Brick is a product made of burnt clay or mixture of sand and lime. It is generally used for constructing walls, columns, roofs, paving floors etc. Bricks are available in different sizes depending on type of construction. However, the common size of brick is 19 x 9 x 9 cm.
Ingredients used in making of brick are as follows:
Silica :
1. The presence of silica in brick is 50-60%.
2. Silica enables brick to retain its shape and imparts durability.
3. Excess silica makes the brick brittle and weak on burning.
Alumina :
1. The presence of alumina in brick is 20-30%.
2. Alumina imparts plasticity to the clay so that it can be moulded.
3. Excess alumina produces cracks in brick on drying.
Lime :
1. The presence of lime in brick is < 10%.
2. Lime prevents shrinkage of raw bricks.
3. Excess lime causes brick to melt and looses its shape.
Ferric Oxide :
1. The presence of ferric oxide is < 7%.
2. Ferric Oxide imparts red colour to brick.
3. Ferric Oxide improves impermeability and durability.
Magnesia :
1. The presence of magnesia is < 1%.
2. Magnesia imparts yellowish tint to bricks.
3. Excess magnesia leads to decay of bricks.
Alkales :
1. The presence of alkales in bricks is < 10%.
2. The presence of alkales in bricks causes efflorescence.
Classification of bricks :
1. First Class Bricks : These bricks are in perfectly rectangular shape and has uniform reddish colour. These bricks are well burnt. These bricks should not absorb water more than 20% of its own weight on 24 Hrs immersion in water. The minimum crushing strength is 10.5 N/mm2 .
2. Second Class Brick : These bricks are not in perfectly rectangular shape. These bricks are slightly over burnt. These bricks should not absorb water more than 22% of its own weight on 24 Hrs immersion in water. The minimum crushing strength is 7 N/mm2.
3. Third Class Bricks : These bricks are very soft and can be broken easily, this is because these bricks are not burnt properly in a kiln. These bricks should not absorb water more than 25% of its weight own weight on 24 Hrs immersion in water. The minimum crushing strength is 3.5 N/mm2.
Special Bricks :
1. Perforated Bricks : These bricks are light weight bricks providing better thermal insulation and are free from flaws, cracks and nodules of free lime.
The standard size is 19 x 19 x 9 cm.
The minimum compressive strength is 7 N/mm2.
The water absorption capacity of this brick is 15%.
2. Heavy Duty Bricks : These bricks are very heavy in weight and are used in heavy construction like bridges, industrial foundations and multistoreyed buildings.
The minimum compressive strength is 40 N/mm2.
The water absorption capacity of this brick is 10%.
3. Fly-Ash Bricks : These bricks are made of fly-ash, lime, gypsum and sand. These bricks are lighter and stronger than standard bricks. These bricks are cheaper than other bricks. These bricks can be used in all construction works.
The minimum compressive strength is 10 -12 N/mm2.
The water absorption capacity is ≤ 12%.
4. Paving Bricks : These bricks are extensively used for pavements, floors, garden walls etc.
Important Note :
1. Frog : It is an indent of 1-2 cm deep formed on the top of brick. It’s purpose is to form key for holding the mortar.
2.
3. Specific Gravity of brick is = 2.
4. Modular size of brick = 20 x 10 x 10 cm (with mortar).
