Environmental Impacts of Recycled Asphalt for Slow Mobility Infrastructures

Cycling and pedestrian infrastructures are pivotal in encouraging zero-impact transportation and complying with the European Commission’s policies to fight climate change. Innovative and sustainable pavements for light mobility can recycle milled pavements. Up to 100% secondary aggregates can be used to pave low-impacting bituminous layers for urban areas. This study presents a quantitative life cycle analysis of alternative materials currently used in the design of the Grande Raccordo Anulare delle Biciclette (GRAB), which is a 44-km-long cycle ring planned in Rome. Within the H2020 InfraROB project (Grant Agreement n. 955,337) “Main-taining integrity, performance, and safety of the road infrastructure through autonomous robotized solutions and modularization,” some trial sections have been paved using a cold-mixed asphalt composed of 100% recycled asphalt and a rejuvenator additive. The authors compared the environmental performances of six asphalt mixtures suitable for cycling paths by varying components, mixing techniques, and laying processes. The European stan-dard EN 15804:2021 and the software SimaPro enabled the “from-cradle-to-gate” life cycle assessment of the compared materials. The emissions to air, elements, and fossil depletion, and net use of fresh water derived from primary data from asphalt producers and secondary data from international libraries. The production of 1 Mg of a cold innovative mixture with 100% recycled aggregates implies 40 kg CO2 eq emissions of, 6.35E-04 kg Sb eq of biogenic depletion, 1613 MJ of fossil consumption, and 0.92 m3 of fresh water consumption compared to 60 kg CO2 eq, 9.10E-05 kg Sb eq, 2604 MJ, and 0.42 m3 of a traditional mixture, respectively. The outcomes highlight the low-impact strategy to preserve fossil resources and reduce greenhouse gas emissions to build durable infras-tructures for vulnerable users in urban areas.