CLASSIFICATION OF BRICKS
On the basis of field practice. • Clay bricks are classified as. • first class, • second class, • third class, • fourth class. First class bricks. 1. These are thoroughly burnt and are of deep red, cherry or copper colour. 2. The surface should be smooth and rectangular, with parallel, sharp and straight edges and square corners. 3. These should be free from flaws, cracks and stones. 4. These should have uniform texture. 5. No impression should be left on the brick when a scratch is made by a finger nail. 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 12–15% 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 Second class bricks. 1. They are supposed to have the same requir...