Investigating Permanent Deformation of Recycled Asphalt Concrete Containing Waste Oils as Rejuvenator Using Response Surface Methodology (RSM)

In this research, the permanent deformation property of asphalt concrete containing different percentages of recycled asphalt pavement (RAP) and dosages of waste engine and cooking oil has been investigated using response surface methodology (RSM). 25, 50 and 75% of total aggregates have been replaced with RAP, and each rejuvenated with 5, 10 and 15% (by the weight of total binder) of waste engine oil (WEO) and waste cooking oil (WCO). Experiments were designed using composite central design method in RSM, and the permanent strain accumulated after applying 1000 cycles of 300 kPa vertical stress at a frequency of 1 Hz and temperature of 40 degrees C was measured. Using RSM in Design Expert program, a polynomial quadratic model was found to be capable for predicting the permanent strain. It was found that the significant terms for prediction of permanent strain are RAP and oil content, the squared oil content and type of oil. Results reveal that permanent strain decreases with increasing RAP content; however, for each RAP content, the lowest permanent strain is achieved at a certain level of oil content. At the same dosage of use, WEO results in lower strain than WCO. Interaction effect was found between RAP content and oil type, such that the decrease of strain with RAP content is higher with WCO than WEO. Using optimization in RSM, the content of oils to achieve a mixture with similar deformation property of control mix was obtained.