Abstract
The performance enhancing effect of crumb rubber modified (CRM) binders has received considerable research attention, and the benefits are well understood. However, research has typically considered high dosages (>20%) in gap and open-graded asphalt mixtures, whereas the potential of low-dosage CRM binders (5%–15%) as an anti-aging modifier for local roads has received comparatively little attention. To better understand these potential benefits, low-dosage CRM binders (5%, 10%, and 15% rubber by weight of binder) were prepared using both short and long blending durations and were conditioned in the laboratory to replicate production and field aging. Rheological analysis using a dynamic shear rheometer subjected binders to temperature-frequency sweeps to better understand intermediate temperature responses post-aging. It was found that increasing crumb rubber contents improved the high-temperature performance, whilst maintaining reduced stiffness in the low-temperature test regions. Further analysis of master curves and Black space diagrams, in addition to rheological properties such as Glover-Rowe parameter, R-value (rheological index), GC (crossover modulus), and other index parameters, found that increasing rubber contents improved binder durability and reduced thermo-oxidative aging impacts. While higher dosages (15%) were observed to perform best, it was concluded that the incorporation of any amount of crumb rubber using either blending approach provided anti-aging benefits relative to the unmodified base binder.