Answer:

White washing is a process of applying a white mixture of lime and water to the exterior surfaces of buildings. It is commonly used to improve the appearance and protect the walls from weathering and decay. One of the key components of white washing is lime, which helps in binding the mixture and providing durability to the coating.

Types of Lime used in White Washing:

1. Quick Lime: Quick lime, also known as calcium oxide (CaO), is produced by heating limestone at a high temperature. It is highly reactive and has a strong affinity for water. When mixed with water, quick lime undergoes a chemical reaction called slaking, which produces slaked lime or calcium hydroxide (Ca(OH)2). Quick lime is commonly used in white washing due to its affordability and availability.

2. Fat Lime: Fat lime, also known as non-hydraulic lime, is produced from high calcium limestone. It is a pure form of lime that does not contain any impurities. Fat lime reacts slowly with carbon dioxide in the air and hardens by absorbing carbon dioxide over time. It is commonly used in white washing as it provides good workability and a smooth finish to the coating.

3. Hydraulic Lime: Hydraulic lime is produced by adding a small amount of clay or other pozzolanic materials to fat lime during the manufacturing process. It has the ability to set and harden in the presence of water, similar to cement. Hydraulic lime is commonly used in areas where higher strength and durability are required, such as in damp conditions or for exterior applications.

Correct Answer:

The correct answer to the question is option 'B' - Fat lime. Fat lime is commonly used in white washing due to its workability, smooth finish, and ability to absorb carbon dioxide over time, resulting in a hardened and durable coating. Quick lime and hydraulic lime are also used in other construction applications, but they are not as commonly used in white washing as fat lime.

In conclusion, fat lime is the commonly used type of lime in white washing due to its desirable properties and affordability. It provides a smooth and durable coating, enhancing the appearance and protecting the walls from weathering and decay.