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BRICK
The brick is the most commonly used building material
and used for constructing walls, column, paving floors
etc.
A good brick clay contains:1. Alumina – It is the chief constituent of brick
clay. A good brick earth should contain about
20% to 30% of alumina. This constituent imparts
plasticity to the earth so that it can be moulded.
The excess of alumina in the clay makes the
brick crack and warp on drying.
2. Silica – A good brick earth should contain about
50% to 60% of silica. This constituent prevent
cracking, shrinking and warping. It thus imparts
uniform shape to the bricks. The exes of silica in
the clay makes the brick brittle and week
3. Lime – A small quantity of lime not exceeding
5% is desirable in good brick earth. This
constituent prevent shrinkage of raw bricks. The
excess of lime causes the brick to melt and
distort during burning.
4. Oxide of iron – A small quantity of oxide of iron
to the extent of about 5% to 6%is desirable in
good brick earth. It imparts red colour to the
bricks. The excess of oxide of iron makes the
bricks dark blue. If, on the other hand the
quantity of iron oxide comparatively less, the
brick will be yellowish in colour.
5. Magnesia – A small quantity of magnesia in
brick earth imparts yellow tint colour to bricks
and decreases shrinkage. But excess of
magnesia leads to the decay of bricks.
the kiln during burning and they cause brick
to fuse, twist and warp
4. Pebbles – The presence of pebbles or grits
of any kind is undesirable in brick earth
because it will not allow the clay to be
mixed uniformly and thoroughly which will
result in week and porous brick
5. Organic matter - Presence of organic
matter in brick earth assist in burning. But if
such matter is not completely burnt, bricks
become porous.
Manufacture of bricks
Preparation of clay:(I)
(II)
(III)
(IV)
(V)
(VI)
Unsoiling
Digging
Cleaning
Weathering
Blending
Tempering
Note : First of all, the earth is dug out in clear weather
and cleaned off stones, pebbles, grits, vegetable matter
etc. the earth after digging out is left to atmospheric
action for few weeks. The process is known as
weathering. It is found it is found that 1.5 m3 to 2.5m3 of
earth is required for moulding 1000bricks. The clay is
then tempered in pug mill.
Moulding:-
Harmful ingredients in Brick earth:1. Lime – It causes unsoundness in brick if
present in excess amount
2. Iron pyrites – It causes bricks are
crystallized and disintegrated during
burning.
3. Alkalies – These are mainly in the form of
soda and potash. The alkalies act as a flux in
The moulding of bricks is carried out either by
hand or by machine.
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In hand moulding, the bricks are moulded by hand i.e.
manually. The bricks prepared by hand moulding are of
two types.
so that they become sufficiently hard to be handled
safely. These bricks are now arranged in rows on their
edges on a slightly raised ground called hacks.
1) Ground-moulded brick
The artificial drying is used when bricks are
required on a large scale and at a rapid rate.
Burning of bricks:-
2) Table-moulded brick
The bricks prepared by dipping mould in water
every time are known as slop-moulded brick. The fine
sand or ash may be sprinkled on the inside surface of
mould instead of dipping mould in water, Such bricks are
known as sand-moulded bricks and they have sharp and
straight edges.
The bricks are moulded in machine, when large
number of bricks are to be manufactured in a short time.
The machine moulding may be performed either by
plastic method (plastic clay machine) or dry process
method (dry clay machine).wire cut bricks are obtained
from plastic clay machine and pressed bricks are
obtained from dry clay machine
Drying of bricks:After the bricks are moulded, they are dried. The drying
of bricks may be natural or artificial. In natural drying,
the moulded bricks are kept in the sun for a day or two
The burning of dry bricks is done either in clamp or kilns.
The clamp are temporary structure and they are
adopted to manufacture bricks on a small scale for local
demand. But the kilns are permanent structure and they
are adopted to manufacture bricks on a large scale. It
may be noted that the average out turn of first class
bricks in clamp is about 60% whereas for kiln burning it
is about 80 to 90%
Test for bricks:Compressive strength – As per BIS-1077-1992,
the minimum compressive strength of brick is
3.5N /mm2.Thebrick with compressive strength
of 7 to 14 N/mm2 are graded A and those
having above 14 N/mm2 are graded as AA
Water absorption - 20% of weight of dry brick
for first class bricks, 22% for second class and
25% for third class bricks.
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Hardness – in this test, a scratch is made on
brick surface with the help of a figure nail. If no
impression is left on the surface, brick is treated
to be sufficiently hard.
Presence of soluble salt – Soluble salt, if
present in brick, will cause efflorescence on the
surface of brick. If white deposit cover about
10% surface, the efflorescence is said to be
slight and the white deposit cover about 50% of
surface, then it said to be moderate .if grey or
white deposit are found on more than 50% of
surface ,the efflorescence become heavy and it
is treated as serious
Shape and size – its shape should be truly
rectangular with sharp edges.20 bricks are
randomly selected of standard size (190 x 90x
90 mm) for good quality brick, the result should
be within the following permissible limits:
Length : 3680 mm to 3920mm
Width : 1740 mm to 1860 mm
Height : 1740 mm to 1860 mm
Soundness - in this test, two bricks are taken
and they are struck with each other, the brick
should not break and clear ringing sound
should be produced
Structure – it should be homogeneous,
compact and free from any defects such as
holes, lumps, etc.
Second class bricks: These bricks are
ground moulded and burnt in kilns.
These bricks may have hair cracks and
their edges may not be sharp and
uniform, and it is commonly used at
place where brick work is to be
provided with a coat of plaster.
Third class bricks: these are ground
moulded and they are burnt in clamps.
These bricks gives dull sound when
struck together. They are used for
unimportant and temporary structure.
Fourth class bricks: these are over
burnt with irregular shape and dark
colour. These bricks are used as
aggregate for concrete in foundations,
floors, roads, etc.
Size and weight of bricks:
Standard size of bricks is 190mm x 90mm
x90mm
Nominal size (with mortar) is 200mm x 100mm
x 100mm
The commonly adopted nominal size of
traditional bricks is 230mm x 114mm x 76mm
It is found that the weight of 1m3 bricks earth is
about 1800 kg. Hence the average weight of
brick will be about 3 to 3.5 kg.
Classification of Bricks:1. Unburnt bricks – The unburnt or sun dried
bricks are dried with the help of heat received
from sun after the process of moulding. These
bricks are used in the construction of temporary
structure and should not be used at place
exposed to heavy rains.
2. Burnt bricks –
First class bricks: These bricks are table
moulded and standard size, shape and
they are burnt in kiln. These bricks are
used for superior work of permanent
nature.
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Special bricks:Bullnose bricks – A brick moulded with a
rounded angle is termed as a bull nose. It is used
for a rounded quoin
Cownose bricks - A brick moulded with a
double bullnose on end is known as Cownose.
Channel bricks – These bricks are moulded to
the shape of a gutter or a channel and they are
very often glazed. These bricks are used to
function as drain.
Coping bricks – These bricks are made to suit
the thickness of walls on which coping is to be
provided. Such bricks take various forms such as
chamfered half round or saddle-back.
Round bricks – These bricks are used for circular
pillars.
Perforated bricks – These brick contain
cylindrical holes throughout their thickness. The
distance between the side of brick and edge of
perforation should not be less than 15mm, and
its water absorption should not exceed 15% by
weight. These bricks are used in the
construction of light weight structure and
multistoried framed structures.
Hollow bricks – These are also known as cellular
or cavity bricks. Such bricks have wall thickness
of about 20mm to 25mm. they also reduce the
transmission of heat, sound and damp.
Curved sector bricks – These bricks are in the
form of curved sector and they are used in the
construction of circular brick masonry pillars,
Brick chimneys, etc.
Paving bricks – these bricks are extensively used
for street pavements, stable floors, garden walk
etc.
Refractory bricks – A good refractory brick
should have the capability of withstanding high
temperature and low coefficient of expansion
and contraction. Following are three type of
refractory bricks
1. Acid brick (Fire brick and silica
brick)
2. Basic brick (Magnetite brick,
dolomite brick, and bauxite brick)
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3. Neutral brick (Chromite brick and
chrome-magnetite brick)
Fire-clay:
The fire-clay is a refractory clay which is capable
of resisting a high temperature without being melted or
softened. It is used for making refractory material like
fire brick. The constituent of a good fire-clay are two alumina and silica. The percentage of alumina varies
from 25 to 35 and that of silica from 65 to 75. Fire-clay
are classified in to three categories.
a) High duty fire clay: The high duty fire clay can
resist temperature range of 14820c to 16480c
b) Medium duty fire-clay: The medium duty fireclay can resist temperature range 13150c to
14820c
c) Low duty fire clay: The low duty fire clay can
resist temperature up to 8700c only.
Objective Type Questions
1. According to IS 1077-1992, the standard
modular size of common building brick is
1. 190mm x 90mm x 90mm
2. 190mm x 90mm x 40mm
2. According to IS 1077-1992, the non-modular
sizes of the bricks may also be used
1. 230mm x 110mm x 70mm
2. 230mm x 110mm x 30mm
3. The brick moulded with rounded edge is termed
as - Bull nose bricks
4. A bricks moulded with double bull nose on end
is known as
- Cow nose brick
5. A bull nose brick is not used for - Arches
6. A pug mill is used for
- Tempering
7. A typical kiln which is used for burning of tiles
accommodating about 30000 to 40000
- Sialkote kiln
8. Bricks containing relatively large proportion of
soluble salts are liable to become discolored by
the formation of whitish deposit, is known as
- Efflorescence
9. Bricks with crushing strength of 150kg/cm2 are
graded as - AA grade
10. During moulding of bricks, the mould are
dipped in water every time before filling the
clay, the bricks so prepared are called
- Slope moulded bricks
11. Over burnt bricks are
Fourth class brick
12. Minimum compressive strength for common
brick is - 35kg/cm2
13. Refractory bricks resist
- High temperature
14. Sand or silica in the earth used for brick
moulding helps - Prevent shrinkage
15. The average weight of standard brick is
3 to 3.5 kg.
16. The bricks contain cylindrical holes throughout
their thickness is called
- Perforated bricks
17. The bricks prepared by dipping mould in water
every time are known as
Slope moulded bricks
18. The bricks which can resist high temperature is
- Refractory bricks
19. The burning temperature of brick is
- 1100°C
20. The compound which prevent cracking,
shrinking and warping of raw brick is
- Silica
21. The compressive strength of a first class brick
should be - 140kg/cm2
22. The compressive strength of a perforated brick
should not be less than
- 70kg/cm2
23. The compressive strength of a paving brick
should be - 400kg/cm2
24. The constituent which gives plasticity of brick
earth is - Alumina
25. The daily average output of a Hoffman’s kiln is
....... number of bricks -25000
26. The frog of a brick is normally made on its
- Top face
27. The height of pug mill is
- 2m.
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28. The indention in the brick provide to form a key
for holding the mortar are known as
- Frog
29. The main ingredient of a good brick earth
is
- Alumina
30. The kiln which may work regularly throughout
the year - Hoffman’s kiln
31. The maximum water absorption of a first class
brick is..... when soaked in cold water for 24
hours - 20 %
32. The maximum water absorption of a second
class brick is..... when soaked in cold water for
24 hours
- 22 %
33. The process of mixing clay, water and other
ingredient to make brick is known as
Kneading
34. The minimum compressive strength of first
class bricks should be - 100Kg/cm2
35. The minimum compressive strength of second
class bricks should be
2
75Kg/cm
36. The most commonly used kiln in India
- Bull’s trench kiln
37. Specific gravity of good brick is
- 1.8 to 2
38. The mould for bricks are made longer by about
...... in all directions for compensating for
shrinking
- 8 to 12%
39. The percentage of alumina in good brick earth
is
- 20 to 30%
40. The percentage of silica in good brick earth is
- 50 to 60%
41. The percentage of silica content in silica brick is
about - 95 to 97%
42. The red colour obtained for the brick is due to
the presence of - Iron oxide
43. The silica brick can stand a high temperature up
to about -2000°C
44. The size of mould for bricks is generally kept
longer by about ...... percent in all directions
- 8 to 12
45. The water absorption of a perforated brick after
immersing for 24 hours in water should not
exceed ......... by weight - 15%
46. Fire clay is otherwise known as
Refractory clay
47. The bricks are moulded to the shape of a gutter
is known as - Channel brick
48. Hollow bricks is otherwise known as
Cellular brick or Cavity brick
49. Standard size of a brick - 19cm x 9cm x 9cm
50. Nominal size of a brick
- 20cm x 10cm x 10cm
51. Wall thickness of hollow bricks about
- 20mm to 25mm
52. Which bricks are dried with the help of heat
received from sun after process of moulding is
- Unburnt or Sun-dried bricks
53. The process of grinding clay with water and
making it plastic is known as
- Pugging
54. Period for natural drying of moulded brick is
taken about - 7 to 10 days
55. While laying bricks in a wall frog of the brick
must be kept - Upwards
56. The natural drying of brick is also called
- Hack drying/Sun drying
57. The burning of bricks in kiln is complete with in
- 24 hours
58. The shape of bricks deformed due to rain water
falling on hot brick. this defect is known as
Chuffs
59. Bloating / Swelling of bricks is due to:
1. Presence of excess carbonaceous matter in
the clay
2. Presence of gas forming material in the clay
3. Bad or rapid burning
60. Usually depth of frog is
10mm to 20mm
61. Minimum thickness of steel mould for using
hand moulded brick is
- 6mm
62. The wire cut brick is obtained from
- Plastic clay machine
63. Pressed bricks are obtained from
- Dry clay machine
64. Types of continuous kilns are
1. Bull’s trench kiln
2. Hoffman’s kiln
3. Tunnel kiln
65. To improve the quality of bricks sometimes
sand is added to the powdered soil. The process
is known as
Blending
66. The process clay is exposed to atmosphere for
softening is known as
- Weathering
67. Which ingredients gives hardness to the brick
earth - Silica
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