Use of bitumen encapsulated cigarette butts in stone mastic asphalt

Around the world, 75 percent of smokers do not dispose of their cigarette butts properly, thereby resulting in a large amount of mephitic waste cigarette butts (CBs) being dumped into the environment. Waste CBs take years to decompose with most containing a cellulose-acetate based filter, tar, nicotine, tobacco, and many highly toxic chemicals that leach into the soil and water bodies and cause contamination and toxicity. Mohajerani et al. in 2017 developed the encapsulation method for cigarette butts and investigated the incorporation of bitumen and wax encapsulated cigarette butts in dense asphalt concrete. This research work investigated the possible recycling of bitumen encapsulated CBs in stone mastic asphalt (SMA). Waste CBs were processed and encapsulated with bitumen class PMB A10E. Stone mastic asphalt samples were prepared by replacing coarse aggregates by 1%, 2%, and 3% (by weight) with bitumen encapsulated CBs. Marshall stability, flow, resilient modulus, and volumetric properties of SMA manufactured samples were investigated and the results were compared with those of the control SMA samples prepared without CBs. The experimental procedures and some of the significant outcomes of the study, along with some results from a leachate analysis have been presented and discussed. Average results show that the use of encapsulated CBs in Stone Mastic Asphalt samples manufactured in this study improved the stability and resistance to permanent deformation. Furthermore, the leaching of heavy metals from encapsulated CBs compared with those of unprocessed CBs reduced significantly. Based on the promising results found in this study, further investigations, and development of practical implementation procedures for recycling cigarette butts in asphalt concrete on an industrial scale are recommended.