Superpave adopted ASTM Test Methods for Uncompacted Void Content of Fine Aggregate (C1252 Method A) to determine fine aggregate angularity (FAA). This is an indirect method for estimating fine aggregate angularity and texture. The FAA test is based on the assumption that more fractured faces will result in higher void content in the loosely compacted sample; however, this is not always true. The paving and aggregate industries have found that cubical shaped particles, even with 100 percent fractured faces, may not meet the FAA requirement for high-volume traffic. State agencies are concerned that local materials previously considered acceptable and which have provided good field performance, now cannot meet the Superpave requirements.
A study was undertaken to evaluate the ability of current Superpave FAA method to measure fine aggregate angularity, to determine if it can distinguish between good performing and poor performing aggregates, and compare FAA test results with other measures of particle angularity. Fine aggregates from different regions of USA were collected along with their performance history. Those aggregates were tested with ASTM C 1252, Method A, ASTM Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions (D 3080), Compacted Aggregate Resistance (CAR) test, visual inspection, and surface area analysis. SHRP-LTPP database was also used to find any correlation between FAA and field rutting.