Aggregates as a constituent of concrete

Flakiness Index Test and Elongation Index Test on Aggregates

Posted by

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

The Elongation Index is the percentage by weight of particles whose greatest dimension is greater than 1.8 times its mean dimension. The test applies 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 the Indian Standard code on methods of test for aggregates for concrete. IS 2386 (part-1) 1963 PDF

Also read –
Manufacture Sand (M-Sand)
Different types of Admixtures used in concrete
SP 23 (1982) Handbook On Concrete Mixes [PDF] Download
SP 24:1978 Explanatory Handbook On IS 456 [PDF] Download

Leave a Reply

Your email address will not be published. Required fields are marked *