To increase mortar bonding, what should be added?

To increase mortar bonding, what should be added?

• A. Add Water
• B. Add Fly Ash
• C. Add Hydrated Lime
• D. Add Cement

Answer: (C)

Introducing hydrated lime into mortar enhances bonding because lime-based mixes are more plastic, breathable, and flexible. This allows the mortar to adhere better to porous masonry like brick or stone and to accommodate slight movements without cracking. Hydrated lime forms a cohesive matrix with the sand that grips the substrate through capillary action and elasticity, improving long‑term adhesion with traditional masonry surfaces. Water is only needed for achieving the right workability; adding more water won’t increase bond and can weaken the mortar. Fly ash can alter workability and strength but doesn’t specifically boost bonding to historic masonry. Cement increases strength but makes the mortar less compatible with old substrates, reducing breathability and long‑term bonding.

Introducing hydrated lime into mortar enhances bonding because lime-based mixes are more plastic, breathable, and flexible. This allows the mortar to adhere better to porous masonry like brick or stone and to accommodate slight movements without cracking. Hydrated lime forms a cohesive matrix with the sand that grips the substrate through capillary action and elasticity, improving long‑term adhesion with traditional masonry surfaces. Water is only needed for achieving the right workability; adding more water won’t increase bond and can weaken the mortar. Fly ash can alter workability and strength but doesn’t specifically boost bonding to historic masonry. Cement increases strength but makes the mortar less compatible with old substrates, reducing breathability and long‑term bonding.