Chemical upcycling of waste PET into sustainable asphalt pavement containing recycled concrete aggregates: Insight into moisture-induced damage

Abstract

Waste polyethylene terephthalate (PET) plastic and construction and demolition waste are main municipal solid wastes. If they are not properly disposed of, they will cause continuous damage to the ecological environment. Previous studies have shown that recycled concrete aggregate (RCA) can be successfully adopted to replace natural aggregate (NA) for asphalt pavement construction. However, the moisture-induced damage, as one of the pavement engineering performances, is very prominent for asphalt concrete containing RCA (RCA-AC), due to the high absorption of RCA and the weakness of the adhered mortar. Given this, PET additive, derived from waste bottle bodies, is considered to improve the resistance of RCA-AC to moisture-induced damage in this study, which has been previously identified effective to enhance the anti-stripping characteristics of asphalt mixtures containing NA. To achieve this goal, this study applied a series of tests including contact angle, image recognition, boiling water test, immersed Marshall test, freeze–thaw (F-T) splitting test, wheel tracking test, and field emission scanning electron microscope (FESEM) to evaluate the moisture-induced damage of RCA-AC containing PET additive. The results showed that PET additive has a significant ability to improve the bonding strength and adhesion of asphalt binder to RCA and reduce the stripping percentage and moisture-induced susceptibility of RCA-AC, especially under the F-T cycles. In addition, the 60 °C rut deformation resistance of RCA-AC after immersion can be improved as the PET additive is used. Furthermore, the interfacial bonding layers (IBL) of PET additive modified asphalt binder between RCA particles are still existent and its width is not significantly increased after immersion and F-T cycles by contrast to that of virgin binder. In general, the appropriate use of PET additive is a good approach to promote the high-quality recycling of RCA into sustainable asphalt pavement.