brick

2. Burnt clay bricks commonly known as bricks can
be classified in two ways:-
 Traditional classification
 IS classification

3. Depending upon its overall qualities Bricks are
generally classified into four classes as follows:-
 First class or class I brick
 Second class or class II brick
 Third class or class III brick
 Kiln rejected brick

4.  1. They shall be well burnt with even surface and
perfectly rectangular shape.
 2. They shall emit a clear ringing sound when
struck.
 3. The water absorption shall not be more than
20 percent by weight.
 4. The compressive strength of First class brick
shall not be less than 10.5 N/mm2.
 5. The rating of efflorescence shall not be more
than ‘slight’.

5.  1. They may be slightly over burnt with slightly
uneven surface and slightly distorted rectangular shape.
 2. They shall emit a ringing sound when struck.
 3. The water absorption shall not be more than 22
percent by weight.
 4. The compressive strength shall not be less than
7 N/mm2.
 5. The rating of efflorescence shall not be more
than ‘slight’.

6.  1. They shall be over burnt or under burnt with
irregular surface and shape.
 2. They shall emit a dull sound when struck.
 3. The water absorption shall not be more than
25 percent by weight.
 4. The compressive strength shall not be less
than 3.5 N/mm2.
 5. The rating of efflorescence shall not be more
than ‘moderate’.

7.  They are Kiln rejected bricks. They are also
called Jhamas (over burnt brick) or Pilas (under
burnt bricks). Jhama bricks are the dark
coloured, brittle, over burnt, hard and of highly
irregular shape. They are used as agaggregate for
concrete in foundation soling and as road metal.
 Pila bricks are yellow in colour, half burnt
and of low strength. These bricks are powdered
and used as surkhi.

8.  IS:1077-1992, classifies brick into 11 classes
depending upon its average compressive strength .
They are class 3.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, 25, 30,
35. For example, class 12.5 means that the average
compressive strength the brick should not be less
than 12.5 N/mm2.
 Moreover, the bricks shall have smooth
rectangular faces with sharp corners and shall be
uniform in colour.
 The water absorption up to class 12.5 shall be less
than or equal to 20% and for higher class it should
be less than or equal to 15%.

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