Bricks may define as a structural unit of rectangular shape and convenient site that is made from suitable types of clays by different processes involving molding, drying, and burning. In this article, you will learn about the materials used to make brick and its properties.
Even at present, brick is the most basic and favored material for common constructions though out the world.
The popularity of brick as a material of constructions is because of their local and cheap availability, strength, durability, reliability and insulating property against heat and sound.
Composition of brick or materials used in making brick
In general, it is observed that any soil that contains one-fourth part of clay and three by fourth parts of sand and silt is suitable for making bricks.
Good brick earth should be such that when prepared with water it can be easily molded dried and burnt without cracking or warping. It should contain a small quality at finely divided lime to help in binding the particles of brick together by melting the particles of sand.
A little oxide of iron should also be present which would give the brick its peculiar red color and act as a flux in the same manner as lime.
However, suitable brick earth should have various constituents in the following proportion.
i) Alumina or clay (20% – 30%)
- It shows the plastic character to the clay in wet conditions and is capable of being molded to any shape.
- When alumina is greater than 30% brick will become more plastic and also shrink more and develop cracks on drying.
- If less than 20%, it may be difficult to mold to proper shapes and develop cracks on a
molding. So it provides plasticity resistance against shrinkage and makes the brick hard.
ii) Silica or sand (50% to 60%)
- Silica is present in much clay in two forms as a constituent of clay minerals and also as free. It is in the form of sand or quartz.
- Silica is infusible except at very high temperature but in the presence of alumina is nearly equal proportions and the oxide of iron it fuses at low temperature.
- Unlike the silicate of Alumina, its presence in clay produces hardness, resistance to heat, durability and prevents shrinkage and warping.
- Excess of it makes the bricks brittle.
iii) Lime (4% to 6%)
- When present in small quantities in the finely divided state it reduces shrinkage of brick, helps silica to melt at lower temperature and binds the particles of the brick together resulting in greater strength of brick.
- Excess of lime causes the brick to melt and lose its shape.
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iv) Iron oxide (4% to 6%)
- Iron oxide acts as a flux, it lowers down the softening temperature of silica and other clay components during firing.
- The iron oxide imparts the very characteristic red color to the burnt brick.
- The excess of iron oxide makes the brick too soft during the burning stage, they suffer deformation in shape and make the dark blue color.
- A deficiency of iron oxide in the clay may make their burning difficult and also give then a yellowish appearance.
v) Magnesia: (1% to 2%)
- Small qualities at magnesia in brick earth make the brick of yellowish color and reduce shrinkage.
- But excess of magnesia leads to the delay of bricks.
If you are confused or unclear about this topic. Kindly check out a similar type of article by civil today: Click Here
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