Use of recycled plastics as a second raw material in the production of road pavements: an example of circular economy evaluated with LCA methodology*

The road pavement sector contributes significantly to Europe-wide climate-altering gas emissions. Emissions related to road pavement are mainly due to the production of bituminous conglomerate (asphalt), which represents the main contribution to roads construction and maintenance activities. The aim of this work is to assess the extent of potential environmental impacts mitigation due the use of newly formulated bitumen modifiers, containing recycled non-recyclable hard plastics. The considered new additives containing hard plastics substantially improve the performance and durability of road pavements, which allows reducing material amount required to obtain the same functionality. This opens up two different application scenarios addressed in this work which provide an alternative to the conventional road pavement design and management. Given the same service time frame, the first scenario considers the extension of the asphalt maintenance-free operating periods (MFOP) of each pavement layer. The second scenario considers the possible reduction of the pavement asphalt layers thickness. The new bitumen modifier also allows implementing a circular model for hard plastics alternative to their incineration at end-of-life. In the circular model hard plastics are given a second life by incorporating them into the modifier as a raw material, thus entering the closed-loop of periodic pavement maintenance cycles. This study compares the environmental performance of the innovative road pavements life cycle by considering production-, use-, and maintenance phases with respect to conventional pavements. The results show that the asphalt production represents the major environmental impact source within the whole functional system considered. The overall reduction of required material in the first scenario is obtained by MFOP extension along the whole pavement life cycle, while in the second scenario by the reduced thickness of each asphalt layer since first paving. These enhanced performance-driven effects due to the hard plastic-based new modifier determine an overall environmental impact reduction.