Optimization of asphalt and modifier contents for polyethylene terephthalate modified asphalt mixtures using response surface methodology

• Effect of PET modification was evaluated in asphalt mixture.
• Response surface methodology was used to find interactions between selected variables.
• Good agreements between experimental results and predicted values were obtained.
• Optimal amounts of asphalt and PET were obtained to meet mix design requirements.

Optimization of polymer and asphalt content in polymer modified asphalt mixture is the aim of road engineers and designers. The purpose of this study is to characterize Stone Mastic Asphalt (SMA) mixture’s properties containing waste polyethylene terephthalate (PET) which is a type of polymer material. Response Surface Methodology (RSM) was designated as a new method to measure mixture properties at different PET content and asphalt binder value. To fabricate the mixture fresh 80/100 penetration grade asphalt binder with different percentages (5–7% by weight of aggregate particles) was utilized. Different amounts of PET were used from 0% to 1% by weight of aggregate particles. Marshall Stability and Flow test was performed on the mixtures. Specific gravity and volumetric properties of mixtures were obtained. RSM was used to analyze Marshall and volumetric properties of unmodified and PET modified asphalt mixtures. Models were produced to fit the experimental results. As shown in this study suggested models were successfully fitted to the experimental results. Based on the results achieved amounts of 5.88% of asphalt content and 0.18% of PET were found to be the optimal values.