Functionalized Waste Plastic Granules to Enhance Sustainability of Bituminous Composites

Abstract

This paper evaluates the merits of using waste plastic granules made from functionalized polyethylene terephthalate (PET) to enhance bitumen's bond strength to endure extreme environmental conditions such as aging and moisture. The applicability of PET as a modifier for bitumen has been hindered by PET's low compatibility with bitumen, causing phase separation. In this study, to improve PET's compatibility with bitumen, PET flakes were functionalized by grafting bio-oils onto their surface. This study optimized the method of PET functionalization by selecting the optimal time for exposure to microwave irradiation based on the following criteria: PET temperature below the melting temperature of PET, reduction in phase separation of PET-modified bitumen, multiple stress creep recovery, and shear thinning behavior. It was found that the optimized irradiation time for functionalization is 10 minutes. The efficacy of functionalized PET and non-treated PET as modifiers to improve bitumen's bond strength was then studied after exposure to various levels of aging and moisture damage. Bitumen's interaction with siliceous surfaces was evaluated by the bitumen bond strength (BBS) test and the moisture-induced shear-thinning index (MISTI) test. The results of the BBS test, performed on glass substrates , showed that bitumen modified with functionalized PET granules (OTPG) exhibited the highest pull-off tensile strength and the greatest resistance to moisture damage after exposure to adverse environmental conditions. It was found that modifying bitumen with OTPG reduced moisture susceptibility by 25% as measured by the pull-off test. This improvement was also noticed in the results from the MISTI test, which showed that the lowest moisture susceptibility was found for bitumen modified by OTPG. The outcome of this study shows the merits of using functionalized waste plastics in pavements to enhance their durability while promoting sustainability and resource conservation.