Physico-mechanical properties of asphalt concrete incorporated with encapsulated cigarette butts

Abstract

Discarded cigarette butts (CBs) are among the most common types of litter found around the world. As a possible solution to this problem, this study investigated the possibility of encapsulating CBs with different classes of bitumen and paraffin wax, and incorporating them into asphalt concrete (AC) for pavement construction. The idea behind encapsulation involves restricting the interaction of CBs with fluids and thus preventing chemical translocation. This paper presents and discusses the results of two investigations. The first involved assessing the effects of incorporating different amounts of CBs (10kg/m3, 15kg/m3 and 25kg/m3) encapsulated with different classes of bitumen (C170, C320, C600) into an AC mix manufactured with Class 170 bitumen. The second involved assessing the effects of incorporating 10kg/m3 of CBs encapsulated with paraffin wax into AC mixes that were manufactured with different classes of bitumen (C170, and C320). All samples, including the control AC samples (no CBs), were tested for mechanical and volumetric properties, including stability, flow, resilient modulus, bulk density, maximum density, air voids, and voids in mineral aggregates. For the first investigation, involving encapsulation of CBs with bitumen, using 10kg/m3 and 15kg/m3 of CBs in an asphalt mix gave results that satisfied the requirements for light, medium and heavy traffic conditions. For the second investigation, involving encapsulation of CBs with paraffin wax, the changes in mechanical and volumetric properties for 10kg/m3 CBs only satisfied the light traffic conditions for road pavements. The reduction in bulk density of AC caused by incorporating encapsulated CBs, increases the porosity, particularly when encapsulating in higher grade bitumen, which, in turn, lowers its thermal conductivity. This helps reduce the Urban Heat Island effect in urban environments.