Characterization of aggregate interlocking in hot mix asphalt by mechanistic performance tests

The interlocking of aggregate is critical during compaction. Nevertheless, few mix design specifications include any specific requirements for locking points, mainly because it is difficult to determine when interlocking happens during compaction precisely. This study's objectives were to validate the locking point concept by applying performance tests and evaluating aggregate interlocking influence on the rutting resistance and the fatigue cracking. Two types of asphalt mixture composed of limestone aggregates and PG 64–22 binder and designed at different Ndesign were used in this study. Two types of performance tests, the Flow Number and the IDEAL CT, were used to determine and confirm the locking point's definitions. Results showed that the locking point (LP)2-2-3 and LP3 definitions during Superpave gyratory compaction were the most reasonable to define the locking point based on the vertical axial strain from the Flow Number and the Cracking Tolerance Index (CTindex) from the IDEAL CT test.