Aggregate flakiness index — mass weighted

Combine thickness-gauge mass observations across sieve fractions without averaging their individual percentages.

Observations and units

• Passing sieve (mm)
• Retained sieve (mm)
• Total mass in this fraction (g)
• Mass passing thickness gauge (g)

Calculation

Within-fraction flaky mass (%) x = 100 × flaky mass / fraction mass; fraction mass share (%) y = 100 × fraction mass / whole sample mass. Weighted contribution = x × y / 100 percentage points; overall flakiness index = sum of contributions = 100 × total flaky mass / total fraction mass. Use exact masses throughout, not a mean of fraction percentages.

Method reference and limitations

IS 2386 (Part 1):1963, clauses 4.1–4.5; Table V; supplied amendments 1–4. One worksheet is one complete sample passing 63 mm and retained on 6.3 mm. Enter every occupied supported Table V fraction exactly once; each row is a sieve fraction, not a replicate. Do not omit a fraction with no flaky particles: enter its full mass and zero flaky mass. Material above 63 mm or below 6.3 mm is outside this bounded profile. Amendments 2/3 change count-based wording to the mass-weighted calculation used here; retain the prescribed piece-count record in the laboratory. Gauge apparatus, preparation and minimum 200 pieces per tested fraction remain operator checks. Amendment 3 prescribes the 21.50 mm gauge for 40–31.5 mm; do not replace it with a recomputed nominal value. No decimal reporting increment is invented from clause 4.5, and no specification acceptance or combined shape index is supplied.

Calculation and reporting rules audited within the documented profile; physical test execution and specification acceptance remain the operator’s responsibility. Independent qualified review is not recorded. No certificate or compliance decision.

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