# Performance Assessment of Waste Cooking Oil-Modified Asphal Mixtures
## 1 Introduction
Previous studies mainly used the results of physical binder tests (e.g., penetration, viscosity, softening point, flash point, Fraass Breaking Point, and ductility test) to assess the effectiveness of WCO and determine its suitable dosage (or optimum). However, such empirical binder assessment tests do not represent any performance criteria of the studied binders and may provide inconsistent results. For instance, [PERSON] et al. (2019) and [PERSON] et al. (2016) recommended the optimum WCO dosage to be 1% and 15% of binder weight, respectively, although they relied on the same binder tests (penetration, softening point, and ductility tests) to determine the optimum dosage [21; 27; 28]. Similarly, there was a wide range of recommended optimum WCO dosages in the literature (i.e., from 1% to 33% [20; 21]). Although other factors contribute to determining the optimum WCO dosage, such a wide range of recommended dosages would negatively affect the performance of asphalt mixtures. In fact, [PERSON] et al. (2021) and [PERSON] (2022), in their review, highlighted the importance of addressing this issue [20; 26; 29]. In addition, the currently implemented asphalt mix design methods (i.e., SuperPave and Marshall) lack the capability to design modified asphalt mix properly. These methods rely on volumetric parameters (i.e., design air voids (V\({}_{\text{a}}\)) and volume of effective binder (V\({}_{\text{be}}\))) to determine the optimum binder content (OBC). However, these parameters do not provide any indication of the interaction between the virgin binder and modifiers [28]. Therefore, the impact of such modifiers (enhance/decline) on the designed mix's performance (e.g., resistance to cracking) cannot be appropriately assessed. The review studies indicated that limited studies assessed the performance of modified asphalt mixtures [26; 29]. For instance, [PERSON] et al. (2021) [26] stated that limited studies examined WCO-modified asphalt mixtures' cracking resistance. Nowadays, greater emphasis is placed on utilizing asphalt mixture performance assessment tests [30]. The primary objective of such tests is to discern mixtures that exhibit inadequate performance (e.g., rutting, cracking) during the mix design or production phases using well-established performance thresholds. Several studies have proved the ability of such tests to assess the performance of asphalt mixtures [31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48]. A new design concept called \"_Balanced Mix Design (BMD)_\" is being developed. The BMD overcomes the current volumetric methods (i.e., SuperPave and Marshall) by incorporating performance assessment tests, indicators, and specifications during the mix design process. It is defined as \"_Asphalt mix design using performance tests on appropriately conditioned specimens that address multiple modes of distress taking into consideration mix aging, traffic, climate, and location within the pavement structure_\" [49]. There is a national interest in implementing the BMD approach [2; 30]. In light of the previous discussion, there is a need to utilize the BMD approach to address the raised concerns with WCO-modified asphalt mixtures. It would enhance our understanding of the impact of WCO on asphalt mixture performance. Such findings would optimize the usage of WCO without declaring the mixture performance, which would offer a sustainable, cost-effective, and performance-enhancing solution for road construction, contributing to waste reduction, resource conservation, and environmental protection.