Recycling of waste E-cigarette butts as engineered pelletized fibres for sustainable stone mastic asphalt

The disposal of discarded E-cigarette butts (E-CBs) presents significant environmental challenges due to their detrimental impacts on ecosystems. To find an environmentally sustainable method for managing this waste, the potential for recycling E-CBs in asphalt pavements was investigated in this study. By focusing on the two primary components of E-CBs, namely cellulose fibre and polylactic acid (PLA), this research introduced a novel approach for recycling E-CBs in stone mastic asphalt (SMA) as a fibre additive in engineered pellet form. The prepared fibre pellets were directly added to aggregates to produce the SMA mixture. The resulting mixtures underwent a comprehensive evaluation through a series of standardized laboratory tests, including assessments of volumetric properties, indirect tensile strength (ITS), stiffness modulus, moisture susceptibility, and rutting resistance. The results were compared with SMA mixtures containing conventional cellulose fibres. Additionally, to examine the potential influence of PLA, a third mixture was prepared, incorporating both cellulose fibre and PLA. The findings indicate that the SMA using pelletized fibre can satisfy the technical specifications regarding the tests performed in this study, showing higher ITS and rutting resistance compared to the reference mixture. Moreover, the incorporation of PLA plastic reduced air void content and improved tensile strength, stiffness, and rutting resistance. This study highlights the potential for recycling E-CBs in asphalt mixtures, offering technical support for further development of sustainable recycling methods for this waste.