The size of the fine aggregates does not exceed:
Try it first: pick an option, then read the explanation.
Correct answer: D. 4.75 mm
Detailed Explanation: Upper Size Limit of Fine Aggregate
The upper size boundary for fine aggregate is universally defined at 4.75 mm in Indian Standards (IS 383, IS 456). Any aggregate particle that is retained on the 4.75 mm sieve is classified as coarse aggregate. This boundary aligns with the international No. 4 sieve (4.76 mm in ASTM).
Why D (4.75 mm) is correct: Fine aggregate, by definition, passes through a 4.75 mm IS sieve. The size therefore does not exceed 4.75 mm. The other options (2.75, 3.00, 3.75 mm) are not standard sieve sizes and are not correct boundaries. The lower limit of fine aggregate is 75 microns (0.075 mm); material finer than this is classified as silt, clay, or dust.Size Ranges of Aggregate Fractions
| Fraction | Size Range |
|---|---|
| Silt / Clay | <75 µm (0.075 mm) |
| Fine Aggregate (Sand) | 75 µm to 4.75 mm |
| Coarse Aggregate | 4.75 mm to 80 mm |
| Cyclopean Aggregate | >75 mm |
Key Concepts for Students
- 4.75 mm is the FA/CA dividing sieve — the most frequently tested size boundary in aggregate classification questions.
- Fine aggregate between 75 µm and 150 µm is retained on the 150 µm sieve and is the finest fraction counted in the fineness modulus calculation.
- Material passing 75 µm is classified as deleterious fine material and limited to ≤3% by weight in fine aggregate for concrete.