Determination of flakiness index of the coarse aggregate

Dnyan Deshmukh

Staff member
Flakiness Index

Ref : IS 2386 (Part I)

Purpose : To determine the flakiness index of the coarse aggregate.

Significance : Coarse aggregate having flakier particles will adversely affect the strength of concrete.

Definition : The flakiness index of the aggregate is the percentage by weight of particles in it, whose least dimension (thickness) is less than three fifth of their mean dimension.

Apparatus : Balance, Metal guage, Sieve set.

Test procedure:

Take a sample of about 3 Kg.

Divide the sample into four quadrants.

Select two opposite quadrants and sieve them through the sieves arranges in the following order 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 12.5mm, 10mm, 6.3mm.

Take the aggregate sample sieved through 63mm and retained on 50mm sieve. Find the weight W1 gm.

Pass that sample through 63-50mm size of thickness gauge.

Find the weight of the aggregate passing through the respective slot (ie through 63-50mm) of the gauge w1 gm.

Repeat the same procedure with 50-40mm, 40-25mm, 31.5-25mm, 25-20mm, 20-16mm, 16-12.5mm and 10-6.3mm size of the thickness gauge.

Observation table (As per the clause 4.5 & table V of IS 2386 – part I)
Flaky observ table.png

Flaky index calcu.png


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