An ordinary Portland cement when tested for its fineness, should not leave any residue on I.S. Sieve No. 9, more than ..........
🧪 The Sieve Test for Fineness
Fineness of cement is a measure of the size of its particles. The sieve test is the simplest method to check for coarse particles. It involves sieving a known weight of cement through a standard sieve for a specified time.
- Sieve Used: The standard sieve for this test is the IS Sieve No. 9, which has a mesh size of 90 microns (90µm).
- Purpose: The test ensures that the cement has been ground properly and does not contain an excessive amount of large particles, which would hydrate slowly and contribute less to early strength.
📝 Detailed Analysis of the Options
(a) 5%
This is the limit for Rapid Hardening Cement (RHC) and Portland Pozzolana Cement (PPC), which are required to be finer than Ordinary Portland Cement (OPC). It's a common distractor for the OPC question.
(b) 10%
This is the correct answer. According to IS 4031 (Part 1), when testing Ordinary Portland Cement (OPC), the weight of the residue left on the IS Sieve No. 9 after sieving should not be more than 10% of the original weight of the cement sample.
(c) 15% & (d) 20%
These values are too high and would indicate that the cement is too coarse. Such a high percentage of residue would lead to a slow rate of hydration and lower early strength, failing to meet the quality standards for OPC.
📊 Fineness Limits (Sieve Test) for Different Cements
| Type of Cement | Maximum Residue on 90µ Sieve |
|---|---|
| Ordinary Portland Cement (OPC) | 10% |
| Rapid Hardening Cement (RHC) | 5% |
| Portland Pozzolana Cement (PPC) | 5% |
| Low Heat Cement | 10% |
💡 Study Tips
- OPC = 10%: This is a fundamental value in cement testing. Directly associate Ordinary Portland Cement with a 10% limit in the sieve test.
- Finer Cements, Lower Limits: Notice that cements known for being finer (like RHC and PPC) have a stricter limit of 5%. This helps in remembering the relative values.
- Sieve No. 9 = 90 microns: Remember that IS Sieve No. 9 corresponds to a 90-micron opening size.