Permeable wearing courses from recycling RAP for low-volume roads: optimization procedures

The recycling of reclaimed asphalt pavement (RAP) in hot-mix asphalt (HMA) is an important opportunity in regard to transportation infrastructure construction and maintenance because it helps to achieve more sustainable road transport systems (reduction of waste production and reduction of resource consumption). In particular, totally recycled HMAs can be a good alternative for road paving even if performance can be an issue. As is well known, the type of low-volume road pavement (gravel, coarse rocky soil, crushed aggregate, cobblestone, concrete block, or some type of bituminous seal coat or asphalt pavement) depends on traffic volume, native in-place soils, and the need to control surface and depth erosion. The objectives and scope of this research were confined to the formalization of strategies and technical procedures for recycling RAP from porous asphalt concretes to obtain permeable wearing courses for low-volume roads. Different solutions were investigated. High percentages of RAP were used in the recycling process, and traditional and advanced tests on RAP and recycled mixes were carried out. RAP variability was examined, and a method for facing its consequences was proposed. Mechanical performance was adequate. Recycling porous European mixes could be a proper way to achieve environmental sustainability in pavement construction, as the functional performance results are very promising and encouraging. Practical applications and perspectives in rehabilitation, maintenance, and research are outlined.