Performances and Durability of Asphalt Mixtures Made with Reclaimed Asphalt Pavement

According to most recent surveys, 265 mil tonnes of asphalt for road applications were produced in the European area in 2014. In the same year, the amount of available RAP was more than 50 mil tonnes. The use of RAP in new blended mixes reduces the need of neat bitumen, making RAP recycling economically attractive. In spite of its economic and environmental benefits, the use of RAP is often subjected to restrictive policies pursued by agencies due to uncertainty related to RAP mixes field performances. This thesis focuses on the effects of RAP on performances and durability of new asphalt mixes produced incorporating RAP with a standard hot-in-plant process. The influence of RAP being incorporated in new mixes was investigated through an extensive laboratory testing campaign on asphalt mixtures and on bitumen recovered from the same mixes. A specific typology of asphalt mixture has been produced with different RAP percentages of 10%, 20% and 30%. In the first phase of the research, asphalt materials have been characterized and compared in terms of resistance to fatigue, stiffness and volumetric properties. The second phase of the research aims to investigate the effects of RAP on asphalt binder as a composite blend of neat and RAP bitumen. Bituminous samples have been recovered from asphalt samples tested in phase 1 and then have been studied and compared with standard and dynamic laboratory tests. Findings show that HMA can be successfully produced incorporating up to 20% of RAP in the fresh mix. For these percentages of RAP being recycled, no negative effects on performances and durability of recycled mixtures have been noted. However, the final bitumen grade of the mix may be adjusted if more than 20% of RAP is added. Furthermore, practical implications regarding production methods and paving of RAP mixes are proposed.