Mechanical and functional performance assessment of ultra-thin porous asphalt pavements produced with EAF steel slags aggregates

The quantity of impervious surfaces in urbanized areas has grown dramatically in recent decades, increasing the risk of flooding and significant water runoff phenomena. Porous asphalt systems have gained popularity as a viable solution to counter this tendency, though their use remains limited to highway and suburban areas due to technical and practical limitations. Ultra-thin layered porous pavements (UTPA) may represent a solid alternative to address these issues, allowing, at the same time, to reduce the use of virgin materials and energy consumption during production. Nevertheless, obtaining a functional porous structure in this configuration is often challenging, and the scientific literature lacks reference case studies. In this regard, six different UTPA systems were proposed in this study, both resorting to virgin and second-use materials (steel slags). A complete mechanical and functional laboratory assessment of their performance was carried out, including %voids, ITS, ITSR, particle loss, Marshall stability, stiffness modulus, WTT, PTV, drainability, and surface texture analysis. The findings highlighted the excellent behaviour of steel slags in replacing virgin aggregates, enhancing the general performance of the porous asphalt system in many cases. The results and their relationships were thoroughly commented on, and further research activities were proposed.