Recycling of high percentages of reclaimed asphalt using a bio-rejuvenator – a case study

Worldwide, hot recycling of reclaimed asphalt (RA) has actually raised interest because of the many advantages related to environmental issues. The benefit of reusing RA is associated not only to the reduction of aggregate requirements and the preservation of natural resources, but also to the reuse of aged bitumen from the RA, implying a reduction of the required amount of virgin bitumen. However, the aged bitumen contained in the RA is typically oxidized and hardened, leading to a fragile behavior in the pavement layers, especially when high amounts of RA has to be recycled (more than 30% RA). For this reason, the use of specific additives is strongly recommended in order to restore the desired bitumen properties and consequently produce an asphalt concrete with the expected mechanical characteristics. This paper presents the results from a trial section on the highway connecting Ancona to Perugia in the center of Italy. An asphalt mixture, for a base course, containing 50% of RA and a bio-based rejuvenator was characterized in the laboratory and then produced in a mix-plant and laid down in the field for the final validation of the hot recycling process. The results shows that, by using the rejuvenating additive, high percentages of RA can be reused in the production of new asphalt concretes, maintaining good mechanical characteristics of the final mixture and thus complying with the existing technical specifications.