Variability of Reclaimed Asphalt Pavement (RAP) Properties within a State and Its Effects on RAP Specifications

Abstract

Reclaimed Asphalt Pavement (RAP) is a highly recyclable material that provides a source of aggregates and asphalt binder to be re-utilized in new paving mixtures. State transportation agencies in the U.S. have constructed their specifications to allow for the use of RAP in new paving mixtures, but with conditions so that suitably performing mixtures are developed. These conditions are imposed because of concerns that the aged binder contained within the RAP may negatively impact the resultant mixtures performances. Many state transportation agencies have constructed their specifications with respect to the AASHTO guidance on utilizing RAP in Superpave mixtures. Questions remain as to the accuracy of these methods, especially if the RAP stockpiles’ properties vary greatly. The purpose of this study was to characterize and compare the properties of the RAP stockpiles being used throughout Massachusetts and to determine the impacts that these properties have on the currently utilized specifications for RAP. The properties of the RAP stockpiles within Massachusetts varied greatly. No geographical or regionalization of RAP properties could be made. By default, the current specifications for using RAP makes no distinction between RAP stockpile properties, especially at smaller percentages like <15% or at low RAP binder ratios (RAPBR). The data from this study demonstrated that this could lead to mixtures without the appropriate virgin binder grade and therefore they could exhibit subpar performance. Specifications should be revised to require more thorough testing of RAP for each mixture design, regardless of the allowable percentage or RAPBR, to ensure adequate mixture performance is maintained.