Brick As A Building Material

The Brick is the most commonly used building material and used for constructing walls, columns, roofs, paving floors, etc.

Clay is an earthen mineral mass or fragmentary rock capable of mixing with water and forming a plastic viscous mass which has a property of retaining its shape when molded and dried, when such masses are heated to redness, they acquire hardness and strength.

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Manufacture of Brick:-

Preparation of brick clay:- At first, the earth is dug out in clear weather and cleaned off stones, pebbles, kankar, grits, vegetable matter, etc. The earth after digging out is left to atmospheric action for a few weeks. This process is known as weathering. The clay is then tempered in pug mills.

Molding bricks:- After preparing the clay, the molding of bricks is carried out either by hand or by machine. In hand molding, manpower is cheap and available.

The bricks are molded in the machine, when a large number of bricks are to be manufactured in a short method.

Drying of bricks:- After the bricks are molded, they are dried. The drying of bricks may be natural or artificial. In natural drying, the molded bricks are kept in the sun for a day or two so that they become sufficiently hard to be handled safely. These bricks are now arranged in rows on their edges on a slightly raised ground called hacks. A little space for the free circulation of air is kept for each brick. The air and sun-dried bricks are adequately strong and durable. If the bricks are not properly dried before they are brunt, they may get cracked and distorted during the burning process.

Burning of bricks:- The burning of dry bricks is done either in a clamp or in the kiln. In India, both clamp and kiln burning is practiced.

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Sl.no	Constituent	Function	Effect if in excess
1	Silica(50-60%)	· Responsible for strength, shape, and hardness. · Prevent shrinking and cracking.	Bricks become brittle and weak.
2	Alumina(20-30%)	· It absorbs water and renders the clay plastic.	It causes cracks in bricks on drying and becomes too hard when burnt.
3	Lime(>5%)	· Acts as a flex. · It causes silica to fuse during burning and bind the brick particles together. · Prevent shrinkage on drying.	In the form of lumps cause bricks to disintegration and hence bricks shape & lost.
4	Magnesia(>1%)	· Imparts yellow color when present in small quantity · Decrease shrinkage.	Leads to decay of bricks.
5	Iron oxide(5-6%)	· Acts as a flux · Provide strength & hardness · Improve durability & impermeability.

Classification of Bricks or Types of Bricks :-

First Class Brick:- These bricks are well brunt having smooth and even surface with perfect rectangular shape and uniform reddish colour.

Second Class Brick:- These bricks are slightly over burnt having rough surface and not perfectly rectangular in shape.

Third Class Bricks:- These bricks are not properly burnt (under burnt) in the kiln and hence these soft and can be easily broken.

Jhama Bricks:- These bricks are over burnt with irregular shape. These bricks are dark bluish in colour.

Sl. No	Types of Bricks	Compressive strength (N/mm²)	% water absorption limit after 24 hours
1	Common building brick	3.5	25%
2	Third Class brick	5	23%
3	Second class brick	7	22%
4	First class brick	10.5	20%

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What is frog ?

Frog is the depression made in the surface of brick.

Note:

· Purpose of providing frog is to form a key for holding the mortar and work as a shear key.

· Bricks are laid with frogs on top.

· Frog is generally 1-2 cm deep.

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Defects of Brick :-

Efflorescence :- This is the caused because of alkalies present in bricks.

When bricks come in contact with moisture, water is absorbed and the alkalies crystallize.

After drying grey or white powder patches on the brick surface.

Chuffs:- Deformation of the shape of bricks caused by the rain water falling on the hot bricks is called Chuffs.

Black Core :- When brick clay contains bituminous matter or carbon and they are not completely removed by oxidation, the brick results in black core mainly because of improper burning.

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Bloating :- The defect is observed as spongy swollen mass over the surface of burned bricks.

It is caused due to the presence of excess carbonaceous matter and sulphur in brick clay.

Spot :- If sulphur is present in the brick clay, it cause dark surface spots on the brick surface. Such bricks are not only harmful but also unsuitable for exposed masonry work.

Blisters :- Broken blisters are generally caused on the surface of sewer pipes and drain tiles due to air imprisoned during their moulding.

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Brick As A Building Material