Laboratory evaluation on high temperature viscosity and low temperature stiffness of asphalt binder with high percent scrap tire rubber

The objective of this research is to utilize crumb rubber from scrap tires as an environmental friendly and sustainable additive for enhancing the high temperature and low temperature rheological properties of asphalt binders for asphalt pavements. Two different crumb rubber sources with different gradations – fine and coarse – were used in this project. The crumb rubber-modified (CRM) binder was produced by adding 10, 15, 20 and 25% crumb rubber particles by weight of a Superpave PG 64-22 asphalt binder. The CRM binders with and without Rolling Thin Film Oven (RTFO) aging were characterized by the AASHTO rotational viscosity test at 135, 140, 150, 160, 170, 177, and 190 °C (AASHTO T316). Furthermore, the low temperature cracking resistance of the binders was evaluated using the AASHTO Bending Beam Rheometer (BBR) test procedure at −12 and −18 °C (AASHTO T313). The statistical analysis of variance (ANOVA) was applied to quantify the effect of the influencing factors such as temperature, rubber particle size, and rubber concentration on the CRM binders’ performance. From the laboratory tests and ANOVA results in this study, it is evident that the addition of crumb rubber into asphalt binder can both significantly improve the viscosity of binder at high temperature and lower the creep stiffness at low temperature, which is beneficial to better both high temperature stability and low temperature cracking resistance of asphalt pavements. After RTFO aging, the viscosity decreases with increasing rubber concentration. Finer crumb rubber attains higher viscosity at high temperature and lower creep stiffness at low temperature. Considering the viscosity–temperature relationship, RTFO aging effects, creep stiffness decreasing percentage, and economical factors, 15% to 20% rubber asphalt ratio is proposed for the production of CRM binder.

► The crumb rubber significantly promotes the viscosity of asphalt binder.
► The crumb rubber betters the performance of low temperature stiffness.
► Finer size crumb rubber has better performance in the modification.
► There is no significant performance difference between 20% and 25% ratio CRM binders.