Workability and Rheological Property Evolution of Active Rejuvenated Styrene-Butadiene-Styrene-Modified Bitumen in the Early Stage

To improve the performance of rejuvenated styrene-butadiene-styrene (SBS)-modified bitumen mixture and realize its high-value recycling, active rejuvenators and biorejuvenators were combined to regenerate the aged SBS-modified bitumen. The effect of active rejuvenators on the workability of active rejuvenated SBS-modified bitumen (ARSMB) was studied; meanwhile, the evolution of rheological properties and chemical structure of ARSMB in the early stage was also investigated comprehensively. The results show that active rejuvenators can lower the viscosity of the rejuvenated binder and improve its workability, which is attributed to the large amount of carbon dioxide produced during the mixing process of reaction regeneration. The complex modulus and rutting factor of ARSMB increase gradually with the extension of curing time, and a higher curing temperature can significantly accelerate this process. In addition, the phase angles of ARSMB at 0 degrees C decrease by only 1.5 and 2.3 degrees for the curing temperatures of 25 and 50 degrees C after 15 days, implying that the negative effect on its low-temperature performance is very limited. The analysis of repeated creep recovery performance indicates that the high-temperature deformation resistance and deformation recovery ability of ARSMB would be improved significantly after paving for several days in practice. The infrared spectrum shows that the residual isocyanate rejuvenators would continue to react gradually, and the reaction index decreases sharply in the first few days, then its decrease rate slows down with the extension of curing time, which also confirms the evolution law of rheological properties of ARSMB.