Aggregate Test

Flakiness & Elongation Index Test – Method Statement Flakiness & Elongation Index Test Procedure • Apparatus • IS Sieve Table • Results format Contents Object Apparatus Theory Procedure IS Sieve & Gauge Table Observations & Formulae Result Notes & References OBJECT To determine the elongation index of the given aggregates To determine the flakiness index of the given aggregates APPARATUS The apparatus for the shape tests consists of the following: A standard thickness gauge A standard length gauge IS sieves of sizes: 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3 mm A balance of capacity 5 kg, readable and accurate up to 1 g THEORY The particle shape of aggregates is determined by the percentages of flaky and elongated particles contained in it. For base course and construction of bituminous and cement concrete types, the presence of flaky and elongated particles is considered undesirable as these cause inherent weakness with possibilities of breaking down under heavy loads. Thus, evaluation of shape of the particles, particularly with reference to flakiness and elongation is necessary. The Flakiness Index of aggregates is the percentage by weight of particles whose least dimension (thickness) is less than three-fifths (0.6 times) of their mean dimension. This test is not applicable to sizes smaller than 6.3 mm. The Elongation Index of an aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than nine-fifths (1.8 times) their mean dimension. This test is not applicable for sizes smaller than 6.3 mm. PROCEDURE Sieve the sample through the IS sieves (as specified in the table below). Take a minimum of 200 pieces of each fraction to be tested and weigh them, or take the maximum number available up to 200 pieces. To separate the flaky materials, gauge each fraction for thickness on a thickness gauge. The width of the slot used should be of the dimensions specified in column (4) of the table for the appropriate size of the material. Weigh the flaky material passing the gauge to an accuracy of at least 0.1% of the test sample. To separate the elongated materials, gauge the non-flaky material for length on a length gauge. The width of the slot used should be of the dimensions specified in column (6) of the table for the appropriate size of the material. Weigh the elongated material retained on the gauge to an accuracy of at least 0.1% of the test sample. … IS SIEVE & GAUGE TABLE Passing through IS Sieve, mm Retained on IS Sieve, mm Weight of fraction (200 pieces), g Thickness gauge size, mm Weight passing thickness gauge (Xi) Length gauge size, mm Weight retained on length gauge (Yi) 63 50 W1 23.90 X1 – – 50 40 W2 27.00 X2 81.00 Y1 40 31.5 W3 19.50 X3 58.00 Y2 31.5 25 W4 16.95 X4 – – 25 20 W5 13.50 X5 40.5 Y3 20 16 W6 10.80 X6 32.4 Y4 16 12.5 W7 8.55 X7 25.5 Y5 12.5 10 W8 6.75 X8 20.2 Y6 10 6.3 W9 4.89 X9 14.7 Y7 Total W = X = Y = OBSERVATIONS & FORMULAE Record every fraction’s weights clearly. Use at least two significant figures for percentages and record sample piece counts. Flakiness Index = ((X1 + X2 + …) / (W1 + W2 + …)) × 100 Elongation Index = ((Y1 + Y2 + …) / (W1 + W2 + …)) × 100 Fraction Total pieces taken (Wi) Flaky weight (Xi) Elongated weight (Yi) Remarks 63–50 mm 50–40 mm 40–31.5 mm 31.5–25 mm 25–20 mm 20–16 mm 16–12.5 mm 12.5–10 mm 10–6.3 mm Total RESULT I. Flakiness Index = X II. Elongation Index = Y NOTES & REFERENCES This document preserves the original technical content. Do not alter the definitions if your contract specification references a specific IS edition. Reference: IS:2386 (Part 1) — Methods of test for aggregates for concrete (shape tests). Use the latest edition for definitive gauge slot values. Record environmental conditions and the balance calibration status with every test batch for traceability. Document: • Generated: 20 Nov 2025 Enter Values to Calculate Indices W Values X Values Y Values Calculate Results: Flakiness Index: 0% Elongation Index: 0% Quick Reference: Flakiness & Elongation Index Test Applicable Aggregate Size: Only aggregates ≥6.3 mm are tested. Minimum Sample Count: 200 pieces per sieve fraction (or maximum available). Flakiness Index Criterion: Particles with thickness < 0.6 × mean size. Elongation Index Criterion: Particles with length > 1.8 × mean size. Required Gauges: Thickness gauge for flakiness; Length gauge for elongation. Accuracy: Weigh materials to at least 0.1% accuracy of sample weight. Outcome: FI = (Flaky Weight / Total Weight) × 100; EI = (Elongated Weight / Total Weight) × 100. Purpose: Ensures aggregates are suitable for pavement and concrete strength requirements. Top FAQs – Flakiness & Elongation Index Test What is the minimum aggregate size for these tests? Aggregates smaller than 6.3 mm are not tested. Why are flaky and elongated particles undesirable? They reduce pavement strength and break easily under heavy loads. How many aggregate pieces must be tested? A minimum of 200 pieces from each sieve fraction. Which gauges are required? A standard thickness gauge for flakiness and a length gauge for elongation. What are the formulas used? Flakiness Index = (Total Flaky Weight / Total Sample Weight) × 100; Elongation Index = (Total Elongated Weight / Total Sample Weight) × 100. Prepared by Kishor Kumar Related Aggregate Tests for Highway & Concrete Works Explore detailed test procedures, calculations and acceptance criteria as per IS, MoRTH & IRC specifications: ✅ Aggregate Impact Value (AIV) Test – Toughness of Aggregates ✅ Los Angeles Abrasion Test – Wear & Abrasion Resistance ✅ Aggregate Crushing Value (ACV) Test – Strength Evaluation ✅ Flakiness & Elongation Index Test – Shape Characteristics ✅ Water Absorption Test – Durability & Porosity Check 📌 Pro Tip: Use AIV, ACV, Los Angeles Abrasion, and Shape & Water Absorption Tests together to ensure aggregate suitability for bituminous layers & cement