Recyclability of reclaimed asphalt rubber pavement

Rubberized asphalt technology has been developed and applied in the production of hot-mix asphalt (HMA) for several years, as it represents a profitable solution to dispose of the waste rubber from end-of-life tires and to improve bitumen rheological and mechanical behaviour. However, the question about the recyclability of reclaimed asphalt rubber pavement (RARP) into new HMA has not been still solved. To this aim, the present study dealt with characterization of HMA including 30% RARP, in comparison with reference mixtures with 30% of ordinary reclaimed asphalt pavement (RAP) and with only virgin materials. The experimental programme included the preliminary analysis of RARP and RAP binders, then the HMA design and testing in terms of strength, stiffness, linear viscoelastic properties and fatigue resistance. The results demonstrated that RARP can be recycled into new mixtures without negatively influencing the overall HMA performance. In particular, the RARP entailed an increase of mix stiffness and brittleness, but with a lower severity with respect to RAP. The use of a rejuvenating agent allowed achieving a mechanical behaviour similar to that of the reference mix with only virgin components.