Final answer:
A wall made of Portland cement mortar with lime is indeed more watertight than one without lime, making the statement false. Lime enhances mortar's water retention, durability, and self-healing properties, contributing to better watertightness.
Step-by-step explanation:
The question asks whether a wall made of Portland cement mortar without lime is more watertight than a wall made from Portland cement and lime mortar. The answer is false. Adding lime to Portland cement mortar generally enhances the mortar's ability to retain water, leading to a more watertight construction.
Lime in the mortar improves workability and helps it bind more cohesively with masonry units, resulting in a tighter seal against water penetration. Historically, mortars with lime have been known for their durability and ability to self-heal fine cracks, which contributes to long-term watertightness.
Roman concrete, consisting mainly of lime mortar, volcanic sand, and water, set an early example of a durable and watertight masonry material that has endured for centuries. The role of mortar is critical in construction, as it affects the overall strength, longevity, and water resistance of the wall.