly ash and other waste residue.