Classification of bricks based on their physical and mechanical properties
- first class,
- second class,
- third class and
- fourth class
First Class Bricks:
- These are thoroughly burnt and are of deep red, cherry or copper colour.
- The surface should be smooth and rectangular, with parallel, sharp and straight edges and square corners.
- These should be free from flaws, cracks and stones.
- These should have uniform texture.
- No impression should be left on the brick when a scratch is made by a finger nail.
- The fractured surface of the brick should not show lumps of lime.
- A metallic or ringing sound should come when two bricks are struck against each other.
- Water absorption should be 12–15% of its dry weight when immersed in cold water for24 hours.
- The crushing strength of the brick should not be less than 10 N/mm2.
- This limit varies with different Government organizations around the country.