The role of gradation type with respect to the restricted zone, nominal maximum aggregate size (NMS), coarse aggregate type, and fine aggregate angularity (FAA) on HMA rutting performance was evaluated using the prototype scale INDOT/Purdue Accelerated Pavement Testing facility (APT).

Asphalt mixtures were designed in accordance with Superpave criteria employing two NMS (19 and 9.5 mm), two coarse aggregate types (limestone and granite), three FAA levels (39, 44, and 50), and three aggregate gradations relative to the Superpave restricted zone (above, through, and below).

Significant difference in rutting performance of 19 and 9.5 mm mixtures was not observed. Granite mixtures were more rut resistant than limestone mixtures. FAA effect was apparent when comparing mixtures with FAA of 39 against those with FAA of 44. However, mixtures incorporating very high FAA values did not perform better than those incorporating typical FAA values. Equally adequate performance was obtained with mixtures having gradations plotting above (ARZ), through (TRZ), and below (BRZ) the restricted zone.