Which type of lime is best to use with Portland cement for mortar?

Which type of lime is best to use with Portland cement for mortar?

• A. Type N
• B. Type S
• C. Type I
• D. Type III

Answer: (B)

When you mix lime with Portland cement in mortar, you want a lime that provides good bond, workability, and durability in a cement-rich mix. Type S lime is designed for cement–lime mortars, offering higher strength and better bond with Portland cement while still retaining the plasticity and water retention that lime provides. This combination helps the mortar grip masonry well and resist cracking from movement and moisture. Type N is a lighter-duty lime and doesn’t offer the same bond strength with cement, making it less ideal for cement-rich mixes. Type I and Type III are cement classifications, not lime types, so they don’t provide the lime properties that improve cement–lime mortars.

When you mix lime with Portland cement in mortar, you want a lime that provides good bond, workability, and durability in a cement-rich mix. Type S lime is designed for cement–lime mortars, offering higher strength and better bond with Portland cement while still retaining the plasticity and water retention that lime provides. This combination helps the mortar grip masonry well and resist cracking from movement and moisture.

Type N is a lighter-duty lime and doesn’t offer the same bond strength with cement, making it less ideal for cement-rich mixes. Type I and Type III are cement classifications, not lime types, so they don’t provide the lime properties that improve cement–lime mortars.