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:
Clay bricks are the oldest types of bricks invented 12000 years ago. Clay bricks are the most common bricks widely used for construction. There are several types of clay bricks available in the market. Based on the hardening process, the bricks can be divided into
- Sun Dried bricks or Unburnt bricks &
- Burnt bricks.
1) Sun Dried Bricks Or Unburnt Bricks:
These bricks are molded on the ground and allowed to harden through natural sunlight. They are weak and cannot be used for permanent buildings. These types of brick are suitable for temporary structures like huts.
- Easy making.
- They are cheap.
- Low compressive strength, low resistance to water penetration, and weather exposure.
- Cannot be used in permanent structures.
2) Burnt Bricks:
Burnt bricks are either table molded or ground molded. They are burnt in kilns, autoclaves, or clamps. Burning increases strength and makes bricks more robust. 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 molded and wire cut. They are heated in kilns and allowed to dry. These bricks are uniform in shape and color and have properly 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:
- Higher compressive strength of minimum 10.5 N/mm2
- Best bricks for permanent structures.
- They have even surfaces thus easing the finishing processes like plastering.
- Improves the facade of the building.
- Can be used as load-bearing walls.
- The water absorption will not be more than 15%.
Disadvantages Of First Class Bricks:
- Not suitable for cold weather regions that are susceptible to freeze and thaw conditions.
- They expand slightly with time.
- Prone to chemical attacks.
- Burning of bricks makes pollution.
- 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:
- Less costly than 1st class bricks.
- Can be used in permanent structures with plastering on them.
- Can be used for single-storeyed load-bearing structures.
Disadvantages Of Second Class Bricks:
In addition to the disadvantages of the first-class bricks,
- The water absorption is 22% thus making it more susceptible to seepage and freeze-thaw cycles.
- They don’t have well defined edges.
- The minimum compressive strength is only 7 N/mm2.
C. Third Class Bricks:
These types of brick are table molded but burnt in clamps instead of kilns. This imparts poor quality to the bricks. These bricks are slightly under burnt. These 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.|
In addition to the disadvantages of the second-class bricks,
- The water absorption is 25% thus making it more susceptible to seepage and thus cannot be used in areas with heavy rains.
- They don’t have well defined edges or smooth finishes.
- The minimum compressive strength is only 3.5 N/mm2.
D. Fourth Class Bricks:
These types of brick are also called 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, size, and color. 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 are also known as flint lime bricks. They are made up of calcium and silica. These bricks are not hardened by burning. Instead, they are hardened by chemical processes. Various pigments can be added to the bricks to produce different colors such as black, green, grey, red, brown, and yellow.
- Due to the impressive colors, they are ideal for ornamental purposes.
- Compressive strength is 10 N/mm2.
- Due to smooth finish requires less amount of plastering.
- Produce greater fire resistance than clay bricks.
- Provide sound insulation and improve the acoustics of the building.
- Perform well against efflorescence.
- They have low abrasive strength and hence not usable for wearing surfaces like pavements, sidewalks, etc.,
- They can shrink after placing. Require Special considerations to counteract the shrinking of the bricks.
3. Concrete Bricks:
Advantages Of Concrete Bricks:
- Higher compressive strength than clay bricks.
- Provides a very pleasing appearance and can be used for the façade of the building.
- Have a smooth finish thus requires less amount of plastering.
- Provide greater fire resistance than clay bricks.
Disadvantages Of Concrete Bricks:
- Concrete bricks shrink and are not suitable for foundations.
- The maximum lifespan of a concrete block is only 65 years.
- It does not resist acid attack or efflorescence.
- 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:
- Clay is a precious mineral on the earth. The use of clay is replaced with fly ash – a waste product of the coal industry.
- Fly ash bricks are more resistant to freeze-thaw cycles.
- Higher compressive strength of 30 N/mm2.
- Reduces mercury pollution.
- Saves 20% of the cost.
- Possible to produce in 24 hours.
- Low water absorption percentage than clay bricks.
- Light in weight and thus reduce the cost of the foundation.
- Do not require soaking in water before usage.
Disadvantages Of Fly Ash Bricks:
- Not all fly ash is compatible with concrete.
- Due to the smooth finishes, the bonding may be less.
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 type of brick can be made of clay, silica, bauxite, chromite, or magnesite.
- Low thermal coefficient of expansion helps to withstand high temperatures.
- High strength and resistance for palling.
- High water absorption capacity.
Uses: Chimneys, boilers, kilns, and furnaces.
6. Engineering Bricks:
Engineering bricks are 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:
- Suitable for cold weather regions.
- Can be used in underground construction.
- No pleasing appearance hence suitable for underground works like sewers, tunnels, and manholes.
- Costly 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 the best types of brick 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 the 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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