Feasibility of using micronized recycled Polyethylene Terephthalate (PET) as an asphalt binder additive: A laboratory study

Abstract

The limited cost-effective avenues available for recycling Polyethylene Terephthalate (PET), widely used in packing bottled water, has turned it into a global environmental challenge. A number of studies have evaluated use of recycled PET bottles as an aggregate replacement in asphalt mixes. However, their outcomes indicated that performance of mixes did not significantly benefit from strength and high elasticity of PET. This study was undertaken to investigate the effect of incorporating different amounts (0, 5, 10, 15, and 20%) of Micronized PET (MPET) as a modifier in a PG 58-28 asphalt binder on its viscosity and adhesion to different types of aggregates. Also, the effectiveness of using MPET-modified asphalt binder in mixes for improving their resistance to rutting, cracking, and moisture-induced damage was evaluated. For this purpose, binder blends’ dynamic viscosities were measured using a rotational viscometer. Pull-off strength of MPET-modified binders with aggregates (two granite and one quartzite) was determined by conducting binder bond strength tests on dry and moisture-conditioned specimens. Surface Free Energy (SFE) analysis was also carried out to further understand the adhesion, cohesion, and debonding mechanisms. Furthermore, Superpave asphalt mixes containing MPET-modified PG 58-28 asphalt binder blends were prepared in the laboratory and their resistance to cracking, rutting, and moisture-induced damage was evaluated by conducting semi-circular bend, Hamburg wheel tracking, and tensile strength ratio tests. Testing asphalt binders and SFE analysis showed that, incorporation of MPET in asphalt binder significantly improved viscosity and binder-aggregate adhesion as well as their resistance to stripping. Additionally, testing asphalt mixes showed that, an increase in MPET content resulted in an increase in resistance to cracking, rutting, and moisture-induced damage. It was concluded that use of MPET as an asphalt binder modifier is an effective method for improving mechanical properties of asphalt pavements while addressing an environmental concern and preserving natural resources.