Waste PET in asphalt pavements: statistical modelling and performance assessment

The objective was to identify the optimum polyethylene terephthalate (PET) dosage and statistically validate its effects on durability, rutting resistance and cost efficiency. PET was incorporated into VG-10 binder at 0–11% by weight and evaluated using the Marshall mix design. Performance assessments included Marshall stability, rutting resistance, freeze–thaw durability and volumetric parameters, supported by regression analysis, R² and p-value statistics. Additional evaluations such as indirect tensile strength, tensile strength ratio and Fourier transform infrared (FTIR) spectroscopy were performed to assess binder modification and durability, while a 15-year life-cycle cost analysis (LCCA) determined economic viability. Results revealed that the 7% PET-modified mix (TM-3) achieved optimal performance, increasing Marshall stability from 10.2 to 12.8 kN, reducing rutting depth by 15.2% and slowing freeze–thaw degradation by 20%. The mix also maintained acceptable air void levels and exhibited improved binder film thickness. FTIR analysis confirmed chemical bonding enhancement, while statistical analysis and LCCA indicated comparable costs to conventional mixes, with TM-3 becoming more cost-effective beyond a 9.6% discount rate. Overall, a 7% PET addition provides a sustainable, durable and high-performance pavement solution without increasing life-cycle costs.