.

1. Building Construction Materials
Mr. K. R. Patil
Assistant Professor
Department of Civil Engineering
D. Y. Patil College of Engineering & Technology,
Kolhapur

2. 2. Bricks
• Clay bricks are commonly used as they are
cheap, readily available and easy to handle
and work with.
• Clay bricks are used for construction of
walls, partitions and other load bearing
structures.
• Bricks are prepared by moulding clay in
rectangular blocks of uniform size and then
drying and burning these blocks.
• Size of standard brick (modular brick)
should be 19 cm X 9 cm X 9 cm.
• Considering the mortar thickness; this
becomes 20 cm X 10 cm X 10 cm.
• An impression called frog is provided to
form a key for holding the mortar. The size
frog is usually 10 cm X 4 Cm X 1 cm.
• Generally, the bricks available in most parts
of the country are 9ˮ X 4½ˮ X 3” (230 mm
X 114 mm X 76 mm)

3. Constituents of good brick earth
In order to get a good quality brick, the brick earth should contain the
following constituents.
• Silica
• Alumina
• Lime
• Iron oxide
• Magnesia
1. Silica
• Brick earth should contain about 50 to 60 % of silica. It is
responsible for preventing cracking, shrinking and warping of raw
bricks. It also affects the durability of bricks.
2. Alumina
• Good brick earth should contain about 20% to 30% of alumina. It
is responsible for plasticity characteristic of earth, which is
important in moulding operation.

4. 3. Lime
• The percentage of lime should be in the range of 5% to 10% in
a good brick earth. It prevents shrinkage of bricks on drying. It
causes silica in clay to melt on burning and thus helps to bind
it.
4. Iron oxide
• A good brick earth should contain about 5% to 7% of iron
oxide. It gives red colour to the bricks. It improves
impermeability and durability. It gives strength and hardness.

5. Manufacturing of bricks
• In the process of manufacturing bricks, the following distinct
operations are involved.
1. Preparation of clay
2. Moulding
3. Drying
4. Burning
1) Preparation of clay
(a) Unsoiling: The top layer of the soil, about 200mm in depth, is
taken out and thrown away. The clay in top soil is full of impurities
and hence it is to be rejected for the purpose of preparing bricks.
(b) Digging: The clay is then dug out from the ground. It is spread
on the leveled ground, just a little deeper than the general level. The
height of heaps of clay is about 600mm to 1200mm.

6. ( c) Cleaning:
The clay as obtained in the process of digging should be cleaned of stones,
pebbles, vegetable matters.
(d) Weathering:
The clay is then exposed to atmosphere for softening and mellowing. The
period varies from few weeks to full season.
(e) Blending:
The clay is made loose and any ingredient to be added to it, is spread out
at its top.
The blending indicates intimate or harmonious mixing.
It is carried out by taking a small amount of clay every time and turning it
up and down in vertical direction.
The blending makes clay fit for the next stage of tempering.
(f) Tempering:
In the process of tempering, the clay is brought to a proper degree of
hardness and it is made fit for the next operation of moulding .
The clay is kneaded or pressed under the feet of man or cattle.
The tempering should be done exhaustively to obtain homogeneous mass
of clay of uniform character.

7. 2. Moulding:
The clay which is prepared as above is then sent for the text
operation of moulding.
Following are two types of moulding:
• Hand Moulding
• Machine Moulding
• Hand moulding:
• In hand moulding, the bricks are moulded by hand i.e.; manually.
It is adopted where manpower is cheap and is readily available for
the manufacturing process of bricks on a small scale.
• The moulds are rectangular boxes which are open at top and
bottom. They may be of wood or steel.
• The bricks prepared by hand moulding are of two types,
a) Ground moulded
b) Table moulded.

8. Ground moulded bricks:
• The ground is first made level and fine sand is sprinkled over it.
The mould is dipped in water and placed over the ground.
• The lump of tempered clay is taken and is dashed is the mould.
The clay is pressed in the mould in such a way that it fills all the
corners of mould.
• The surplus clay is removed by wooden strike or framed with
wire. A strike is a piece of wood or metal with a sharp edge.
• It is to be dipped in water every time. The mould is then lifted
up and raw brick left on the ground. The mould is dipped in
water and it is placed just near the previous brick to prepare
another brick.
• The process is repeated till the ground is covered with raw
bricks. The lower faces of ground moulded bricks are rough and
it is not possible to place frog on such bricks.
• The ground moulded bricks of better quality and with frogs on
their surface are made by using a pair of pallet boards and a
wooden block.

9. • A pallet is a piece of thin wood. The block is bigger than the
mould and it has projection of about 6mm height on its surface.
• The dimensions of projection correspond to internal dimensions
of mould. The design of impression or frog is made on this
block.
• The wooden block is also known as the moulding block or stock
board. The mould is placed to fit in the projection of wooden
block and clay is then dashed inside the mould.
• A pallet is placed on the top and the whole thing is then turn
upside down. The mould is taken out and placed over the raw
brick and it is conveyed to the drying sheds.
• The bricks are placed to stand on their longer sides in drying
sheds and pallet boards are brought back for using them again.
• As the bricks are laid on edge, they occupy less space and they
dry quicker and better.

10. • Table Moulded Bricks:
• The process of moulding of bricks is just similar as above. But
in this case, the mould stands near a table size 2m x 1m.
• The bricks are moulded on the table and send for further process
of drying.
• The cost of brick increases when table moulding is adopted.
2. Machine Moulding:
• This type of moulding is carried out by two processes: i) Plastic
clay machine ii) Dry clay machine.
• For drying, the bricks are laid longitudinally in the stacks of
width equal to two bricks. A stack consists of ten or eight tiers.
• The bricks are laid along and across the stock in alternate
layers. All the bricks are placed on edges.
• The bricks are allowed to dry until the bricks are become leather
hard of moisture content about 2%.

11. 3.Burning:
• Bricks are burned at high temperature to gain the strength,
durability, density and red color appearance.
• All the water is removed at the temperature of 650 degrees
but they are burnt at a temperature of about 1100 degrees
because the fusing of sand and lime takes place at this
temperature and chemical bonding takes between these
materials after the temperature is cooled down resulting in
the hard and dense mass.
• Bricks are not burnt above this temperature because it will
result in the melting of the bricks and will result in a
distorted shape and a very hard mass when cooled which
will not be workable while brickwork.
• Bricks can be burnt using the following methods:
(a) Clamp Burning
(b) Kiln Burning

12. • The Clamp is a temporary structure and it
can be constructed nearer to the
construction site.
• Approximately 20000 to 1 lakh bricks can
be burnt in a period of one to two months.
• Continuous demand for bricks cannot be
met with clamp burning.
• Small scale projects adopt clamp burning.
• The Time period of burning and cooling is
about 2 to 6 months.
• Greater than or equal to 60% good quality
bricks can be obtained from clamps.
• Low-cost fuels such as cow dung, grass,
etc. are used.
• Once the burning starts, fire is not under
control which sometimes may cause over-
burning of bricks.
• he heat generated is wasted in case of
clamp burning.
• Skilled supervision is not necessary.
Clamp Burning

13. • The Kiln is a permanent structure for
brick burning. The bricks should be
transported from kilns to the construction
sites.
• An average of 25000 bricks per day can
be burnt in a kiln.
• Continuous demand for bricks can be met.
• Large scale projects adopt kiln burning.
• The Time period of burning and cooling is
about 12 to 13 days.
• Greater than or equal to 90% good quality
bricks can be obtained from kilns.
• Costly fuel like coal dust is used as fuel
for burning.
• Fire can be controlled and the required
range of temperature can be adjusted.
• The heat generated during burning is used
to dry the raw bricks thereby reducing the
wastage of heat.
• It requires skilled supervision.
Kiln Burning

14. Classification of Bricks
Burnt bricks are classified into four categories on the basis of its manufacturing and
preparation, as given below,
1. First class bricks
2. Second class bricks
3. Third class bricks
4. Fourth class bricks
1. First Class Bricks:
• These bricks are table moulded and of standard shape and they are burnt in
kilns.
• The surface and edges of the bricks are sharp, square, smooth and straight.
• They comply with all the qualities of good bricks.
• Water absorption of these bricks ranges from 12 to 15 %.
• The crushing strength is not less than 10 N/mm2.
• These bricks are used for superior work of permanent nature.
2. Second Class Bricks:
• These bricks are ground moulded and they are burnt in kilns.
• The surface of these bricks is somewhat rough and shape is also slightly
irregular.
• These bricks may have hair cracks and their edges may not be sharp and
uniform.

15. • Water absorption of these bricks ranges from 16 to 20 %.
• The crushing strength is not less than 7 N/mm2.
• These bricks are commonly used at places where brick work is to be
provided with a coat of plaster.
3. Third Class Bricks:
• These bricks are ground moulded and they are burnt in clamps.
• These bricks are not hard and they have rough surfaces with irregular and
distorted edges.
• These bricks give dull sound when struck together.
• Water absorption of these bricks is about 25 %.
• They are used for unimportant and temporary structures and at places where
rainfall is not heavy.
4. Fourth Class Bricks:
• These are over burnt bricks with irregular shape and dark colour.
• These bricks are used as aggregate for concrete in foundations, floors, roads
etc, because of the fact that the over burnt bricks have a compact structure
and hence they are sometimes found to be stronger than even the first class
bricks.

16. Tests on Bricks
To know the quality of bricks following 7 tests can be performed.
In these tests some are performed in laboratory and the rest are on field.
• Compressive strength test
• Water Absorption test
• Efflorescence test
• Hardness test
• Size, Shape and Colour test
• Soundness test
• Structure test
1. Compressive strength test:
• This test is done to know the compressive strength of brick. It is also called crushing
strength of brick.
• Generally 6 specimens of bricks are tested in the laboratory.
• The bricks are immersed in water at room temperature for 24 hours.
• These are taken out of water and surplus water is wiped off with a moist cloth.
• The frogs are filled with cement mortar and the bricks are stored under damp cloth for
24 hours and then immersed in water for 3 days.
• The specimen is put in compression testing with mortar filled face upwards.
• Load is applied at a uniform rate of 14N/mm2 till it breaks.
• All six brick specimens are tested one by one and average result is taken as brick’s
compressive/crushing strength.

17. 2. Water Absorption test:
• In this test bricks are weighed in dry condition and let them immersed in fresh
water for 24 hours.
• After 24 hours of immersion those are taken out from water and wipe out extra
surface water with cloth.
• Then brick is weighed in wet condition. The difference between weights is the
water absorbed by brick.
• The percentage of water absorption is then calculated.
• The less water absorbed by brick the greater its quality.
• Good quality brick should not absorb more than 20% water of its own weight.
3. Efflorescence test:
• The presence of alkalies in bricks is harmful and they form a grey or white layer
on brick surface by absorbing moisture.
• To find out the presence of alkalis in bricks this test is performed.
• In this test a brick is immersed in fresh water for 24 hours and then it is taken out
from water and allowed to dry in shade.
• If the whitish layer is not visible on surface it proofs that absence of alkalis in
brick.
• If the whitish layer visible about 10% of brick surface then the presence of alkalis
is in acceptable range.
• If that is about 50% of surface then it is moderate.
• If the alkalies presence is over 50% then the brick is severely affected by alkalies.

18. 4. Hardness test:
• In this test a scratch is made on brick surface with a hard thing or nail of a finger.
• If that does not left any impression on brick then that is good quality brick.
5. Size, shape and colour test:
• In this test randomly collected 20 bricks are staked along lengthwise, width wise
and height wise and then those are measured to know the variation of sizes as per
standard.
• Bricks are closely viewed to check if its edges are sharp and straight and uniform
in shape.
• A good quality brick should have bright and uniform colour throughout.
6. Soundness test:
• In this test two bricks are held by both hands and struck with one another.
• If the bricks give clear metallic ringing sound and don’t break then those are
good quality bricks.
7. Structure test:
• In this test a brick is broken or a broken brick is collected and closely observed.
• If there are any flows, cracks or holes present on that broken face then that isn’t
good quality brick.

19. • Requirements of Good Bricks
• Size and Shape: The bricks should have uniform size and plane,
rectangular faces with parallel sides and sharp straight edges.
• Colour: The bricks should have uniform red colour indicating uniform
chemical composition and proper burning.
• Texture and Compactness: The surfaces of brick should not be too
smooth to cause slipping of mortar. The brick should have pre-compact
and uniform texture. A fractured surface should not show cracks, holes or
lumps of lime.
• Soundness: The brick should give a clear metallic ringing sound
when struck with hammer or another brick.
• Hardness: The brick should be so hard that when scratched by a finger
nail no impression is made. The brick should not break when dropped on
the ground on their flat face in a saturated condition from a height of 600
mm.
• Efflorescence: It should not be than 10% of the exposed area of the
brick.
• Water absorption: After immersion in cold water for 24 hours,
absorption by weight should not exceed 20 percent of the dry weight of
the brick.
• Compressive Strength: The crushing strength of the brick to be used in
all types of works should not be less than 35 N/mm2.

20. Autoclave Aerated Concrete (AAC)
Blocks
• Autoclaved Aerated Concrete is a lightweight, load-bearing, high-
insulating, durable building product, which is produced in a wide
range of sizes and strengths.
• AAC Blocks are lightweight and as compared to the red bricks, AAC
blocks are three times lighter.
• AAC is produced from the common materials lime, sand, cement and
water, and a small amount of rising agent.
• After mixing and moulding, it is then autoclaved under heat and
pressure to create its unique properties.
• AAC has excellent thermal insulation and acoustic absorption
properties.
• AAC is fire and pest resistant, and is economically and
environmentally superior to the more traditional structural building
materials such as concrete, wood, brick and stone.

21. • Properties of AAC blocks:
1. Faster Construction
• As the AAC block is very easy to handle, manipulate and use ordinary tools for
cutting the wood such as the drill, band saws, etc. could be easily used to cut and
align the AAC.
• Moreover, the AAC blocks come with larger sizes and fewer joints. This
ultimately results in faster construction work as the installation time is
significantly reduced due to fewer amounts of blocks and the masonry amount
involved is also lowered resulting into reduced time-to-finish.
2. Cost Saving
• AAC block weighs almost around 80% less as compared to the conventional red
brick ultimately resulting into great reduction of deadweight.
• Further, the reduced deadweight results into reduction of the use of cement and
steel which helps great in cost savings.
3. Lightweight
• One of the biggest features of AAC blocks is its light weight.
• These blocks possess a cellular structure created during manufacturing process.
• Millions of tiny air cells impart AAC blocks very light weight structure. Density
of these lightweight blocks usually ranges between 550 – 650 kg/m³ making them
lighter than water.

22. 4. High Compressive Strength
• The AAC blocks has an average compressive strength of (3-4.5) N/mm2.
• High Resistance to Water Penetration
• The AAC blocks, because of their cellular and discontinuous micro structure are
superior to the normal clay brick in resistance of water penetrability and thus the
external surface of AAC walls provides superior resistance to moisture penetration
than the traditional clay bricks.
5. Moisture Resistance
• Moisture from both external and internal sources can cause damage to buildings;
therefore, moisture protection is a primary consideration.
• External moisture sources include rain and water from the soil. Internal moisture,
usually in the form of humidity, can cause condensation on the surface of the walls as
well as condensation inside the wall itself.
• AAC has a very porous structure which is characterized by "macro" pores. Macro
pores are small air bubbles evenly distributed throughout the material. Therefore,
absorption of water into the AAC material is minimal.
6. Thermal Insulation
• AAC block has exceptional thermal insulating qualities. The thermal conductivity of
the AAC blocks helps maintaining the inner temperature to be warm during the
winters and cool during the summers which ultimately leads to savings in air
conditioning load and consequently enhanced energy efficiency.

23. 7. Sound Proof
• The porous structure of the AAC blocks results into enhanced sound absorption. The
Sound Transmission Class (STC) rating of the AAC blocks up to 45 db. Thus, AAC
blocks have been the most ideal material for the construction of walls in auditorium,
hotels, hospitals, studios, etc

24. Comparison between AAC Blocks and Clay
Bricks
Property Units AAC Block Clay Brick
Size mm 600 x 200 x (75 to 300) 230 x 75 x 115
Compressive
Strength
N/mm2 3 – 4.5 2.5 to 3.5
Normal Dry
Density
Kg/m3 550 – 650 1800
Sound Reduction
Index
Db 45 for 200 mm
Thick Wall
50 for 230 mm
Thick Wall
Fire Resistance Hrs 2 to 6
(Depending on Thickness)
2
Thermal
Conductivity “K”
W / m-k 0.16 – 0.18 0.81

25. Fly Ash Bricks
• Fly Ash bricks are made of fly ash, lime, gypsum and sand.
• These can be extensively used in all building constructional activities similar to that of
common burnt clay bricks.
• The fly ash bricks are comparatively lighter in weight and stronger than common clay
bricks.
• Since fly ash is being accumulated as waste material in large quantity near thermal power
plants and creating serious environmental pollution problems, its utilization as main raw
material in the manufacture of bricks will not only create ample opportunities for its
proper and useful disposal but also help in environmental pollution control to a greater
extent in the surrounding areas of power plants.
• In view of superior quality and eco-friendly nature, and government support the demand
for Fly Ash Bricks has picked up.
• Process of Manufacture:
• Fly ash, lime sand and gypsum are manually fed into a pan mixer where water is added in
the required proportion for intimate mixing.
• The proportion of the raw material is generally in the ratio 60-80% of fly ash 10-20%
lime, 10% Gypsum and 10% sand, depending upon the quality of raw materials.
• After mixing, the mixture is shifted to the hydraulic/mechanical presses.

26. • The bricks are carried on wooden pellets to the open area where they are dried and
water cured for 21 days. The bricks are tested and sorted before dispatch.
• Fly ash bricks are controlled by IS 12894-2002.
• Available sizes
• For Modular Size: Length 190± 4mm , Width 90±2 mm , Height 90±2 mm and 40±2
mm
• For Non-modular Size: Length 230± 4mm, Width 110±2 mm , Height 70±2 mm and
30±2 mm
• Merit of Fly Ash Brick:
1. Fly ash bricks are light weight, therefore, transportation is easy.
2. Fly ash bricks are uniform in shape and size in comparison to burnt clay brick,
therefore, require less mortar in brick work and finishing work resulting saving of
cement mortar.
3. As, fly ash brick are machine made, quality control is better in comparison to burnt
clay bricks.
4.Fly ash bricks are environment friendly. They use fly ash, which is a waste product of
thermal power plants having no value itself. Saves agricultural land which is used for
manufacturing clay bricks. Less energy intensive compared to clay bricks and help in
keeping clean environment.

27. • Demerit of Fly Ash Brick:
1. Mechanical bonding strength is weak. But this can be improved by adding
marble/ stone dust and cementing materials.
2. Limitation of size. Only modular size can be produced.
3. Air exchange is poor in comparison to normal clay bricks. Hence proper
ventilation of house is important.

28. Comparison of Clay brick and Fly ash Brick
Clay Brick Fly Ash Brick
Not in uniform colour as the colour of
brick depends upon type of soil and
quality control during production
The colour of fly ash brick is same as the
manufacturing is carried out using machinery
in controlled condition.
Clay brick are uneven in shape as the
mostly clay bricks are made manually.
Uniform in shape and smooth in finish as the
manufacturing is carried out using machinery
As the surface finish is not even, plastering
is necessary
As the surface is even and joints are thinner,
no plastering required in normal cases.
Clay bricks are heavier Fly ash brick are lighter as the main
composition is fly ash
Clay bricks are more porous Fly ash bricks are less porous
The cost of clay brick is higher than fly ash
brick
The cost of fly ash brick is approximate
30%lower than clay brick
Continuing use of clay bricks in
construction industry will lead to extensive
loss of fertile top soil. This could be a
devastating environmental hazard
This is made by using by-product of Thermal
Power Plant. Which save environment from
being polluted.

29. Manufacturing Process of Fly Ash Brick:
• Fly Ash Bricks are made bricks manufactured by hydraulic or
vibratory press.
• Raw material required are fly ash shall conform to Grade 1 or Grade
2 of IS 3812 (60-65%), Bottom ash used as replacement of shall not
have more than 12 percent loss on ignition when tested according IS
1727, lime shall conform to class C hydrated lime of IS 712(8-12%),
gypsum (5%), locally available sand/stone dust (18-27%) and water.
• Ordinary Portland Cement can also be used in place of hydrated lime
and gypsum.
• Raw materials in the required proportion are mixed in the pan mixer
to have a semi dry uniform mix.
• Semi dry mix is placed in the moulds of hydraulic/ vibro press.
Moulded bricks are air dried for one/two days in a shed depending
upon the weather conditions and then water curred for 14-21 days.
• The bricks thus produced are sound, compact and uniform in shape.