# Testing of industrial products - Aggregates for construction

## The Flakiness Index test method

### The principle of the method

The test consists of two sieving operations. In the first operation, the test portion is sieved into size fractions d_{i}/D_{i} using test sieves with square holes. The sieves used for this operation are members of the ISO R20 series such that d_{i} / D_{i} = 0.8 (approximately). In the second operation, each size fraction d_{i}/D_{i} is sieved using a bar sieve with parallel slots of width D_{i}/ 2.

The Flakiness Index (FI) is calculated as the mass of particles that pass the bar sieves, expressed as a percentage of the mass of the test portion.

If the three dimensions of a particle are denoted by L_{1}, L_{2} and L_{3}, with L_{1} < L_{2} < L_{3}, then for the particle to fall within a size fraction d_{i}/D_{i}, the middle dimension must satisfy, approximately, the inequality:

0.8 D_{i} < L_{2} < D_{i}

and for the particle to be classed as flaky, the smallest dimension must satisfy, approximately, the second inequality:

L_{1} < 0.5 D_{i}

so that, according to this test method, flaky particles are those for which, approximately, their smallest two dimensions satisfy:

L_{1} < 0.625 L_{2} .

### The proposed CEN method

The CEN test method has been developed from the French Standard P 18-561 (*AFNOR, 1990. P 18-561 Granulats. Mesure du coefficient d'aplatissement.*). The methods are identical except that the tolerances allowed on the widths of the slots in the bar sieves are stricter in the CEN method than in the French method.

Participants in the cross-testing experiment were sent copies of the method that was sent to CEN members for formal voting in May, 1995.