Experimental study on innovative sustainable recycled fibres for high performance asphalt concretes

The growing consumption of heated tobacco products (HTPs) has led to a significant accumulation of electronic cigarette butts (E-CBs), which degrade slowly and contain toxic chemicals, contributing to environmental pollution. To address this issue, this thesis explores the potential of recycling E-CBs as fibre additives in asphalt mixtures, providing a sustainable alternative to traditional cellulose fibres. The study specifically investigates the use of E-CBs in Stone Mastic Asphalt (SMA), mixtures containing Reclaimed Asphalt Pavement (RAP), and Warm Mix Asphalt (WMA). E-CBs were processed through shredding and pelletizing, and their effects on drain-down, volumetric, and mechanical properties were assessed. The results show that shredded E-CBs effectively absorb bitumen, resulting in acceptable air void content and mechanical properties in SMA. However, E-CB powders were found to negatively affect the thermal stability and rutting resistance of the mastic. Larger shredded E-CBs (15 mm) demonstrated better performance in terms of tensile strength, stiffness, and rutting resistance compared to smaller ones (10 mm). While the plastic content of E-CBs increased thermal susceptibility, it enhanced resistance to permanent deformation. Further innovation was achieved through the development of engineered fibre pellets made from shredded E-CBs using 3D printed molds. The SMA using Pellet Ⅰ (composed solely of E-CBs) can satisfy the technical specifications regarding the tests performed in this study. Pellet Ⅱ, which incorporated both E-CBs and a recycling agent, improved fatigue performance in SMA mixtures with 40% RAP without compromising other mechanical properties. The use of pelletized fibres containing Fischer-Tropsch wax enabled WMA production at lower temperatures, but their impact on workability and mechanical properties was limited compared to the conventional method of adding the wax. The conclusions drawn from this thesis highlight the potential of recycling E-CBs as a sustainable fibre additive in asphalt mixtures, presenting an eco-friendly alternative to conventional materials.