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Flakiness Index Test for Coarse Aggregates for Concrete 50


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

 The flakiness index of an aggregate is the percentage by weight of particles in it whose least dimension (thickness) is less than three-fifths of their mean dimension. (The test is not applicable to sizes smaller than 6.3 mm).

 This method covers the determination the flakiness of the coarse aggregate.

Procedure for flakiness test

  1. The sample size is taken and is sieved through IS Sieve (63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3) mm.

  2. Minimum 200 pipes of each fraction (such as passing 50 mm and retained on 40 mm and so on) to be tested are taken and weighed (as W 1, W 2,———- gm.).

  3. Separate the flaky material by using the standard flakiness gauge as shown below:


  1. Take the weight of flaky material which passes through standard gauge for each fraction such as w1, w2, ——-gm.



Flakiness Index (FI)


Weight of all fraction material passing the gauge

x 100

Total weight of all fractions sample


Flakiness 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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