Enhancing the Contribution of Recycled Asphalt Shingles to Asphalt Binders Using Rejuvenators

Abstract

Recycled asphalt shingles (RAS) have been a valuable recycled component in asphalt mixes for decades. However, research into how the aged and oxidized air-blown RAS binder interacts with the neat asphalt binders in asphalt mixtures is underway. Furthermore, due to the stiffness of RAS binders, RAS-containing asphalt mixtures are prone to significant cracking, particularly at low temperatures. As a result, an innovative technique was developed and used in this study to increase the contribution of RAS particles in the asphalt binder. This technique was primarily dependent on interacting RAS particles with rejuvenators before mixing them with the asphalt binder. Moreover, this technique allowed the oxidized and aged binders in the RAS to absorb aromatics to compensate for the lost low-molecular-weight fractions during the air-blowing process and alter their aged behavior. Five rejuvenators were utilized, including four pyrolysis oils (B2A, P4, P8, and P4D) and one recycling agent (Evoflex). One source of post-consumer RAS was collected, milled, and sieved into two sizes. The rejuvenator was chosen to weigh 45% of the RAS, except for the P4D, which contained a double amount of P4 oil and weighed 90% of the RAS. RAS or the RAS that interacted with oils, was mixed with one source of asphalt binder with a performance grade of 76−16. The RAS with rejuvenator samples weighing 7.5% and 15% of the asphalt binder interacted with the neat binder. The addition of P4D or Evoflex to RAS reduced the stiffness and elasticity of the modified asphalt binders due to the RAS particles' absorption of aromatics in oils. This trend improved the modified binders' fatigue and thermal cracking resistance. Milled RAS particles of a smaller size (50-100) reacted with oils more than RAS particles of a bigger size (30-50), which caused stiffer properties for the binders modified with the smaller RAS particle size.