Brick || Definition
A Brick is building material used to make walls,pavements and other elements in masonry construction. |
| Brick |
Constituents
of good brick earth:
* Silica
* Alumina
* Lime
* Iron oxide
* Magnes
Silica
* Brick earth should contain about 50 to % of silica.
* It is responsible for preventing cracking, shrinking and warping of raw bricks.
* It also affects the durability of bricks.
* If present in excess, then it destroys the cohesion between particles and the brick becomes brittle.
Alumina
* Good brick earth should contain about 20% to 30% of alumina.
* It is responsible for plasticity characteristic of earth, which is important in moulding operation.
* If present in excess, then the raw brick shrink and warp during drying.
Lime
* The percentage of lime should be in the range of 5% to 10% in a good brick earth.
* It prevents shrinkage of bricks on drying.
* It causes silica in clay to melt on burning and thus helps to bind it.
* Excess of lime causes the brick to melt and brick looses its shape.
Iron oxide
* A good brick earth should contain about 5% to 7% of iron oxide.
* It gives red colour to the bricks.
* It improves impermeability and durability.
* It gives strength and hardness.
* If present in excess, then the colour of brick becomes dark blue or blakish.
* If the quantity of iron oxide is comparatively less, the brick becomes yellowish in colour.
Magnesia
* Good brick earth should contain less a small quantity of magnesia about1%)
* Magnesium in brick earth imparts yellow tint to the brick.
* It is responsible for reducing shrinkage.
* Excess of magnesia leads to the decay of bricks.
Classification
of Bricks as per common practice:
1. First class bricks
2. Second class
bricks
3. Third class bricks
4. Fourth class
bricks
First Class Bricks:
Second Class Bricks: These bricks are ground moulded and they are burnt in kilns. The surface of these bricks is somewhat rough and shape is also slightly irregular. These bricks may have hair cracks and their edges may not be sharp and uniform. These bricks are commonly used at places where brick work is to be provided with a coat of plaster.
Classification
of Bricks as per constituent materials:
• Common
Burnt Clay Bricks
• Sand
Lime Bricks (Calcium Silicate Bricks)
• Engineering
Bricks
• Concrete
Bricks
• Fly ash Clay Bricks
Common Burnt Clay Bricks:
Sand Lime Bricks:
Engineering Bricks:Engineering bricks are bricks manufactured at extremely high temperatures, forming a dense and strong brick, allowing the brick to limit strength and water absorption.Engineering bricks offer excellent load bearing capacity damp-proof characteristics and chemical resisting properties.
Concrete Bricks:
Fly Ash Clay Bricks:Fly ash clay bricks are manufactured with clay and fly ash, at about 1,000 degrees C. Some studies have shown that these bricks tend to fail poor produce pop-outs, when bricks come into contact with moisture and water, causing the bricks to expand.
Tests on Bricks:To know the quality of bricks following 7 tests can be performed. In these tests some are performed in laboratory and the rest are on field.
• Compressive
strength test
• Water Absorption test
• Efflorescence
test
• Hardness
test
• Size,
Shape and Colour test
• Soundness
test
• Structure
test
Compressive strength test: This test is done to know the compressive strength of brick. It is also called crushing strength of brick. Generally 5 specimens of bricks are taken to laboratory for testing and tested one by one. In this test a brick specimen is put on crushing machine and applied pressure till it breaks. The ultimate pressure at which brick is crushed is taken into account. All five brick specimens are tested one by one and average result is taken as brick’s compressive/crushing strength.
Water Absorption test: In this test bricks are weighed in dry condition and let them immersed in fresh water for 24 hours. After 24 hours of immersion those are taken out from water and wipe out with cloth. Then brick is weighed in wet condition. The difference between weights is the water absorbed by brick. The percentage of water absorption is then calculated.The less water absorbed by brick the greater its quality. Good quality brick doesn’t absorb more than 20% water of its own weight.
Efflorescence test: The presence of alkalies in bricks is harmful and they form a grey or white layer on brick surface by absorbing moisture. To find out the presence of alkalis in bricks this test is performed. In this test a brick is immersed in fresh water for 24 hours and then it’s taken out from water and allowed to dry in shade.If the whitish layer is not visible on surface it proofs that absence of alkalis in brick. If the whitish layer visible about 10% of brick surface then the presence of alkalis is in acceptable range. If that is about 50% of surface then it is moderate. If the alkalies’ presence is over 50% then the brick is severely affected by alkalies.
Hardness test:In this test a scratch is made on brick surface with a hard thing. If that doesn’t left any impression on brick then that is good quality brick.
Size, shape and colour test:In this test randomly collected 20 bricks are staked along In this test randomly collected 20 bricks are staked along sizes as per standard. Bricks are closely viewed to check if its edges are sharp and straight and uniform in shape. A good quality brick should have bright and uniform colour throughout.
Soundness test:In this test two bricks are held by both hands and struck with one another. If the bricks give clear metallic ringing sound and don’t break then those are good quality bricks.
Structure test:In this test a brick is broken or a broken brick is collected and closely observed. If there are any flows, cracks or holes present on that broken face then that isn’t good quality brick.
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