A typical Type S mortar mix uses 1 part Portland cement, 1 part hydrated lime, and 6 parts sand. What is the resulting strength and why is the lime included?

• A. It yields high bond strength and water resistance; lime provides workability and flexibility.
• B. It yields high strength but poor workability; cement only.
• C. It yields low strength; lime makes it rigid.
• D. It yields moderate strength; lime reduces shrinkage.

Answer: (A)

Type S mortar is built to deliver strong bonding and durable performance in masonry joints, balancing strength with workability. The cement provides the bulk of compressive strength, while the lime adds plasticity and elasticity. That plasticity lets the mortar fill joints more completely, adheres well to bricks or blocks, and accommodates slight movements from temperature changes or settling without cracking. The result is a mortar that bonds tightly to units and resists water intrusion more effectively than a cement-only mix. The lime portion is included specifically to improve workability and flexibility, not to increase rigidity; this combination yields high bond strength and good durability in wet or exposed conditions.