Part 1 covers particle size and shape: sieve analysis (grading curve, fineness modulus, sand grading zones), and the flakiness and elongation indices. Grading governs water demand, workability and packing; excessive flaky/elongated particles reduce strength and increase water demand. These are the most-run aggregate tests because they drive the mix.
Key Requirements
•Sieve analysis on a representative sample (sampled per IS 2430) → grading curve, fineness modulus, sand grading zone
•Grading judged against IS 383 limits — out-of-zone sand/aggregate inflates water demand and harms the mix
•Flakiness index and elongation index limited — excessive flaky/elongated particles weaken concrete and raise water demand
•Combined flakiness + elongation considered for shape quality
•Results feed the IS 10262 mix design (grading, FM, shape)
Reference Tables
IS 2386 Part 1 — what it measures
Property
Drives
Sieve analysis / grading
Water demand, workability, packing
Fineness modulus (sand)
Sand zone, mix proportioning
Flakiness index
Strength, water demand (shape)
Elongation index
Strength, workability (shape)
Judge grading/indices against IS 383 limits and the current BIS edition.
Practical Notes
✓Grading and silt vary across one stockpile by more than the IS 383 tolerance — the test only protects the mix if the sample was drawn per IS 2430.
✓Flaky/elongated aggregate is a hidden water-demand and strength problem — shape matters as much as size.
Common Mistakes
⚠Sieve analysis on a non-representative (convenience) sample.
⚠Ignoring flakiness/elongation when only checking grading.
⚠Accepting out-of-zone sand and compensating with extra water (kills strength).