Deriving and Characterising Alternative Bitumen from Waste Plastics

Abstract

This study presents research on laboratory production and experimental characterisation of an alternative bitumen using municipal waste plastics. Six different waste plastics (A1 - A6) produced by a local waste recycling manufacturers were selected and characterised to investigate their feasibility in modifying the bitumen binders. Thermal characteristics were firstly obtained using Differential Scanning Calorimetry (DSC) device and the chemical functional groups were identified by Fourier Transform Infrared Spectroscopy (FT-IR) test to determine the plastic types existing in the recycled plastics. Then the rheological properties of the bitumen modified with two nominated plastic waste (A1 and A2) were examined using the Dynamic Shear Rheometer (DSR) device by conducting frequency sweep tests. Additionally, the engineering performance of waste plastics-derived bitumen was also obtained and compared against the control bitumen, including fatigue, rutting and healing performance using Time Sweep (TS) test, Multiple Stress Creep and Recovery (MSCR) test and Healing test, respectively. Results show that A1and A2 consist of low-density polyethene (LDPE) and polypropylene (PP), respectively. The recycled waste plastic A5 and A6 (both classified under the same category but collected from different plants and batches) are mainly consisting of LDPE. Whereas, other recycled plastics (A3 and A4) consist of a variety of materials and impurities. Thus, A1 and A2 were chosen as bitumen binder extenders. A1-modified bitumen exhibited more elastic and less viscous behaviour than the control bitumen, showed by increased shear modulus and reduced phase angle. Whereas, A2 (consisting of PP) caused a significant drop in the shear modulus. Both recycled LDPE and PP-modified bitumen had a substantially improved resistance to rutting and fatigue cracking compared to the control bitumen. Furthermore, waste LDPE-modified bitumen sustained increased healing potential compared to waste PP-modified bitumen, where the latter did not show noticeable improvement to the healing performance.