Pick up the correct statements from the following
Correct Answer: D. All option are correct
📚 Detailed Explanation: Sieve Sizes and Particle Classification
This question verifies knowledge of the standard sieve boundaries used in aggregate classification. All three statements reflect correct standard values from IS 383 and IS 2386.
Why D (All option are correct) is correct:
Statement A — The standard IS sieve series for coarse aggregate goes up to 80 mm (IS 460). Aggregate retained on 80 mm is classified as cyclopean/plum aggregate.
Statement B — The 75 µm IS sieve is the lower boundary for fine aggregate. Particles passing 75 µm are silt, clay, or dust and are deleterious beyond specified limits.
Statement C — Silt and clay (fine-grained soils) are defined as particles <0.075 mm (75 µm) in the IS soil classification. Their individual size is <0.06 mm by the Wentworth scale and IS soil classification, with clay being <0.002 mm.
Statement A — The standard IS sieve series for coarse aggregate goes up to 80 mm (IS 460). Aggregate retained on 80 mm is classified as cyclopean/plum aggregate.
Statement B — The 75 µm IS sieve is the lower boundary for fine aggregate. Particles passing 75 µm are silt, clay, or dust and are deleterious beyond specified limits.
Statement C — Silt and clay (fine-grained soils) are defined as particles <0.075 mm (75 µm) in the IS soil classification. Their individual size is <0.06 mm by the Wentworth scale and IS soil classification, with clay being <0.002 mm.
Particle Size Classifications
| Material | Size Range | IS Reference |
|---|---|---|
| Coarse aggregate | 4.75 mm to 80 mm | IS 383 |
| Fine aggregate | 75 µm to 4.75 mm | IS 383 |
| Silt | 2 µm to 75 µm (0.002–0.075 mm) | IS 1498 |
| Clay | <2 µm (<0.002 mm) | IS 1498 |
Key Concepts for Students
- 75 µm = the critical boundary: particles finer than this are deleterious when present in excess amounts in aggregate.
- Fine material content (<75 µm) in fine aggregate must not exceed 3% for concrete and 15% for plaster per IS 383.
- Standard IS sieve sizes: 80, 63, 40, 20, 10, 4.75 mm; 2.36, 1.18, 0.6, 0.3, 0.15 mm (= 150 µm).