Brick
Clay bricks are classified as first-class, second class, third class and fourth class based on their physical and mechanical properties.
First Class Bricks:
1. These are thoroughly burnt and are of deep red, cherry or copper color.
2. The surface should be smooth and rectangular, with parallel, sharp and straight edges and square comers.
3. These should be free from flaws, cracks, and stones.
4. These should have a uniform texture.
5. No impression should be left on the brick when a scratch is made by a fingernail.
6. The fractured surface of the brick should not show lumps of lime.
7. A metallic or ringing sound should come when two bricks are struck against each other.
8. Water absorption should be 20% of its dry weight when immersed in cold water for 24 hours.
9. The crushing strength of the brick should not be less than 10 N/mm2. This limit varies with different Government organizations around the country.
Uses: First class bricks are recommended for pointing, exposed face work in masonry structures, flooring and reinforced brickwork.
Second Class Bricks are supposed to have the same requirements as the first-class ones except that
Third Class Bricks are under burnt. They are soft and light-colored producing a dull sound when struck against each other. Water absorption is about 25 percent of dry weight.
Fourth Class Bricks are over burnt and badly distorted in shape and size and are brittle in nature.
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