Comparing Fine Aggregate Angularity with Aggregate and Hot-Mix Asphalt Performance Tests.

This paper describes how the Fine Aggregate Angularity (FAA) was determined for thirteen different fine aggregate sources (angular and round) and eight aggregate blends. AASHTO T304, Methods A, B, and C, as well as the Kansas DOT test procedure, KT-50, were used to determine the FAA value. The Direct Shear test and the Compacted Aggregate Resistance (CAR) test were also used to provide a more performance-based aggregate parameter for comparison. The eight different aggregate blends were used to construct eight different fine-graded 12.5mm Superpave HMA mixtures, each having similar gradation and volumetric properties. The HMA mixtures were tested in the Asphalt Pavement Analyzer and Repeated Shear and Frequency Sweep at Constant Height test modes of the Superpave Shear Tester to evaluate their respective rutting properties. The results indicated that if cubical shaped fine aggregates are not present, the FAA and CAR correlate well, as did the CAR to the angle of internal friction calculated from the direct shear tests. Comparing the FAA value of the aggregate blends to published criteria of the HMA permanent deformation tests, the Superpave recommended FAA value of 45 was validated. The results of the HMA mixture testing and FAA comparison also allowed for the recommendation of a pass/fail CAR value for use in Superpave Mix Design.