Effects of Liquefied Waste Plastics on Chemical and Rheological Properties of Bitumen

This paper studies the merits of applying liquified polyethylene (PE) as a modifier for bitumen. Chemical recycling of PE is often incomplete and generates some amount of waste “PE oil”. The viscoelasticity and chemical characteristics of bitumen modified with PE oil were examined using dynamic shear rheometry, infrared spectroscopy, and adhesion measurements in comparison and in conjunction with bitumen modified with wax, which is one of the most common additives in warm-mix bitumen. The study found that PE oil softens bitumen without severely increasing the creep compliance or viscoelastic damping properties. Wax-modified bitumen showed enrichment of crystallized alkanes at the free bitumen surface that negatively impacted adhesion and interface healing. The introduction of PE oil to wax-modified bitumen did not appreciably decrease the fraction of crystallized wax. Thus, PE oil may not be effective as an additive for warm-mix wax-modified bitumen. However, the PE oil showed potential in protecting bitumen against ultraviolet (UV) aging, and it is worth further exploration as an anti-aging agent, or as a rejuvenator for reclaimed asphalt pavement. The outcomes of this study promote plastic recycling by presenting the merits of applications of liquefied waste PE in the design and engineering of bituminous composites.