Manufacture Process Of Bricks

 Manufacturing of Bricks 

Brick is widely used material in construction industry whose major raw material is clay. To manufacture the brick, various activities are been carried out from preparation of the Brick earth to the process of burning of bricks in kilns. Today in this topic we are going to see how the Manufacturing of Bricks is carried out.

1) Preparation of Brick Earth

The preparation of brick earth is carried out in four process

• Unsoiling
• Digging
• Cleaning
• Weathering
• Blending
• Tempering

Unsoiling

The soil top is considerably full of impurities such as large lumps, stones, shales etc making the soil unfit for the use, to overcome the issue the top soil of about 20cm  or 200mm  is dug out with the help of powerful equipment such as JCB's , poclain etc and thrown away.

Digging

After the impure soil is removed, the clay underneath the impure soil is dug out and is spread over the leveled ground or the plant storage area in the form of heaps for maximum 1.5m of height. 

Cleaning

The clay is cleaned is this process by removing the lumps, stones, pebbles, shales etc because they will lead in generating voids inside the bricks which will result is degrading the compressive strength or the crushing strength of the brick. the cleaning is done by washing off the materials if are in excess and the lumps are crushed with help of crushing tools or rollers.

Weathering

In this process the cleaned clay is left in the ground under the atmosphere for certain weeks to month so as the clay gets homogeneous and soft in nature

Blending

Water is added of about 12-15% of the weight of clay to make the clay loose

Tempering

The clay is kneaded by feet of people or with the help of kettle, which been carried out within 36 hrs of the blending process just to make the mixing homogeneous and uniform.For Large scale the tempering is done with the help of pug mills which is known as ' pugging', which can yield about 1500 bricks a time. 

2) Moulding

Moulding is a technique in which, the cohesive clay which we have prepatred by the process of tempering is put inside the rectangular moulds of bricks make of steel or wood. The moulding is carried out in two ways

• Hand Moulding
• Machine Moulding

(i) Hand Moulding

Ground Moulding

Mostly Soft-mud is preferred in this technique.The ground moulding is done where large land is available. The land is first leveled as if the surface is uneven, the bricks prepared will not be straight and will tend to show uneven surface of brick, than the ground is covered with sand so to overcome the problem of absorption of water to the ground and impurities getting stuck to the clay particles from the soil.

Once the land is prepared, The mould inner surface are applied with certain substance such as water or sand etc so as the wet clay which we are about to fill in moulds dont get stick to the surface.

Once we  done with sprinkling of sand or water to the inner surface, the clay is filled inside the moulds and is pressed manually with a force and the extra clay coming out from the top surface is removed with a metal blade or wire for better finish. The mould is than removed and washed with water and the process is repeated again.

They have certain disadvantages as

• They dont have frog (provided of shear whose dimension is 100mm x 40mm x 10mm or 20mm) .
• Bottom surface of these bricks are rough in nature.

Table Moulding

Same procedure as ground moulding is followed in this but the only difference is, Table moulded bricks are moulded on Table mould whose dimension is 2m x 1m whereas ground moulded bricks are prepared on ground surface. Table moulding is adopted when the frogs are required on the brick surface. In this technique the mould is not removed right after filling of clay due to which economically the cost of this type increases as compared to ground moulding technique.

After moulding is done, the bricks are carried to dry area or the dry site of the bricks.

(ii) Machine Moulding

Mostly Stiff mud is preffered in this technique.When we have to do brick production in large scale, than the machine moulding technique is implied. There are many advantages of machine moulding such as

• Less time required.
• More Economical.
• Less Space Required.
• Large Production.
• Less Labour required.
• Hard, Durable and Sound bricks are manufactured.

Machine moulding is carried out in two ways 

1. Plastic Method
2. Dry Press Method

Plastic Method

In this technique, the stiff clay is is forced to move out from a rectangular opening which is provided in machine. Once the Brick cake is moved out in a large rectangular form, the bricks are been cut in the form of brick shape and length required with help for cutting blades or sharp wires by machine only, After that the bricks are moved to dry.

Dry-Press Method

In this technique, the stiff clay is help in the mechanical operated press mould and is pressed at a high pressure which result in taking up the shape of bricks with frog to it. After that they are moved to dry.

3) Drying

• The moisture of the moulded bricks are removed maintaining shrinkage of the bricks by drying the bricks under sun which leads in saving fuel and time in burning them.
• Within a period of 3-4 days the moisture content is brought down to 3%.
• As we arrange bricks on stack which normally consist for 10 stairs, there are space kept between them for the movement of air, and within stacks a width of 1m is left for the movement of people and ventilation.

4) Burning

The burning process is carried out in 3 ways,

1. Dehydration Period - In dehydration period, the bricks are burnt in temperature ranging between 400-600C. The process is done to ensure complete vaporization of the moisture content inside bricks.
2. Oxidation Process - In the oxidation process, the bricks are burnt in the temperature ranging between 650-900C resulting in oxidation of ferrous iron to ferric forms, which improves impermeability and ductility of the bricks resulting in giving strength to them.
3. Vitrification Process - Bricks are burnt ranging between 900-1200 C which results in making them cherry red, making brick strong and sound.

The Burning can further be done in 

• Clamps - They yield 60% of First Class Bricks
• Kilns -  They yield about 90% of First Class Bricks.

Brick Kiln

Related Topics

• Brick Masonry
• Classification of bricks / Types of bricks
  
• Bonds In Bricks - Brick Masonry
  
• Brick Kilns