Sieve sizes used in grading — identify coarse vs. fine aggregate limits In standard Indian practice, IS sieves of sizes 10 mm and 4.75 mm are commonly employed in grading which category of aggregate?

Introduction / Context:
Proper grading ensures workability, minimized segregation, and optimized paste demand. Understanding sieve thresholds helps distinguish fine and coarse fractions and select appropriate grading curves for each aggregate category.

Given Data / Assumptions:

• IS sieve series and typical cutoffs.
• Boundary between fine and coarse aggregate commonly taken at 4.75 mm.
• 10 mm sieve is a standard size within coarse aggregate grading ranges.

Concept / Approach:
Fine aggregate (sand) is the fraction passing the 4.75 mm sieve. Coarse aggregate is retained on the 4.75 mm sieve and graded through larger sieves such as 10 mm, 12.5 mm, 20 mm, and 40 mm. Therefore, both 4.75 mm (as a boundary) and 10 mm (as a sizing sieve) are integral to grading coarse aggregates in practice.

Step-by-Step Solution:

Verification / Alternative check:
IS grading tables for coarse aggregates specify percentage passing/retained for 10 mm and larger sieves; 4.75 mm is included as the lower boundary for coarse aggregate.

Why Other Options Are Wrong:

• Fine aggregates are mainly graded with sieves below 4.75 mm (e.g., 2.36, 1.18, 600 µm, 300 µm, 150 µm).
• The sieves are not exclusive to both categories in the way implied; they chiefly define and grade the coarse fraction.

Common Pitfalls:
Confusing the boundary sieve (4.75 mm) with full fine aggregate grading ranges; ignoring nominal maximum size selection for mixes.

Final Answer:
Coarse aggregates