Bricks are artificial stones made from clay that harden when heated to high temperatures. The quality of bricks depends on the clay composition and manufacturing process. Good brick clay contains silica, alumina, iron oxide, magnesia, lime, and organic matter in specific percentages. The constituents impact properties like plasticity, density, color, shrinkage, and fusion. Bricks are tested based on hardness, strength, water absorption, and efflorescence. Standard bricks measure 9.5x4.5x2.75 inches and are classified by quality and use in construction.

1. Chapter-3
Bricks
1

2. Definition:
 A brick is an artificial kind of stone made of clay
whose chief characteristics are a plasticity when
wet and stone like hardness after being heated to
high temperature.
2

3. Factors that affect the quality of Bricks:
 Chemical properties of the clay used
 Preparation of the clay
 Process of drying
 Different degrees of burning
3

4. Constituents of Brick clay and their functions:
 A good brick-clay should be such a mixture of pure clay
and sand that when prepared with water, it can easily be
moulded and dried without cracking or warping.
 Chemical analysis of a good brick-clay should give the
following percentage of chemical composition:
Silica 55%
Alumina 30%
Iron oxide 8%
Magnesia 5%
Lime 1%
Organic matters 1%
---------------
100%
4

5. Silica:
 Silica exists in all clays in a state of chemical
combination with alumina forming silicate of
alumina and some times exists in a free state when it
is called sand.
 The presence of sand prevents cracking, shrinking
and warping.
 The higher the proportion of sand, the more shapely
and uniform in texture shall be the brick.
 But too much of sand makes the brick brittle and
weak. 5

6. Alumina (Aluminum oxide):
 This is the principal constituent of brick clay. It
imparts plasticity to clay which is very essential
for the purpose of moulding.
 It also imparts density.
 But the clay containing too much alumina should
not be used because bricks will crack and warp
during drying.
6

7. Iron oxide
 The presence of iron oxide in clay enhances the
impermeable and durable qualities.
 Iron and lime in small quantities give creamy color
to bricks.
 The color of bricks is very much dependent upon
the contents of iron and the color ranges from light
yellow to orange and red.
7

8. Magnesia (Magnesium oxide)
 Presence of magnesia in small quantity decreases
shrinkage and gives yellow tint.
8

9. Lime
 It reduces shrinkage of bricks during drying and
enables the silica to melt in burning and thus
binds the particles of brick together.
 In excess, however, it will cause the brick to fuse
too readily and the shape will be lost.
9

10. Alkalies and Organic matter:
 A small quantity of organic matter will assist
burning bricks.
 Excess is bad, because if it is not completely burnt,
the bricks will be porous.
 Small quantity of alkalies will lower the fusion
point of clay.
10

11. Harmful constituents of Brick-clay
11

12. Iron Pyrites:
 Presence of pyrites causes crystallization and
disintegration of bricks on burning.
12

13. Alkalies:
 They are mainly the chlorides and sulphates of
calcium, magnesium, sodium and potassium. They
produce a dark greenish hue on the surface of
bricks on drying. They cause the bricks to fuse,
twist and warp during burning. Alkalies in bricks
absorb moisture from atmosphere and on drying
cause efflorescence.
13

14.  Efflorescence – If soluble salts are present in
bricks they absorb moisture from atmosphere and
go into solution which appears on the surface in the
form of whitish substance as the moisture dries out
and the salt crystallize.
14

15. Stone particles:
 Small particles of stones do not allow the clay to
be mixed thoroughly and uniformly. These are
harmful to the uniformity of brick texture. These
make bricks porous and weak.
15

16. Vegetation and Organic matter:
 They make the bricks porous and weak because
vegetations and organic matter get burnt during
the burning of bricks leaving small pores in them.
16

17. Lime:
 If Lime present in excess amount causes the brick
to fuse too readily and the shape is lost. Lime in
the form of limestone is very harmful and cause
serious troubles to bricks such as it causes the
bricks to split and crumble to pieces and
deteriorates the quality of a good brick.
17

18. Manufacturing of Bricks:
Different steps are as follows:
 Selection of brick clay
 Preparation of brick clay
 Brick moulding
 Machine moulding
 Brick drying
 Brick burning
18

19. Characteristics of good bricks:
 Bricks should be uniform in color, size and shape.
 They should be sound, hard, well burnt and
compact.
 They should be free from cracks and other flaws
such as air bubbles, stone nodules, holes, grit of lime
etc.
 They should not absorb more than 1/5 of their own
weight of water when immerged in water for 24
hours (15 to 20% dry weight).
 The compressive strength of bricks should be in the
range of 5000 to 8000 psi.
19

20.  The percentage of soluble salts (sulphates of
calcium, magnesium, sodium and potassium)
should not exceed 2.5% in burnt bricks, because
the presence of excess soluble salt causes
efflorescence.
 They should be neither over burnt nor under
burnt.
 Their weight should be generally 6 lbs per brick
and the weight per cu ft should not be less than
125 lbs.
20

21.  They should have low thermal conductivity as it
is desirable that the buildings built of them
should be cool in summer and warm in winter.
 They should be non-inflammable and
incombustible.
 Bricks should not change in volume when
wetted.
21

22. Field tests of bricks
To determine the quality of good bricks:
 Take a brick and try to make mark on the surface
by nail. If you can make it, it is not a good brick.
If not, it is very hard and compact.
22

23.  Take a brick and strike it with a hammer, if it gives
clear ringing or metallic sound, it is a good brick.
 Take two bricks and form a tee (T) and drop from a
height of 6ft on a more or less solid surface. If they
break, they are not good bricks. If they remain
unbroken, they are good bricks
23
Field tests of bricks

24. 24

25. 25

26. Size of Bricks:
 According to P.W.D specification the standard size
of bricks in our country is 9.5” X 4.5” X 2.75”. This
size is most economical.
 With mortar, the final size becomes
10" × 5" × 3".
 The sizes of the walls which are constructed in
Bangladesh are 3", 5", 10", 15", 20", 25" and 30".
 By using, standard size bricks, these sizes of walls
can be built very easily without any breaking of the
bricks.
26

27. Classification of Bricks:
The following is the classification of bricks by P.W.D. in our country.
1. First Class Bricks
2. Second Class Bricks
3. Third Class Bricks
4. First Class Bats
5. Second Class Bats
6. Picked Jhama Bricks
7. Jhama Bricks
8. Jhama Bats
27

28. First Class Bricks
o Uniform size and color
o Well and uniformly burnt
o Emit metallic sound when struck with a hammer
or another brick
o No cracks, rain spots, or flaws on the surface
o Not absorb one sixth of their weight of water
when kept under water for 24 hours
28

29. Second Class Bricks
o These bricks must possess the hardness and
color of first class bricks but are slightly irregular
in shape, size or rough on the surface.
29

30. Third Class Bricks
o Not sufficient burnt
o Uniform shape and size
o Can be used for un-important construction
30

31. First Class Bats
Broken pieces of first and second class
bricks.
Second Class Bats
Broken pieces of the third class bricks
Picked Jhama Bricks
o Uniform vitrified throughout
o Good shape, heavy, selected quality
o Not spongy
31

32. Jhama Bats
Broken pieces of the classes picked jhama and jhama bricks
Special Bricks
(a) Perforated Brick
 For lightweight structure and multistoried framed structures,
perforation may be rectangular, circular, square, or any other regular
shape in cross-section.
 Use in building walls.
b) Hollow Bricks
 Also known as the cellular or cavity bricks. They are light in weight.
They reduce the transmission of heat, sound, and dampness.
 Use in hollow walls in building.
(c) Checkered Bricks
 Less slippery, used for garden walks, street pavements, etc.
 Use in brick masonry.
(d) Stable Bricks
(e) Plinth Bricks
(f) Jamb Bricks
(g) Klinker
32

33.  Different Type of Bricks
33

34. Uses of Brick:
 Construction of walls of any size.
 Construction of floors.
 Construction of arches and cornices.
 Making khoa (broken bricks of required size) to
use as an aggregate in concrete.
 Manufacture of surki (powdered bricks) to be
used in lime plaster and lime concrete.
34

35. 35

36. 36