Engineering Materials·MCQ explained

Pick up the correct statements from the following

Try it first: pick an option, then read the explanation.

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.

Particle Size Classifications

MaterialSize RangeIS Reference
Coarse aggregate4.75 mm to 80 mmIS 383
Fine aggregate75 µm to 4.75 mmIS 383
Silt2 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).