Effects of recycled PET aggregate size and replacement level on hot mix asphalt performance

Abstract The increasing accumulation of plastic waste has intensified the need for sustainable reuse strategies in construction materials. This study investigates the feasibility of using recycled polyethylene terephthalate (rPET) from post‑consumer bottles as a partial replacement for natural aggregates in hot mix asphalt (HMA) using the dry mixing method, emphasizing the influence of particle size and replacement level on HMA performance. rPET particles with natural‑aggregate‑like physical characteristics were produced and sieved into standard size fractions to function as rPET aggregates. The adhesion behavior and mechanical properties of rPET aggregates were evaluated and compared with limestone aggregates used in this study under different temperature conditions. HMA performance was assessed through dynamic creep tests (flow number and permanent deformation) at 40 °C, and moisture susceptibility and indirect tensile fatigue tests at 25 °C. To investigate the effect of particle size, 10% of natural aggregates (by volume) were replaced with rPET aggregates in five size ranges from ≤ 0.3 to 19 mm, and the most effective range was used to determine the optimum replacement level. The results showed that at medium-to-high temperatures, rPET had better interfacial adhesion with bitumen than with limestone, and rPET aggregates performed better in the LAA and AIV tests. Optimal performance was achieved using 4.75–12.5 mm rPET aggregates, where 18% replacement increased creep resistance by 57% and reduced moisture susceptibility by 7%, while 16% replacement improved fatigue life by 295%. These findings demonstrate that rPET aggregates provide an environmentally sustainable alternative for enhancing HMA performance.