What are bricks made of |Composition of Bricks, Uses

Brick may be defined as a structure unit of rectangular shape and convenient size that are made from suitable types of clays by different processes involving moulding, drying and burning. There is a different composition of brick or I have discussed here for What are bricks made of. So read below for all.

The Different Composition of bricks are given below:-

  1. Alumina or clay
  2. Silica or sand
  3. Lime
  4. Magnesia
  5. Iron oxide

Brick is the most basic and favoured material for common constructions throughout the world. The popularity of brick as material construction is because of their local and cheap availability, strength, durability and insulating properties against heat and sound.

What are bricks made of
What are bricks made of

What are bricks made of i.e Composition of good bricks

In general, it is observed that clay any soil that contains 1/4 part of clay and 3/4  parts of sand and silt is suitable for making brick. Good brick earth should be such that when prepared with water it can be easily moulded dried and burnt without cracking. Suitable brick earth should have various constituents in the following portion.

  1. Alumina or clay (20%-30%): It makes brick earth plastic so that it can be moulded after drying impact hardness. If brick contains an excess amount of clay, they shrink, crack and warp in the process of drying and burning. 
  2. Silica or sand (50%-60%): It prevents shrinkage, cracking and warping of bricks. Excess amount of silica destroy the cohesion between particles and makes the brick brittle and weak.
  3. Lime(4%-6%): It acts as flux helping the grain of sand to melt and bind the particles of clay together.
  4. Magnesia(1%-2%): Magnesia present in clay with oxide of iron make the brick yellow, but larger amounts of magnesia may cause bricks to decay.
  5. Iron oxide(4%-6%): Iron oxide acts as flux, it lowers down the softening temperature of silica and another clay component during firing.

Qualities of good brick

  • It should have a rectangular shape, rectangular surface and red coloured appearance.
  • It should have a standard size to the specified dimension(230*110*55)mm.
  • A good brick should not absorb water more than 20% of its dry weight.
  • It should not have a fracture surface.
  • Its colour should be uniform.
  • Edges should be sharp and at right angles to each other.
  • Its crushing strength should not be less than 100kg/cm2.

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Types of brick

Bricks may primarily be divided as sun-dried brick and brunt brick. Sun-dried bricks are not burnt brick generally used for temporary construction. Depending upon the strength, appearance and usefulness of burnt brick, they are further classified as:

1) First-class brick: First class bricks are the good quality bricks with the following characteristics:

Characteristics of first Class Bricks

  • A first-class brick should be free from stones, cracks etc.
  • It should have a rectangular plane surface with parallel sides and straight, sharp and right-angled edges.
  • It should not break when dropped from a 1-2m height.
  • It should have a minimum crushing strength of 10.5mpa.
  • Its specific gravity should be greater than 1.8.
  • Its compressive strength should not be less than 140kg/cm2.

2) Second class brick: second class bricks are the inferior quality of bricks that are used for minor structural purpose. Following are the characteristics of the second class brick.

  • A  second class brick should be well brunt but may not be uniform in shape, size and colour.
  • It may have a rough surface.
  • It may have some cracks, lumps etc.
  • It may not have well defined fair surface and parallel edge.
  • It should have minimum crushing strength of 7mpa.

3) Third class brick: These are light yellow coloured, unsuitable for the structural purposes and sometimes suitable in water. They are soft and easily broken. They are used in temporary construction.

4) Over brunt brick: these are vitrified bricks with irregular shape and dark or blue colour. They are hard and strong. They are used in the soil as road metal. These bricks may also be classified as machine-made bricks or chimney made bricks.

Uses of bricks

  • It is used for the construction of any type of wall.
  • It is used for the construction of floors.
  • It is used for the construction of arches.
  • It is used for the construction of brick retaining wall.
  • It is used for ornamental works.

Advantages of bricks

  • It has a uniform shape and size.
  • It is economical.
  • It is hard and durable.
  • light in weight as compared to stone.
  • Raw materials of bricks are easily available.
  • It has good compressive strength for ordinary construction.
  • Maintenance cost is low.
  • It is highly fired resistant.

Disadvantages of bricks

  • It has less tensile strength.
  • It is not strong than other materials such as stone.
  • It is not durable as compared to stone.
  • It cannot be used in high seismic zones.
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"Structural Engineer" with over 5 years of experience in estimation, structural design, and surveying. I am passionate about using his skills to create safe and sustainable structures. I am also a keen writer, and I enjoy sharing my knowledge and experiences with others.