The water absorption (expressed in percentage) for burnt clay perforated bricks should not be more than
🧱 Understanding Perforated Bricks
Perforated bricks are a type of building brick characterized by vertical holes (perforations) passing through them. These perforations reduce the weight of the brick and improve its thermal insulation properties. Because they are often used in structural walls, their quality, including water absorption, is strictly regulated by specific standards, such as IS 2222:1991.
🔬 Detailed Analysis of the Options
B. 15
This is the correct answer. According to Indian Standard IS 2222, the average water absorption for burnt clay perforated bricks, after 24 hours of immersion in cold water, should not exceed 15% of their dry weight. This stricter limit (compared to some solid bricks) ensures they are dense, durable, and suitable for their intended purpose.
A. 5
This is incorrect. A 5% water absorption limit is extremely low and is typically associated with vitrified tiles or high-strength engineering bricks, not standard perforated building bricks.
C. 25
This is incorrect. A 25% water absorption limit is the maximum allowed for a low-quality, third-class *solid* brick. Perforated bricks are expected to meet a higher quality standard.
D. 35
This is incorrect. A water absorption of 35% is unacceptably high for any type of structural brick and would indicate very poor quality and high porosity.
📊 Summary: Water Absorption Limits for Different Bricks
| Brick Type (As per IS Code) | Max. Water Absorption (%) |
|---|---|
| Perforated Brick (IS 2222) | 15% |
| First Class Solid Brick (IS 1077) | 20% |
| Second Class Solid Brick (IS 1077) | 22% |
| Third Class Solid Brick (IS 1077) | 25% |
💡 Study Tips
- Perforated = 15%: This is a key value to memorize. Perforated bricks have a stricter water absorption limit than even first-class solid bricks.
- Distinguish Brick Types: Always be aware that different types of bricks (solid, perforated, hollow, engineering) are governed by different standards and have different property requirements.
- Know the Codes: Associating IS 2222 with perforated bricks helps distinguish their properties from common solid bricks covered by IS 1077.