Environmental and economic assessment of collective recycling waste plastic and reclaimed asphalt pavement into pavement construction: A case study in Hong Kong

The use of waste plastic and reclaimed asphalt pavement (RAP) in roadway construction has been considered as sustainable paving practice due to its potential environmental and economic benefits. For cities with scarce land and mineral resource, such as Hong Kong, these benefits are expected to be greater. However, no study has yet attempted to quantitively assess the benefits of simultaneously recycling waste plastic and RAP into road. To fill this gap, this study investigated the technical, environmental, and economic feasibility of using Polyethylene Terephthalate (PET) modified asphalt containing RAP in pavement maintenance and rehabilitation (M&R) from a life cycle perspective. The technical feasibility was demonstrated by laboratory test results. Life cycle assessment (LCA) and life cycle cost analysis (LCCA) were performed to quantify the environmental and economic impact. This was followed by a sensitivity analysis, which was conducted to identify the critical variables, determine the tolerable variable variations, and estimate the potential loss under the pessimistic scenario. The results show that incorporating waste PET and RAP into pavement could reduce the life cycle costs and greenhouse gas (GHG) emissions by up to 26.2% and 29.0%, respectively. The durability was the key factor in maintaining their advantages throughout the pavement life cycle. It was also found that the benefits of using PET modified asphalt were significantly greater than the potential losses. The outcomes of this study are expected to help the practitioners to enhance the sustainability of roadway infrastructure and improve waste management in metropolitan cities like Hong Kong.