Hybrid Waste Modifiers for Performance Enhancement of Asphaltic Concrete

Abstract

Growing concerns of resource depletion, environmental pollution and the burden of traffic on pavements have led to a global move to sustainable asphalt technologies. This research examines performance improvements in asphaltic concrete by hybrid integration of three waste-based modifiers namely lignite, waste polythene (WPT) and worn-out tyre rubber (WOT). The goal of the research was to upgrade the mechanical, microstructural and durability characteristics of asphalt, and also solve the waste management and sustainability issues. Standard laboratory tests were performed to assess the bitumen characteristics, aggregate quality and mechanical behaviour such as Marshall stability, flow, tensile strength, and resilient modulus. Microstructural analyses by the techniques of X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) were carried out to characterise the mineral phases as well as elemental content. The results revealed that the hybrid mixture with a mixture proportion of bitumen, lignite, WPT and WOT ratios of 7 %, 2 %, 2 % and 5 %, respectively (sample R17) provided the highest stability Marshall of 11.38 kN and indirect tensile strength (ITS) of 341.02 kN/m2 which were excellent and better than the control mix. The resilient modulus of 820 kN/m2 and Marshall flow of 3.73 mm showed an excellent stiffness and deformation resistance. Results of the SEM-EDS analyses showed carbon dominant microstructures (84-94 % atomic) and the greater content of silicon in the modified samples, whereas XRD showed major crystalline phases of quartz, orthoclase, muscovite, and graphite. These findings confirm the adequacy of the application of hybrid waste modifiers to improve the mechanical and durability performance of asphaltic concrete. The research presents a sustainable approach to road building through the conversion of lignite, plastic and tyre waste into high-value engineering materials.