Effects of recycled shingle and virgin asphalt binder mixing on mixture performance

Abstract

The use of recycled asphalt shingles (RAS) in asphalt concrete leads to questions regarding the mixing of recycled and virgin asphalt binders. These questions concentrate on: the degree of mixing, whether mixing or blending of the asphalt binders occurs, and how the degree of mixing affects performance. Researchers to date have focused efforts on vetting out the degree of blending through various asphalt binder and mixture tests. Research at the University of Illinois used mixture performance tests to evaluate blending. Mixture designs were developed using traditional Superpave methods with 2.5 and 5.0 % RAS. Then, samples with the same virgin aggregate structure and RAS pulp (material remaining post-extraction) and completely mixed asphalt binder were created for high and low temperature evaluation using Hamburg wheel and Disk-Shaped Compact Tension (DCT) tests. In addition, the recently developed Hamburg-DCT Performance Space Diagram was employed to consider mixture property shifts. Research findings demonstrated that up to 20 % asphalt binder replacement met volumetric and performance specifications for both high and low temperature tests. Furthermore, the completely mixed asphalt binder and RAS pulp mixtures performed approximately similar to the traditionally mixed samples at both high and low temperatures.