Used to determine if the aggregate particles are classified as flaky or not, when they have a thickness (smallest dimension) of less than 0.6 of their mean sieve size, this size being taken as the mean of the limiting sieve apertures used for determining the size fraction in which the particle occurs.

The flakiness index of an aggregate sample is found by separating the flaky particles and expressing their mass as a percentage of the mass of the sample tested.

The test cannot be used for material that either passes through a 6.30 mm test sieve or is held back by a 63.0 mm test sieve.