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Closely following the attempt of the pavement engineering industry to comply with the principles of Circular Economy (CE) while simultaneously promoting its principles, it can be detected that a significant effort is being made towards the minimization of the energy and raw materials usually utilized. In this regard, Reclaimed Asphalt (RA) is a product that exhibits a tremendous exploitation potential. Knowing that by definition CE is restorative [1], regenerative, and aims to keep products, components, and materials at their highest utility and value at all times [2], i.e. it supports the “re-circulation” of materials and energy within the same or alternative product systems and thus the elimination of avoidable wastes [3], RA is the ideal candidate to be recirculated into a closed or even open loop product system and/or approach and thus, ideal material that can re-enter the cycle of asphalt mixture production [4]–[8]. RA can be defined as existing asphalt pavement materials that have been removed during the resurfacing, rehabilitation or reconstruction operations of asphalt pavements and accordingly processed [9]. All of the motorways within the EU member-countries consist of asphalt pavements, which -as anticipatedsuffer from various types of distresses [10]. Maintaining them can be environmentally, economically, and socially intensive. RA recycling and re-use are well-established practices within the road engineering industry with the aim of minimising the environmental and economic impacts asphalt mixtures and move towards more sustainable and circular recycling [10]–[15]. The available annual average quantity of RA within Europe reaches approximately 45.5 Mt; while the average annual utilized RA only 23.2 Mt [16]-[30]. The main techniques with which RA can be utilized are in hot in-plant recycling, hot in-place recycling, full depth reclamation, cold in-plant recycling and cold in-place recycling [11], [31]. The percentage of RA incorporated in road pavements is usually limited between 10% and 30%, despite the advantages that its use might imply, due to legislation limitations and technical issues such as the variability of the RA properties, the lack of complete understanding of the mechanisms taking place during the asphalt mixture production, and uncertainty of the mixture performance [15], [32]. Many studies have concluded that higher use of RA is possible when attention is paid to the mixture design and the RA’s properties so that a consensus between the laboratory mix design and the full-scale realization of the asphalt pavement can be achieved [33]–[39]. In this case study, a comparative analysis between two countries of the Mediterranean basin is performed. The Material Circularity index (MCIMRA) as defined by K. Mantalovas [8], of Italy and Spain in terms of their motorways’ asphalt mixtures are compared for the period 2006-2019. Both countries belong to the Southern region of Europe, have similar GDP, and experience similar climatological conditions. Therefore, these countries were selected for the comparative analysis. Since the Material Circularity Index as tailored and defined by K. Mantalovas corresponds to specific and individual end products the current analysis takes place for surface, binder, and base 3rd Symposium on Circular Economy and Sustainability Chania, Greece 27-29 June, 2022 2 courses separately since these are the typical asphalt layers that constitute the asphalt pavements of the motorways. The necessary data for the completion of the quantitative aspect of the case study were collected from reputable literature sources [5], [8], [28]–[30], [40]. Utilizing the methodological framework developed by K. Mantalovas and G. di Mino, the quantification of the Material Circularity Index for surface, binder, and base courses for the Italian and Spanish motorways became possible for the period 2006-2019, and the results can be seen in Figure 1 Table 1. Product Material Circularity Index per pavement layer per country From the results obtained from this case study we can immediately identify the significant gap between the MCIMRA of the two countries for all the layers. Spain’s MCIMRA for all the layers is on average 44% higher than the equivalent of Italy’s. This could be a projection of a plethora of different circumstances. For instance, in Italy the maximum allowed RA% for surface, binder, and base courses are 20%, 25%, 30% respectively, while in the Spanish regulations asphalt mixtures with RA% up to 50% are allowed and promoted. Moreover, Italy according to data from the European Asphalt Pavement Association (EAPA), recycles 25% of the available RA while Spain reaches the threshold of 72%. Hence, the regulatory context, apparently influences the circularity and sustainability implications of the road engineering industry dictating the maximum circularity thresholds that can be achieved through the limitation of RA use. Although numerous studies by now have proven the functionality, viability, and necessity of RA use, it can still be observed that a lot of countries, regions and/or governments are still not willing to follow the scientifically established facts. For this reason, the authors believe that some key actions must be taken urgently: • Establishment of compulsory and regulated E-o-L strategies for RA prior to its production • Increased budget allocation to the training of stakeholders about CE, and sustainability • Use of material flow tracking along with material passports • Harmonised benchmarking of the mechanical/environmental performances of RA mixtures • Target setting towards the exploitation of all the available RA • Change utilization patters (sharing models, product as service).

Among several goals of the road agencies, one of the most relevant is the maintenance and rehabilitation of the road pavement. The growth of traffic, the longstanding lack of funding and, sometimes, an emergency-based planning of intervention, are common drivers leading to low level of pavement conditions in terms of ride quality and safety. In addition both cost and environmental concerns due to monitoring stage are relevant issues within the management system of local and urban road network, especially. With the purpose of implementing sustainability in the road pavement management, this paper provides an approach based on coupled low- cost 3D image modelling distress identification and Life Cycle Assessment (LCA) tool. A case study in Palermo is considered by comparing current practices to the optimized system to define environmental impacts. The results show the use of this approach is able to achieve both environmental and economic benefits for road agencies by providing crucial savings and furthermore by optimising the Pavement Management System.

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. 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.

Construction and demolition waste (CeDw) is mainly produced during the construction, demolition, or renovation activities of civil engineering structures and it accounts for a remarkable amount of the total C&Dw generated, as it is estimated to be around 30%. This proportion differs between countries belonging to different types of economies and tends to be greater in countries with developing economies reaching 74% of total annual production. There is a plethora of applications that C&Dw can be used for under a circular economic model and in this research a focus is being given in the exploitation of C&Dw within the pavement engineering sector, and more specifically, in the utilization of said waste in road earthworks. Circular Economy can act as a steppingstone towards the uptake of C&Dw recycling and exploitation. To understand the state of practice that exists, a market and an implementation analysis have been conducted in Italy. The current applications of C&Dw recycling into road projects were analyzed along with the existing regulations, and local producers. The results projected the various challenges faced by the involved stakeholders, along with the barriers that hinder the wide recycling of C&Dw in road engineering projects. Finally, the proposed national action plans are analyzed and the future potential exploitation of C&Dw is put into context. The future of the specific research is going to involve a full scale, on-site implementation of C&Dw in a defined road segment.

Although the benefits of asphalt recycling have been scientifically proven and several best practices are being implemented, further research is required in specific and specialized areas. One of these circumstances is the recycling of Reclaimed Asphalt Pavements (RAPs) that contain asphalt modifiers such as elastomers and/or plastomers. Following the principles of the circular economy and considering the sustainability implications of asphalt mixtures, this paper deals with the multi-recyclability of asphalt mixtures containing 50% RAP with and without a recycled plastic asphalt modifier and rejuvenating agent. The recycled plastic asphalt modifier was made of hard recycled plastics and was introduced to the mixture via a dry method. The research focuses on the characterization of binders via conventional, rheological, and chemical analysis. To control the consistency and variables of the mixtures, the RAP was produced artificially in the laboratory following an ageing protocol for loose asphalt mixtures. According to the obtained results, at all three cycles of binder recycling, comparable properties for (i) the extracted binders from the recycled plastic-modified asphalt mixture, (ii) the extracted binders from the control un-modified mixture, and (iii) the reference bitumen 50/70 were obtained. This was even noticed when a nearly similar quantity of the rejuvenator was needed during the rejuvenator optimization process. Overall, it can be deduced that from the binder-scale point of view, the mixture containing the introduced recycled plastic additive could be recycled for multiple life cycles without any degradation of its mechanical and physical properties.

Rising concerns about the impacts that the road engineering industry is imposing to the environment have redirected national road authorities to firmly re-consider the sustainability implications of their operations. Lately, though, sustainability has established a forceful correlation with the Circular Economy and its principles. The road engineering industry, therefore, is moving towards more circular approaches. However, this is occurring without the assessment of the potential impacts of such a transition. For this reason, in this study, a composite indicator, namely, Environmental Sustainability and Circularity indicator (ESCi), for investigating the potential effects that increased circularity could have at the environmental sustainability of asphalt mixtures is developed. It can be utilized as a decision-making support tool from stakeholders involved in both asphalt mixture production and road pavement management. In addition, in this study, four asphalt mixtures with different percentages of Reclaimed Asphalt (RA) were assessed in terms of their &ldquo, cradle-to-gate&rdquo, environmental impacts and circularity, by means of Life Cycle Assessment, and Material Circularity Index, respectively. Their fatigue and permanent deformation performances play a key role in the assessment and distinctive results obtained for the asphalt mixtures with increasing RA% and thus, significant environmental benefits and increased circularity are observed after specific RA% thresholds.

Road agencies are constantly being placed in difficult situations when making road maintenance and rehabilitation decisions as a result of diminishing road budgets and mounting environmental concerns for any chosen strategies. This has led practitioners to seek out new alternative and innovative ways of monitoring road conditions and planning maintenance routines. This paper considers the use of innovative piezo-floating gate (PFG) sensors and conventional strain gauges to continuously monitor the pavement condition and subsequently trigger maintenance activities. These technologies can help develop optimized maintenance strategies as opposed to traditional ad-hoc approaches, which often lead to poor decisions for road networks. To determine the environmental friendliness of these approaches, a case study was developed wherein a life cycle assessment (LCA) exercise was carried out. Observations from accelerated pavement testing over a period of three months were used to develop optimized maintenance plans. A base case is used as a guide for comparison to the optimized systems to establish the environmental impacts of changing the maintenance workflows with these approaches. On the basis of the results, the proposed methods have shown that they can, in fact, produce environmental benefits when integrated within the pavement management maintenance system.