engineering

1. MODERN BUILDING MATERIALS

2.  Decisions taken both in the design process of buildings and their
modernization should comply with basic requirements, such as: strength
and stability, resistance to dampness and water, resistance to fire, heat
insulation, sound insulation, durability, comforts and conveniences.
Building materials should not have harmful effects on human health
The aspects of utilization, safe storage and recycling possibilities are also
important.
In the case of insulating materials, not only heat requirements, but also
other than thermal ones are taken into consideration (including
appropriate mechanical properties, noise attenuation, vibration
resistance, non-flammability, moisture absorption), as well as
technological and economic conditions

11. In this step the soil is excavated in steps and then laid on leveled
ground.
Then the soil is cleaned of impurities such as vegetation matter,
stones or pebbles etc. After removing impurities it is exposed to
weather for few months.
This is called the process of weathering. After completion of
weathering process the soil is blended with other material to
prepare good brick earth.
Then the mixed soil is tempered by being thoroughly broken up,
watered and kneaded.The tempering is usually done in pug mill.

13. Bricks are moulded in many ways depending on the quality of the product to
be made. Generally the moulding is done in the following two ways
Hand moulding
Machine moulding
For hand moulding the tempered clay is forced in the mould in such a way that
it fills all the corners of the mould. Extra clay is removed either by wooden
strike or frame with wire. Mould is then lifted up and raw brick is left on
ground.
Machine moulding is used where large numbers of bricks are to be made.
Machines used for moulding is generally of two types.
Plastic clay machines
Dry clay machines

14. In plastic clay machine the clay in plastic state is forced to rectangular openings of a
size equal to the length and breadth of the bricks and are then cut into strips of
thickness of the brick with wires in frames.
In dry clay machines, dry clay is reduced to powder, filled dry into mould by the
machine and then are subjected to high pressure to form hard and well shaped bricks.

16. Drying
Drying is usually done by placing the bricks in sheds with open sides so as to ensure
free circulation of air and protection from bad weather and rains.
The bricks are allowed to dry till they are left with 5 to 7 percent moisture content.
The drying period usually varies from 7 to 14days.
The moulded bricks are dried because of the following reasons.
If damp bricks or green bricks are directly taken to burning then, they are likely to
be cracked and distorted
To remove maximum moisture from the brick so as to save time and fuel during
burning
To increase the strength of raw bricks so that they can be handled and stacked in
greater heights in the kiln for burning without damage.

18. It is the very important step in manufacture of bricks. Bricks may be burnt by two
distinct methods given below.
Burning in a clamp or Pazawah known as clamp burning
Burning in a flame kiln or Bhatta known as kiln burning

19. Clamp burning
• A portion of the ground usually in trapezoidal shape is selected. The floor of the kiln
is made in such a way that the wider edge of the trapezoidal is raised at an angle of
15 degrees from the ground.
• After making the ground, the layer of fuel of about 70-80 cm thickness is placed.
The fuel consists of cow dunk, husk or rice, and grass, etc. More superior fuel like
wood and coal dust can also be used.
• A stack of brick containing 4 to 5 layers is placed over this fuel leaving small spaces
in between for the circulation of air.
• The second layer of fuel is placed over it and then another layer of brick is placed.
The total height of the clamp is about 3 to 5 meters.
• Either it is fired during the stacking process or after the completion of the stacking.
The top and sides of the kiln are then covered with mud to prevent the escape of
heat. Burning to take place for about 2 to 3 months and additional 2 to 3 months are
required for cooling the burnt bricks

21. This type of brick burning is superior to the burning in clamps. These types of brick
burning methods consist of a permanent structure.
Kiln is a large oven used for the burning of bricks. Generally coal and other locally
available materials like wood, cow dung etc can be used as fuel.They are of two types:
(a) Intermittent Kilns.
(b) Continuous Kilns.
Intermittent kiln
• In this type of kiln after loading raw bricks, it is fired, cooled, and unloaded. Only then
next set of bricks is again loaded and a similar process continues.
• They have a major disadvantage over continuous kiln that after unloading the bricks,
the kiln gets cooled.
• Thus have to be reheated again and in doing so there is a wastage of fuel.This type of
kiln is usually provided over ground and is rectangular in shape.These kilns are of two
types

22. Intermittent up drought kilns
Intermittent down drought kilns
Intermittent up drought kilns
• These kilns are rectangular in shape and consist of thick outer walls. Bricks are stacked in
rectangular shapes and some space is left between the stacks for the movement of flue
gases.
• In these kilns, flue gases move horizontally while in down drought kilns flue gases move
vertically towards the roof. Bricks are burnt for 48 to 60 hours during this time strong fire is
maintained.

23. Intermittent down drought kilns
• These kilns are more or less similar to the up-drought kilns and are rectangular or
circular in shape.
• They are also provided with permanent thick walls and roofs.
• The only difference is that flue gases are carried vertically up to the `roof and then
these gases move downward by the chimney drought and in doing so they burn
the bricks.

24. Continuous kiln
• Bull’s trench kiln and Hoffman’s kilns are examples of the continuous kiln.
• These types of kilns are divided into different chambers.The bricks are heated differently in
different chambers.
• When the brick in one chamber is fired, the bricks in the next chamber are dried and
preheated.
• Bricks in some chambers are loaded and in some chambers, it is cooled. So the brick burning
process is continuous and the kiln always remains heated
• When one chamber is heated the hot flue gases from this chamber moves to another
chamber and bricks placed on this chamber get preheated which will save the amount of
fuel for burning these bricks.
• Kiln burnt bricks yield about 80-90 % of the first-class bricks

25. Bull’sTrench Kiln
• Bull’s trench kiln consist of a rectangular, circular or oval plan shape. They are constructed
below the ground level by excavating a trench of the required width for the given capacity of
brick manufacturing
• This Trench is divided generally in 12 chambers so that 2 numbers of cycles of brick burning
can take place at the same time for the larger production of the bricks. Or it may happen that
one cycle is carried out at one time in all the 12 chambers by using a single process in the 2-3
chambers at the same time.
• The structure is under-ground so the heat is conserved to a large extent so it is more efficient.
• Once fire is started it constantly travels from one chamber to the other chamber, while other
operations like loading, unloading, cooling, burning and preheating taking place
simultaneously.
• Such kilns are generally constructed to have a manufacturing capacity of about 20,000 bricks
per day.
• The drawback of this kiln is that there is not a permanent roof, so it is not easy to manufacture
the bricks in the monsoon seasons

27. Hoffman’s kiln
• Hoffman’s kiln is an over the ground structure while Bull’s Trench Kiln is an
underground structure.
• Hoffman’s kiln have a permanent roof while Bull’s trench Kiln do not have
so it former can be used in 12 months a year to manufacture bricks but later
is stopped in the monsoon season.
• Hoffman’s kiln is generally circular in plan, and is constructed over the
ground.
• The whole structure is divided into the 12 chambers and all the processes
takes place simultaneously like in Bull’s trench Kiln.

33. First Class Bricks
These bricks are table moulded and burnt in kilns.
These are thoroughly burnt and are of deep red, cherry or copper colour.
The surface should be smooth and rectangular; parallel, sharp and straight edges and
square corner.
It should be free from flaws, cracks, and stones.
It should have a uniform texture.
No impression should be left on the brick when a scratch is made by a fingernail.
Fractured surface of the brick should not show lumps of lime.
Metallic ringing sound should come when two bricks are struck against each other.
On allowing immersed in cold water for 24 hours, water absorption should not be more
than 20% its dry weight.
Compressive strength >10.5 N/mm2.
Uses: First class bricks are recommended for pointing exposed face work in masonry
structure flooring and reinforced brickwork

39. Silica:
• It is about 50 to 60% of dry weight of bricks in provided plasticity to bricks for easy
moulded and cast their rectangular shape, it prevent from cracking shrinking and
warping of bricks and also provide durability and uniform shape to bricks.
Alumina :
• Alumina is about 20%- 30% of dry weight of red clay bricks and it absorb water and
provide plasticity to bricks such that it can be easily moulded in Desire shape and gain
rectangular shape. if alumina is present in excess quantity it causes cracks in bricks and
drying and become too hard when burnt.
Lime:
Lime is about less than 10% of dry weight of bricks. it provide withstand of particles of
bricks at high temperature about 1600 degree Celsius in hot furnace during melting.
and get It original rectangular shape. excess of lime causes bricks to melt and loses its
shape.

40. Iron Oxide:
• it is used about less than 7% of dry weight of bricks. it provide red colour to
brick on burning when excess of oxygen is available and dark brown or even
black colour when oxygen is insufficient amount available but excess of ferric
oxide make the bricks to change its colour dark blue and also ferric oxide give
it strength and hardness
Magnesia :-
it can be used less than 1% of dry weight of bricks .it can be used in small
quantity ,magnesia in brick impart yellow colour and also provide decrease in
shrinkage but excess of magnesia lead to decay of red bricks.

42. Various types of tests on bricks are conducted to check the qualities of bricks for
construction purposes.
Tests on bricks are conducted at construction site as well as in laboratory
To produce good quality of structure, good quality materials are required
Following tests are conducted on bricks to determine its suitability for construction work.
Absorption test
Crushing strength test
Hardness test
Shape and size
Color test
Soundness test
Structure of brick
Presence of soluble salts (Efflorescence Test)

43. Absorption test
• Absorption test is conducted on brick to find out the amount of moisture content absorbed
by brick under extreme conditions.
• In this test, sample dry bricks are taken and weighed. After weighing these bricks are placed
in water with full immersing for a period of 24 hours.
• Then weigh the wet brick and note down its value. The difference between dry and wet brick
weights will give the amount of water absorption.
• For a good quality brick the amount of water absorption should not exceed 20% of weight of
dry brick.

44. Crushing Strength or Compressive Strength
• Crushing strength of bricks is determined by placing brick in compression testing
machine.
• After placing the brick in compression testing machine, apply load on it until brick breaks.
Note down the value of failure load and find out the crushing strength value of brick.
Minimum crushing strength of brick is 3.50N/mm2.if it is less than 3.50 N/mm2, then it is
not useful for construction purpose.

45. HardnessTest
• A good brick should resist scratches against sharp things. So, for this test a sharp tool or
finger nail is used to make scratch on brick. If there is no scratch impression on brick
then it is said to be hard brick

46. Shape and SizeTest
Shape and size of bricks are very important consideration.
All bricks used for construction should be of same size.
The shape of bricks should be purely rectangular with sharp edges. Standard brick size consists
length x breadth x height as 19cm x 9cm x 9cm.
To perform this test, select 20 bricks randomly from brick group and stack them along its length ,
breadth and height and compare.
So, if all bricks similar size then they are qualified for construction work.

49. EfflorescenceTest
• A good quality brick should not contain any soluble salts in it. If soluble salts are there, then
it will cause efflorescence on brick surfaces.
• To know the presence of soluble salts in a brick, placed it in a water bath for 24 hours and
dry it in shade. After drying, observe the brick surface thoroughly.
• If there is any white or grey color deposits, then it contains soluble salts and not useful for
construction

50. Uses of DifferentTypes of Bricks
Bricks are widely used in construction industry for different purposes as following.
Good quality bricks (1st and 2nd class) are
 used in the construction of buildings, tunnels, pitching works etc.
3rd class and unburnt bricks are used for temporary structures.
4th class bricks are used as aggregate for making concrete.
Bricks are also used for architectural purposes to give aesthetic appearance to
the structure.