Optimised asphalt overlay configuration to mitigate reflective cracking using a new innovative full-scale testing

Reflective cracking is a major challenge in asphalt concrete (AC) overlays, particularly in Illinois, which has one of the highest percentages of overlay roads in the U.S. This study focused on optimising AC mix and thickness selection to mitigate reflective cracking of overlays. A survey of Illinois’ neighboring state agencies identified four overlay configurations for interstate and non-interstate applications. A large-scale testing device was designed and built in-house to simulate a moving dual-tyre assembly using two hydraulic actuators. Eight large-scale laboratory tests were conducted to assess the combined impact of material and thickness on its performance to control reflective cracking. The study concluded that the most effective overlay combines a high-modulus, flexible wearing surface with a flexible binder course. Key strategies for further mitigation include treating deteriorated PCC joints/cracks, ensuring AC mixtures have adequate flexibility, applying polymer-modified lifts, achieving proper interlayer bonding and maintaining sufficient overlay thickness and density.