Page 1
CHAPTER-2
BRICKS
Bricks are obtained by moulding clay in rectangular blocks of uniform
size and then by drying and burning these blocks. As bricks are of
uniform size, they can be properly arranged, light in weight and hence
bricks replace stones.
2.1 Composition - Manufacture Process.
Composition – Following are the constituents of good brick earth.
Alumina: - It is the chief constituent of every kind of clay. A good brick
earth should contain 20 to 30 percent of alumina. This constituent
imparts plasticity to earth so that it can be moulded. If alumina is present
in excess, raw bricks shrink and warp during drying and burning.
Silica-A good brick earth should contain about 50 to 60 percent of silica.
Silica exists in clay either as free or combined form. As free sand, it is
mechanically mixed with clay and in combined form; it exists in
chemical composition with alumina. Presence of silica prevents crackers
shrinking and warping of raw bricks. It thus imparts uniform shape to the
bricks. Durability of bricks depends on the proper proportion of silica in
brick earth. Excess of silica destroys the cohesion between particles and
bricks become brittle.
Lime – 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 last due to the splitting of bricks.
Page 2
CHAPTER-2
BRICKS
Bricks are obtained by moulding clay in rectangular blocks of uniform
size and then by drying and burning these blocks. As bricks are of
uniform size, they can be properly arranged, light in weight and hence
bricks replace stones.
2.1 Composition - Manufacture Process.
Composition – Following are the constituents of good brick earth.
Alumina: - It is the chief constituent of every kind of clay. A good brick
earth should contain 20 to 30 percent of alumina. This constituent
imparts plasticity to earth so that it can be moulded. If alumina is present
in excess, raw bricks shrink and warp during drying and burning.
Silica-A good brick earth should contain about 50 to 60 percent of silica.
Silica exists in clay either as free or combined form. As free sand, it is
mechanically mixed with clay and in combined form; it exists in
chemical composition with alumina. Presence of silica prevents crackers
shrinking and warping of raw bricks. It thus imparts uniform shape to the
bricks. Durability of bricks depends on the proper proportion of silica in
brick earth. Excess of silica destroys the cohesion between particles and
bricks become brittle.
Lime – 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 last due to the splitting of bricks.
Bricks
Oxide of iron- A small quantity of oxide of Iron to the extent of 5 to 6
percent is desirable in good brick to imparts red colour to bricks. Excess
of oxide of iron makes the bricks dark blue or blackish.
Magnesia- A small quantity of magnesia in brick earth imparts yellow
tint to bricks, and decreases shrinkage. But excess of magnesia decreases
shrink leads to the decay of bricks.
The ingredients like, lime, iron pyrites, alkalies, pebbles, organic
matter should not present in good brick earth
Manufacture of bricks:
The manufacturing of brick, the following operations are involved
1. Preparation of clay
2. Moulding
3. Drying
4. Burning
(i) Preparation of clay :- The preparation of clay involves
following operations
a) Unsoiling :- Top layer of 20cm depth is removed as it contain
impurities.
Page 3
CHAPTER-2
BRICKS
Bricks are obtained by moulding clay in rectangular blocks of uniform
size and then by drying and burning these blocks. As bricks are of
uniform size, they can be properly arranged, light in weight and hence
bricks replace stones.
2.1 Composition - Manufacture Process.
Composition – Following are the constituents of good brick earth.
Alumina: - It is the chief constituent of every kind of clay. A good brick
earth should contain 20 to 30 percent of alumina. This constituent
imparts plasticity to earth so that it can be moulded. If alumina is present
in excess, raw bricks shrink and warp during drying and burning.
Silica-A good brick earth should contain about 50 to 60 percent of silica.
Silica exists in clay either as free or combined form. As free sand, it is
mechanically mixed with clay and in combined form; it exists in
chemical composition with alumina. Presence of silica prevents crackers
shrinking and warping of raw bricks. It thus imparts uniform shape to the
bricks. Durability of bricks depends on the proper proportion of silica in
brick earth. Excess of silica destroys the cohesion between particles and
bricks become brittle.
Lime – 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 last due to the splitting of bricks.
Bricks
Oxide of iron- A small quantity of oxide of Iron to the extent of 5 to 6
percent is desirable in good brick to imparts red colour to bricks. Excess
of oxide of iron makes the bricks dark blue or blackish.
Magnesia- A small quantity of magnesia in brick earth imparts yellow
tint to bricks, and decreases shrinkage. But excess of magnesia decreases
shrink leads to the decay of bricks.
The ingredients like, lime, iron pyrites, alkalies, pebbles, organic
matter should not present in good brick earth
Manufacture of bricks:
The manufacturing of brick, the following operations are involved
1. Preparation of clay
2. Moulding
3. Drying
4. Burning
(i) Preparation of clay :- The preparation of clay involves
following operations
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 heaps.
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.
e) Blending:- Clay is made loose and any ingradient to be added
to it 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,
tempering is usually done in pug mill as shown in the fig 2.1
Page 4
CHAPTER-2
BRICKS
Bricks are obtained by moulding clay in rectangular blocks of uniform
size and then by drying and burning these blocks. As bricks are of
uniform size, they can be properly arranged, light in weight and hence
bricks replace stones.
2.1 Composition - Manufacture Process.
Composition – Following are the constituents of good brick earth.
Alumina: - It is the chief constituent of every kind of clay. A good brick
earth should contain 20 to 30 percent of alumina. This constituent
imparts plasticity to earth so that it can be moulded. If alumina is present
in excess, raw bricks shrink and warp during drying and burning.
Silica-A good brick earth should contain about 50 to 60 percent of silica.
Silica exists in clay either as free or combined form. As free sand, it is
mechanically mixed with clay and in combined form; it exists in
chemical composition with alumina. Presence of silica prevents crackers
shrinking and warping of raw bricks. It thus imparts uniform shape to the
bricks. Durability of bricks depends on the proper proportion of silica in
brick earth. Excess of silica destroys the cohesion between particles and
bricks become brittle.
Lime – 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 last due to the splitting of bricks.
Bricks
Oxide of iron- A small quantity of oxide of Iron to the extent of 5 to 6
percent is desirable in good brick to imparts red colour to bricks. Excess
of oxide of iron makes the bricks dark blue or blackish.
Magnesia- A small quantity of magnesia in brick earth imparts yellow
tint to bricks, and decreases shrinkage. But excess of magnesia decreases
shrink leads to the decay of bricks.
The ingredients like, lime, iron pyrites, alkalies, pebbles, organic
matter should not present in good brick earth
Manufacture of bricks:
The manufacturing of brick, the following operations are involved
1. Preparation of clay
2. Moulding
3. Drying
4. Burning
(i) Preparation of clay :- The preparation of clay involves
following operations
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 heaps.
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.
e) Blending:- Clay is made loose and any ingradient to be added
to it 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,
tempering is usually done in pug mill as shown in the fig 2.1
Bricks
Fig 2.1 Pug Mill
Process:- Clay with water is placed in pug mill from the top. When the
vertical staff is rotated by using electric pair, steam or diesel or turned by
pair of bullocks. Clay is thoroughly mixed up by the actions of
horizontal arms and knives when clay has been sufficiently pugged, hole
Page 5
CHAPTER-2
BRICKS
Bricks are obtained by moulding clay in rectangular blocks of uniform
size and then by drying and burning these blocks. As bricks are of
uniform size, they can be properly arranged, light in weight and hence
bricks replace stones.
2.1 Composition - Manufacture Process.
Composition – Following are the constituents of good brick earth.
Alumina: - It is the chief constituent of every kind of clay. A good brick
earth should contain 20 to 30 percent of alumina. This constituent
imparts plasticity to earth so that it can be moulded. If alumina is present
in excess, raw bricks shrink and warp during drying and burning.
Silica-A good brick earth should contain about 50 to 60 percent of silica.
Silica exists in clay either as free or combined form. As free sand, it is
mechanically mixed with clay and in combined form; it exists in
chemical composition with alumina. Presence of silica prevents crackers
shrinking and warping of raw bricks. It thus imparts uniform shape to the
bricks. Durability of bricks depends on the proper proportion of silica in
brick earth. Excess of silica destroys the cohesion between particles and
bricks become brittle.
Lime – 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 last due to the splitting of bricks.
Bricks
Oxide of iron- A small quantity of oxide of Iron to the extent of 5 to 6
percent is desirable in good brick to imparts red colour to bricks. Excess
of oxide of iron makes the bricks dark blue or blackish.
Magnesia- A small quantity of magnesia in brick earth imparts yellow
tint to bricks, and decreases shrinkage. But excess of magnesia decreases
shrink leads to the decay of bricks.
The ingredients like, lime, iron pyrites, alkalies, pebbles, organic
matter should not present in good brick earth
Manufacture of bricks:
The manufacturing of brick, the following operations are involved
1. Preparation of clay
2. Moulding
3. Drying
4. Burning
(i) Preparation of clay :- The preparation of clay involves
following operations
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 heaps.
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.
e) Blending:- Clay is made loose and any ingradient to be added
to it 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,
tempering is usually done in pug mill as shown in the fig 2.1
Bricks
Fig 2.1 Pug Mill
Process:- Clay with water is placed in pug mill from the top. When the
vertical staff is rotated by using electric pair, steam or diesel or turned by
pair of bullocks. Clay is thoroughly mixed up by the actions of
horizontal arms and knives when clay has been sufficiently pugged, hole
at the bottom of tub, is opened cut and the pugged earth is taken out from
ramp for the next operation of moulding.
Moulding: Clay, which is prepared form pug mill, is sent for the next
operation of moulding. Following are the two ways of moulding.
Hand Moulding: Moulds are rectangular boxes of wood or steel, which
are open at top and bottom. Steel moulds are more durable and used for
manufacturing bricks on large scale as shown in fig 2.2. Bricks prepared
by hand moulding are of two types.
Fig 2.2 Wooden mould & Steel mould
a) Ground moulded bricks
b) Table moulded bricks
(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. Extra clay is removed by wooden or metal
strike after the mould is filled forced mould is then lifted up and raw
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