Life cycle assessment of use of recycled materials in asphalt pavements

Abstract

The increasing use of recycled materials in asphalt pavements asks for prescriptive environmental assessment on associated impacts such as the energy and CO2 footprint. Accredited by a number of industries already, life cycle assessment (LCA) is being accepted by the road industry to measure and compare the key environmental impacts of its product or process throughout the whole pavement life time, and present the results for communication with stakeholders. This thesis reviews the technical performance of asphalt pavements containing recycled materials; searches for relevant LCA resources worldwide; identifies the gap for the road industry, and the key environmental impacts of recycling in asphalt pavements. It describes the development of a LCA model for pavement construction and maintenance that accommodates recycling practice and up-to-date research findings. Details are provided of both the methodology and data acquisition. 3 real case studies are carried out during the model development, and their findings described in this thesis. This is followed by a discussion of the challenges of applying LCA to road practice, and recommendations for further work. Data in this model come from a mixed source of UK plants, EU standards and relevant LCA results. Methodology follows the ISO14040 norms. Unit processes in asphalt pavement construction are analysed and represented in this LCA model. The most significant variables in the process are identified, followed by data analysis and sensitivity check. This LCA model can be further tested and calibrated as a decision supporting tool for the asphalt industry. In order to achieve sustainable construction however, environmental assessment must be placed alongside the outcome of technical and economic studies.