Table of Content for Bricks-
- Uses of Brick
- Size of Brick
- Classification of Brick on the basis of-
- Raw material
- Manufacturing Process
- Composition of Brick and Function of Compounds
- Quality Control of Brick-
- Site Inspection
- Laboratory Inspection
A brick is a rectangular block used for masonry works of civil structures. The brick is used by applying mortar on it and arranging it in the required shape. The brick commonly used in India are made of clay or fly ash. The concrete blocks are also gaining popularity due to their workability and cost-effectiveness.
The first brick ever found dates back to 7500 BC in modern-day Syria. These were block-shaped sun-dried clay-based bricks.
The properties of the brick depend on its’ material. The manufacturing process of the bricks of different material is also different.
The work involving brick masonry is termed as brickwork. In brickwork, the bricks are laid in courses. These courses are joined by either cement concrete or lime concrete. Special types of interlocking bricks are also used that need no concrete. Such bricks are used in pavements.
Uses of Bricks
- Strip Footing for Walls
- Reinforced Brick Slabs
- Drain Lining
- Sewer and Manholes
- Low Traffic Roads
- For Lining of kilns and furnaces
- Canal Lining
Size of Brick
The standard size of the brick is 190mm x 90mm x 90mm. With the mortar, this size becomes 200mm x 100mm x 100mm. However, the bricks of different sizes are also available in the market and commonly used across India. Other available sizes are 210mm x 115mm x 90mm and 90mm x 90mm x 90mm.
Terminology of Brick
Side of Bricks- The side of the brick are called beds, cull, side, end and face.
Frog- The depression on the bed of the brick is called the frog. It is provided to bond the mortar with the brick.
Cut Brick Shape- The brick can be cut across its’s length, width or height. When the brick is cut along the width is called half or bat. The cut along the length is called queen closure. The cut along the height is called split.
Classification of Bricks
The bricks can be classified on the basis of material, quality, manufacturing process, shape etc.
1. Classification of Brick on the basis of Material
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- Clay Brick- This brick is made of clay and has silica as the main constituent. This brick is reddish-brown in colour and is commonly used across India.
- Fly ash Brick- This brick is made by blending clay with the fly ash. It has a greyish colour and is gaining popularity.
- Concrete Brick- Concrete brick is made by casting cement concrete into moulds and then cured. It is are easier to work with.
- Sand-Lime Brick- Calcium Silicate Brick or Sand-Lime Brick is used for its’ thermal and sound insulation properties. This brick is made by imposing high pressure on lime and sand mixture and burning in the autoclave.
- Refractory Brick- This brick has higher silica content and used for the lining of kilns, furnaces and chimneys etc. It is also called fire-resistant brick.
2. Classification of Bricks on the basis of Quality
- First Class Brick- This brick is table-moulded and kiln burnt. It complies with all the requirements of a good brick. This brick is used for external and ornamental works.
- Second Class Brick- It is ground moulded kiln-burnt brick. The quality is inferior to first-class brick. The surface of the brick may be rough. This brick is used for inner works or walls that are to be covered with plaster.
- Third Class Brick- It is ground moulded and clamp burnt brick. The size and shape may not perfectly comply with the norms. It is used for temporary works.
- Fourth Class Brick- It is over burnt brick and has a dark colour. This brick is used as aggregate for foundations.
3. Classification of Bricks on the basis of Manufacturing Process
- Unburnt Brick- It is sun-dried clay brick. It is the cheapest brick and has very low strength. This brick is used for unimportant works where no load is to be taken by the structure.
- Burned Brick- The burned brick is mostly used all over. They have a well-defined shape and size and have sufficient strength.
- Over-burnt Brick- The over-burnt brick generally has a twisted, warped or deformed shape. The size of this brick may also not comply with the specified size. It brick are used as aggregate for filling works for foundation works, flooring works and road works etc.
4. Classification of Bricks on the basis of Shape
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- Hollow Brick- Hollow brick is light-weight brick used for partition works. It has higher thermal insulation than conventional clay brick.
- Perforated Brick- This brick has perforations of 35-40% of the area. However, the perforation of the brick should not be more than 500 mm2.
- Paving Brick- This brick has such a shape that they can be interlocked. They are used for low traffic roads.
- Brick Veneers- Brick veneers is brick of very small thickness as compared to its’ length and width. They are used for decoration purpose.
- Specially Shaped Bricks- These bricks are specially made for ornamental works or requirement of the structure. These bricks have different shapes and used at different places of the structures. Some of these are Bull Nosed Brick, Cant Brick, Plinth Brick, Coping Brick, Cornice Brick and Channel Brick.
Chemical Composition of Clay Bricks
The composition of clay brick is as follows-
Functions of Compounds of Clay Brick
The silica prevents cracking, shrinkage and warping; therefore, it imparts uniform shape. If silica is present in excess it destroys the cohesion between the particles hence brick becomes too brittle.
The alumina imparts plasticity so that the clay can easily be moulded in any shape. It’s excess causes shrinkage and warping and also makes the brick too hard to work with.
The lime prevents shrinkage of the brick. The excess of lime causes the brick to melt when heating.
Oxides of Iron helps in the fusing of lime and silica, hence leads to the development of strength. The reddish-brown tint of clay brick is due to iron oxides.
Magnesia prevents shrinkage during burning and imparts yellowish tint to the brick.
Quality Control of Bricks
1. Site Inspection
- Size- The size of the brick should conform to the specification.
IS code permits the following limits-
- Length- 3680 to 3920 mm
- Width- 1740 to 1860 mm
- Height- 1740 to 1860 mm.
2. Shape- The brick should have uniform-sharp edges and true right-angled corners.
3. The brick should be table moulded. These bricks are known to have better quality control in terms of shape and size.
4. Colour Test- The colour of the brick should be reddish-brown and same throughout. This shows a lesser percentage of magnesia and uniform burning of the brick. Yellowish colour of brick indicates under-burned brick.
5. Sound Test- Bricks should give a clear metallic ringing sound when struck together. This test indicates the denseness of the brick.
6. Toughness Test- The brick should not break into pieces when dropped freely from a height of 1 meter.
7. Hardness Test- No marks should be observed on the brick when scratched with a nail.
8. Structure Test- No voids should be visible when the brick is broken into two.
2. Laboratory Inspection
- Compressive Strength Test- The compressive strength of brick is tested in the compression test machine. The minimum value of the compressive strength of the brick are as follows-
- First Class- 10.5 N/mm2
- Second Class- 7.5 N/mm2
- Third Class- 3.5 N/mm2
- 2. Absorption Test- The brick is absorbed in water for 24 hours. The weight of the brick before (W1) and after (W2) soaking in water is recorded. The absorption of water is calculated as-
Water Absorption of Brick= (W2-W1)/W1
The maximum value of water absorption are as follows-
- First Class- 20%
- Second Class- 22%
- Third Class- 25%
- 3. Alkali Test- Brick is placed in glass disk filled with water up to 25mm height. When the water is evaporated or absorbed the disk is again filled with water having 25mm height. After evaporation of second water, the soaked surface of the brick is observed for efflorescence or patches. The efflorescence shows the presence of alkalis which is undesirable.
The severity of alkali presence is calculated as follows-
- Efflorescence cover up to 20% area of brick- Acceptable
- Efflorescence cover up to 50% area of brick- Moderate
- Efflorescence cover more than 50% area of brick- Severe
- 4. Attrition Test- This test is done for bricks to be used for road works. This test determines the rate of wear and tear of brick under the action of traffic.
- 5. Other Tests- Tests for tensile strength, shear strengths are also conducted for bricks.
- The average tensile strength of hand moulded brick is 2.0 N/mm2.
- The average shear strength of hand moulded brick is 6.0 N/mm2.
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