Multi-scale evaluation of the effect of ras on the fracture properties of asphalt mixtures

Abstract

A comprehensive laboratory testing program was conducted to examine the blending between recycled asphalt shingles (RAS) and virgin asphalt binders and to evaluate the effect of RAS on resistance of asphalt mixes to fatigue and low-temperature cracking. To this end, atomic force microscopy (AFM) was utilized to study the blending between the RAS and the virgin asphalt binders. Manufacturing waste RAS and tear-off RAS were used in this paper. A new sample-preparation procedure was developed to simulate the blending between the RAS and the virgin asphalt binders that occurs during the asphalt mixture production. The stiffness and the adhesive properties were evaluated along the blending zone between the RAS and virgin binders. Several asphalt mixtures were also used to evaluate the effect of the incorporation of RAS on the mix performance, including a control mixture with virgin materials only, and two mixtures containing 5% RAS materials. The resistance of the asphalt mixtures to fatigue cracking was evaluated using the semi-circular bend (SCB) test. In addition the potential for low-temperature cracking was evaluated using the asphalt concrete cracking device (ACCD). The AFM test results showed that very limited to no blending between manufacturing waste or tear-off RAS materials and the virgin binder considered. The asphalt mixture test results also showed that the use of tear-off RAS in asphalt mixes significantly reduced their resistance to low-temperature and fatigue cracking, which can be attributed to the very limited blending observed in the AFM experiments between the RAS and the virgin asphalt binders.