Based on particle size, aggregates are classified as fine and coarse. The standard dividing sieve size is
- A2.36 mm
- B4.75 mmCorrect
- C10 mm
- D1.18 mm
Solution
Concept
Sieve size boundary for aggregates
Formula
Fine Aggregate < 4.75 mm ≤ Coarse Aggregate
Step-by-step solution
1. Aggregate particles are divided into fine and coarse fractions according to particle size. 2. Indian Standard IS 383 and international codes establish the 4.75 mm IS sieve as the standard threshold. 3. Material predominantly passing the 4.75 mm sieve is termed fine aggregate (sand). 4. Material predominantly retained on the 4.75 mm sieve is designated coarse aggregate. Answer: B
Explanation
As specified in standard aggregate testing specifications such as IS 383, the boundary dividing fine and coarse aggregate is the 4.75 mm sieve. Particles predominantly passing through a 4.75 mm sieve down to 75 microns are classified as fine aggregate. Particles predominantly retained on the 4.75 mm sieve are designated as coarse aggregate.
Why the other options are wrong
A) 2.36 mm is an intermediate sieve in the fine aggregate grading series. C) 10 mm is a coarse aggregate grading size, not the dividing boundary. D) 1.18 mm is an intermediate fine aggregate grading sieve.
Shortcut
4.75 mm sieve: Passing = Fine aggregate; Retained = Coarse aggregate.
Common mistake
Selecting 2.36 mm or 75 microns instead of the 4.75 mm dividing boundary.
Correct answer: B) 4.75 mm