Significance of Flakiness Index and Elongation Index Test of Aggregate

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The Significance of Flakiness Index and Elongation Index Test of Aggregate

The test Flakiness index of aggregate is used to determine the particle shape of the aggregate specimen and each particle shape being preferred under specific condition.

The Significances of Flakiness and Elongation Index of Aggregate are Following:-

1. The degree of packing of the aggregate particles of one size depends upon their shape.
2. Due to high surface area to volume ratio, the flaky and elongated aggregate particles lower the workability of concrete mixes.
3. For cement concrete types and base coarse construction and bituminous-construction, the presentence of flaky and elongated aggregate particles are considered undesirable as they may cause inherent weakness with possibility of breaking down under heavy loads.
4. According to BS-1241, a flakiness index should not exceed 30% irrespective of the aggregate size.
5. Maximum permitted elongated index is 35%, 40% or 45% for aggregate size 2¹/₂” – 2”, 1¹/₂” - ¾” and ¹/₂” - ⅜”.
6. Both Flakiness index Elongation Index tests are not applicable to the materials of sizes smaller than 6.3 mm i.e. ¼” sieve.

 

Read also -

Angularity number test of coarse aggregate (shape test of aggregate)

Flakiness Index and Elongation Index Test on Coarse Aggregate

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