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Elongation Index Test for Coarse Aggregates for Concrete 51

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 IS: – 2386 (Part – I) 2016 Method of test for aggregates for Concrete – Particle Size and Shape (Coarse aggregates)

The elongation index of an aggregate is the percentage by weight of particles whose greatest dimension ( length) is greater than one and four-fifths times their mean dimension. The elongation test is not applicable to sizes smaller than 6’3 mm.

 Procedure for Elongation Index Test

  1. The sample size as per clause 3 of the code is taken and is sieved through IS Sieve (63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3) mm.

  2. The sample retained on sieved through IS sieve 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3 mm are collected.

  3. Minimum 200 pieces of each fraction to be tested are taken and weighed (W gm = W 1+W 2+———).

  4. Separate the elongated material by using the standard elongation gauge.

  1. Take the weight of elongated material which retained through standard gauge (w gm = w1+w2+w3+———-gm).   



Elongation Index (EI)


Total Weight of material retaining on the gauge

x 100

Total weight of sample


Elongation Index Test Format

The workability of fresh concrete, pumping of concrete, and the strength of cement concrete are adversely affected by shape of particles. Flaky aggregates are avoided and should not exceed 15 percent .


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