• Energy Research

This study applies the life cycle assessment methodology to evaluate the environmental impacts of shock-absorbing pavements fabricated with recycled materials (crumb rubber and a colored pigment called ferrotone), employing the “cradle-to-grave” approach, in which the impacts of all life cycle phases (from materials’ acquisition to the end-of-life of the pavement) are included. The analysis compares the impacts of standard and innovative asphalt materials, considering cold and hot production processes. In addition, three different lifespans are simulated for the pavement structures: the reference service life until the first intervention is considered to be 5 years, and the following scenarios consider that the alternative asphalt materials may last 20% less (4 years) or 20% longer (6 years) than the reference service life. The analysis uses non-renewable cumulative energy demand (nr-CED) and global warming potential (GWP) as main indicators to determine the environmental impacts over a 45-year analysis period. The results show that adopting the “dry process” (consisting of adding the rubber as a partial substitution for aggregates) increases the overall impacts due to the need for higher contents of binder. However, if the alternative pavement structures last 20% longer than the reference, they would generate lower impacts in terms of nr-CED and GWP.

Cyclists, pedestrians and elderly people’s specific needs in urban road infrastructures are often neglected. They rarely benefit from safety measures or innovations. Inspired by playgrounds and aiming to reduce vulnerable road users (VRUs) injuries, the development of the rubber-based impact-absorbing pavements (IAP) offers a possibility to rethink the design of urban pavements and address safety on roads, which constitutes a major challenge in terms of attaining more sustainable, resilient, and safe cities. Therefore, bituminous mixtures with four different crumb rubber contents, 0%, 14%, 28%, and 33% (in total weight), were produced by partial aggregates substitution using the dry process. After the assessment of the geometrical and volumetric properties, the mechanical performances were evaluated. Finally, the samples were tested to measure the abrasion and impact attenuation with the well-known head injury criterion (HIC), at different temperatures from −10 to 40 °C, to obtain a wide range of values referring to possible weather conditions. A significant effect of the rubber percentage and layer thickness on impact attenuation was observed. All observations and results confirm the feasibility of the IAP concept and its positive effect on future injury-prevention applications.