The crushing strength of a first class brick is
Try it first: pick an option, then read the explanation.
Understanding Crushing Strength of Bricks
Crushing strength, also known as compressive strength, is one of the most important properties of a brick. It measures the maximum compressive load a brick can withstand per unit area before it fails or crushes. This value is a direct indicator of the brick's quality and its ability to bear loads in a structure, especially in load-bearing walls. It is typically measured in Newtons per square millimeter (N/mm²), which is equivalent to a Megapascal (MPa).
Detailed Analysis of the Options
C. 10.5 N/mm²
This is the correct answer. According to Indian Standard IS 1077, the minimum average compressive strength for a first-class brick should not be less than 10.5 N/mm². This level of strength ensures the brick is durable and suitable for high-quality, permanent, load-bearing structures.
D. 7.5 N/mm²
This is incorrect. A minimum crushing strength of 7.5 N/mm² is the standard requirement for a second-class brick. These are suitable for internal walls and structures that will be plastered.
B. 5.5 N/mm²
This is incorrect. A strength of 5.5 N/mm² is closer to the requirement for a third-class brick, which is typically specified to have a strength not less than 3.5 N/mm² or 5 N/mm² depending on the local authority. These are used for temporary, non-load-bearing structures.
A. 3 N/mm²
This is incorrect. This value is below the minimum standard for even a third-class brick and would be considered very low quality, unsuitable for any significant construction work.
Summary: Crushing Strength by Brick Class (IS 1077)
| Brick Class | Minimum Crushing Strength (N/mm²) | Typical Application |
|---|---|---|
| First Class | ≥ 10.5 | Load-bearing walls, exposed masonry, arches. |
| Second Class | ≥ 7.5 | Internal walls, plastered structures. |
| Third Class | ≥ 3.5 | Temporary structures, non-load-bearing partitions. |
Study Tips
- The "10.5" Benchmark: Memorize 10.5 N/mm² as the key minimum strength for a first-class brick.
- Strength Hierarchy: Remember the clear order of strength: First Class > Second Class > Third Class. The required strength value decreases as the class number increases.
- Strength = Load-Bearing: Directly associate high crushing strength with the brick's suitability for use in load-bearing walls.
- Check the Code: For exams, it's helpful to associate these strength values with the Indian Standard IS 1077.