Evaluation of modified bitumen properties using waste plastic pyrolysis wax as warm mix additives

Abstract

The existing disposal methods of waste plastics are mainly landfill and incineration, and they will migrate to the surrounding ecosystems and bio-magnify in plants and animals that endanger the human food chain. To reduce environmental pollution and realize waste reuse, the waste plastics were recycled to produce the pyrolysis wax (PW) as warm mix additives of bitumen by using the high-temperature pyrolysis method in this study. The PW was produced at different pyrolysis temperatures (T) and pressures (P), and then bitumen was blended with different PW content (C). Firstly, the optimal production condition of PW modified bitumen was determined based on orthogonal experimental analysis. Then, the conventional, viscosity-temperature, storage stability, differential scanning calorimetry, Fourier transform infrared and rheological tests were conducted to evaluate the performances of the optimal PW modified bitumen before and after aging. Results show that the optimal production condition is T = 400 °C, P = 0.5 MPa, C = 6%. After adding matrix asphalt (MA), pyrolysis waxes can be used as a colloid dispersion medium, thus reducing the viscosity of MA. In addition, the PW led to a lower penetration, a higher softening point and a lower viscosity, and ductility was still within specification. The PW modified bitumen still has better storage stability and there is no obvious chemical reaction that occurred in the PW modified bitumen. Meanwhile, the incorporation of PW enhanced the viscoelastic properties, high-temperature performance, permanent deformation resistance, short-term and long-term aging resistance ability and anti-fatigue ability as revealed by the differential scanning calorimetry and rheological tests.