Correct Answer - Option 2 : 105
Explanation:
Clay bricks are classified as first-class, second class, third class, and fourth class based on their physical and mechanical properties.
1) First Class Bricks:
1. The crushing strength of the brick should not be less than 10.5 N/mm2. This limit varies with different Government organizations around the country.
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. These are thoroughly burnt and are of deep red, cherry, or copper color.
Uses: First class bricks are recommended for pointing, exposed face work in masonry structures, flooring, and reinforced brickwork.
2) Second Class Bricks are supposed to have the same requirements as the first-class ones except that
1. Small cracks and distortions are permitted.
2. A little higher water absorption of about 22 % of its dry weight is allowed.
3. The crushing strength should not be less than 7.0 N/mm2.
Uses: Second-class bricks are recommended for all important or unimportant hidden masonry works and centering of reinforced brick and reinforced cement concrete (RCC) structures.
3) 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.
Uses: It is used for building temporary structures.
4. Fourth Class Bricks are over burnt and badly distorted in shape and size and are brittle in nature.
Uses: The ballast of such bricks is used for foundation and floors in lime concrete and road metal.
