Aggregate elongation index — 25–6.3 mm

Calculate a standalone elongation index from length-gauge retained masses for a complete sample passing 25 mm and retained on 6.3 mm.

Observations and units

• Passing sieve (mm)
• Retained sieve (mm)
• Total mass in this fraction (g)
• Mass retained by length gauge (g)

Calculation

Elongation index (%) = 100 × total mass retained by the length gauges / total mass of all fractions gauged. Within-fraction percentage = 100 × retained mass / fraction mass; contribution = 100 × retained mass / whole sample mass. Sum contributions, not fraction percentages; use exact masses throughout.

Method reference and limitations

IS 2386 (Part 1):1963, clauses 5.1–5.5; Table V; supplied amendments 1–4 reviewed. Standalone elongation profile only, for one complete sample passing 25 mm and retained on 6.3 mm. Enter every occupied supported fraction once, including fractions with zero retained elongated mass. Use prescribed Table V length gauges: 25/20 = 40.5 mm; 20/16 = 32.4 mm; 16/12.5 = 25.6 mm; 12.5/10 = 20.2 mm; 10/6.3 = 14.7 mm. Do not recompute them from the nominal 1.8 multiplier. Larger fractions are excluded: the source has blank length-gauge entries for some bands, and the amended 64.4 mm larger gauge is outside this profile. Minimum 200 pieces per tested fraction and apparatus checks remain laboratory responsibilities. Clause 5.5 gives a mass ratio, not a count ratio; no fixed reporting increment is invented. This is not a combined flakiness/elongation index and must not be applied to only the non-flaky residue of a different procedure.

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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