2. Clay is a finely-grained
natural rock or soil material
that combines one or more
clay minerals with possible
2
traces of quartz (SiO2), metal oxides (Al2O3 , MgO etc.)
and organic matter. Geologic clay deposits are mostly
composed of phyllosilicate minerals containing
variable amounts of water trapped in the mineral
structure.
Clay Products
3. 3
• Wet clay has a very high degree of plasticity due
to particle size and geometry as well as water
content and can be molded in desired shape.
• Free water is removed by drying but to remove
combined water the clay has to be heated to high
temperature and become hard, brittle and non–
plastic .
• Depending on the minerals content in which it is
found, clay can appear in various colors from
white to dull grey or brown to deep orange-red.
• At high temperature, different constituents
combine with each other chemically and new
products are formed.
4. • The new formed products are generally very
compact and hard.
• The main products which are commonly used in
engineering works are
• Bricks,
• tiles,
• terra-cotta,
• stoneware,
• porcelains etc.
4
7. • A brick is a regular sized rectangular unit or block of
clay material used in masonry construction, usually
laid using various kinds of mortar.
• are obtained by moulding clay in rectangular blocks
of uniform size and then by drying and burning
these blocks.
7
• As bricks are of uniform size,
they can be properly
arranged and they are light in
weight, hence it is used as
substitute for stone, where
stone is not available.
8. Building bricks should have sufficient strength in crushing,
regular in size, a proper absorption rate and a pleasing
appearance.
• Size and Shape:
should have uniform size and plane, rectangular surfaces with
parallel sides and sharp straight edges.
• Color:
The brick should have a uniform deep red or cherry color and care
should be taken while burning of the brick.
• Texture and Compactness:
The surfaces should not be too smooth
to cause slipping of mortar.
8
Characteristics of brick
9. • should have uniform texture.
• A fractured surface should not have split, holes
grits(pebbles) or swelling of lime.
• Hardness and Soundness:
The brick should be hard that when scratched by a
finger nail no impression is made.
9
10. 10
• When two bricks are struck together
a metallic sound should be produced
• Water Absorption
should not exceed 20 % of its dry weight
when kept immersed in water for 24 hours.
11. 11
• Crushing Strength should not be less than 10
N/ mm2.
• Brick Earth should be free from stones,
organic matter, etc.
• Brick should not break when it is let to fall
from the height of 1 meter .
16. Brick Sizes
• Bricks may be made in various sizes.
• But in all the cases, the length should be twice the width
plus the thickness of one vertical joint.
• NBC 230mm X 110mm X 55mm
• According to I.S. the size of the brick without the thickness
of mortar joint is 19 cm x 9 cm x 9 cm.
• Common Brick Dimensions
• In the United States, the typical bricks are (203 × 102 × 57
mm)
• Australia (230 x 110 x 76)mm.
16
17. Composition( ingredients)of Bricks
1. Alumina(clay):
• chief constituent of every kind of clay.
• A good brick earth should contain 20 - 30 % of alumina.
• Provides plasticity to earth so that it can be molded.
• If it exceed, raw bricks shrink and warp during drying and
burning.
2. Silica(sand):
• A good brick earth should contain about 50 - 60% of silica.
• Imparts the qualities of Hardness and strength, Resistance
against cracker, shrinking and warping of raw bricks and
thus gives uniform shape to the bricks.
• Excess of silica destroys the cohesion(porous) between
particles and bricks become brittle.
• Durability depends on the proportion of silica in bricks 17
19. 3.Lime
• Burning of bricks quicker
• A small quantity of lime is desirable in finely powdered
state to prevents shrinkage of raw bricks.
• Excess of lime causes the brick to melt and hence, its
shape is lost due to the splitting of bricks.
4.Oxide of iron:
• A small quantity of oxide of Iron to the extent of 4 to 6 % is
desirable in good brick to imparts red colour to bricks.
• Excess of oxide of iron makes the bricks dark blue or
blackish.
5.Magnesia - A small quantity of magnesia in brick earth
imparts yellow color to bricks and decreases shrinkage.
• But excess of magnesia leads to the decay of bricks.
19
20. 4. Oxide of iron:
• It helps as lime to fuse sand.
• It also impart red colour to the bricks.
• The excess of oxide of iron makes brick dark blue or blackish.
• If the quantity of iron oxide is comparatively less, the bricks will be
yellowish in colour.
5. Magnesia:
• A small quantity of magnesia in brick earth imparts yellow colour
to the bricks and decreases shrinkage.
• But excess of magnesia leads to the decay of bricks.
20
23. Comparison of Stone Work and Brick Work:
I. Stone is much more strong, durable and weather resisting than brick.
2. stone is used in the constructions, subjected to more severe and exact
conditions. Under such conditions brick construction may not last
long.
3.Stone work is generally not plastered to preserve the natural color .
But brick masonry is generally plastered to conceal the defects of the
bricks.
4. Bricks, may disintegrate and thus may affect the life and appearances
of the brick work . Stone is not easily affected by such conditions.
5. Brick is a very good fire resistant material in comparison with stone.
6. Bricks absorb more water than stones and this moisture can easily
reach inside the brick work
7. Brick masonry is easy to raise where as stone masonry can be done
by skilled masons only.
23
24. 9. Bricks being in regular shape and size, can be used in definite pattern
known as ' bond', Stone masonry does not require any definite
pattern.
10. Progress of brick masonry is always more than that of stone
masonry.
11. Bricks do not require any dressing but stone masonry involves lot of
dressing. '
12. Bricks can be moulded in any shape or size as per requirements, but
dressing or shaping of is not that easy,
13. Bricks being small, do not require any lifting device as in stone.
14. Brick work requires very little mortar.
15 . Brick work does not create the feeling of massiveness, in
Comparison to stone work.
16. In case of monumental structures, stone work is more useful than
brick work.
17. Brick walls as thin as 10 cm can be constructed, but thickness of
stone masonry is generally not less the 38 cm.
18. Good railway counterbalance can be obtained from stone only.
19. Good aggregate for concrete and road construction also can be had
from stone only. 24
26. Bricks can broadly be divided into two categories.
(i) Un burnt or Sun dried bricks-
• Un burn or sun dried with the help of heat received
from sun after the process of molding.
• These bricks can only be used in the constructions
of temporary and cheap structures.
• Such bricks should not be used at places exposed to
heavy rains.
26
27. 27
(ii) Burnt Bricks:
The bricks used in construction works are
burnt bricks and they are classified into the
following four categories.
28. BURNT BRICK
A. First Class bricks
• The surface and edges of the bricks are sharp,
square, smooth and straight.
• used for superior work of permanent nature.
• First class bricks are identified by their uniform
color and a ringing sound when struck.
• These bricks do not have any cracks.
• First class bricks do not absorb water more than
20% of their weight while kept immersed in cold
water for 24 hrs.
28
29. B. Second class bricks
• The surface of bricks is some what rough and shape is also
slightly irregular.
• These bricks are commonly used at places where brick
work is to be provided with a coat of plaster.
• These bricks should not be used for load bearing walls for
more than two storey buildings.
• These bricks do not absorb water more than 22% of their
weight while kept immersed in cold water for 24 hrs.
29
30. C. Third class bricks
• These bricks are usually under burnt, soft and light
in color.
• These bricks give dull sound when struck together.
• Have rough surfaces with irregular and distorted
edges.
• It should not absorb water more than 25%. of its
own weight when kept immersed in water for 24
hrs..
• They may suffer from serious efflorescence.
• used in temporary structure
30
31. D. Fourth(Over burnt)class bricks
• These are over burnt bricks with irregular shape
and dark color.
• These bricks are used for making aggregate for
concrete in foundation, floors, roads, etc and at
places where rainfall is not heavy.
• They are not used in construction works.
31
33. Qualities of Good Brick
(i) Bricks should be table molded, well burnt in kilns,
copper colored, free from cracks and with sharp and
square edges.
(ii) should be uniform shape and should be of standard
size.
(iii)should give clear ringing sound when struck each
other.
(iv) when broken should show a bright homogeneous and
compact structure free from voids.
(v) should not absorb water more than 20% by weight for
first class bricks and 22 % by weight for second class
bricks, when soaked in cold water for a period of 24
hours. 33
34. vi) should be sufficiently hard, no impression should be
left on brick surface, when it is scratched with finger
nail.
(vii) Bricks should be low thermal conductivity and they
should be sound proof.
(viii) should not break when dropped flat on hard ground
from a height of about one meter.
(ix) when soaked in water for 24hours, should not show
deposits of white salts when allowed to dry in shade.
34
36. Tests for bricks :
1) Absorption: A good should not absorb not more than
20 % of weight of dry brick
2) Compressive strength: Minimum crushing strength of
brick is 35kg/cm2 and for superior bricks, it may vary
from 70 to 140 kg/cm2.
3) Hardness: No impression is left on the surface the brick
is treated to be sufficiently hard.
4) Presence of soluble salts: The bricks should not show
any grey or white deposits after immersed in water for
24 hours.
5) Shape and size: It should be standard size and shape
with sharp edges
6) Soundness: The brick should give clear ringing sound
struck each other
7) Structure: The structure should be homogeneous,
compact and free from any defects.
36
37. Manufacture of bricks
The manufacturing of brick, the following
operations are involved
1. Preparation of clay
2. Molding
3. Drying
4. Burning
37
38. Manufacture of bricks
38
Preparation
of clay
Moulding Drying Burning
Unsoiling
Digging
Cleaning
Tempering
Weathering
Blending
Hand Moulding
Ground Moulding
Table Moulding `
Machine Moulding
OR
OR
Natural Drying
Artificial Drying
OR
Kiln
Burning
Clamp
Burning
OR
39. 39
(1) Preparation of clay
a) Unsoiling :-
Top layer of 20cm depth is removed as it contain
impurities.
b) Digging: -
Clay dug out from ground is spread on level ground
about 60cm to 120cm.
40. 40
c) Cleaning:-
Stones, pebbles, vegetable matter etc.
removed and converted into
powder form.
d) Weathering:-
Clay is exposed to atmosphere from few weeks to full
season.
41. e) Blending:-
Clay is made loose and any ingredient to be added is
spread out at top and turning it up and down in vertical
direction.
f) Tempering:-
Clay is brought to a proper degree of hardness, then water is
added to clay and whole mass is kneaded or pressed under
the feet of men or cattle for large scale
41
42. (2) Moulding
• Hand Moulding :
i. Moulds are rectangular boxes of wood or
steel, which are open at top and bottom.
ii. Steel moulds are more durable and used for
manufacturing bricks on large scale.
iii. Bricks prepared by hand molding are of two
types.
• Wooden mould & Steel mould
a) Ground moulded bricks
b) Table moulded bricks
42
45. 45
(a) Ground moulded bricks:
• Ground is first made level and fine sand is sprinkled over it.
• Mould is dipped in water and placed over the ground to fill the
clay.
• Ground moulded bricks of better quality
46. (b) Table-moulded bricks: Process of moulding of
these bricks is just similar to ground bricks on a
table of size about 2m x 1m.
46
51. 3)Drying
• The damp bricks, if burnt are likely to be
cracked and distorted.
• Hence moulded bricks are dried before they
are taken for the next operation of burning.
51
52. (i) Artificial drying – drying by tunnels about 1 to 3 days
(ii) Circulation of air- Stacks are arranged in such a way that
sufficient air space is left between them free circulation of air.
(iii) Period for drying – usually about 3 to 10 days to bricks to
become dry
(iv) Screens – screens are necessary, may be provided to avoid
direct exposure to wind or sun.
52
55. (4) Burning
• This is very important operation in the
manufacturing of bricks to impart hardness,
strength and makes them dense and durable.
• Burning of bricks is done either in clamps or in
kilns.
• Clamps are temporary structures and they are
adopted to manufacture bricks on small scale.
• Kilns are permanent structures and they are
adopted to manufacture bricks on a large scale.
55
68. DEFECTS OF BRICKS:
• Over-burning of Bricks:
• Under-burning of Bricks:
• Bloating: This defect observed
as spongy swollen mass over the
surface of burned bricks is
caused due to the presence of
excess carbonaceous matter and
sulfur in brick-clay. 68
69. • Black Core: the brick results in
black core mainly because of
improper burning. Bricks, which
contains bituminous matter or
carbon and they are not completely
removed by oxidation, will
commonly experience such
problem.
69
• Efflorescence: This defect is caused because of alkalies present
in bricks.
70. • Chuffs: The deformation of the
shape of bricks caused by rain water
falling on hot bricks is known as
chuffs.
• Checks Or Cracks: this defects
may be because of swelling of lime
or excess of water.
70
https://theconstructor.org/building/defects-bricks-identification/6941/
71. Lime stone:
• excess lime present in the bricks forms stone or kankar and
get converted into quick lime.
• Quick lime absorbs moisture and swells that causes the
cracks, crumble to pieces.
Alkalies:
• Presence of alkalies lower the fusion point of clays and
causes the bricks twist and warp during burning
• Causes efflorescence after evaporation of moisture from
the brick structures
Iron Pyrites:
• Due to the presence of iron pyrite ,disintegrated during
burning
72
72. Pebbles:
• Pebbles or grits is undesirable in brick earth because it will
not allow the clay to be mixed uniformly and thoroughly
which will result in weak and porous bricks.
• reduces the workability and homogeneity of brick earth.
Organic vegetation:
• The presence of vegetation and organic matter in brick
earth assists in burning.
• This is due to the fact that the gases will be evolved during
the burning of the carbonaceous matter and resulting in
the formation of the pores.
73
73. Tiles
• Tiles are clay product, used mainly for roof covering
and paving.
• They are manufactures from superior type of clay.
• being thinner than bricks, they should be carefully
handled to avoid any damage.
74
74. Classified in following two groups
I. Common tiles.
These tiles are of different shapes and sizes and
are mainly used for flooring, paving and roofing.
75
75. 2. Encaustic TiIes
These tiles are used for decorative purposes in
floors , walls, roofs ceilings.
Pigments are mixed to give pleasant appearance
76
76. Manufacture of Tiles
• Manufacture of tiles can be
carried out in following four
operations:
1. Preparation of clay.
2. Moulding of tiles.
3. Drying of tiles and
4. Burning of tiles.
77
77. Properties of Good tiles
• Tiles should be true to shape and size.
• They should possess uniform color.
• Fractured surfaces should show the compact and even
structure.
• It should be free from warps, cracks etc.
• It should be strong, hard, sound and durable.
• It should be well burnt.
• Thickness (minimum) of machine made tiles should be
10 mm and hand mould tiles 12 to 15mm.
78
80. Types of Tiles
• Depending upon their use.
I. Drain tiles.
2. Floor tiles.
3. Roofing tiles.
4. Wall tiles
5. Glazed earthenware tiles
81
81. 82
1. Drain tiles
These tiles may be circular, semi-circular or segmental.
They are used for covering irrigation water, or for
discharging surface rain water out of cities.
82. 2. Floor tiles
• They are manufactured in a variety of sizes, shapes
and colors square, polygonal etc.
• They are flat tiles. Thickness of these tiles varies
from 12 mm to about 50 mm.
• Size of the tiles may be 15cmx 15cm to as much as
30 cm x 30cm.
• The top surface of the tiles used in water closets,
bath rooms, kitchens etc . should be glazed,
• They may be vitrified(like glass) to prevent water
absorption.
83
84. 3. Roofing tiles
• These tiles are made for pitched roofs to act as
a covering material.
• There are so many types of tiles available in the
market.
• Some important varieties have been given here.
85
88. 4. Wall tiles
• Similar to floor tiles except for their design and
degree of burning
• Burned at low temperature
• Can be built in any size
• Used in face works, arches, architectural ceilings
89
89. 5. Glazed tiles
-Tiles are of earthenware having top surface glazed
and underside unglazed
-Two sizes: 149mm x 149mm and 99mm x 99mm
having thickness 5mm, 6mm,7mm
-The joint thickness is 1mm
-Used: kitchen, hospitals, water closets, bathrooms, etc
90
90. Earthen Ware
• The term is used to indicate the wares, prepared from brick
earth or clays, which have been burnt at comparatively low
temperature and cooled down slowly.
• They are usually unglazed but can be glazed and enameled
so that it is not affected by acids and atmospheric
agencies.
• Terracotta is also a kind of earthenware.
• Used for making ordinary drain pipes, cheap lavatory
(toilet)fittings etc.
91
94. Glazing
• The process of covering the earthen ware, stone ware and
porcelain products with an impervious film a glossy coat of
about 0.1 to 0.2 mm thickness, applied on the surface
• It is done to protect from the action of sewage, acids,
atmosphere and other destructive agents
• To give decorative finish and make durable
• There are two methods of glazing
i) Salt glazing
ii) Opaque glazing
95
95. i) Salt glazing
-Done by throwing common salt (sodium chloride) in
the kiln at the close of burning operation.
-Temperature about 1200 – 1300 o C the salt gets
vaporized and the vapors spread over the entire
surface of the articles being burnt.
-A thin layer of sodium silicate or glaze is formed.
-The color of articles is brownish.
-Not practicable in case of inferior type of clay
96
96. ii) Opaque glazing
• It improves the appearance and durability of the burnt
article
• Superior clay is finely powdered and dried and sufficient
water is added to make this clay plastic cream like mass
called slip
• The articles are dipped in slip
• Opaque glazed surface is obtained after burning
97
