BRICKS Chapter No. 1 Of Building Meterial Of Diploma in civil engineerig 3rd semester of 2 year Diploma

Bricks

I.                              Composition

II.                           Harmful Ingrediants

III.                        Manufacturing

IV.                       Quality and tests

V.                           Bricks Masonary and Types of Bonding in bricks

 

Bricks

A small rectangular block typically made of fired or sun-dried clay, used in construction.

Size of Bricks

Brick : Questions

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1.    Standard Size

 

         

2.    Nominal Size

Or Size of Brick

Along with mortar

 

3.    Conventional

Size of  Brick

 

I.                            Composition of Brick

 

1.  Silica (50-60%)

Ø  Silica prevents the cracking, shrinkage and warping of the bricks, thereby imparts uniform Shape to it.

Ø  If it is in excess, it destroys cohesion between the particles, hence bricks become too brittle.

2.  Alumina (20-30%)

Ø  Alumina impacts plasticity to the brick earth so that it can be easily moulded in any designed shape.

Ø  If it is in excess, it causes shrinkage and warping during the drying of the bricks and makes the bricks too hard during the working process.

3.  Lime (4-55%)

Ø  Lime also prevents the shrinking of the bricks.

Ø  If it is in excess, it causes the brick to melt during the burning thereby it results in loss of the shape of bricks.

Note: During the burning of the bricks, calcium carbonate (limestone) is converted into quick lime that undergoes slaking process which in turn, results in the cracking & disintegration of the bricks due to increase in volume.

4.  Oxides of iron (5-6%)

Ø  Oxide of iron helps silica and lime to fuse with each other, hence leads to the development of strength in the bricks.

Ø  It also imparts reddish brown colour in bricks.

5.   Magnesia (1%)

Ø Magnesia also prevents the shrinkage in bricks and in bricks and imparts yellowish tint in bricks.

II. Harmful Ingredients in Brick

1. Lime slaking:

• Slakingvolume increase cracking & disintegration 

2. Iron Pyrites 

• Presence of the Iron Pyrites leads to crystallization and disintegration of bricks during burning due to the oxidation of these pyrites 

3. Alkalies 

• Alkali act as a flux during the burning of bricks but if it is in excess it causes the bricks to fuse with each other thereby resulting in its twisting and warping 

• Presence of Alkalies also leads to efflorescence and staining in bricks.

4. Pebbles or Stones 

• Presence of stones and pebbles brick earth leads to the formation of weak and porous bricks, load carrying capacity of which is comparatively reduced. 

5. Organic and vegetative matter 

• Presence of organic & vegetative matter helps in the burning of bricks but if they are left unburnt, it results in the formation of gases during the decomposition, which when escapes through the body of the bricks leads to the development of numerous voids, which results in decreasing of load carrying capacity of bricks

III. Manufacturing of Bricks

1. Preparation of Clay 

A. Unsoiling: top 200 mm of soil is thrown and is not as it consists of majority of impurities in it 

B. Digging: soil is dug out and spread over the level filed to prepare it for next operation of cleaning 

C. Cleaning: Impurities like stones, pebbles, organic matter, vegetation matter is removed from the brick earth 

D. Weathering: after cleaning the clay it is imposed to the atmosphere for few weeks to few months for its softening, ripening and weathering.

E. Blending: It is process in which different ingredients of bricks earth is spread over the weathered clay in definite proportion and mixed. 

F. Tempering: Tempering is the process in which requested degree of hardness is induced in the brick earth to make it suitable for the next operation of moulding.

 - Tempering of the brick is done in “pug mill”

2. Moulding of Clay 

The process of giving desired shape and size to the bricks is termed as moulding. 

• Steel or wood moulds are used, size of which is approximately kept to be 8-12% greater than the size of the bricks in order to account for its shrinkage. 

• During moulding a mark of depth 10-20 mm is placed over the surface of the brick that is termed as frog mark, which serves following two purpose:

i) Trade name of the manufacturer. 

ii) If acts a key for mortar when the layer of bricks is placed over it.

Moulding of the bricks can be done with the help of hand or with the help of machines. 

• Hand moulded bricks are further of two types: 

a) Ground moulded bricks 

b) Table moulded bricks 

 Qualities of table moulded bricks in comparatively better than the quality of ground moulded bricks and its rate of moulding is also comparatively better than ground moulded bricks. 

• Machine moulded bricks are also of two types: 

a) Plastic clay moulded bricks 

b) Dry clay moulded bricks 

Quality of dry clay moulded bricks is also comparatively better than plastic clay moulded bricks.

3. Drying 

Moulded bricks , if are directly burnt without drying are to liable to get crack due to excessive shrinkage, hence its drying is carried out before the burning of pressure in which moisture content of the brick is reduced up to 2%

• Drying of the bricks is carried out either naturally or artificially 

• During drying, bricks are always placed along their edge and never placed along there face, in order to speed up the process of drying.

4. Burning of Bricks

Burning impacts strength and hardness to the bricks, it makes them dense and durable

• Burning should be done properly 

            • Overburnt- Brittle/easily broken 

            • Underburnt- Soft/unable to carry designed load 

• Burning of the bricks is carried out at 11000C at which silica and lime fuse with each other thereby imparting strength to the bricks.

a) Burning of Bricks in Clamps 

• Trapezoidal section of ground is taken and longer side is raised with 150 

• A brick wall in mud is constructed along the shorter side and the fuel layer having thickness of 700 to 800 mm spread over the level ground. 

• Fuel used for burning of the bricks in clamps constitutes grass, rice husk ash, wood, cow dung, coal dust etc