Flakiness Index

Each particle in a sample is passed through a thickness gauge to identify flaky (thin, plate-like) pieces. The flakiness index is the combined weight of flaky particles expressed as a percentage of the total sample weight.

Flaky aggregate packs poorly, increases void content, and tends to align under compaction, all of which reduce the strength and workability of concrete and bituminous mixes — so most specifications cap the allowable flakiness index.