## 1 Introduction  
The contemporary Society is stimulated by consumption, resulting in increasing demands for the use of scarce natural resources and in the production of large amounts of waste. This unsustainable scenario is also observed in the road infrastructure sector, where significant amounts of construction and demolition waste are sent to landfills every year. Therefore, the development of solutions that promote road pavement durability and reduce the amount of waste shall be promoted. Furthermore, several other wastes are difficult to recycle and may even need some treatment before being disposed. Taking that into account, it would be interesting to use wastes to improve the performance of road pavements. Among the wastes used in road pavements, reclaimed asphalt pavement (RAP) materials are those that have been most successfully incorporated [1, 2], even though some sort of rejuvenation additive may be needed [3, 4]. Nevertheless, there are other wastes with high potential to be used in this type of application. Plastic wastes are one of the most promising solutions [5], while millions of tons of are sent to landfills every year [6]. Most of these plastics have a simple process of recycling, but the thermosetting plastics cannot be reprocessed, so finding the proper use for the disposal of this plastic waste is an emerging need [7]. Polymers can be incorporated into asphalt mixtures by a wet process, as bitumen modifier, or by a dry process, as partial substitute of the aggregates [8; 9; 10]. The wet process is the most widely used [11], since this method requires a smaller amount of polymer, which in its virgin state significantly increases the price of the binder. There are several examples of the use of virgin polymers in bitumen modification. Among the most commonly used are styrene-butadiene-styrene (SBS), styrene-butadiene rubber (SBR), ethylene-vinyl acetate (EVA), polyethylene (PE) and polypropylene (PP) [12; 13; 14]. According to some authors, it is possible to use plastic wastes in substitution of virgin polymers to achieve that goal, which leads to ecological and possibly economic benefits [15; 16]. There are some plastic wastes with potential to be used in bitumen modification, but polyethylene has the advantage of being the most used polymer and thus resulting in the plastic waste available in higher quantities [6; 17]. Some authors concluded that the use of recycled polyethylene by the wet method promoted improvements in the resistance to permanent deformation, decreasing the thermal susceptibility [18], increasing the stiffness [19] and promoting the best fatigue performance, when compared to unmodified asphalt mixtures [20]. The dry method was also studied by some researchers, which added recycled and virgin polymers directly to the aggregates [11]. This technique may reduce pavement deformation, increasing fatigue resistance and providing a better adhesion between the bitumen and the aggregates [10; 17; 21]. As mentioned above, some other plastic wastes are more difficult to recycle due to their nature, namely the thermosets, which are not possible to melt again after being produced. Cross-linked polyethylene (PEX) is a material used in the production of pipes and cables. Every year, in Europe, 400,000 tons of plastics from cable recycling are sent to landfills, and 20% of those are PEX [22]. Thus, based on a literature review and a market survey, it was concluded that it would be interesting to include this waste material in the production of asphalt mixtures with superior performance, while giving a new life to this polyethylene-based polymer that is difficult to recycle. Therefore, the possibility of using this thermoset plastic waste in asphalt mixtures as a partial substitute of the aggregates would promote the use of higher amounts of this waste material, increasing its value, while saving landfill space and reducing the extraction of mineral aggregates.