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
Apparatus for test
- Balance
- Metal gauge
Procedure
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 its mean dimension. The test is applicable only to aggregates whose least dimension is not smaller than 6.3 mm.
Determination of elongation index
Download the 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
SP 23 (1982) Handbook On Concrete Mixes [PDF] Download
SP 24:1978 Explanatory Handbook On IS 456 [PDF] Download