Effect of Pyrolysis Products From High Impact Polystyrene Waste Plastic on the Performance of Warm Mix Asphalt

Abstract

High impact polystyrene (PS) type plastics constitute an important part of electronic waste. Due to limited recycling, they are disposed of by incineration or landfilling, which leads to environmental problems. Therefore, increasing recycling is of great importance. This study explored the effect of the char (C) and liquid (L) components obtained by recycling PS waste plastic via pyrolysis method on the performance properties of warm mix asphalt (WMA). In the study, modified bitumen were prepared by blending base bitumen (50-70 penetration grade) with pyrolysis char and/or liquid at 0-3-6-10 % ratios (by weight of bitumen). The effects of pyrolysis products on WMA were investigated by binder tests including penetration, softening point, Fourier Transform Infrared spectroscopy, Rotational Viscometer, Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR) as well as mixture tests like Marshall Design, Hamburg Wheel Tracking (HWT), and Thermal Stress Restraint Specimen Test (TSRST). The binder test findings indicated a significant alteration in the characteristics of bitumen while utilizing 6 % of the char and liquid component additions. The incorporation of PS 6 %C-6 %L resulted in an increase in bitumen penetration, accompanied by a drop in softening point and viscosity. The reduction in viscosity culminated in a 15 degrees C decrease in the mixing-compaction temperature of the mixture. From the DSR and BBR analyses, the addition of PS 6 %C-6 %L decreased the performance grade (PG) high temperature of base bitumen by 1 grade, while the PG low improved by 1 grade. Marshall and HWT tests demonstrated that the stability and rutting resistance of WMA (PS 6 %C-6 %L) was equal to 89 % of that of hot mix asphalt (HMA). TSRST results also indicated that the low-temperature performance of WMA was 29 % and 8 % higher than HMA in terms of fracture temperature and thermal stress, respectively. To conclude, this study shows that pyrolysis products obtained from PS waste plastic have a high potential as a WMA additive.