Comparative Environmental Analysis for Using Waste Polyethylene and Steel Slag in Semi-dense Asphalt Pavements

Abstract This study presents a life cycle assessment (LCA) evaluating the use of virgin materials, waste polyethylene (PE), and electric arc furnace steel slag (EAFSS) in semi-dense asphalt (SDA) surface courses, which is primarily used for low-noise pavements. Three types of SDA mixtures with virgin materials, waste PE, and EAFSS were prepared and water sensitivity tests were conducted to determine the mechanical performance. The LCA defined three scenarios using system expansion, namely (1) the reference scenario using virgin materials in SDA and disposal of waste PE and EAFSS by municipal solid waste incineration (MSWI) and landfill, respectively; (2) the test scenario using waste PE and straight run binder in SDA, with landfilling of EAFSS; (3) the test scenario using EAFSS in SDA, with the disposal of waste PE by MSWI. The data from the experiments, Swiss industries, official reports, and standard databases were used for the inventory analysis. The results show that compared to the reference, the scenarios using waste PE and EAFSS in SDA would reduce 15 % and 36 % of greenhouse gases emissions, respectively. The reason for the improved environmental performance when waste PE is used in asphalt can be attributed to the use of straight run binder to replace polymer-modified binder and the avoided MSWI. For the EAFSS scenario, the improved environmental performance is attributable to the avoided landfilling. The results also indicate that the recycling of waste PE and EAFSS in SDA would not have benefits in nonrenewable cumulative energy demand.