Life cycle assessment and life cycle cost analysis of recycled solid waste materials in highway pavement: A review

Highway pavement construction with recycled solid waste materials had become a sustainable topic of great concern recently, due to the potential environmental and economic benefits behind. This review focused on the emerging Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) studies concerning the recycling of solid waste in highway pavement. Firstly, based on the existing studies, the application of most recycled solid waste materials (e.g. recycled asphalt pavement, steel slag and coal fly ash) in highway pavement performed satisfactorily from the environmental and economic perspectives, concretely manifested in the reduction of energy consumption, greenhouse gas emissions, costs and other indicators. However, several factors, such as lengthened transport distance of recycled waste solid materials and potential leaching of heavy metals, might hinder the recycling. Moreover, it was necessary to pay more attention to pavement use phase, allocation procedure and transport distance of recycled solid waste materials, which had significant impacts on LCA result. In terms of existing LCCAs, the importance of analysis period and discount rate was highlighted and the most practical economic indicator was Net Present Value (NPV). For future study, allocation was still an important issue for future LCA studies and further sensitivity analyses could focus on the selection of transport modes (in LCA), analysis periods and discount rates (in LCCA). Meanwhile, future research should emphasis on the recycling of solid waste in pavement maintenance and rehabilitation projects rather than new construction. A multi-criteria assessment integrated LCA and LCCA as well as other considerations (e.g. an advanced risk assessment) was recommended to determine the most sustainable recycling scenarios.