Shape characteristics of coarse aggregates are important to performance of materials or mixes. This test method covers the determination of the percentages of flat particles, elongated particles or flat and elongated particles in coarse aggregates

For shape determination of flat particle sizing, set the width of a particle in the larger end of the Caliper, then tighten the pivot screw. Without adjusting the Caliper, determine the thickness of the same particle in the smaller measuring end of the Caliper. If the particle fits within the smaller gap, it is considered flat. Elongated particle determination uses the same steps. If the particle is larger than the small measurement in both situations then the particle is considered neither flat nor elongated.

TESTING STANDARD
ASTM D 4791-95
RSNI T-01-2005