Improving compatibility of devulcanized rubber/bio-oil composite rejuvenated SBS modified asphalt using maleic anhydride-grafted polymer toward sustainable waste utilization

Rejuvenating aged SBS modified asphalt (SBSMA) is a low-carbon and eco-friendly approach; however, poor compatibility and long-term stability hinder the effective reuse of the rejuvenated material. To address this issue, a base composite rejuvenator (RM60) was prepared by blending devulcanized rubber (DVCR) with epoxidized soybean oil (ESO). Three maleic anhydride grafted polymers with different rigidities, maleic anhydride (MA), MA grafted styrene–ethylene–butylene–styrene block copolymer (FG03), and MA grafted tackifier resin (M-960), were introduced as compatibilizers. The results indicate that 12 wt% RM60 provides optimal performance, with M-960 enhancing low-temperature properties and FG03 improving high-temperature stability. MSCR and BBR results confirm that compatibilizers effectively improve rutting resistance and low-temperature stress relaxation. RASEBS achieved J nr values of 0.5564 and 0.9133 under 0.1 kPa and 3.2 kPa, respectively. At −24 ℃, RAER reduced the S value to 331.8 MPa from 564.6 MPa for SBSMA, with m-value increased to 0.290. Grafted polymers also enhance storage stability, with RAER achieving a segregation index of 1.1 ℃, outperforming unaged SBSMA (1.4 ℃). FTIR analysis reveals that anhydride groups in FG03 and M-960 react with hydroxyl groups in aged asphalt through esterification, while grafted polymers facilitate network reconstruction via physical entanglement. These combined effects significantly improve compatibility and suppress polar oxidation product aggregation. Thermal and microstructural analyses verify enhanced stability and homogeneous microstructure, particularly in M-960-modified systems. Overall, MA-grafted polymers are effective compatibilizers for rejuvenated SBSMA, providing insights for synergistic reuse of waste rubber, bio-based oil, and aged asphalt. • A novel dual-component rejuvenator combining devulcanized rubber and bio-oil for aged SBS modified asphalt was developed. • MAH-grafted polymers significantly enhanced compatibility and storage stability via interfacial reactions. • FG03 significantly improved high-temperature rutting resistance, while M-960 enhanced low-temperature flexibility. • TGA and SEM analysis confirmed the improved thermal stability and reconstructed microstructure in rejuvenated asphalt.