- 2081 Bhadra · 5 marks
Fineness modulus of coarse aggregate (numerical)
Short answer
Sum of cumulative percentages retained on sieves 80mm to 150μm is 713.33; dividing by 100 gives a fineness modulus of 7.13.
A sieve analysis conducted on a sample of coarse aggregate reveals the following data. Determine the fineness modulus of the coarse aggregate.
| IS sieve size | 80 mm | 40 mm | 20 mm | 10 mm | 4.75 mm | 2.36 mm | 1.18 mm | 600 micron | 300 micron | 150 micron | Lower than 150 micron |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Weight retained (kg) | 0 | 0 | 6 | 5 | 4 | 0 | 0 | 0 | 0 | 0 | 0 |
Fineness modulus = (sum of the cumulative percentages retained on the standard sieves 80, 40, 20, 10, 4.75, 2.36 and 1.18 mm, and 600, 300 and 150 micron) / 100 (IS 2386 Part 1).
Total weight of sample = 0 + 0 + 6 + 5 + 4 = 15 kg.
| IS sieve | Weight retained (kg) | % retained | Cumulative % retained |
|---|---|---|---|
| 80 mm | 0 | 0 | 0 |
| 40 mm | 0 | 0 | 0 |
| 20 mm | 6 | 40.00 | 40.00 |
| 10 mm | 5 | 33.33 | 73.33 |
| 4.75 mm | 4 | 26.67 | 100.00 |
| 2.36 mm | 0 | 0 | 100.00 |
| 1.18 mm | 0 | 0 | 100.00 |
| 600 micron | 0 | 0 | 100.00 |
| 300 micron | 0 | 0 | 100.00 |
| 150 micron | 0 | 0 | 100.00 |
| Total | 15 | 100 | 713.33 |
Answer: Fineness modulus of the coarse aggregate = 7.13 (all particles lie between 40 mm and 4.75 mm, and the value is within the usual range of about 5.5-8.0 for coarse aggregate).
✓ Answer checked by Claude Opus 5.5 (high effort)
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