Impact of Nonrecyclable Plastics on Asphalt Binders and Mixtures

Low-density polyethylene (LDPE) and polystyrene (PS) were evaluated for incorporation as binder additives to enhance the potential performance of asphalt concrete (AC) mixtures, as well as addressing global rising concerns over nonrecyclable plastics accumulation. Incorporation of LDPE and PS in asphalt binder resulted in an increase in its complex moduli over a range of temperatures and frequencies, as determined using frequency sweep (FS) and linear amplitude sweep (LAS) tests. AC performance tests were conducted, including the Hamburg wheel-tracking test (HWTT) to assess potential rutting, the Illinois flexibility index test (I-FIT) to determine cracking potential, the indirect tensile strength test (ITS) to assess moisture susceptibility, and the dynamic modulus for structural capacity. Two control AC mixes were designed, utilizing aggregates from different sources. For each AC mix, the aggregate blend and binder content were kept constant, with only the binder type changed. LDPE and PS were added through a wet process in one mix. Dry and wet processes were used in the other mix. Waste plastics–modified AC mixes, in both wet and dry processes, exhibited reduced rutting potential. However, the cracking potential and moisture damage susceptibility varied, depending on the modified AC mix. The addition of waste plastics had no impact on AC dynamic modulus. The results for waste plastics–modified AC mixes were compared with those for styrene-butadiene-styrene (SBS)–modified AC mixes. While waste plastics modification provided improvement over the control mixes, the performance fell short of that of the double-pump SBS-modified mix.