Performance Evaluation of Post-Consumer and Post-Industrial Recycled Plastics as Binder Modifier in Asphalt Mixes

Abstract This study aims to analyse the behaviour of asphalt concrete produced from recycled plastic-modified bitumen. This particular production process is known as the wet method, which involves the blending of low melting point recycled plastics, mostly polyolefins, in hot bitumen before mixing with preheated aggregate. Based on a comprehensive research study that investigated several recycled plastics for the wet method, two common low melting point plastics from two different collection streams were evaluated: a low-density polyethylene from post-industrial recycling operations and a source of commingled plastic (polyethylene and polypropylene) from the collection of post-consumer plastics. Plastic-modified bitumen was produced with different recycled plastic contents ranging from 0.5 to 6% of the bitumen weight. First, the storage stability of the plastic-modified bitumen was evaluated. Then, asphalt mixes were produced using the plastic-modified bitumen. The testing scheme included measurements of the compactability and densification behaviour of the mixes, moisture resistance, viscoelastic behaviour via the flexural stiffness test, IDEAL-CT test to evaluate cracking tolerance, fatigue resistance through the four-point bending beam test, and rutting resistance via Hamburg wheel tracking. The study found that adding a high plastic content significantly reduced the storage stability of the plastic-modified bitumen. Adding plastic was found to have a minor impact on the compactability, while it reduced the moisture resistance with increasing plastic addition and modified the viscoelastic behaviour of the asphalt mixtures. Finally, the study found that plastic provided benefits to the cracking and rutting resistance of asphalt mixtures to different extents depending on the plastic type and plastic content.