Waste plastic as potential high-value solution for asphalt road applications

ANAS, the main Italian road agency, manages over 30,000 km of both local and national roads. In all cases, maintenance actions involve the reconstruction of the bituminous layers that require new aggregates and binder. This aspect, together with the need of acting in compliance with the new environmental regulations that increasingly push towards the recovery of waste and/or recycled materials for the construction of new bituminous mixtures, entails the study of innovative solutions that can be considered sustainable both from an environmental, technical and economic point of view. Among the waste materials currently available on the market (open-loop materials), the so called “light plastics” recovered from municipal solid waste (MSW) represent a potential solution still under development. Plastics constitute a large percentage of the waste material that is difficult to recycle in other fields. However, waste plastics have a high potential for recovery in bituminous mixtures since their polymeric nature could act as a modifying agent in replacement and/or integration of the synthetic polymers usually added to the bitumen. This action can significantly improve the overall mixture performance and decrease production costs. In order to validate this potential, ANAS has developed a study on the reuse of “light plastics” in the production of hot bituminous mixtures. The study includes a preliminary laboratory analysis to verify the effects on mechanical, volumetric and durability properties. Three different pre-treated wasted plastic materials were tested in different dosages to determine the optimum mix design and the most suitable mixing process. The results described in this paper, baseline to set up full-scale trial sections, represent the kick-off step to develop efficient, innovative and sustainable technological options for the production of new bituminous mixtures both from an environmental and economic point of view.