## 1 Introduction  
Currently, there is a growing concern to reuse waste materials and to conserve or minimize the use of natural resources in road paving. Thus, many studies have recently emerged in which these issues, or part of them, are discussed [1; 2; 3]. Under this assumption, the study of new asphalt binders that partially incorporate wastes is essential to reduce the use of bitumen directly obtained from oil sources, which is important for the sustainable development of road paving construction. Some studies related to this matter refer to non-petroleum binders [4] and synthetic binders made up of used oils, resins and polymers [5].  
One example of a bitumen substitute or asphalt rejuvenator that has been studied lately is bio-oil, mainly produced from fast pyrolysis of biomass materials [6; 7]; i.e., renewable organic matter, namely from agriculture, forestry or urban wastes. Bio-oil behavior at intermediate and high temperatures is similar to that of a conventional bitumen [8], but it is too stiff, and is quite brittle at low temperatures. However, that problem could be solved by adding ground rubber from used tires (GTR) in order to obtain a bio-binder with a very good performance [9].  
The incorporation of waste motor oil in asphalt mixtures is also being tested to prevent aging, or as a bitumen rejuvenator [10; 11], due to its lower viscosity, which results in lower mixing and compaction temperatures [12; 13]. This solution is also environmentally friendly, because waste motor oil is not totally recyclable [14]. However, the addition of waste motor oil could bring some disadvantages for asphalt mixture performance, namely a reduced elastic recovery and rutting resistance [15]. Thus, polymer modification should be used to minimize some of these problems, and the elastomer styrene-butadiene-styrene (SBS) could be considered the most suitable modifier [16] of bitumen after addition of waste motor oil. In fact, SBS increases the asphalt mixtures rutting resistance at high temperatures and cracking resistance at low temperatures, and it also improves the tensile strength and elastic recovery properties of bitumen [17].  
Taking into account that bio-oil from fast pyrolysis was not available in the necessary amounts for road paving works in several countries because this technology is not used globally at an industrial scale, this work focused on studying an alternative solution using waste motor oil to partially replace the amount of bitumen used in asphalt mixtures. Therefore, an asphalt mixture was produced with a bitumen modified with waste motor oil and SBS, and its performance was evaluated and compared with a conventional control mixture produced with 35/50 bitumen, and with the mixture previously studied by [PERSON] et al. [6] with bio-oil and ground rubber.  
This new binder can be seen as a sustainable solution for road paving works, because both the economic and environmental criteria are being considered, as suggested by other authors [18; 19]. In fact, by reducing the amount of bitumen used in asphalt mixtures, a high amount of waste materials can be used, with a consequent reduction in the global cost of the mixtures. However, the asphalt mixture produced with this new binder must perform as well as a conventional mixture produced with a current bitumen in order to ensure real advantages in a comprehensive way, and this factor is assessed in this work.