Performance and Ageing Evaluation of Bituminous Mixtures with High RAP Content

The implementation of a circular economy implies turning waste into resources, avoiding its disposal in landfills and minimizing the extraction of raw materials. Every year, a considerable amount of Reclaimed Asphalt Pavement (RAP) is generated, as the road network requires pavement maintenance to ensure the safety and comfort of the users. RAP contains both constituents of a bituminous mixture (bitumen and aggregates), and is 100% recyclable, therefore being able to be re-introduced back into the cycle without its use being downgraded. However, RAP is currently being employed solely as an aggregate in unbound layers or in small percentages in new bituminous mixtures, rather than taking advantage of the aged bitumen. This paper presents a study which aimed to evaluate the performance of a surface dense-graded hot bituminous mixture before and after being subjected to an ageing procedure. The bituminous mixture containing a high RAP content—75%—was treated with a commercial vegetable rejuvenator. Short Term Oven Ageing (STOA) and Long Term Oven Ageing (LTOA) procedures were used to simulate the ageing that occurs during the mixture’s production and service life, respectively. The evaluation of the recycled bituminous mixture’s performance was based on stiffness, fatigue resistance, and permanent deformation tests carried out in the laboratory. In comparison with a conventional bituminous mixture, it was found that, in general, the recycled bituminous mixture, before and after ageing, showed higher stiffness and resistance to permanent deformation, yet had very similar fatigue resistance.