Stiffness of High-RAP Asphalt Mixtures: Virginia’s Experience

Abstract

In the year 2006, the price of asphalt binders in the United States increased by almost 50% over the 2005 prices. The use of higher recycled asphalt pavement (RAP) percentages with locally available binders was adopted as an approach to reduce the demand on specialty more expensive virgin binder and virgin aggregates in Virginia. The purpose of this study was to investigate concerns that the performance of these higher RAP mixtures could be compromised because of excessive mixture stiffening due to the aged RAP binder. The results indicated that measured binder stiffnesses of high-RAP mixtures are not significantly affected by RAP amount, high temperature true grade of high-RAP mixtures averaged only approximately 2.0°C above that of base virgin binder, and that the correlation between binder stiffness and flow number for the selected high-RAP mixtures considered was good. The study concludes that the addition of higher amounts of RAP to asphalt-concrete mixtures currently produced in Virginia has not resulted in excessively stiffened mixtures as previously thought; the stiffnesses of high-RAP mixtures are primarily governed by the virgin binder stiffness.