Classification of Bricks

Classification of Bricks

Brick is one of the oldest building materials in civil engineering. Different types of bricks are used according to different work. Classification of Bricks can be divided based on their properties. Brick is the most popular and leading construction material, due to the cheap, durable and easy to use, it is used a lot in construction. Clay bricks are used for building exterior and interior walls, partitions, piers, footings and other load-bearing structures.

Brick is rectangular in shape. Brick can be made of clay or a mixture of sand and lime or Portland cement concrete. Clay bricks are commonly used because they are economical and easily available.

The length, width and height of a brick are interlinked as below:

Length of  brick = 2 × width of the brick + thickness of the mortar

Height of  brick = width of brick

Size of a modular brick (also known as standard bricks)  should be 19 × 9 × 9 cm and 19 × 9 × 4 cm.

However, the bricks available in most parts of the country are still 9 “× 4.5” × 3 “in size, these are called field bricks.

Weight of such a brick is 3.0 kg. An indent called a frog is given in the bricks which is 1-2 cm deep for bricks 9 cm high.

The frog size is 10 × 4 × 1 cm. The purpose of providing the frog is to make a key to hold the mortar when the bricks are laid with frogs on top. Frog is not given in bricks that are 4 cm high.

Read more : Brick size, Dimension test for Standard brick

Classification of bricks

Clay bricks are classified based on their physical and mechanical properties.

1. First class
2. Second class
3. Third class
4. Fourth class

First class bricks

1. They are well burnt, and are of dark red, cherry or copper color.
2. They should be free from defects, cracks and stones.
3. It should be of similar texture.
4. The surface should be smooth and parallel, with sharp and straight edges, with bricks, rectangular, square corners.
5. When two bricks are struck against each other, a metallic or ringing sound should be heard.
6. When it is immersed in water for twenty four hours, its absorption should be 12-30.

Uses: First class bricks are can be used for pointing, exposed face work in masonry structures, flooring and reinforced brick work.

Second class bricks

1. Minor cracks and slight deformities may occur.
2. Water absorption allowed around 16–20% of its dry weight.
3. Crushing strength should be at least 7.0 N / mm2.

Uses: Second-class bricks can be used for all important or insignificant hidden masonry. This is used at places where the masonary is to be plastered.

Third class bricks

1. Third class bricks are underburnt.
2. These are soft and light colored which when struck against each other produces a dull sound.
3. The water absorption of third class is about 25 percent of the dry weight.

Uses : It is used for building temporary structure not subjected to heavy load.

Fourth class bricks

They are overburnt and badly distorted in shape and size and are brittle in nature.

Uses: This bricks are used for foundation, floors and as aggregate in concrete.

Classification of brick based on Compressive strength as per IS : 1077

Class	Average compressive strength not less than (N/mm²)
35	35.0
30	30.0
25	25.0
20	20.0
17.5	17.5
15	15.0
12.5	12.5
10	10.0
7.5	7.5
5	5.0
3.5	3.5

Properties of good bricks

Size and shape: The bricks should have uniform size, rectangular shape and sharp straight edges.

Colour: Bricks should have the uniform dark red color.

Texture and compactness: The surface of the brick should not be very smooth which causes the mortar to slip. The brick should have compacted with uniform texture.

Hardness and soundness: There should be no impression when the brick is scratched with the finger of the brick, the brick should be so hard  that when two bricks collide, the sound of metal is produced.

Water absorption: Water  Absorption should not exceed 20 percent of its dry weight when the bricks are immersed in water for 24 hours.

Crushing strength: Crushing strength should be at least 10 N / mm2

Brick earth: Brick earth should not contain stones, sanders, organic matter, salt, etc. They affect the quality and durability of the brick.

Ingredients of Good bricks

To preparation  bricks, the clay is molded into the desired shape after going through many processes. After the bricks dry, it should not shrink and no cracks should develop. Silica and alumina are mainly added to the soil used for brick-making, which causes the soil to behave like plastic when water is mixed into the soil. It also contains some amount of iron, manganese, sulfur, etc.

Silica	50–60%
Alumina	20–30%
Lime	10%
Magnesia	< 1% ( Less than 20% )
Ferric oxide	< 7% ( Less than 20% )
Alkalis	< 10% ( Less than 20% )
Carbon dioxide	Very small percentage
Sulphur trioxide	Very small percentage
Water	Very small percentage