Performance of Two Overlay Strategies Under Heavy Vehicle Simulator Trafficking

Abstract

The California Department of Transportation (Caltrans) has two primary strategies for the overlay of flexible pavements: overlay with dense-graded asphalt concrete (DGAC) and overlay with asphalt rubber hot mix gap graded (ARHM-GG). Caltrans ARHM-GG overlays typically are designed to be about half the thickness of DGAC overlays for a given set of conditions. The results of a study using heavy vehicle simulator trafficking to evaluate the relative performance of the two strategies for typical California conditions and to analyze the distress mechanisms are presented. The study showed that the half-thickness ARHM designs used by Caltrans are reasonable and that the primary distress mechanism is reflection cracking. Continued hardening of the asphalt-bound and unbound layers was shown to occur in the overlaid pavements. Details of deflection studies are included.