North Carolina General Contractors Practice Exam

What is the purpose of using hydrated lime in mortar?

1. To increase the color

2. To enhance water retention

3. To improve workability and bond

4. To reduce the weight

The correct answer is: To improve workability and bond

Using hydrated lime in mortar primarily serves to improve workability and bond. Hydrated lime acts as a plasticizer, which enhances the mortar's ability to be manipulated easily during application. This quality is crucial for ensuring that the mortar can be spread and shaped effectively, allowing for better adhesion between the bricks or stones being laid. The improved workability means that the mortar can fill gaps more efficiently, resulting in a stronger bond as it sets. Additionally, lime contributes to the durability and flexibility of the mortar mix. When mortar contains hydrated lime, it can absorb small amounts of movement or settling in the structure without cracking, thereby enhancing the overall longevity of the construction. This characteristic is particularly beneficial in climates where temperature fluctuations may cause expansion and contraction. While some of the other options touch on aspects related to mortar composition, they do not capture the primary purpose of hydrated lime. For example, increasing color is typically achieved through other means, and while water retention is important in many mixes, hydrated lime's main role is more aligned with workability and bonding rather than just retaining moisture.