Evaluation on performances restoration and warm-mix effect of rejuvenated SBS modified bitumen incorporating a compound rejuvenator

It is important to fully restore the performance of aged styrene-butadiene-styrene (SBS) modified bitumen (SMB) and reduce its construction temperatures in high-value recycling the waste SMB mixtures. This study aims to assess the performances regeneration and warm-mixing effects on aged SMB by using a compound rejuvenator, i.e. reactive warm-mix rejuvenator (RWR), which consisted of rubber oil, epoxy-terminated polybutadiene ether, cardanol (CA), modified polyethylene (PE) wax and antiaging agent. Two commercial rejuvenators were employed to compare with the RWR. The rejuvenating effects were evaluated through frequency sweep test, multiple stress creep test, cracking temperature test, linear amplitude sweep test, and chemical and morphological structure analyses. The warm-mixing effect was explored by the rotational plate viscosity test. Results indicate that RWR can react with oxygen-containing functional groups on broken molecular chains of SBS polymer with the catalysis of triethanolamine, which enables fractured crosslinking network structure to be repaired successfully. Meanwhile, light components supplied by RWR is able to restore the bitumen matrix of aged SMB to a similar level of original SMB. The RWR is able to effectively restore the viscoelasticity and plateau region of phase angle of aged SMB to the level that is mostly close to that of original SMB, while those two commercial rejuvenators are barely satisfactory. When the RWR content is 12%, the rejuvenated SMB exhibits the satisfactory high- and low-temperature performances, and the better fatigue resistance ability by comparing with original SMB. The modified PE wax in RWR has a lubrication effect on the interaction between macromolecular polymer chains, which gives rise to significant reduction in construction temperatures of rejuvenated SMB incorporating the RWR.