As per IS 3495 part-3 (1992), soluble salts, if present in bricks, will cause efflorescence on the surface of bricks. If the white deposits cover about 10% of the surface, the efflorescence is said to be ________.
💧 Understanding Efflorescence on Bricks
Efflorescence is the white, powdery deposit of soluble salts that appears on the surface of bricks, concrete, or other masonry. It occurs when water containing dissolved salts (like sulphates of calcium, sodium, and potassium) seeps into the brick, and then evaporates, leaving the salt crystals behind. The test and classification for this phenomenon in bricks are detailed in IS 3495 (Part 3): 1992.
🔬 Detailed Analysis of the Classifications
C. slight
This is the correct answer. According to IS 3495 (Part 3), efflorescence is classified as "slight" when the area of white deposits is not more than 10 percent of the exposed area of the brick. Since the question states the coverage is "about 10%", it falls squarely into this category.
B. moderate
This is incorrect. "Moderate" efflorescence is defined as having coverage of more than 10 percent but not more than 50 percent. While 10% is the boundary, the term "slight" is used for coverage *up to* 10%.
D. heavy
This is incorrect. "Heavy" efflorescence means the salt deposits cover more than 50 percent of the surface, which is far more than the amount stated in the question.
A. nill
This is incorrect. A "nill" or "nil" rating means there are no perceptible deposits of efflorescence, which contradicts the premise of the question that deposits are present.
📊 Summary: Efflorescence Ratings as per IS 3495 (Part 3)
| Rating | Area Covered by Deposits |
|---|---|
| Nil | 0% (No perceptible deposit) |
| Slight | ≤ 10% |
| Moderate | > 10% and ≤ 50% |
| Heavy | > 50% (but not powdering or flaking) |
| Serious | Heavy deposits that result in powdering or flaking of the surface. |
💡 Study Tips
- The 10% and 50% Rule: These are the key boundaries to remember for efflorescence ratings. Slight (≤10%), Moderate (10-50%), Heavy (>50%).
- Visualize the Cause: Think of efflorescence as "salts + water". If you remove either, you prevent the problem. This is why using clean water and well-burnt bricks (which have lower salt content) is important.
- Test Method: The test involves placing a brick on end in a shallow dish of distilled water, allowing it to absorb water, and then observing the deposits after the water has evaporated.