Aggregates as a constituent of concrete

Flakiness index test and elongation index test (shape tests on aggregate)

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Coarse aggregate constitutes the biggest part of concrete. It is desirable that aggregates are of desired properties. Two shape tests namely elongation index test and flakiness index test are being useful for selection of proper aggregates.

Flakiness index

It is the percentage by weight of particles in it whose least dimension is less than three-fifth of their mean dimension.

Determine the flakiness index

Gauge for flakiness index test

Apparatus for test

  • Balance
  • Metal gauge


At first the sample is seived with Indian standard sieve.

Then each fraction of seived material is gauged in turn on flakiness index.The total amount passing the
gauge shall be weighed to an accuracy of at least 0.1 percent of the weight of the test sample.

This test is not applicable to sizes smaller than 6.3 mm.

Elongation index

Elongation index is the percentage by weight of particles whose greatest dimension is greater than 1.8 times than its mean dimension. The test is applicable only to aggregates whose least dimension is not smaller than 6.3 mm.

Determination of elongation index

Length gauge to determine elongation gauge
length gauge

Download Indian standard code on methods of test for aggregates for concrete. IS 2386(part-1) 1963.

Also read => Manufacture Sand (M-Sand)

Different types of Admixtures used in concrete

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