Fineness modulus of fine aggregate varies from
Correct Answer: A. 2.0 to 3.5
📚 Detailed Explanation: FM Range of Fine Aggregate
The fineness modulus (FM) summarises the particle size distribution in a single number. Knowing the typical FM range for fine aggregate is important for mix design and for quickly identifying whether a given aggregate is suitable for concrete.
Why A (2.0 to 3.5) is correct: Per IS 383 and standard concrete technology texts, the FM of fine aggregate (sand) ranges from approximately 2.0 (Zone IV — finest) to 3.5 (Zone I — coarsest). Option B (2.5–3.0) is too narrow — it excludes Zone I and Zone IV sands. Option C (1.5–2.0) is below the minimum; FM <2.0 is too fine for concrete. Option D (3.5–6.5) overlaps with coarse aggregate range; FM above ~4.0 is coarse aggregate territory.
FM Ranges by Aggregate Type
| Aggregate Type | FM Range |
|---|---|
| Fine aggregate (sand) | 2.0–3.5 |
| Coarse aggregate (10–20 mm) | 5.5–6.5 |
| Coarse aggregate (20–40 mm) | 6.0–8.0 |
| Combined aggregate | Usually 5.0–7.0 |
Key Concepts for Students
- Fine aggregate FM: 2.0 to 3.5 — the lower the FM, the finer the sand and the more water it needs.
- Medium sand (FM 2.6–2.9) is the most widely used for general concrete mixes.
- An FM below 2.0 indicates too many fines; above 3.5 indicates too coarse for typical fine aggregate classification.