Hybrid Steel Fibers and RCA in RCC Pavements: Mechanical Recovery, Freeze–Thaw Durability, and Eco-Efficiency

This study investigates the combined use of recycled concrete aggregate (RCA) and steel fibers—industrial (ISF), recycled (RSF), and hybrid ISF/RSF (HSF)—to enhance the mechanical performance, freeze–thaw durability, and environmental efficiency of roller-compacted concrete pavement (RCCP). Twenty mixtures incorporating two RCA levels (0% and 25%) and different fiber systems were tested. The results showed that, although RCA slightly reduced strength, hybrid fibers effectively compensated for this loss, improving toughness, tensile capacity, and resistance to freeze–thaw degradation. A life-cycle assessment demonstrated that substituting natural aggregates and industrial fibers with RCA and RSF lowers the embodied carbon and energy demand. A multi-criteria decision analysis identified mixtures with 25% RCA and hybrid fibers (0.9% HSF) as the most balanced solutions, combining an improved performance with a reduced environmental burden. The findings highlight hybrid fiber-reinforced, RCA-based RCCP as a practical and eco-efficient option for sustainable pavement infrastructure.