Bioregenerant for the Regeneration of Waste Asphalt Materials: Exploring Optimal Dosage, Regeneration Efficacy, and Mechanism

To determine the optimal dosage of bioregenerant (BR) and investigate its regeneration efficacy and mechanism on aged asphalt, regenerated asphalts with different BR dosages were prepared in this research. First, the basic physical properties, high- and low-temperature rheological behaviors of the regenerated asphalts were measured, and then based on the macroindexes, the optimal BR dosages suitable for different aged asphalts were determined according to Pearson correlation coefficient analysis and comprehensive performance evaluation. Finally, the microcharacteristics of bioregenerated asphalt with the optimal BR content were tested to verify the regeneration effect of BR and reveal its regeneration mechanism. Results show that BR significantly restored the basic physical properties and rheological properties of aged asphalt, demonstrating a favorable recycling effect. Compared with the two commercial regenerants, the regeneration effect of BR was better at the same dosage of regenerants. However, the regeneration effect of BR on aged matrix asphalt differentiated that on aged SBS (Styrene butadiene styrene block copolymer) modified asphalt (SBSMA), and for aged SK-70 (South Korean-70) matrix asphalt, it was suggested that the optimal dosage of BR was 7%–9%, whereas for aged SBSMA, the optimal dosage of BR was suggested as 3%–5%. BR performed remarkable adjustment and regeneration effect on the four-component, colloidal structure and chemical functional groups of aged asphalt, and the component distribution and colloidal structure of the sample regenerated by BR basically aligned with that of the original asphalt. It was not found that chemical reaction between BR and aged asphalt existed, which belonged to a physical mixing process. Moreover, the LMS%, MMS%, and SMS% of BR regenerated SK-70 asphalt were 17.2, 57.1, and 25.7, respectively, and those of BR regenerated SBSMA was 18.5, 55.7, and 25.8, respectively, which were reached or close to that of original asphalt, illustrating that BR possessed excellent regeneration effect and was better than the commercial regenerant.