A Circular Economy Challenge: Turning Wastes into Sustainable Asphalt Binders by Pyrolysis

The present study aims to investigate the potential of waste pyrolysis products to act as alternative binders or additives in asphalt preparation with the ultimate goals of effective resource use, recovery and recycling, conservation of non-renewable resources, reduction of production costs and achievement of a regenerative circular economy. Char and oil deriving from the pyrolysis of civil and agricultural wastes have been considered as new-concept alternative additives for asphalt preparation. Following an in-depth chemical and structural characterization, oil and char samples have been tested as additives in asphalt binder preparation. After the standard rheological characterization, to test the possible anti-ageing effect exerted by char and oil samples used as additives, the bituminous preparations were subjected to a short-term simulated ageing (RTFOT method) and the resulting mechanical properties evaluated. The results indicate that all the biochar samples were able to strength the overall chemical structure of bitumens and are therefore suitable to be used as bitumen modifier. It is noteworthy that two char samples (char from tires and char from lemon peels) exhibited also anti-ageing properties. As concerns bio-oil samples, in one case (oil from tires pyrolysis) a rejuvenating action is highlighted.