Optimization of Repurposed Waste Plastics in Asphalt Mixture’s Binder
Advisor: Professor Imad L. Al-Qadi
Abstract Plastics are moldable organic polymers with desired mechanical properties, which could be useful for application in asphalt concrete (AC) pavements. The objective of this study was to repurpose waste plastics in AC pavement, quantify the impact on its potential performance, and the environment. Chemical-and rheological-based tests were conducted to understand the interaction between waste plastics and asphalt binders at various dosage levels. In addition, the effect of waste plastics on typical AC mixes was assessed using rutting, cracking potential, and moisture-induced damage. The leaching of waste plastic-modified AC was measured, and a comparative life cycle assessment (LCA) was conducted. The study concluded that waste plastic may be incorporated into AC mixtures. However, binder and waste plastic must be compatible. An additive may be needed to control potential separation. When 3% LDPE is added in the wet process, the potential for AC rutting would be decreased, while the cracking potential would be maintained. However, waste plastic-modified AC may not outperform the potential performance of SBS-modified AC. Leachate testing of waste plastic-modified AC revealed that concentrations of certain trace elements exceeded EPA enforcement levels. Leachate concentrations of antimony, arsenic, and cobalt exceeded regulatory limits, raising concerns related to blood pressure, skin irritation, and carcinogenicity. A cradle-to-grave comparative LCA results demonstrated that the environmental impacts of an AC mix incorporating recycled plastics are highly dependent on the method of incorporation of waste plastics. However, the availability and quality of data are important. Further studies are needed to optimize the LDPE dosage in AC in the wet process and other waste plastics may be considered. In addition, an extensive leaching framework is recommended, incorporating percolation column tests and pH-dependent leaching protocols to better assess long-term environmental risks of waste-plastic AC.