Influence of Polyethylene Melting Characteristics on Volumetric Properties and Performance of Asphalt Mixtures

Abstract

The main goal of the study is to evaluate the influence of polyethylene (PE) source variability on the design air voids and performance of asphalt mixtures. In this process, PEs from three different sources were collected and their thermal characteristics were captured using a differential scanning calorimeter. After identifying PEs with respect to the degree of crystallinity (X_c) instead of the source, plastic was incorporated in asphalt mixtures through the dry mixing method as a replacement for asphalt binder at 3%, 6%, and 9% by weight of asphalt binder. From air void and aggregate-PE coating assessment, PE with a low X_c was observed to act as a binding agent, while PE with a high X_c was found to act as a filler. With respect to performance, PE incorporation was effective in improving the rutting tolerance index (RT_index) at 58°C and tensile strength ratio of asphalt mixtures regardless of the X_c property. The cracking tolerance index (CT_index) at 19°C declined for PE with a low X_c (60% and 65%) and was enhanced for PE with a high X_c (92%). However, a fracture energy (G_f) versus post-peak parameter (l₇₅/m₇₅) plot conveyed that PE with a high X_c imparted ductile behavior to the mixture, which facilitates the design of effective plastic-modified mixtures against cracking. The fracture energy evaluated at −18°C using a disk-shaped compact tension test embodied the undesirable performance of PE-modified mixtures at all X_c levels. Overall, identifying PE with respect to the X_c rather than source can be an effective way of predicting volumetric parameters and performance of PE-modified mixtures.