The compressive strength of common building bricks should not be less than
💪 Understanding Compressive Strength of Bricks
Compressive strength is a fundamental property indicating a brick's quality. It measures the maximum load a brick can bear before crushing. The term "common building bricks" refers to the range of bricks used in general construction. Indian Standard IS 1077 classifies these bricks into different grades based on their average compressive strength. The question asks for the absolute minimum strength any brick must have to be considered a "common building brick" fit for use.
🔬 Detailed Analysis of the Options
A. 3.5 N/mm²
This is the correct answer. This value represents the minimum compressive strength for a third-class brick as per IS 1077. Since a third-class brick is the lowest grade considered for use in any form of permanent (though non-load-bearing) construction, its minimum strength is the baseline for all "common building bricks". Any brick with a strength lower than this would not be suitable for general construction.
B, C, and D
These options are incorrect because they represent the minimum strengths for higher classes of bricks.
- 10.5 N/mm² is the minimum for a first-class brick.
- 7.5 N/mm² is the minimum for a second-class brick.
- 5.5 N/mm² is a strength that falls within the second or third class range, but it is not the absolute minimum requirement.
📊 Summary: Crushing Strength by Brick Class (IS 1077)
| Brick Class | Minimum Compressive 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
- "Common" means "Lowest Standard": In this context, interpret "common building brick" as the lowest acceptable grade for any standard construction, which is the third-class brick.
- Know the Baseline: Memorize 3.5 N/mm² as the absolute minimum strength for any classified building brick.
- Review the Hierarchy: Keep the strength classification in mind: 10.5 (1st) > 7.5 (2nd) > 3.5 (3rd). This helps in quickly identifying which value corresponds to which class.