Fineness limit for OPC by sieve residue — IS 90-µm (IS Sieve No. 9) An Ordinary Portland Cement, when tested for fineness by dry sieving, should not leave more than what percentage residue on the 90-µm IS sieve (IS Sieve No. 9)?

Introduction / Context:
Fineness influences early strength gain, rate of hydration, and water demand. Sieve residue is a quick field check for coarser particles that might delay hydration or cause non-uniformity.

Given Data / Assumptions:

• Ordinary Portland Cement (OPC) fineness by 90-µm sieve test.
• Dry sieving procedure per IS practice.

Concept / Approach:
IS limits typically restrict the residue on the 90-µm sieve to not more than about 10% for OPC. This ensures adequate fineness for predictable setting and early strength while controlling excessive ultra-fines that raise water demand.

Step-by-Step Solution:

Verification / Alternative check:
Laboratory certificates of OPC typically report residue well below 10%, aligning with this limit.

Why Other Options Are Wrong:

• 5%: overly restrictive for a general limit.
• 15–25%: too coarse; may impair performance.

Common Pitfalls:
Using sieve residue alone to judge fineness; Blaine specific surface is also used to characterize fine fraction.

Final Answer:
10%