# Effect of Waste Engine Oil and Waste Cooking Oil on Performance Improvement of Aged Asphalt
## 1 Introduction  
Recent societal and economic developments have resulted in an annual increase in the total mileage of highways in China. Less than 10 years after construction or operation, many asphalt pavements required different degrees of maintenance due to the different damages sustained during their service lives. This in turn led to the generation of large quantities of reclaimed asphalt pavement materials [1]. Asphalt pavement maintenance was facing the problems of disposal of waste asphalt concrete. The continued use of nonrenewable sources caused environmental pollution as a result of improper waste disposal [2; 3]. Therefore, the recycling technology of waste asphalt pavement is becoming more and more attractive from the perspective of energy and environmental protection in the world [4; 5]. On the other hand, with the development of automobile and living conditions, large amounts of waste oils, such as waste cooking oil (WCO) and waste engine oil (WEO), are generated. In previous studies, many scholars have proposed various asphalt rejuvenators and analyzed their effects on the properties of aged asphalt [6; 7; 8]. It was also important to develop new rejuvenators using the WEO and waste cooking oil (WCO). Researchers found that WCO and WEO were similar in molecular structure to asphalt, which was a favorable condition for their reuse. It was well known that the reused ofaged asphalt was the key to recycling asphalt pavement. From the chemical point of view, asphalt regeneration is a reversal of its aging. As such, adding new asphalt binders or regenerators with appropriate chemical compositions and properties that had been reduced in aged asphalt could recover the performances of aged asphalt [9]. Asphalt binders consist of four fractions including saturates aromatics resins and asphaltenes. Based on the compatibility theory of rejuvenation, WCO and WEO can be used as a low viscosity component to recycle aged asphalt. Compared with other low viscosity components, flash points of WCO and WEO were above 200\({}^{\circ}\)C, which showed that the use of WCO and WEO in hot mix asphalt mixes had high structural safety. The effective treatment or reuse of these materials not only reduced environmental pollution and conserves energy, but also represented an innovative method of recycling waste. The proposed method could recover or improve the properties of aged asphalt and provide an effective method to regenerate the aged asphalt using waste oils. Therefore, it was practically significant and would provide a broad application prospect for WEO and WCO in the asphalt pavement recycling field. In recent years, many studies were carried out on the use of WEO or WCO as asphalt rejuvenators. Due to similarity in molecular structure of WEO and WCO with asphalt, several attempts had been made to use WEO and WCO in conjunction with asphalt binder. [PERSON]. [10] studied, by thermochemical characterization, the bituminous binders modified with different WEO and recycled engine oil bottoms combined with polymers were studied with penetration, softening point and viscosity tests. The modified bituminous binders had similar penetration values and softening point temperatures higher than those of commercially modified binders. [PERSON] [11] studied the effect of WEO on the rheological properties of asphalt. The results indicated that WEO-modified asphalt had lower elastic portion, heat sensitivity, zero shear viscosity, and antirutting ability, but had higher fatigue resistance and temperature sensitivity. [PERSON] [12] showed the improvement of rheological properties of aged asphalt using dynamic shear rheometer with up to 5% WEO content. However, [PERSON] and [PERSON] [13] found that it could result in poor low temperature performance of rejuvenated asphalt with the WEO content beyond 15%. [PERSON] [14; 15; 16] also studied the physical and chemical properties of rejuvenated asphalt to prove its application. [PERSON] et al.