Clay is a key ingredient in making structural clay products like bricks. It consists mainly of kaolinite along with other minerals. Good brick earth contains 20-30% alumina, 50-60% silica, and small amounts of lime, iron oxide, and magnesia. Harmful ingredients to avoid include alkalis, limestone, iron pyrites, pebbles, and organic matter. Bricks are manufactured by preparing the earth, moulding, drying, and burning in kilns. Common brick bonds used in construction include stretcher bond, header bond, English bond, and Flemish bond.

1. STUCTURAL CLAY
PRODUCTS:
 MADE BY:
 SHWETABH SINHA
 AMBUJ SHANDILYA
 ANAND ABHISHEK
 SALON SUNJOH

2. Clay and its classification:
1.Clay is generally earthen mineral or fragmentory rock
capable of mixing with water and farming.
2.After geting heated it forms get’s reddish and then aquire
hardness and strength.
3.Purest clay consists mainly of kaolinite (2Sio2Al203.2H2O)
with small quantities of mineral such as quartz,mica ,
felspar,calcite etc..
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3. COMPOSITION OF GOOD BRICKS EARTH
HARMFULL INGREDIENTS IN BRICK EARTH
MANUFACTURE OF BRICKS
KILNS

4. Alumina:
 A good brick earth should contain 20–30
per cent of alumina.
 It imparts the property of plasticity to the
earth.
 An excess of alumina causes shrinkage and
warping of bricks during drying and
burning and it becomes too hard when burnt.
COMPOSITIONOF GOODBRICKS EARTH

5. Silica:
Silica forms 50–60 per cent of good brick
earth.
 It is seen either in the free or combined state.
 In the free state, it is mechanically mixed with clay and in
the combined form it exists in a chemical composition
with alumina.
 The cracking, shrinking and warping of raw bricks are
being prevented by the presence of silica.
 The durability of bricks depends upon the proportion of
silica.
 An excess of silica destroys the cohesion between
particles and the bricks become brittle.

6. lime
• A small quantity of lime not exceeding 5% is
desirable in good brick .lime prevents shrinkage of
raw brick.
• the sand is infusible .but is slightly fuses at kiln
temperature in presence of lime .the excess of lime
cause the brick to melt and hence its shape is lost.
• the lumps of lime are converted into quick lime
after burning this quick lime slakes and expand in
presence of moisture such an action results in
splitting of brick into pieces

7. OXIED OF IRON
• A small quantity of oxide of iron
to the extent of about 5 to 6% is
desirable in good bricks earth.
• It helps as lime to fuse sand .it
also imparts red colour to bricks.
• the excess of oxide of iron
makes the brick comparatively less,
the brick will be yellowish in colour

8. MAGNESIA
 A small quantity of magnesia in brick earth
imparts yellow tint to the bricks and decreases
shrinkage.
 But excess of mangnesia leads to the decay of
bricks.

9.  ALKALIS:
Alkalis present in the brick earth lower the fusion
temperature abnormally making the brick deform and
twist. In addition, alkalis have hygroscopic properties.
 They absorb water from atmosphere and make the
walls damp resulting into unhealthy atmosphere and
weaker structure.

10. LIME :
 If these are present, as explained earlier, on
heating get converted into quick lime.
 This quick lime in the presence of water is highly
brittle and the brick crumbles.
IRON PYRITES
 If iron pyrites are present in bricks earth ,the
bricks are crystallized and disintegrated during
burning because of the oxidation of the iron pyrites.
HARMFULL INGREDIENTS IN BRICK
EARTH :

11. PEBBLES
 In the presence of these, there is hindrance in
molding the brick.
 In addition, the bricks cannot be cut to the required
size, if needed, while erecting the wall.

12.  VEGETATION AND ORGANIC MATTER:
 Organic matters like roots, leaves etc. burn while
the brick is burnt producing CO2.
 This Carbon dioxide creates porosity in bricks
affecting the strength of bricks.
 Hence, organic matter should be avoided in brick-
earth.

13. MANUFACTURING OF BRICKS

14. MANUFACTURING OF BRICKS
 Preparation of brick earth
 Moulding of bricks
 Drying of bricks
 Burning of bricks

15. PREPARATION OF BRICK EARTH
Removal of loose soil
The top layer of the loose soil about 30 cm depth contains a lot of impurities
like organic matter and hence it should be taken out and thrown away.
Digging, spreading and cleaning
The earth is then dug out from the ground. This earth is spread into heaps
about 50 to 150 cm height.
Weathering
The earth is then exposed to atmosphere for softening. The period may be Of
few weeks to a season.
Blending and tempering
The clay is then mixed with suitable ingredients . It is carried out by taking a
small portion of clay every time and by turning it up and down in vertical
direction

16. MATERIAL PREPARATION

17. MOULDING
Hand moulding
When moulding is done with hand it is called hand moulding.
A wooden rectangular mould made in the shape of a brick is normally used for this purpose.
Machine moulding
The clay is placed in the machine, it comes out through the opening under
pressure.
It is cut to bricks by steel wires fixed into frames.
These bricks are also called wire cut bricks.

18. Manufacturing
( HAND MOULDING)

19. Manufacturing
( MACHINE MOULDING)

20. DRYING OF BRICKS
Wet brick from molding or cutting machines contain 7 to 30 percent moisture, depending upon
the
forming method.
Before the firing process begins, most of this water is evaporated in dryer chambers at
temperatures ranging from about 100 ºF to 400 ºF (38 ºC to 204 ºC).
The extent of drying time, which varies with different clays, usually is between 24 to 48 hours.
Heat and humidity must be carefully regulated to avoid cracking in the brick.

21. After Mining, Clay is Extruded Through a Die and Trimmed to Specified
Dimension Before Firing

22. BURNING OF BRICKS
INTERMITTENT KILN - CLAMP , SCOVE & SCOTCH
Highly inefficient & labor-intensive.
Use coal + scavenged fuels
Most common, most primitive, most polluting
Temporary Structures
A typical scove kiln.
A typical clamp kiln.
A typical scotch kiln.

23. CONTINOUS KILN BURNING – HOFFMAN, BULL’S TRENCH,
VERTICAL SHAFT & HABLA
These are permanent structures.
Burning is done continuously in kilns.
Bricks from kilns are of correct size, perfect shape and good quality.
Rate of burning is also high in kilns.
But initial investment for kiln is very high.
Efficient and potentially clean –
Hybrid Hoffman
VSBK
Habla
Tunnel (modern – several variations)

24. HOFFMANN KILN – ORIGINAL

25. HOFFMANN KILN – MODERN & HYBRID
• Widely used in China
= 90% of bricks
• Can use coal or
natural gas

26. BULL’S TRENCH KILN
Used in India, Pakistan,Nepal, Bangladesh
Uses coal and scavenged fuels
“Movable chimney” (MC) and “Fixed” Fixed (FC)
MCBTK banned (but still used) in India, parts of
Nepal & Pakistan due to very high emissions
KILN with
Movable chimney

27. KILN with
Fixed Chimney

28. HABLA ZIGZAG KILN
Effective tunnel length of Hoffmann increased
with “zigzags” made of green bricks
Larger capacity and more efficient than
other kilns
Needs fan to draw air through = needs
source of electricity

29. Loaded at top, bricks removed from bottom
• High efficiency, low emissions
• Kiln of choice for aid agencies
India, Nepal, Pakistan, Vietnam
VERTICAL SHAFT BRICK KILN (VSBK)

31. Brick Bonds:
Common types used are:
i. Stretcher Bond
ii. Header Bond
iii. English Bond
iv. Flemish Bond

32. I. Stretcher Bond
Stretcher/Common
Bond
Only used for walls of
half brick
thickness(partition
wall) , this is the
only practical bond
which can be used
on a wall of this
thickness .

34. Header Bond:
Header Bond also
known as Spanish
bond) was a very
common bond for
bearing walls. It is
composed of header
bricks, set in rows
that are offset ¾ of
a brick ,which
produces a solid
easy to lay bond.

36. English Bond:
 The strongest bond
 This bond
maximizes the
strength of wall
 Pattern on the face
of the wall shows
distinctive courses
of headers &
stretchers.

39. Flemish Bond
 Not such a strong as
English bond
 Decorative pattern
on face of the wall
shows alternate
headers & stretchers
in each with the
headers centered
under and over
stretchers in
adjacent courses.