During the last decades, extensive research has been carried out on using reclaimed asphalt pavement (RAP) material in the production of hot recycled mix asphalt. Unfortunately, the aged, stiff, and brittle binder in the RAP typically increases the mixture stiffness and can therefore cause fatigue and low-temperature damages. In the scientific literature, there are many studies concerning the aging and rejuvenation of bitumen, but there is a lack of up-to-date reviews that bring them together, especially those facing the phenomena from a chemical point of view. In this paper, a recap of the chemical aspects of virgin, aged, and rejuvenated bitumen is proposed in order to provide a useful summary of the state of the art, with the aim of both encouraging the use of an increasing quantity of RAP in hot mix asphalt and trying to give indications for further research.

Road construction and maintenance involve huge amounts of materials that can include wastes from the demolition of old asphalt pavements. Recycling allows environmental and economic benefits to be achieved, by reducing the consumption of natural resources. These advantages are maximised with cold-recycling, in particular when full depth reclamation (FDR) is adopted as road rehabilitation technique. The aim of this research was to compare different FDR techniques, which produce cement-treated material and cement_–bitumen treated material (CBTM) combining the use of cement and bitumen emulsion or foamed bitumen. The FDR was applied in a trial section built along an in-service highway and monitored with annual falling weight deflectometer (FWD) surveys in order to evaluate the performance evolution. Results highlighted that, because of the effect of temperature, the FWD deflections were not suitable to accurately evaluate the evolution of the mechanical behaviour of the cold recycled mixture (CRM) layers. However, the temperature-corrected FWD moduli allowed to conclude that the performance of the CRM layers was similar.