What additive is added to mortar to increase its bonding abilities?

• A. Plaster of Paris
• B. Hydrated lime
• C. Gypsum
• D. Portland cement

Answer: (B)

Hydrated lime is commonly added to mortar to enhance its bonding abilities. The addition of hydrated lime increases the plasticity and workability of the mortar, making it easier to apply and improving the adhesion to masonry surfaces. It also helps to retain moisture, which is essential for the curing process, leading to a stronger set once the mortar hardens. Hydrated lime helps in creating a more flexible bond that can accommodate minor movements in the structure without cracking.

In contrast, while plaster of Paris, gypsum, and Portland cement are components used in various building materials, they do not serve the same function as hydrated lime when it comes to improving bonding in mortar. Plaster of Paris is primarily a quick-setting material used for decorative finishes, gypsum is mainly used for plastering and drywall applications, and Portland cement is a key ingredient in concrete and mortar but does not specifically enhance the bonding ability in the same way lime does.