Presents Building Materials - wifistudy.com · Moulded bricks , if are directly burnt without drying are to liable to get crack due to excessive shrinkage, hence its drying is carried

Building Materials

A Presentation by

Sandeep Jyani

Presents

1

Bricks

I. Composition

II. Harmful Ingredients

III. Manufacturing

IV. Quality and Tests

V. Brick Masonary and Types of Bonding in bricks

2

Brick

Brick

Civil Engineering by Sandeep Jyani3

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

1. Standard Size

2. Nominal Size or Size of Brick along with mortar

Brick: Questions Start Right Here!

Size of Brick

Civil Engineering by Sandeep Jyani 4

3. Conventional Size of Brick

Size of Brick


1. Composition of Brick


•50-60%Silica

•20-30%Alumina

•4-5%Lime

•5-6%Oxide of iron

•1%Magnesia


I. Composition of Brick

1. Silica (50-60%) Silica prevents the cracking, shrinkage and warping

of the bricks, thereby imparts uniform Shape to it.

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

2. Alumina (20-30%) Alumina impacts plasticity to the brick earth so that

it can be easily moulded in any designed shape.

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 (4-5%)Lime also prevents the shrinking of the bricks

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 intoquick 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%)Oxides of iron helps silica and lime to fuse with each

other, hence leads to the development of strength in the bricks

It also imparts reddish brown colour in bricks.



5. Magnesia (1%)Magnesia also prevents the shrinkage 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.

II. Harmful Ingredients in Brick


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

2. Moulding

3.

Drying

4. Burning


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


1. Preparation of ClayE. 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 ClayThe 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.


2. Moulding of ClayMoulding 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 bricksb) Table moulded bricksQualities 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 bricksb) Dry clay moulded bricksQuality of dry clay moulded bricks is also comparatively

better than plastic clay moulded bricks.


3. DryingMoulded bricks , if are directly burnt without drying are to liable to getcrack due to excessive shrinkage, hence its drying is carried out before theburning of pressure in which moisture content of the brick is reduced up to2%

• 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 BricksBurning 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

Burninga) Clamps

b) Kilns

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


a) Burning of Bricks in Clamps• Burning of the brick in

clamp is carried out for 2-3 months that is further following by its cooling for same duration.

• No supervision is required in clamps, moreover since locally available fuel is used, the entire process is comparatively economical.

• There is no control over the fire in clamps, hence the bricks obtained are not of uniform quality.


b) Burning of Bricks in Kilns

Kiln

s

i) Intermittent Kilns

a. Up Draught Kilns

b. Down draught Kilns

ii) Continuous Kilns

a. Bull Trench Kilns

b. Hoffmann Kiln

c. Tunnel Kiln


Kilns are large sized oven that are used for the burning of bricks.

Supply of the bricks from these kilns may either be continuous or intermittent accordingly. They are classified as-

b) Burning of Bricks in Kilns

• All the operations of loading, burning, cooling and unloading is done sequentially and , hence the supply of the bricks is not continuous from these kilns

• Consists of two sets of main doors that are used for loading and unloading the bricks.

• Bricks are placed in these kilns in the rows of approximately 4-5 brick thick and height of approximately 6-8 brick thick

• An open space between the two rows of approx 2-3 bricks thick is left which is used for placing the fuel.


i) Intermittent Kilns

1. Up Draught kilns : If the movement of the gases is allowed to take place in vertically upward direction, it is termed as Up Draught kilns

2. Down draught kilns: If the movement of gases is allowed to take place in vertically downward direction, it is termed as Down draught kilns

• In down draught kilns permanent roof is provided along with the central chimney that permits the movement of the gases in downward direction.

Qualities of the brick obtained from Down draught kilns is comparatively better than that of bricks obtained from up draught kilns.


b) Burning of Bricks in Kilnsi) Intermittent Kilns

1. Bull Trench Kiln


ii) Continuous KilnsIn continuous kilns, the supply of the bricks is maintained to be continuous as all the operations of loading, burning, cooling and unloading is done simultaneously

• It includes two sets of movable chimneys that are always placed ahead of the section in which burning is to be carried out. Such an arrangement allows the pre heating of the bricks in the chamber over which chimney is placed.

• This kiln consists of number of sections in which all the operations of loading, burning, cooling and unloading is done simultaneously.

• These kilns are generally oval, circular & rectangular in plan

2. Hoffmann Kiln



• This kiln is circular in plan and consists of fixed central chimney unlikely Bull trench kiln that consists of moveable chimneys

• This kiln consists of number of sections in which all the operations of loading, burning, cooling and unloading is done simultaneously

2. Hoffmann Kiln



• The supply of the bricks is maintained to be continuous in these types of kiln by sequential opening and closing the different sets of doors.

• Initial cost of Hoffmann kiln is comparatively more than that of Bull Trench kiln, but its operational cost is comparatively less than that of Bull trench kiln.

• Capacity of Hoffmann kiln is also more than that of Bull trench kiln.

• As fire can be regulated in these type of kilns, quality of the bricks is also comparatively better


3. Tunnel Kiln• This kiln is in the form of tunnel which may either be rectangular,

circular or oval in plan.

• It consists of different stationary zones in which all the process of loading, burning, cooling and unloading is done simultaneously.

• Bricks are placed either on trolley or on conveyer belts and is passed through different stationary zones in the tunnel


IV. Quality/Testing of Bricks

1. The bricks should be at least table moulded, well burnt and free from cracks

2. The bricks should be of uniform shape & sizeConventional size of bricks= 22.4 cm x 11.4 x 7.6 cmStandard size of brick= 19cmx 9cm x 9cmWith mortar = 20cm x 10 cm x 10 cmWt of 1m3 bricks = 1800 kgWt of 1 brick= 3.5- 3.6 kg

3. Sound Test- The bricks should produce clear metallic ringing sound when struck with each other.

4. Structure test- the bricks should have uniform homogenous structure across all the section i.e. it should be free from any voids.


5. Absorption Test: The bricks when immersed in water for 24 hours should not absorb water by more than-• 20% in case of 1st class bricks• 22% in case of 2nd class brick• 25% in case of 3rd class bricks

6. Compressive Strength Test: The bricks should process minimum compressive strength of:

1st class- 10 N/mm2

2nd class- 7.5 N/mm2

3rd class- 3.5 N/mm2

7. Toughness test: The brick should not break into pieces when dropped on levelled ground from the height of 1m.

8. Hardness/ Abrasion: the brick should possess sufficient hardness and does not show any sign of impression when scratched with finger nails.

9. Alkali test: the Bricks when immersed in water for 24 hours should not show any sign of efflorescence and staining.


IV. Quality/Testing of Bricks

V. Brick Masonary

1. Stretcher: Longer side face of the brick

2. Header: The shorter side face of the brick• Used for Hearting of

walls


V. Brick Masonary3. Closures: The portion of brick cut along its length



4. Bats: The portion of brick cut along its width

5. Quoin: It is the interior angle at the face of the wall that is greater than equal to 900.

V. Bonding in Brick Masonary

1. English Bond• Alternate layer of header

and stretcher placed over each other.

• To break the alignment of vertical joints to be in straight line Queen closure is placed next to Quoin header.

• Queen closure is never placed either at the starting or at the end of the coarse. As it is liable to get displaced.


V. Bonding in Brick Masonary

1. English Bond• For the walls having thickness in odd multiples

of half brick thick, each course shows harder on one face and stretcher on other face.

• Minimum lap available for stretcher in each course is ¼ th the length of brick.



2. Flemish Bond• It is the arrangement of

bonding in which each course consists of alternate header and stretcher placed next to each other.

• In order to break the alignment of vertical joints to be in straight line, Queen closures is placed next to quoin header in each alternate course.

• For walls having thickness in odd multiples of half brick thick. English bond is found to have higher strength than Flemish bond.


2. Flemish Bond• Flemish bond is

aesthetically more pleasing than English bond but it requires skilled masonary work.

• Flemish bond is found to be more economical than English bond as no of half bats is used in this case due to which wastage of brick is comparatively less


3. Stretcher Bond

• To break alignment in stretcher bond, half bats are used.

• It is arrangement of bonding in which all the bricks are laid along the stretcher.

• In order to break the alignment of vertical joints to be in straight line, half bats are used in each alternate course.


4. Header Bond• It is the arrangement of

bonding in which all the bricks are laid along the header in each course.

• In order to break the alignment of vertical joints, to be in straight line there quarter bat is used in each alternate course.


Documents

Presents Building Materials - wifistudy.com · Moulded bricks , if are directly burnt without drying are to liable to get crack due to excessive shrinkage, hence its drying is carried