Application of Design-Expert Response Surface Methodology for the Optimization of Recycled Asphalt Mixture with Waste Engine Oil

In this paper, waste engine oil was used as the base oil to produce a competent rejuvenator for the recycled asphalt mixture based on the Design-Expert surface response method. From the surface response in terms of penetration, ductility, softening point, glass transition temperature, and mass-loss percentage, the optimum waste engine oil-based rejuvenator had 5% plasticizer, 6.33% antiaging agent, and 7.3% fusogen. The thermogravimetric (TG) analysis indicated that the prepared rejuvenator possessed excellent thermostability at 200°C. The optimum dosage of the rejuvenator was determined as 6% by the weight of asphalt binder based on the penetration, ductility, and softening point results. Then, the effects of the rejuvenator on the asphalt binder properties were evaluated through Fourier transform infrared spectroscopy (FTIR), dynamic shear rheometer (DSR), and differential scanning calorimetry (DSC). The binder test results implied that the rejuvenator significantly reduced the glass transition temperature of aged asphalt and restored the chemical composition, which also increased the rheological properties. Subsequently, the effects of the rejuvenator on the asphalt mixture properties were also evaluated through freeze-thaw splitting, beam bending, and dynamic stability tests. The mixture test results showed that the rejuvenator effectively increased the moisture resistance and low-temperature cracking resistance of aged asphalt mixture, which yielded comparable mixture properties with virgin asphalt mixtures.