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Size and shape

Size
and shape – Brick
Should have uniform size and plane and rectangular surfaces with parallel sides
and sharp straight edges.

20
bricks of standard size (190 mm ╳ 90 mm ╳  90 mm) are selected at random and they
are stacked length wise, along the width and height.

Brick Size

For a good brick result should be within the
following permissible limit.

 Length – 3680mm to 3920mm

 Width – 1740mm to 1860mm

 Height – 1740mm to 1860mm

Water absorption

Water
absorption – A brick is
taken and it is weighed dry then it is immersed in water for 24 hours. and
again weight. For a good brick, water absorption after 24 hours of immersion,
water absorption should be 20% and in no case absorption should exceed 20%.

Crushing strength

Crushing
strength – The crushing strength of brick is found out by
placing it in the compression testing machine. As per IS 1077 : 1970, 
minimum compressive strength of brick is 3.5 N/mm.

For a good brick compressive strength >10N/mm2.

                Grade A brick – 7 – 14 N/mm2

                Grade B brick – 14N/mm

Hardness

Hardness – In this test a scratch is made on
the brick surface with the help of a fingernail. If no impression is left on
the surface the brick is to be treated sufficiently hard.

Soundness

Soundness – Properties of a good brick for the soundness test, When two similar bricks struck
together. A metallic sound should be produced.

Texture and compactness

Texture and compactness – A brick is broken and its structure
is examined. It should be homogeneous, compact and free from any defects such
as holes, lums etc.

Colour

Colour – Brick should be uniformly dark red or cherry colour as
indicated for uniformity in chemical composition and completeness in burning of
brick.

Presence of soluble salts / Efflorescence

Presence of soluble salts / Efflorescence – The soluble salt, if present in brick, will cause
efflorescence on the surface of the brick. After 24 hours immersion in water
and allowed to dry in Shade, it should not show so any grey or white deposit on
its surface (i,e showing absence of salt)

Classification of bricks

First class brick

Second class brick

• The crushing strength compressive strength of
  second class brick is 70 kg/㎠  (7 N/㎟)

• The water absorption of second class brick should
  not be more than 22% of dry weight (⊁22%)

• Second class brick is a smooth surface, and edges
  are defective and rectangular in shape.

• The thickness of mortar joint is 12 mm.

• The colour of the second class brick is a yellow
  and red colour.

• When two similar bricks are struck each other
  then metallic sound is to be produced.

• In second class brick when a scratch is made by a
  nail finger no impression should be left on the brick.

• Thoroughly burnt.

• Second class brick is to be used for interior
  brick works or load bearing walls.

Third class brick

• The crushing strength
  compressive strength of third class brick is 50 kg/㎠  (5 N/㎟)

• The water absorption of third
  class brick should not be more than 24 – 25 % of its dry weight (24 – 25 %)

• Shape distorted and size is not regular.

• In third class brick texture
  is non – uniform.

• The colour of the third class
  brick is light red.

• Third class brick is to be
  used for interior brick works.

• This brick is only for used
  partition wall, cavity wall, sleeper wall and non-loading bearing wall or temporary structure.