Which of the following IS sieve size is used, to check the fineness of cement by sieve test?
🔬 Understanding Fineness of Cement
The fineness of cement is a measure of the size of its particles. It is a crucial property because it influences the rate of hydration. Finer cement has a larger surface area, which leads to a faster reaction with water, quicker strength development, and more heat generation. There are three main methods to test for fineness:
- Sieve Analysis Test: This is a direct method that measures particle size by sieving cement.
- Air Permeability Test: An indirect method (using Blane's or Nurse's apparatus) that measures the specific surface area of the cement particles.
- Sedimentation Method: Another indirect method (using Wagner's Turbidimeter) that also determines the specific surface area based on how particles settle in a liquid.
📝 Detailed Analysis of the Options
B. 90 µm
This is the correct answer. The Sieve Analysis test for cement fineness is standardized using the IS Sieve No. 9, which corresponds to a sieve opening of 90 micrometers (µm). In this test, a 100-gram sample of cement is continuously sieved for 15 minutes. The weight of the cement residue left on the sieve is then measured. For the cement to be of acceptable quality, this residue should not exceed a specified limit (e.g., 10% for OPC). This standard sieve size ensures consistent and comparable results across all tests.
A. 37.5 µm, C. 15 µm, and D. 20 µm
These are incorrect sieve sizes for this specific standard test. While sieves of these sizes exist and are used for analyzing very fine materials or aggregates, they are not the standard specified in the IS codes for the fineness test of cement. Using a sieve that is too fine (like 15, 20, or 37.5 µm) would be impractical and would retain a very high percentage of the cement, making the test meaningless for its intended purpose of quality control. The 90 µm sieve provides the right balance to check for excessively coarse particles without being overly restrictive.
📊 Summary: Sieve Test Requirements for Cement Fineness
| Parameter | Specification |
|---|---|
| IS Sieve Size Used | 90 µm (IS Sieve No. 9) |
| Sample Weight | 100 grams |
| Sieving Duration | 15 minutes |
| Max. Residue for OPC, RHC, LHC | ≤ 10% |
| Max. Residue for HAC, SSC | ≤ 5% |
💡 Study Tips
- 90 is the Magic Number: For the cement sieve test, the number to remember is 90 µm. This is a very common question in exams.
- Sieve Test = Direct Method: Associate the sieve test with being a *direct* measurement of particle size (it physically separates particles). This contrasts with the Air Permeability test, which is an *indirect* measurement of surface area.
- Residue Limit is 10%: The most common limit for residue on the sieve is 10%. Knowing this can help in related questions.