Coupling effect of AO and HDI on the rheological behavior of rejuvenated SBS modified asphalts

SBS modified asphalt (SBSMA) were aged to different levels to obtain aged SBSMAs with various in-situ states. Aromatic oil (AO) and hexamethylene diisocyanate (HDI) were used to rejuvenate the aged SBSMAs (ASBSMAs). The coupling effects of the combined rejuvenator AO and HDI were evaluated through Dynamic shear rheometer (DSR), Fourier transform infrared (FTIR) and fluorescence microscopy tests, as well as molecular dynamics (MD) simulation. The outcomes revealed that ASBSMAs with combined rejuvenators at optimum dosage had similar rheological recovery effects, regardless the aging level of the SBSMA. The rheological properties of rejuvenated SBS modified asphalt (RSBSMA) are superior to SBSMA. Additionally, the effect of HDI dosage on creep recovery performances is more significant than the AO dosage. Furthermore, larger HDI dosage leads to better repair effect of SBS structure, but HDI is unable to restore the fractured SBS structure completely. AO and the repaired SBS molecule chains decrease the cohesive energy density and fractional free volume of RSBSMA, and increase binding energy and surface free energy. The rejuvenated molecules in RSBSMA are more stable than the original molecules in SBSMA.