Advancing Crack Resistance and Environmental Sustainability in Asphalt: Investigating Recycled Cigarette Filters in Stone Matrix Asphalt

Abstract

The disposal of cigarette filters (CFs), primarily composed of cellulose acetate fibers and containing harmful substances like burned tobacco, tar, and heavy metals, poses a significant environmental threat due to their slow degradation. Thus, finding an effective approach for recycling and disposal is a pressing concern. Repurposing CFs in asphalt mixtures offers a promising recycling solution, particularly for improving asphalt crack resistance, which is crucial for performance but underexplored. This study evaluates the effects of incorporating intact and shredded CFs into stone mastic asphalt (SMA) under different wet and dry conditions on crack resistance. Semicircular bending (SCB) tests at 25°C and −12°C were conducted, examining two fracture modes (Mode I and Mixed Mode I/II). Key performance indicators like crack resistance index (CRI), balanced cracking index (BCI), toughness index (TI), peak load (Fmax), and fracture energy (Gf) were calculated. Results indicate that a 3% inclusion of shredded CFs significantly enhances crack resistance, with wet mixing showing the greatest improvements: Gf, CRI, and BCI increased by up to 46%, 15%, and 75% in Mode I, and 28%, 23%, and 76% in Mixed Mode I/II, respectively. Additionally, this study demonstrates the reliability of non-standard samples for SCB testing in mixed Mode I/II and emphasizes the critical role of CF quantity and the mixing method, with wet mixing proving notably more effective than dry mixing in improving the structural performance of asphalt.