Performance of unbound granular mixtures with reclaimed asphalt pavement

This study investigates the mechanical performance of unbound granular mixtures composed of reclaimed asphalt pavement (RAP) and natural aggregates (NA), referred to as NA + RAP mixtures. The aim is to support sustainable practices in pavement design with recycled materials. Alongside several conventional laboratory tests, cyclic load triaxial tests were conducted on NA + RAP mixtures composed of 30% RAP and 70% NA. Tests were conducted at controlled temperatures of 20°C, 30°C, and 40°C on specimens compacted to densities of 95% and 100% of the Optimum Proctor Modified value. The results demonstrate that, while temperature does influence stiffness, density has a more pronounced effect, especially regarding permanent deformation behaviour. Specifically, when compacted to 100%, the NA + RAP mixture exhibited mechanical behaviour similar to that of NA, even at higher temperatures. These laboratory findings were further validated through full-scale pavement sections. In addition, the paper provides a catalogue of flexible pavements that incorporates NA + RAP mixtures in unbound layers for low-volume roads, confirming the viability of these materials and offering practical design solutions. Overall, the experimental findings and design contributions presented in this paper promote the circular use of RAP, contributing to the development of sustainable road pavements.