Life Cycle Assessment for the Use of Waste Plastics in Asphalt Concrete Mixes

Abstract

Improper waste disposal poses the risk of contaminating natural water bodies and soil. The low recycling rate of plastics and their fate in landfills are significant global environmental concerns. Efforts to increase the use of recycled plastics worldwide aim to address the hazardous consequences of improper plastic treatment. One potential solution is incorporating plastics as binder or mixture modifiers in asphalt concrete (AC) mixtures, which repurposes waste plastics while reducing environmental impacts related to AC production. This study calculated the environmental impacts of repurposing waste plastics, specifically low-density polyethylene and polystyrene, into modifiers in AC mixes. Wet and dry processes were considered. The environmental impacts of plastic-modified AC mixes were compared with those of styrene-butadiene-styrene (SBS)-modified mixes. The life cycle assessment covered the following processes: (1) collection, sorting, and shredding of waste plastics; (2) transportation of waste plastics from landfill to recycling facility and then to the asphalt plant; (3) supply and transportation of virgin materials; (4) production of AC mixtures; (5) transport of material and equipment to site; and (6) onsite operations. The study concluded that waste plastic-modified mixes outperformed SBS-modified mixtures with regard to environmental performance, except for ozone depletion resulting from certain recycling process activities. The high-shear mixing in the wet process had a significant impact. Sensitivity analyses revealed the influence of binder content and material transportation on the overall environmental assessment.