Unveiling the role of size characteristics of recycled rubber-polyethylene elastomers on polymer-asphalt interaction and asphalt rheology

Upcycling waste tires and recycled polyethylene (rPE) into asphalt offers a sustainable solution. However, poor compatibility between crumb rubber (CR), rPE and asphalt limits practical application. Accordingly, the size characteristics of modifiers is critical to polymer-asphalt interaction and the resulting rheological behavior, yet remains insufficiently understood in rubber-polyethylene elastomers. In this study, CR and rPE were extruded and cryogenically pulverized to obtain the thermo-mechanical rubber-polyethylene elastomers (TRPE) and micronized elastomers (mRPE). The microphase interaction, phase separation, and rheological behavior of modified asphalt were evaluated. The results indicate that TRPE already establishes a relatively well-dispersed polymeric phase in asphalt, while further micronization improves microstructural uniformity and reduces the softening point difference to 0.8 ℃. Rheological analysis reveals a progressive enhancement in polymer-asphalt interaction of TRPE modified asphalt (TRPEA) and mRPE modified asphalt (mRPEA), as evidenced by a reduction in rheological interaction index (h value) from 0.87 to 0.14. The results show that the Cole-Cole plots are insufficient to distinguish the compatibility of TRPEA and mRPEA under the specific test conditions. Due to the dissolution of large elastic particles, TRPEA and mRPEA exhibit a pronounced shift toward viscous behavior. Moreover, mRPEA shows improved deformation resistance at high temperature and highest fatigue life with 5.66×10 6 at 2.5% strain. Overall, this work provides valuable insights in optimizing waste-derived modifiers for sustainable pavement materials.