Manufacturing of Clay Bricks

REFERENCE:

• BUILDING MATERIAL AND CONSTRUCTION BY V.K. KUMAWAT.

Manufacturing of clay bricks includes following process:

• Preparation of Clay: Preparation of clay is done manually or by mechanically operated machines (excavators). Preparation of clay consists of following methods:

-->Un-soiling: Un-soiling is the process of removal of top layer soil which consists of vegetation, Kankar or other impurities.
-->Digging: Digging is the process of excavation of clay. It is done manually by tools or by machines such as excavators.
-->Cleaning: Cleaning is the removal of impurities such as stones, Kankar and garbage materials. It is done by hand-picking method or by sieves.

-->Weathering: Weathering is done to get the adequate amount of moisture in clay. In this method clay is spread in the form of layers (600 to 1200 mm ) and exposed to atmosphere for natural drying for at least 30 days. Weathering provides proper texture and plasticity to clay.
-->Blending:  Blending is the process of mixing other constituent materials such as chalk, sand, limestone etc. to clay. This provides desired characteristics to clay.
-->Tempering: Tempering is to knead the clay into a homogeneous mass with uniform consistency.
Kneading can be done manually or by machines.

• Moulding: Moulding is the process of giving desired shape to the tempered clay. Moulding is done manually or by machines. Mould is made up of wood or steel. Clay is introduces in the mould firmly. Then mould is lifted with jerk and inverted on aground or table. For getting the depression of frog, moulds are provided with frog arrangement.

• Drying: Drying is to evaporate all superfluous moisture contained at the time of moulding without damaging the bricks and to make brick hard enough so it can handle operations in burning.
  

Drying can be done by 2 methods:
-->Natural Drying:  Moulded bricks are arranged in rows called hacks with space between bricks for circulation of air. Natural drying is not desirable in monsoon season.
-->Artificial Drying: In this method bricks are dried artificially in heated chambers or furnaces. This method is desirable for large scale production.

• Burning: Burning removes water from the clay completely and provides hardness and strength to bricks. Burning makes the brick more durable.
  

Burning can be done by 2 methods:
-->Clamp Burning: In clamp burning bricks and fuel are arranged in alternative layers in open air. It is known as “VITBHATTI” in India. It is cheap and economical process. Main disadvantage of clamp burning is that it is a slow process and heat cannot be transferred uniformly. Hence bricks are under burnt or over burnt. It is suitable for small scale production and cannot be used in rainy seasons.
-->Kiln Burning: In kiln burning bricks are stacked without fuel and fuel is placed below the stacks of bricks. The kiln has a permanent enclosing wall inside which bricks are kept due to which heat can be regulated uniformly. Kiln burning is not economical but it produces good quality and well burnt bricks.

• Cooling:  Cooling is an important stage in brick manufacturing because the rate of cooling has a direct effect on colour. Cooling is done at room temperature.