Investigation of the self-healing, road performance and cost–benefit effects of an iron tailing/asphalt mixture in pavement

As a solid waste, iron tailings urgently need to be addressed to prevent further environmental and social issues. This study attempted to replace natural limestone filler (LSF) with 20%, 40%, 60% and 80% iron tailing filler (ITF) in an asphalt mixture to improve its microwave self-healing properties. For this purpose, the microscopic appearance and chemical composition of the ITF and LSF were first characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) test, while their microwave heating capacity and electromagnetic loss properties were explored. The microwave thermal behaviors of asphalt mixtures containing different substitution ratios of ITF were analyzed via infrared thermography . The self-healing abilities of the various mixtures were tested by five fracture-healing cycles with three-point bending (3PB) test. In addition, the high-temperature stability, low-temperature crack resistance and water stability of the mixtures were evaluated. Furthermore, the economic and beneficial aspects of the ITF-doped mixtures were assessed by cost–benefit analysis (CBA). The experimental results suggest that an ITF with more metal oxides and better electromagnetic loss characteristics exhibits favorable microwave heating ability. After fifth crack-healing cycle, the healing capacity of the mixtures with 60% and 80% ITF increased by 2.5 and 2.75 times, respectively, compared to that of the mixture without ITF. A total of 40% is the recommended appropriate addition of ITF, which helps to improve or has less impact on the road performance. Additionally, based on the CBA method, the incorporation of more than 60% ITF into an asphalt mixture can provide considerable economic efficiency. As a consequence, the potential use of ITF as an eco-friendly filler in asphalt mixture presents new opportunities for waste recycling and resource conservation while also introducing novel approaches for self-healing pavement.