What Is Brick?
Bricks are the building blocks of modern masonry structures. Bricks are rectangular blocks of uniform size that are hardened by heating or chemical processes. There are different types of bricks available in the market such as clay bricks or red bricks (1st class bricks, 2nd class bricks etc.), solid or hollow bricks, interlocking bricks, concrete bricks, etc.
Types Of Bricks:
The different types of bricks are as follows:
1. Clay bricks.
2. Sand lime or Calcium silicate bricks.
3. Concrete bricks.
4. Fly ash bricks.
5. Fire bricks.
6. Engineering bricks.
1. Clay Bricks:
The clay bricks are the oldest types of bricks to be invented by man. The date as back as 12000 years ago. The clay bricks are widely used for construction purposes. But there are many types of clay bricks available in the market. Based on the hardening process, the bricks can be divided into
1) Sun Dried bricks or Unburnt bricks.
2) Burnt bricks.
1) Sun Dried Bricks Or Unburnt Bricks:
These bricks are made by preparing the earth or the base material and moulded on the ground and allowed to harden through natural sunlight. They are weak and cannot be used for permanent buildings. These types of brick can be used to build temporary structures like huts.
i. Easy to make.
ii) They are cheap.
i) These bricks have low compressive strength, low resistance to water penetration and weather exposure.
ii) They cannot be used to build permanent structures.
2) Burnt Bricks:
Burnt bricks are either table moulded or ground moulded. They are burnt in kilns, autoclaves or clamps. Burning increases the strength of the brick and makes it more robust. However, there are four classes in the burnt bricks based on their quality. They are as follows:
A. First Class Bricks:
The first class bricks are the highest quality burnt bricks. They are table moulded and wire cut. They are heated in kilns and allowed to dry. These bricks are uniform in shape and colour and have clearly defined edges. 1st class bricks are used for pavements, walls of permanent structures and even for ornamental purposes.
Properties Of First Class Bricks:
|1st Class Bricks||Properties|
|1. Type||Class 1|
|2. Feature||Table molded.|
|3. Shape & Size||Standard and uniform (rectangular).|
|4. Surface & Edges||Sharp, smooth, square, and straight.|
|5. Color||Uniform red or brown.|
|6. Maximum Water Absorbing||15% of its self-weight when submerged in water for 24 hours.|
|7. Crushing Strength||105 kg/cm2|
|8. Making Process||Burnt in kilns.|
|9. Use||Permanent and superior work.|
Advantages Of First Class Bricks:
i) They have higher compressive strength of minimum 10.5 N/mm2
ii) They can be used for permanent structures.
iii) They have even surfaces thus easing the finishing processes like plastering.
iv) They can be used to improve the facade of the building.
v) They can be used as load bearing walls
vi) The water absorption will not be more than 15 %.
Disadvantages Of First Class Bricks:
i) They cannot be used for cold weather regions that are susceptible to freeze and thaw conditions.
ii) They expand slightly with time.
iii) They are prone to chemical attacks
iv) Burning of bricks is not sustainable to the environment.
v) They require soaking in water before using them.
B. Second Class Bricks:
These types of brick are made using the same method but due to poor supervision, they may be slightly over burnt. They have slight hair cracks and small irregularities on the surface. They can be used in buildings where the walls will be plastered, as a brick ballast in concreting and some load bearing buildings.
Properties Of Second Class Bricks:
|2nd Class Bricks||Properties|
|1. Type||Class 2|
|2. Feature||Table molded.|
|3. Shape & Size||Irregular|
|4. Surface & Edges||Rough, uneven faces, may consist of hairline cracks.|
|5. Color||Uniform color.|
|6. Maximum Water Absorbing||22% of its self-weight when submerged in water for 24 hours.|
|7. Crushing Strength||70 kg/cm2|
|8. Making Process||Burnt in kilns and sometimes may be slightly over burnt.|
|9. Use||Used in internal walls. (Plaster or coating is required.|
Advantages of Second Class Bricks:
i) Less costly than 1st class bricks.
i) They can be used in permanent structures with plastering on them.
ii) They can be used for single storeyed load bearing structures.
Disadvantages Of Second Class Bricks:
In addition to the disadvantages of the first-class bricks,
i) The water absorption is 22% thus making it more susceptible to seepage and freeze thaw cycles.
ii) They don’t have well defined edges
iii) The minimum compressive strength is only 7 N/mm2.
C. Third Class Bricks:
These types of brick are table moulded but burnt in clamps instead of kilns. This imparts poor quality to the bricks. These bricks are slightly under burnt. This types of bricks can be used for non-load bearing walls, boundary walls, low rise walls, etc,
Properties Of 3rd Class Bricks:
|Third Class Bricks||Properties|
|1. Type||Class 3|
|2. Feature||Ground molded.|
|3. Shape & Size||Non-uniform|
|4. Surface & Edges||Irregular and distorted edges.|
|5. Color||Non-uniform and dark.|
|6. Maximum Water Absorbing||25% of its self-weight when submerged in water for 24 hours.|
|7. Crushing Strength||30 kg/cm2|
|8. Making Process||Burnt in kilns and may be overburnt or underburnt|
|9. Use||Used in temporary structures.|
i) They are cheap.
In addition to the disadvantages of the second-class bricks,
i) The water absorption is 25% thus making it more susceptible to seepage and thus cannot be used in areas with heavy rains.
ii) They don’t have well defined edges or smooth finishes.
iii) The minimum compressive strength is only 3.5 N/mm2.
D. Fourth Class Bricks:
These types of brick are also called as rejected bricks and are very similar in properties and quality to the unburnt bricks. They are over burnt and thus very weak and cannot be used as a building block. They are of non uniform shape, colour and size. These bricks can be used as a filling material or be ground into a powder to make the wearing coats called Surkhi on the terrace.
2. Sand lime Or Calcium Silicate Bricks:
Sand lime or Calcium silicate bricks also known as the flint lime brick is made up of calcium and silica. Unlike clay bricks, these bricks are not hardened by burning. These are hardened by chemical processes. Various pigments can be added to the bricks to produce different colours of bricks such as black, green, grey, red, brown and yellow.
i) Due to the impressive colours, they can be used for ornamental purposes.
ii) They have a compressive strength of 10 N/mm2.
iii) They have a smooth finish thus demanding less amount of plastering.
iv) They produce greater fire resistance than the clay bricks.
v) They provide sound insulation and improve the acoustics of the building.
vi) They perform well against efflorescence.
i) They have low abrasive strength and hence not usable for wearing surfaces like pavements, sidewalks, etc.,
ii) They can shrink after placing. Require Special considerations to counteract the shrinking of the bricks.
3. Concrete Bricks:
The concrete bricks are made up of cement, aggregates and water. They are not used widely because of the availability of the concrete wall panels. Concrete bricks, like sand lime bricks are available in different colours.
Advantages Of Concrete Bricks:
i) It has higher compressive strength than the clay bricks.
ii) It provides a very pleasing sight and can be used for the façade of the building.
iii) They have a smooth finish thus demanding less amount of plastering.
iv) They provide greater fire resistance than the clay bricks.
Disadvantages Of Concrete Bricks:
i) Concrete bricks shrink and not suitable for foundations.
ii) The maximum lifespan of a concrete brick is only 65 years.
iii) It does not resist acid attack or efflorescence
iv) The manufacturing process produces greenhouse gases.
4. Fly Ash Bricks:
These are made up of Class C or Class F fly ash, cement, fine aggregate, and water. All the ingredients are mixed and compressed under high pressure and cured at room temperature. The fly ash in the bricks increases the strength of the bricks in the later stages.
Advantages Of Fly Ash Bricks:
i) Clay is a precious mineral on the earth. The use of clay is replaced with fly ash – a waste product of the coal industry.
ii) Fly ash bricks are more resistant to freeze thaw cycles.
iii) They have higher compressive strength of 30 N/mm2.
iv) It reduces mercury pollution.
v) It saves 20% of the cost.
vi) Possible to produce in 24 hours.
vii) It has low water absorption percentage than clay bricks.
viii) They are light in weight and thus reduce the cost of the foundation.
ix) Unlike clay bricks, they do not require soaking in water before usage.
Disadvantages Of Fly Ash Bricks:
i) Not all fly ash is compatible with the concrete.
ii) The bonding may be less due to the smooth finishes.
5. Fire Bricks:
Fire bricks are made of silica (65% to 75%) and alumina (25% to 35%). The high amount of alumina present in the bricks allows it to perform well under high temperatures. Other impurities like magnesium, calcium and iron are limited to less than 5%. The bricks are baked at 1600 to 1900 degrees in a continuous kiln and allowed to cool down naturally. This types of brick can be made of clay, silica, bauxite, chromite, or magnesite.
i) Low thermal coefficient of expansion of the bricks helps to withstand high temperatures.
ii) It has high strength and resistance for palling.
i) They are costly.
ii) They have high water absorption capacity.
Uses: Chimneys, boilers, kilns and furnaces.
6. Engineering Bricks:
Engineering bricks are the special types of bricks that have high compressive strength and low porosity. They are two Types:
Type A brick and Type B brick.
The Type A brick has a minimum compressive strength of 125 N/mm2 and maximum water absorption of 4.5%.
The Type B brick has a minimum compressive strength of 75 N/mm2 and maximum water absorption of 7%. Type B bricks are used widely.
Advantages Of Engineering Bricks:
i) These types of brick can be used in cold weather regions due to low porosity and resistance to freeze thaw cycles.
ii) They can be used in underground construction where there is seepage of water due to its low permeability.
i) They don’t produce a pleasing appearance hence they are suitable for underground works like sewers, tunnels and manholes.
ii) The cost of engineering bricks are higher than clay bricks.
Frequently Asked Questioned:
1. What are the different types of bricks?
The different types of brick are Clay bricks or red bricks, fly ash bricks, sand lime bricks, concrete bricks, and engineering bricks.
2. Which type of brick is best?
Every type of brick has its own advantages. Out all, first class bricks are considered as one of the best types of brick used for permanent structures.
3. How many types of bricks are there in India?
4. Which bricks are best for house construction?
First class bricks are best choice for house construction. Nowadays fly ash bricks are also used due to their high strength, durability, low cost, and eco-friendly nature.
5. What is the standard size of brick?
In India, the standard size of brick is 190 mm x 90 mm x 90 mm or 19 cm x 9 cm x 9 cm.
6. How many bricks are required in 1 m3?
500 Bricks ( If brick size is 190 mm x 90 mm x 90 mm).
7. How many types of brick masonry are there?
Different types of brick masonry: i) Brickwork in mud, ii) Brickwork in cement, and iii) Brickwork in lime mortar.
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