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.
Composition
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.
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
Type of brick closer (cut) with help of 3D video Presentation.
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
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.
(2) 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 & Machine moulding
(3) Drying:
The damp bricks, if burnt, are likely to be cracked and distored. Hence moulded bricks are dried before thay are taken for the next operation of burning. Bricks are laid along and across the stock in alternate layers. The drying of brick is by the following means
(i) Artificial drying – drying by tunnels usually 1200C 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)Drying yard- special yards should be prepared slightly higher level prevent the accumulation of rain water
(iv) Period for frying – usually about 3 to 10 days to bricks to become dry
(v) Screens – screens are necessary, may be provided to avoid direct exposure to wind or sun.
(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.
Types of Brick Bond with 3D video Persentation
practice previous year Qtns
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