Masonry Materials – Minimum compressive strength of mortar for load-bearing brickwork In the context of load-bearing brick masonry, what is the minimum compressive strength that the mortar should achieve (express your choice in N/cm² as given in the options)?

Introduction / Context:
Mortar strength is a key parameter for load-bearing brick masonry because it governs the bond between bricks and the compressive performance of the wall. Codes and handbooks group mortars into classes with specified 28-day strengths. For basic load-bearing work in conventional buildings, a minimum specified strength threshold is adopted to ensure adequate safety and serviceability.

Given Data / Assumptions:

• Brickwork is load-bearing, not merely infill.
• Mortar strength is the 28-day cube/compression value.
• Options are provided in N/cm²; 100 N/cm² equals 1 MPa.

Concept / Approach:
Low-strength mortars may be acceptable for non-load-bearing partitions, but load-bearing masonry requires a minimum class to resist axial compression and to develop reliable bond. A commonly cited benchmark for minimum mortar class in load-bearing brickwork is about 1 MPa (100 N/cm²). This level balances constructability, economy, and performance for typical small to medium structures.

Step-by-Step Solution:
Interpret units: 100 N/cm² = 1 MPa; 50 N/cm² = 0.5 MPa; 150 N/cm² = 1.5 MPa; 200 N/cm² = 2 MPa.Identify the minimum level that is generally specified for load-bearing: ≈ 1 MPa.Choose the option that matches 1 MPa: 100 N/cm².

Verification / Alternative check:
Many schedules of mortar classes show grades around 1 MPa or higher for load-bearing walls, while richer mixes (higher MPa) are used when higher masonry strengths are required or in severe exposure conditions.

Why Other Options Are Wrong:

• 50 N/cm²: too weak for load-bearing work.
• 150 or 200 N/cm²: stronger than the minimum; acceptable, but the question asks for the minimum.
• 250 N/cm²: likewise higher than necessary for the specified minimum.

Common Pitfalls:
Confusing brick compressive strength with mortar strength; both influence masonry strength, but mortar minimums ensure adequate bond and bed performance. Also, ensure proper curing and joint thickness control to achieve the specified strength.

Final Answer:
100 N/cm²