The 'fineness modulus' (FM) of sand is between 2.0 and 3.5, which indicates:
Choose the correct answer
Sand is too coarse (FM should be > 4.0)
Sand is in acceptable range — fine (2.2–2.6) to coarse (2.9–3.5); FM used for grading assessment
Sand is silt (FM < 1.0)
FM has no relevance to concrete mix
Correct Answer
B. Sand is in acceptable range — fine (2.2–2.6) to coarse (2.9–3.5); FM used for grading assessment
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Fineness modulus (FM) = (sum of cumulative % retained on IS sieves 4.75, 2.36, 1.18, 0.6, 0.3, 0.15 mm)/100. Sand FM: fine sand 2.2–2.6, medium 2.6–2.9, coarse 2.9–3.2. Higher FM = coarser sand. FM < 2.0: very fine (undesirable — high water demand). FM > 3.5: too coarse. For concrete: FM 2.6–3.0 preferred. FM of stone aggregate ≈ 6–7.
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