Plastic waste in dense asphalt mixes for road pavements

Recycling plastic waste in asphalt pavements records increasing statistic figures of application during the last decade worldwide. Due to environmental constraints, but also, to some beneficial properties of plastic waste, recycling in asphalt tends to become current practice, in several countries. In the Aristotle University of Thessaloniki (AUTH), the first attempt to produce asphalt mix using plastic waste consisted of mixing recycled plastic flakes with non-modified binder. Following an asphalt mix design in the laboratory, the whole mass of conventional aggregates was replaced by PET flakes. Recycled PET flakes were chosen to be introduced in the asphalt mix since they are hard, resilient and water repellent. Bitumen emulsion was first preferred as a binder to produce a cold asphalt mix. At a second stage of experimental research, plastic flakes replaced a part of the limestone sand while conventional asphalt 50/70 was used as a binder. At this stage, the experimental research provided more encouraging outcomes. Stability of asphalt mixes decreases as the plastics content in the mix increases, but all recorded values were still within limits of acceptance. At a third stage of research, LDPE recycled material of fine gradation was used to replace a part of the asphalt binder in dense mixes. The objective was to produce a modified binder and a more durable asphalt structure. Test results showed a significant improvement of the performance of asphalt mixes, in terms of strength and deformability of the asphalt mix structure. The research is completed by comparing the conventional techniques with the outcomes of the recycling process and by delineating potential fields of application of the recycled plastics in asphalt pavements.