Recommendations for the characterization of RAP aggregate properties using traditional testing and mixture volumetrics

A Federal Highway Administration (FHWA) funded study was conducted to investigate the influence of extraction methods on aggregate properties. The properties of the virgin aggregates were compared with those of aggregates extracted from laboratory-produced recycled asphalt pavement (RAP) from four different aggregate sources. The extracted and actual asphalt binder contents were also compared. The study investigated the influence of the extraction method on tendencies to under- or over-estimated certain mix design properties. The test results were also examined to determine the impact of the RAP aggregate properties on the voids in mineral aggregate (VMA) over different RAP percentages. Recommendations were made for the most appropriate method to estimate the RAP aggregate specific gravities based on acceptable levels of error in VMA for mixtures with varying levels of RAP.