BRICK
Define Bricks: A brick is an artificial kind of stone of clay whose chief characteristics are a plasticity when wet and stone like hardness after being heated to high temperature.
Plasticity: Plasticity is the property of material for which it doesn’t flow when absorbs water.
- a) Composition of brick earth.
- b) Preparation of clay and blending of ingredients.
- c) Nature of molding.
- d) Care taken at drying.
- e) Type of kiln used.
- f) Burning and cooling process.
- g) Care taken in unloading.
What are the constituent of good brick clay? Write down the functions of silica and lime in brick clay.
Clay: One of the principal types of soil which remains mixed with other types likes’ sand. Clay is a fine-grained soil consisting of hydrated silicate or aluminium.
Chemical analysis of good brick clay should give the following chemical.
| Silica | 55% |
| Alumina | 30% |
| Iron Oxide | 8% |
| Magnesia | 5% |
| Lime | 1% |
| Organic Matters | 1% |
Functions of Constituent:
Functions of silica: Silica exist in all clays in a state of chemically combined with alumina forming silicate of alumina and sometimes exists in a free state when it is called sand.
The presence of sand prevents Cracking, Shrinking, Warping.
The higher the proportion of sand, the brick will be more uniform in texture. But too much sand makes the brick brittle and weak.
Function of Alumina:It is the principal constituent of brick clay.
- a) It imparts plasticity to clay, which is very essential for the purpose of moulding.
- b) It imparts density.
Function of Iron Oxide:Its presence enhances
- a) Impermeability, durability.
- b) It gives creamy colour to the bricks.
Functions of Magnesia:Presence of magnesia in small quantity decreases shrinkage and gives yellow tint.
Functions of Lime:
- a) It reduces shrinkage during drying.
- b) It enhances the silicate to melt in burning.
- c) Binds the particles together.
Excess quantity deshapes the bricks.
Harmful constituents of brick clay:
Functions of alkalis and organic matter: A small quantity of these materials help the bricks to burn less, thus it makes porous bricks.
Harmful constituents of brick clay:
Iron pyrites:
Presence of Iron pyrites
Presence of Iron pyrites
- a) Causes crystallization.
- b) Disintegration of bricks on burning. Alaklies:
- a) Produce dark greenish colour on the surface on drying.
- b) Causes the bricks to fuse, twist or warp.
- c) Absorbs moisture and causes efflorescence
- a) Hampers mixing
- b) Harmful to the uniformity of texture.
- c) Makes the bricks porous and weak.
Vegetation and organic metal:
- a) Get burned during burning leaving pores.
- b) It makes the bricks weak.
Lime:
Methods:
- a) Excess quantity causes shape loss.
- b) Causes swelling and splits the bricks.
Selection of brick field: Following consideration should be taken into account to choose the brick filed
- a) Communicating roads should be linked up to transport the materials
- b) It should be situated on a plain ground.
- c) Earth for manufacturing good quality bricks should be ready and available.
- d) Facilities for the workers employed in the process should be there.
Characteristics:
- a) Bricks should be uniform in colour size and shape.
- b) They should be sound and compact.
- c) They should be free from cracks.
- d) They should not absorb 1/5th (or 20%) of their weight of water, when immersed for 24 hours.
- e) They should have compressive strength in the range of 5000 to 8000 psi.
- f) They shouldn’t be over burnt or under burnt.
- g) They should not change in volume when wet.
- h) They should have low thermal conductivity.
Required field test:
- a) Try to make a mark on the brick surface by nail. If it is marked, it is not a good brick.
- b) Strike the brick with a hammer. A good brick will give clear ringing or metallic sound.
- c) Take to bricks and make a form of tee (T) and drop from a height of 6 feet on a solid ground. If it is not broken, it reflects a good brick.
In Bangladesh, according to P.W.D specifications each brick should measure 9.5" x 4.5" x 2.75" .
This is the standard size of bricks in Bangladesh. There are other sized bricks also. But this size is most economical, because when bricks are put in any construction with mortar the size becomes 10" x 5" x 3" (approximately). The size of walls which are constructed by
bricks in our country are 3 inch, 5 inch, 10 inch, 15 inch, 20 inch, 25 inch and 30 inch. So, this size of bricks can be used safely without any breakage. Hence, this standard size is most economical in engineering construction in our country.
This is the standard size of bricks in Bangladesh. There are other sized bricks also. But this size is most economical, because when bricks are put in any construction with mortar the size becomes 10" x 5" x 3" (approximately). The size of walls which are constructed by
bricks in our country are 3 inch, 5 inch, 10 inch, 15 inch, 20 inch, 25 inch and 30 inch. So, this size of bricks can be used safely without any breakage. Hence, this standard size is most economical in engineering construction in our country.
Frog mark:Identification marks (frogs and impression) are given on the face of brick during the process of moulding to indicate the name of the manufacturer of bricks. This is done by fitting a fillet or projection on the corresponding face of mould.
Classification of bricks:The following are the classification of bricks by PWD in our county.
First class bricks:
- a) Faces are plain.
- b) Sharp edges.
- c) Should be well burnt.
- d) Gives metallic sound when hit by hammer.
- e) Free from cracks.
- f) Uniform size and colour.
- g) Should not absorb water 15% by weight of bricks.
Second class bricks:
- a) Distorted faces and edges.
- b) Burning almost same as that of first class bricks.
- c) Presence of cracks.
- d) Water absorption 20 % by weight of bricks.
The uses of bricks are given below.
- a) Construction of walls.
- b) Construction of floors.
- c) Construction of arches.
- d) Making khoa to use in concrete
- e) Manufacturing of surki to be used in lime plaster and lime concrete.
Manufacturing Process of bricks:
1. Selection of Brick clay:
1. Selection of Brick clay:
- a) Should be free from harmful constituents
- b) A sedimentary deposit of clay is most suitable.
- c) Few sample of bricks should be made first to check the suitability of clay.
- d) Best proportion of different component of clay can be adjusted if necessary.
2. Proportion of brick clay:
- a) Weathering: The brick clay is excavated before raining. It spreads out over the ground. This is known as weathering.
- b) Blending: Quality of brick clay is in proved by adding sand, lime, alumina and magnesia is known as blending.
- 1) The clay is cut slashed.
- 2) Worked with spade.
- 3) Water is gradually added.
- 4) Well tempered by kneading under the feet of men and cattle.
- 1) It is used to temper the clay
- 2) It consists of
- a) conical vessel of iron
- b) 5 feet 6 inch in height
- c) Partially 2 feet 6 inch under the ground
- d) Central revolving shaft
- e) Horizontal blades
- f) Vertical wedge shaped steel knife rotated by bullocks or power
- g) Clay and water poured from top
Moulds are rectangular boxes with top or bottom made of hard wood or sometimes lined with iron or blades.
Methods:
- a) Hand mouldingb) Machine moulding.
The noulded bricks are dried by being placed on their edges and then piled in long row and stacks. This should be carried on a slightly raised platform and the surroundings should be anded to keep it dry in wet weather. It generally takes five to twelve weeks.
Brick burning:
- a) It is burnt due tob) Impart hardnessc) Increase densityd) Make less absorbent to watere) Increase durability.
- a) Bricks and fuels (grass, cow dung, wood chips) are places at alternate layers.b) The whole mass is plastered over with mudc) The height is 8 to 12 feetd) First layer of fuel is 2 inch to 6 inche) Upper surface is sloped at 30 degree.f) The clamp is fired from below.
The disadvantages are:
- a) Slow method.b) Bricks are not uniformly burntc) The quality of bricks is not goodd) Not of regular shapee) Not environment friendly
- a) Cheapb) No skilled labour or supervision is required.c) No objection from wind or rain
- a) It is required when large quantities bricks are needed to be burntb) It consists of regular walled structure with proper arrangements of heating.
