Lime is mixed with brick earth to prevent shrinkage.

Explanation:
Brick earth, which is a type of soil used for making bricks, has a tendency to shrink during the drying process. This shrinkage can lead to cracks and deformations in the bricks, reducing their strength and durability. To prevent this shrinkage, lime is mixed with brick earth.

1. Role of Lime:
Lime, also known as calcium oxide (CaO), is a common additive used in the construction industry. When lime is mixed with brick earth, it serves several purposes. One of its important properties is its ability to chemically react with water and carbon dioxide in the atmosphere through a process called carbonation. This results in the formation of calcium carbonate (CaCO3), which has a binding effect and helps to stabilize the soil.

2. Preventing Shrinkage:
The addition of lime to brick earth helps to prevent shrinkage by improving the plasticity of the soil. Plasticity refers to the ability of a material to undergo deformation without cracking or breaking. Lime acts as a plasticizer, making the soil more workable and reducing its tendency to shrink during drying. This ensures that the bricks maintain their shape and size, minimizing the risk of cracking and deformations.

3. Other Benefits:
In addition to preventing shrinkage, lime also offers other benefits when mixed with brick earth:
- Improved workability: Lime improves the workability of the brick earth, making it easier to mold and shape into bricks.
- Increased durability: Lime enhances the strength and durability of the bricks by providing a binding effect, making them more resistant to weathering and erosion.
- Reduced water absorption: Lime helps to reduce the water absorption capacity of the bricks, making them less susceptible to damage from moisture and water.

In conclusion, the addition of lime to brick earth is done to prevent shrinkage during the drying process. Lime improves the plasticity of the soil, making it less prone to cracking and deformations, resulting in stronger and more durable bricks.