Laboratory and Full-Scale Evaluation of 4.75-mm Nominal Maximum Aggregate Size Superpave Overlay

Abstract

A 4.75-mm nominal maximum aggregate size Superpave® mix developed by the Virginia Department of Transportation was placed as a thin treatment over existing, aged sections in an accelerated pavement test facility. Half the loaded wheelpath was paved with and half without the treatment to explore rutting susceptibility and quantify the ability to defer cracking. Loose mix was collected during construction to verify the mix design and for laboratory dynamic modulus, flow number, Hamburg wheel tracking, and axial fatigue testing. The mix was produced according to the volumetric specifications, but the in-place density was higher than the target. Although laboratory tests indicated poor resistance to rutting, full-scale performance illustrated that the total rutting in the treated sections was equal to or less than the total rutting in the sections without the overlay. Top-down cracking was significantly delayed as a result of the presence of the thin overlay, but once the pavement sections were aged and brittle, the treatment could not delay cracking.