COMPOSITION AND MANUFACTURING OF BRICKS.pptx

SILICA ALUMINA .....
PREPARATION OF CLAY
MOULDING
HAND MOULDING
GROUND MOULDED BRICKS
TABLE MOULDED BRICKS
MACHINES MOULDING
PLASTIC CLAY MACHINES
DRY CLAY MACHINES
DRYING
BURNING
KILN BURNING
CLAMP BURNING

1. COMPOSITION AND MANUFACTURE OF GOOD BRICK EARTH

2. COMPOSITION COMPOSITION

3. 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 cracks, shrinking 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. 

4. ALUMINA It is the chief constituent of every kind of clay. 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.

5. LIME A small quantity of lime is desirable in finely powdered state to prevent shrinkage of raw bricks.  Excess of lime causes the brick to melt and hence, its shape is last due to the splitting of bricks. 

6. 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. OXIDE OF IRON A small quantity of oxide of Iron to the extent of 5 to 6 percent is desirable in good brick to impart red colour to bricks. Excess of oxide of iron makes the bricks dark blue or blackish. 

7. Manufacture of Bricks

8. Preparation of Clay  The preparation of clay involves following operations. Unsoiling : - Top layer of 20cm depth is removed as it contain impurities.  Digging: - Clay dug out from ground is spread on level ground about 60cm to 120cm heaps  Cleaning:- Stones, pebbles, vegetable matter etc removed and converted into powder form. Weathering:- Clay is exposed to atmosphere from few weeks to full season.  

9. Preparation of Clay   The preparation of clay involves following operations. Blending:- Clay is made loose and any ingredient to be added to it is spread out at top and turning it up and down in vertical direction.  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. 

10. MOULDING

11. 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. Bricks prepared by hand moulding are of two types.  Ground moulded bricks  Table moulded bricks 

12. HAND MOULDING Ground moulded bricks  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 brick is left on the ground.  Table moulded bricks            Process of moulding these bricks is just similar to ground bricks on a table of size about 2m x 1m. 

13. HAND MOULDING GROUND MOULDED BRICKS TABLE MOULDED BRICKS

14. Machine moulding This method proves to be economical when bricks in huge quantity are to be manufactured at the same spot. It is also helpful for moulding hard and string clay. These machines are broadly classified in two categories Plastic clay machines Dry clay machines

15. Plastic clay machines This machine containing rectangular opening of size equal to length and width of a brick. Pugged clay is placed in the machine and as it comes out through the opening, it is cut into strips by wires fixed in frames, so there bricks are called wire cut bricks. 

16. Dry clay machines  In these machines, strong clay is first converted into powder form and then water is added to form a stiff plastic paste. Such paste is placed in mould and pressed by machine to form hard and well shaped bricks. These bricks are behavior than ordinary hand moulded bricks. They carry distinct and exhibit uniform texture. 

17. Machine  moulding Plastic clay machine s Dry clay machines

18. DRYING The damp bricks, if burnt, are likely to be cracked and distored . Hence moulded bricks are dried before they 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 

19. DRYING

20. DRYING Artificial drying – drying by tunnels usually 1200C about 1 to 3 days  Circulation of air - Stacks are arranged in such a way that sufficient air space is left between them free circulation of air.  Drying yard - special yards should be prepared slightly higher level prevent the accumulation of rain water  Period for drying – usually about 3 to 10 days to bricks to become dry  Screens – screens are necessary, may be provided to avoid direct exposure to wind or sun. 

21. BURNING This is very important operation in the manufacturing of bricks to impart hardness, strength and makes them dense and durable. The temperature required for burning is about 1100oC. If they burnt beyond this limit they will be brittle and easy to break. If they burnt under this limit, they will not gain full strength and there is a chance to absorb moisture from the atmosphere.

22. BURNING Hence burning should be done properly to meet the requirements of good brick. In the process of burning, the dried bricks are burned either in clamps (small scale) or kilns (large scale) up to certain degree temperature. Clamp burning Kiln burning

23. BURNING KILN BURNING CLAMP BURNING

24. CLAMPS The bricks and fuel are placed in alternate layers. The amount of fuel is reduced successively in the top layers. Each brick tier consists of 4–5 layers of bricks. Some space is left between bricks for free circulation of hot gasses. After 30 per cent loading of the clamp, the fuel in the lowest layer is fired and the remaining loading of bricks and fuel is carried out hurriedly.

25. CLAMPS The top and sides of the clamp are plastered with mud. The production of bricks is 2–3 lacs and the process is completed in six months. This process yields about 60 per cent first class bricks.

26. KILNS INTERMITTENT KILN After loading the kiln, it is fired, cooled and unloaded and then the next loading is done. Since the walls and sides get cooled during reloading and are to be heated again during next firing, there is wastage of fuel.

27. INTERMITTENT KILN

28. KILNS CONTINUOUS KILN The bricks are stacked in various chambers wherein the bricks undergo different treatments at the same time. the brick in one of the chambers are fired, the bricks in the next set of chambers are dried and preheated while bricks in the other set of chambers are loaded and in the last are cooled.

29. CONTINUOUS KILN

30. COMPARISION BETWEEN  CLAMP BURNING  KILN BURNING

31. DRYING YARDS