Catalytic cracking of waste polyethylene into wax-based warm-mix agent for optimizing rheological and mechanical properties of asphalt composites

High value-added transformation of waste polyethylene with low recyclability and slow degradation in nature has become increasingly prevalent. To achieve the viscosity-reducing effect of asphalt, the wax-based warm-mix agents from waste polyethylene were synthesized via a catalytic cracking method, followed by the melt-mixing process of such agent and base asphalt. The effective relationship between chemical composition/structure of warm-mix agents and properties of asphalt composites was established, and the effects of synthesized warm-mix agents on viscoelasticity, rutting resistance and strain recovering ability of asphalt composites were systemati-cally demonstrated. The results showed that the obtained asphalt composites containing 3 wt% warm-mix agents not only exhibited the significantly improved complex shear modulus, rutting factor and recovery percent, but also showed the decreased phase angle and non-recoverable creep compliance, suggesting excellent permanent deformation resistance and high elastic recovery; in addition, the low-temperature properties of resultant asphalt composites might be clearly changed. Moreover, the stiffening effect of the synthesized warm-mix agents was confirmed by the increased amounts of "bee structure" and glass-transition temperature. This work demonstrates that the catalytic cracking product of waste plastics is an economical yet efficient alternative for tuning structure and performance of asphalt.