Investigating Asphalt Mix Design Using Reclaimed Asphalt Shingles (RAS)

摘要

Reclaimed Asphalt Shingles (RAS) are being incorporated into asphalt mixes at historic rates in NorthAmerica. Some suggest that a portion of the asphalt binder from RAS should not be counted as binder inthe asphalt mix design. AASHTO PP53-09 includes a method to determine a RAS asphalt binderavailability factor. This factor purports to quantify the percentage of RAS binder that contributes toperformance of the mix, however is actually dependent on the non-bituminous components of the asphaltshingles. As such, the availability factor is considered to be inappropriate for use.This paper evaluates the effect of RAS on volumetric properties of asphalt mixes to better quantify theavailability of asphalt binder from the shingles. An HMA mix was designed using the same percentage ofRAS with the asphalt content of the RAS artificially altered using partial extraction. Volumetric propertiesand asphalt binder availability were determined according to AASHTO PP53-09. The experiment wasrepeated using shingles from three sources.Results indicate that VMA increased as a result of the shingle addition. The VMA increase wasindependent of the shingle asphalt binder percentage. As a result asphalt binder availability factorscalculated according to AASHTO PP53-09 are highly variable and non-intuitive.