Analyzing the impact of PPA and sasobit additives on rubberized asphalt binders: A sustainable approach to improved performance

Abstract

Recycling waste tires into crumb rubber modifier (CRM) provides a sustainable solution for enhancing asphalt properties, yet it faces challenges such as low efficiency, material separation, and potential environmental effects at elevated temperatures. This research explored the combined impacts of Polyphosphoric Acid (PPA) and Sasobit on crumb rubber modified binder (CRMB) through two scenarios: modifying various performance grade CRMB (PG64–22 and PG58–22) with different PPA concentrations and creating warm mix asphalt (WMA) using Sasobit. The findings reveal that the asphalt type and additives like PPA and Sasobit significantly affect the rheological characteristics and fatigue life of CRMB. CRMB 58 binders demonstrate flexibility in low temperatures but are susceptible to softening in high temperatures, whereas CRMB 64 binders exhibit greater resistance to permanent deformation, making them more suitable for heavy loads. The inclusion of PPA improves elastic properties, while CRMB and Sasobit contribute to reduced viscosity and enhanced high-temperature performance. Adding Sasobit and PPA increases fatigue life, although too much PPA may diminish it. Most modified binders met the Extreme (E) criteria and can support traffic exceeding 30 million ESALs at 64 °C. ANOVA results reveal that the type of binder, Sasobit, and PPA have significant effects on the rheological properties of CRMB. Tukey analysis indicates that PPA enhances storage stability and viscosity but is less effective under high strains. Both PPA and Sasobit improve properties, with optimal PPA levels recommended to be between 0.5 % and 1.0 %. Overall, these results emphasize the critical nature of carefully selecting binder types and additives based on temperature and loading conditions to achieve optimal performance.