NTS STUDY: Chemical Changes During the Burning of Bricks

Chemical Changes During the Burning of Bricks

It is very important to understand what happens to the clay when it is burnt.

Physical Changes (Up to 640°C): When clay is heated to approximately 640°C, only physical changes occur. Moisture is driven out, organic matter is burnt away, and the water of crystallization is expelled. If this clay is cooled back down, it absorbs moisture from the air and returns more or less to its original state. If such a block is submerged in water, it disintegrates. Such under-burnt clay is unstable.
Chemical Changes (700°C to 1000°C): If we heat the clay between 700°C and 1000°C, chemical changes occur where the Alumina and Silica fuse together. This results in a compound that is strong and stable. This product is fundamentally different from the original clay and does not revert to mud upon cooling. It does not crumble when immersed in water. Therefore, proper burning at the required temperature is a necessity in brick manufacturing.
Vitrification (Above 1300°C): If the clay is heated beyond 1300°C, the material becomes vitrified. The bricks begin to lose their shape. Tiles heated at these high temperatures are called Vitrified Tiles, which are widely used today as floor tiles.

Bricks are manufactured in traditional sizes and also in metric sizes prescribed by the Bureau of Indian Standards (BIS).

Modular Bricks: Metric-sized bricks conforming to BIS standards are also known as Modular Bricks.
Frog: The depression made on the top face of the brick is called a Frog.
- Purpose: It serves as a "key" for the mortar to bind the bricks together and is also used to house the manufacturer's name.
- Placement: Brickwork is constructed with the frog facing upwards.
Nominal Size: This is the size of the brick including the thickness of the mortar. In standard brickwork, mortar thickness should not exceed 10 mm (3/8").
Tile Bricks: Bricks with a thickness less than normal are called tile bricks and are used for roofing or paving.

Quantity Calculation: For one cubic meter (1 $m^3$ ) of brickwork, approximately 500 metric bricks are required.
FPS System: For 100 cubic feet (100 $ft^3$ ) of brickwork, approximately 1350 bricks are needed (excluding wastage).
Standard FPS Size: The nominal size for FPS bricks is 9" x 4.5" x 3".