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Classification of bricks

Short answer

First-class bricks are well burnt, uniform, with sharp edges, water absorption ≤20%, strength ≥10.5 N/mm², used for load-bearing walls and exposed work. Second-class bricks are slightly irregular, water absorption up to 22%, strength ~7 N/mm², used for plastered walls and general interior work.

How do you classify bricks? Explain the classes of bricks (1st class, 2nd class) and their engineering application.

Bricks are classified in several ways.

1. By manufacture

  • Unburnt (sun-dried) and burnt bricks.

2. By quality (burning)

  • First class: well burnt, uniform red colour, regular shape, sharp edges, ringing sound, water absorption not more than 20%, compressive strength not less than about 10.5 N/mm². Used for superior work: load-bearing walls, brick flooring, face work and exposed structures.
  • Second class: slightly irregular shape and rough surface, less uniform colour, water absorption up to 22%, strength about 7 N/mm². Used for walls that are to be plastered, for general and interior work and for non-load-bearing partitions.
  • Third class: under-burnt and soft, absorbing up to 25% water, strength about 3.5 N/mm²; used for temporary work and in dry places.
  • Fourth class (jhama, over-burnt): used as aggregate in lime concrete, as road metal and in foundations.

3. By use

  • Common bricks, facing bricks, engineering bricks, fire bricks, and perforated and hollow bricks.

4. By strength (IS 1077)

  • Classes 35, 30, 25 ... down to 3.5, according to the minimum compressive strength in N/mm².

✓ Answer checked by Claude Opus 5.5 (high effort)

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