Development of a bio-rejuvenator to counteract performance loss of rejuvenated asphalt during secondary aging

The adoption of sustainable asphalt rejuvenators necessitates that bio-rejuvenated asphalt maintains acceptable performance loss after secondary aging. In this study, a novel bio-rejuvenator was developed. The structure of esterified liquefaction products (ELP) derived from soybean straw was reconstructed by introducing hydroxyl-terminated polybutadiene (HTPB) macromonomer to prepare a durable bio-rejuvenator (DBR). The response surface methodology was used to optimize the synthesis conditions, considering both initial performance levels and secondary aging control indices. The possible microstructural reconstruction within the ELP system was inferred based on analyses of thermal decay behavior, chemical composition and molecular structure. The properties and microscopic characteristics of rejuvenated asphalt were investigated, and changes in these properties during secondary aging were monitored and characterized. The results indicate that the optimal synthesis conditions are the HTPB dosage of 12%, the synthesis temperature of 110 °C and the preparation time of 2 h. Small molecule components in ELP such as acids and esters can be grafted onto the main chain of HTPB and converted into macromolecular ester components, simultaneously inducing etherification and cyclization of alcohols and phenolic compounds. This significantly alters the composition characteristics, chemical structure and molecular polarity. Both ELP and DBR exhibit high rejuvenating efficiency in restoring the physical properties and relaxation capacity of aged asphalt. However, ELP rejuvenated asphalt exhibits a rapid decline in performance. During the four-stage aging process, aged asphalt rejuvenated with DBR shows an orderly and reasonable loss in performance, with its decay behavior restoring to the same level as virgin asphalt.