Characterizing Rheological Properties of Binder and Blending Efficiency of Asphalt Paving Mixtures Containing RAS through GPC

Abstract

Use of recycled asphalt shingles (RAS) into asphalt mixture has become more popular in asphalt paving industry due to dwindling natural resources and potential economic benefits. However, one critical question arises as to how much of aged asphalt binder in RAS can be effectively blended with virgin binder during mixing and construction. This paper presents a laboratory study in which gel permeation chromatography (GPC) was used to determine the blending efficiency of RAS. A correlation was first established between percentages of large molecules (LMS) obtained from GPC and rheological properties of RAS binders. Then the relationship was used to estimate the blending efficiency of RAS binders. The effects of aggregate size, RAS content, and mixing time on blending efficiency were evaluated. The test results show that the percentage of LMS was highly correlated with the complex shear modulus (G*) of asphalt binder. Increasing mixing time led to a better blending of RAS mixture. Aggregate size did not show a significant effect on blending efficiency. In this study, partial blending was achieved and the most efficient blending occurred at approximately 5% RAS by weight.