Makes mortar more workable but less in strength.

• A. Cement
• B. Gypsum
• C. Lime
• D. Sand

Answer: (C)

Mortar properties come from the binder, which controls both how easy the mix is to work with and how strong it becomes. Lime as a binder gives a very workable, plastic mix that’s easy to apply and smooth, and it remains forgiving as the masonry settles. But lime mortars gain strength slowly and have lower early compressive strength than cement-based mortars because they cure by carbonation over a longer period rather than rapid hydration. This makes the mortar less strong in the short term, though it stays flexible and breathable, which is ideal for historic brickwork or structures exposed to moisture. The other materials either provide more strength (cement) at the cost of workability and breathability, are used mainly for plaster (gypsum), or are just inert aggregate (sand) without binding power. So lime best matches the description of making mortar more workable but less in strength.