Sustainable use of COVID-19 discarded face masks to improve the performance of stone mastic asphalt

Since COVID-19 was declared a global pandemic, the production, consumption, and discard of personal protective equipment (PPE), such as face masks, have been rapidly increasing. The massive amount of face mask waste poses a severe threat to the ecology, environment, and public health. Alleviating the adverse effects of mask waste requires the cooperation of professionals from various fields. To reduce the epidemic-generated waste and improve the performance of stone mastic asphalt (SMA) mixes, in this study, comprehensive laboratory experiments, including volumetric assessment, Marshall stability and flow, resilient modulus, dynamic creep, moisture susceptibility, and binder drain-off test were carried out on SMA specimens prepared with 0.3%, 0.5%, 0.7%, and 1.0% of mask fibre (MF) by weight of asphalt mixture. The results were compared with the control SMA specimen (i.e., SMA mixed with 0.3% cellulose fibre (CF)) that complied with the road industry regulations and standards. The results of the study illustrated that the introduction of MF into the SMA mix improved the stability, resilient modulus, indirect tensile strength, resistance to permanent deformation, resistance to moisture damage and binder drain-off performance. Experimental results indicated that the inclusion of 0.3% and 1.0% MF in SMA complied with industry requirements and suggested that MF could be used instead of virgin CF as a fibre additive. Considering the available supply, performance and industry standards, SMA containing 0.3% MF demonstrates more potential for pavement applications.