Evaluation of the compatibility of waste plastics and bitumen using micromechanical modeling

Abstract

Introducing waste plastics in bituminous composites can increase the composites’ durability, provided that the waste plastics are compatibilized with bitumen to avoid phase separation. To enhance the compatibility of plastic particles with bitumen, various treatment methods were used to alter their physical and chemical characteristics. Considering the complex nature of bitumen, knowing the properties of isolated particles is not sufficient to indicate their performance in a bituminous composite. Therefore, there is a need to quantify the efficacy of each treatment method directly. While the plastic-bitumen interface can be examined via advanced characterization instruments such as atomic force microscopy, those methods are often relatively complicated and time consuming for formulators and designers. Here, we use a heterogeneous micromechanical model to calculate compatibility indicators; the model is tailored for viscoelastic bituminous composites containing waste-plastic particles. With experiments using a dynamic shear rheometer and a bending beam rheometer, data were generated on the bitumen with and without waste plastics having various surface treatments. The model was then used to calculate the Effective Volume Filling (EVF) ratio to indicate the interaction between plastics and bitumen as a measure of compatibility. A higher EVF ratio indicates greater compatibility. The corresponding EVF ratio was found to be higher for the oil-treated plastics compared to non-treated plastics, demonstrating higher compatibility of the oil-treated plastics with bitumen. This study promotes sustainability in construction by facilitating the use of waste plastics and enhancing the cracking resistance of bitumen.