WHAT IS CONSTRUCTION BRICK? CLASSIFICATION OF BRICKS AS PER CLASS.

INTRODUCTION


  • A brick is rectangular in shape and of size that can be conveniently handled with one hand. Brick may be made of burnt clay or mixture of sand and lime or of Portland cement concrete. Clay bricks are commonly used since these are economical and easily available. The length, width and height of a brick are interrelated as below:

  • Length of brick = 2 × width of brick + thickness of mortar Height of brick = width of brick

  • Size of a standard brick (also known as modular brick) should be 19 × 9 × 9 cm and 19 × 9 × 4 cm. When placed in masonry the 19 × 9 × 9 cm brick with mortar becomes 20 × 10 × 10 cm.

  • However, the bricks available in most part of the country still are 9" × 4.5"× 3" and are known as field bricks. Weight of such a brick is 3.0 kg. An indent on top of brick called frog, 1–2 cm deep. The size of frog should be 10 × 4 × 1 cm. The purpose of providing frog is to form a key for holding the mortar and therefore, the bricks are laid with frogs on top.


Classification of bricks on bases of class are given below:


  • First class brick

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 10.5 N/mm2. 

Uses : First class bricks are recommended for pointing, exposed face work in masnory structure, flooring and reinforced brick work.


  • Second class brick 
1. Small cracks and distortions are permitted.
2. A little higher water absorption of about 16-20 % 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 structures.

  • Third class brick
1. They are underburnt.
2. They are soft and light colored.
3. When struck against each other it will by sound dull.
4. Water absorption is about 25 % of its dry weight.
5. The crushing strength should not be less than 3.5 N/mm2.

Uses : It is used in building for temporary structures.

  •  Fourth class brick
1. They are overburnt.
2. They are badly distorted in shape and size.
3. They are brittle in nature. 

Uses : The ballast of such bricks is used for foundation and floors in lime concrete and road metal.



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