Evaluating the Macrocrack Self-Healing Properties of Stone Mastic Asphalt Incorporating Cigarette Filters as Microwave-Absorbing Additives

Self-healing technology in asphalt mixtures offers significant potential for reducing construction, repair, and maintenance costs. While microcrack self-healing has been extensively studied, macrocrack self-healing remains largely unexplored. This study evaluates the use of discarded cigarette filters, containing heavy metals, as microwave-absorbing additives in stone mastic asphalt (SMA) to enhance macrocrack self-healing. Two incorporation methods, wet and dry mixing, were investigated. The semicircular bending (SCB) test, performed at 25°C and −12°C, assessed the self-healing performance using indices such as peak load (FMax) for microcracks, and fracture energy (Gf), crack resistance index (CRI), toughness index (TI), and balanced cracking index (BCI) for macrocracks. Results showed a 22% increase in Gf and significant improvements in BCI and TI by 25 and 22%, respectively, at 25°C with wet mixing. The wet mixing method demonstrated superior self-healing performance compared to the dry mixing method. Statistical analysis confirmed the significant effects of the mixing method and cigarette filter content on the TI and BCI indices. In addition, self-healing performance was better at 25°C compared to −12°C. Incorporating cigarette filters into SMA offers dual environmental and performance benefits, providing a sustainable solution for asphalt durability and waste management.