Determination of flakiness & elongation index (FI & EI) of coarse aggregate using thickness & length gauge. Shape and size aggregate is one of the major contributing factors to the quality of concrete. The test methods are given below for flakiness & elongation index of coarse aggregate.

Test standard : IS 2386-Part I: 1963

Test Appratus flakiness & elongation index

  • Weighing Balance
  • IS sieves 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 12.5mm, 10nm, 6.3mm
  • Thickness gauge for flakiness and length gauge for elongation.

Dimension of Thickness and Length gauge

Dimension of Thickness and Length gauge

Test procedure for FI & EI

Prepared the sample of Each fraction as:

  1. Passing 63mm IS Sieve & Retained on 50mm IS Sieve
  2. Passing 50mm IS Sieve & Retained on 40mm IS Sieve
  3. Passing 40mm IS Sieve & Retained on 31.5mm IS Sieve
  4. Passing 31.5mm IS Sieve & Retained on 25mm IS Sieve
  5. Passing 25mm IS Sieve & Retained on 20mm IS Sieve
  6. Passing 20mm IS Sieve & Retained on 16mm IS Sieve
  7. Passing 16mm IS Sieve & Retained on 12.5mm IS Sieve
  8. Passing 12.5mm IS Sieve & Retained on 10mm IS Sieve
  9. Passing 10mm IS Sieve & Retained on 6.3mm IS Sieve
  • Take test sample (Minimum number of 200 pieces ) on any fraction to be tested.
  • Weigh the sample on each sieve fraction
  • Pass the sample of each fraction (Each piece) through respective sizes on thickness gauge.
  • Weigh the sample passed in each size of the thickness gauge and Note it.

Flakiness Index (%) = 100x (Total weight of sample passed in each size of thickness gauge / Total weight of sample )

  • Collect all material retained on thickness gauge
  • Note the weight of each size fraction.
  • Pass the pieces on each fraction through respective sizes in the length gauge manually.
  • Weigh the sample passed in each size of the length gauge and note it.

Elongation Index (%) = 100x Total weight of sample retained in each size of length gauge / Total weight of sample gauged (i.e retained on thickness gauge)

Combined Flakiness & Elongation Index (%) = Flakiness index (%) + Elongation index (%)

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Rajkumar ghagre

Founder & Admin of, I am a civil engineer working as a Assistant Engineer (QA/QC).

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