Performance characterization of asphalt mixtures at high Asphalt Binder replacement with recycled Asphalt Shingles

Recycled materials can be used effectively in asphalt mixtures to replace virgin asphalt binder or virgin aggregates. Virgin material (asphalt binder or aggregate) can be replaced with reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixtures. The study presented in this paper examined the effect of high asphalt binder replacement (ABR) for an asphalt mixture with a low number of design gyrations (a low N-design) and RAP and RAS on performance indicators (e.g., permanent deformation, fracture, fatigue potentials, stiffness). A developed experimental program included complex modulus, fracture, overlay reflective cracking resistance, low-temperature cracking, wheel track permanent deformations, and push-pull fatigue tests. The ABR, combinations of RAS and RAP asphalt binder, and levels in the mix ranged from 43% to 64%. Potential permanent deformation resistance of the mixtures was improved in the presence of RAS. Fracture tests at low temperature revealed no significant difference between the specimens prepared at varying percentages of ABR. Fatigue potential of mixtures increased with an increase in RAS content and ABR. The specimens prepared with 2.5% RAS and PG 46-34 showed the best fatigue potential performance. The impact of asphalt binder bumping was highlighted by the results of all tests. The improvement in fatigue life and fracture energy was noticeable when the asphalt binder type was changed from PG 58-28 to PG 46-34 at the highest ABR level. The complex modulus test results can provide crucial information about the mix viscoelastic properties, such as relaxation potential and long-term stiffness. These results can be used, along with fracture test results, to evaluate mix brittleness at relatively high ABR levels.