Prediction of Absorbed, Inert, and Effective Bituminous Quantities in Reclaimed Asphalt Pavement

Abstract

This paper presents methods to predict quantities of absorbed, inert, and effective bituminous material in reclaimed asphalt pavement (RAP) for particular sets of conditions; three RAP sources were investigated. The approach couples a data set of properties for 568 asphalt mix designs spanning five years of practice and testing of 100% RAP with added virgin binder; 394 compacted specimens and 68 loose specimens of 100% RAP were tested. A method to predict RAP absorbed asphalt was developed requiring two inputs: (1) total asphalt content; and (2) RAP effective specific gravity when coated with virgin binder. The method, was shown to yield more reasonable results than conventional methods, which were shown to very likely give incorrect absorbed asphalt estimates in some conditions. The relative effectiveness of RAP surface asphalt was evaluated, and estimates of inert and effective RAP asphalt were made for a variety of temperature, compactive effort, and warm mix additive conditions. Results showed different behaviors between RAP sources and between hot and warm mix temperatures.