Increasing the Circularity of asphalt mixtures: Integrated Sustainability and Circularity Assessment as a progress monitoring tool towards more Circular and Sustainable asphalt pavements

Sustainability and Circular Economy (CE) are two concepts that lately have been profoundly linked to each other. The road engineering industry has gradually been adapting practices that are considered both circular and sustainable. However, not all of these practices entirely consider the whole life environmental and circularity assessment and implications of asphalt mixtures.; which in turn leads to doubtfully circular and sustainable approaches. For this reason in this thesis, after analysing the ways that National Road Authorities implement and communicate CE through questionnaires and web searches, a Material Circularity Index quantifying framework, based on the proposed methodology of the Ellen MacArthur Foundation, for asphalt mixtures was developed to assess their circularity. Within this framework, aspects relevant to the mechanical performance of the asphalt mixtures have also been incorporated. Furthermore, in order to also include the aspect of sustainability, a combined circularity and environmental sustainability assessment framework and indicator for asphalt mixtures with reclaimed asphalt was developed; by utilising the Material Circularity index methodology and the well-established framework of Life Cycle Assessment. The development of the frameworks was followed by case studies that verified the models and projected their usefulness towards more informed decisions when it comes to more circular and sustainable asphalt mixtures. Results of this thesis highlight that National Road Authorities are still facing a plethora of challenges towards the implementation and communication of CE, along with lack of knowledge and incentives. They do implement CE principles such as recycling and preventive maintenance, but they do not utilise metrics to assess their performance. By utilising the proposed indicator and frameworks circular and sustainable recommendations could be drawn along with a knowledge development map for the involved stakeholders. Most importantly, it was deduced that practices that are considered sustainable and highly circular, after the combined sustainability and circularity assessment , were actually found not to be what believed so far. Thus, when it comes to asphalt mixtures and their life cycles, during the decision-making process, each CE-related action must be thoroughly investigated case by case.