Properties of brick | class of brick

Properties of good bricks | Different class of bricks


The following properties of bricks

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.

Properties of brick
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

  • The crushing strength compressive strength of
    first class brick is 105 kg/㎠ (10.5 N/㎟)
  • The water absorption of first class brick should
    not be more than 20% of dry weight (⊁20%)
  • First class brick is a smooth surface, sharp and
    straight edges parallel and square corner.
  • The thickness of mortar joint is 10 mm.
  • In first class brick when a scratch is made by a
    nail finger no impression should be left on the brick.
  • The colour of the first class brick is a cherry
    and red colour.
  • Uniform texture of brick.
  • Thoroughly burnt.
  • When two bricks are struck each other then
    metallic sound is to be produced.
  • First class brick is used for pointing, exposed
    face work in masonry structure.
  • First class brick is to be used for exterior
    brick work or load bearing wall.

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.


Fourth class bricks

  • The crushing strength compressive strength of
    fourth class brick is around 400 kg/㎠  (40 N/㎟)
  • The water absorption of fourth class brick is 20%
    of dry weight (20%) – IS CODE 1077-1992
  • We get this type of brick by over burning. It is also called over
    burn brick or jhama brick.
  • For more burning, a soft molten mass is produced and the bricks
    lose their shape.
  • Over burn brick is used for filing purposes.

Common building bricks

  • The crushing strength compressive strength of
    first class brick is 35 kg/㎠  (3.5 N/㎟)
  • The water absorption of common building brick
    should not be more than 25% of its dry weight (⊁25%)
  • IS CODE
    1077:1976

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