Good brick earth

Composition and Properties of Good Brick Earth

In this comprehensive article, you are going to learn definition, composition and properties of good brick earth:

Definition of Bricks

The artificial material of construction in the form of clay blocks of uniform size and shape are known as bricks.

Uses of Bricks

The bricks are being commonly used for constructing walls, columns, roofs, paring floors and as course aggregate for concrete work in foundation under floors etc.

Composition of Good Brick Earth

A good brick earth should be such that it can easily be moulded and dried without cracking and wrapping. A good brick earth should have the following composition.

1. Alumina or clay (20% to 30%) by weight.

2. Silica or sand (35% to 50%) by weight.

3. Silit (20% to 30%) by weight.

The total content of clay and Silt shall not be less than 50%.

4. Remaining ingredients which include:

Lime (Cao)

Oxide of iron

Magnesia oxide


Sodium potash

The soluble materials shall not be more than 2% by weight.

Properties of Good Brick Earth

The properties of various ingredients of a good brick earth are discussed below:

1. Alumina

It is the principal constituent of every kind of brick earth. It imparts plasticity to the brick earth which is essential for proper moulding of bricks Alumina or Clay in brick earth shrinks and cracks on drying. It also wraps and becomes very hard on burning unless mixed with sand.

2. Silica

It exists in brick earth either in chemical composition mixed with clay or sand. Sand alone is infusible but it fuses in the presence of lime and oxide of iron at kiln temperature. Sand or silica in brick earth prevents the shrinkage, cracking and wrapping of bricks it also makes the bricks durable. Exess of silica makes the bricks brittle and weak.

3. Lime

A little quantity of lime present in brick earth in a finely and cause the grains of sand to melt. It helps to bind the particles of brick earth together. It also reduces shrinkage of bricks.

4. Oxide of Iron

A small quantity of oxide of iron present in brick earth also acts as a flux. It helps the grains of sand to melt and binds the particles of clay together. It also provides the required red colour to the bricks on burning. But excess of oxide of iron makes the bricks dark blue.

5. Magnesia

Small quantities of magnesia in brick earth makes the brick of yellowish colour and reduces shrinkage. But excess if magnesia leads to be decay of bricks.

6. Manganese

The presence of manganese in small quantity in brick earth makes the brick still darker or even black.

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