This study aims to develop a framework to incorporate Waste Cooking Oil (WCO) into asphalt mixtures. Such a framework utilizes a Balanced Mix Design (BMD) approach to ensure adequate resistance to cracking and rutting. Transportation agencies can use the proposed framework to incorporate recycled materials such as used cooking oils and reclaimed asphalt pavements into asphalt mixtures, which promotes sustainability in asphalt pavement construction. This study evaluated the cracking and rutting performance of the control and modified asphalt mixtures with different WCO dosages (i.e., 2, 3, 4, 5, and 7% by the weight of the binder) using the Indirect Tensile Asphalt Cracking (IDEAL) and High-temperature Indirect Tensile (High-IDT) Rutting Assessment Tests, respectively. The results demonstrated that WCO improved the cracking resistance of the control balanced mixture but reduced its resistance to rutting. A statistically significant effect was observed at high WCO dosages. Furthermore, the interaction plot indicates that the overall performance of WCO-modified asphalt becomes softer and more flexible with the increase in WCO dosage. Thus, the designed balanced control mixture becomes unbalanced when using WCO oil at any dosage. This study proposed several approaches to design a more economically balanced WCO-modified balance asphalt mixture.

Several monotonic performance indicators that use one or more elements of the load–displacement curve (e.g., area under the curve, curve peak) are used to assess the resistance of asphalt mix to cracking. While these indicators have their own merits, they lack the full description of the load–displacement curve. This study developed a new performance indicator called the Weibull cracking resistance index (${\mathrm{Weibull}}_{\mathrm{CRI}}$ ), which describes the entire load–displacement curve. The study performed an extensive laboratory evaluation of 16 different asphalt mixes tested in two different testing protocols [i.e., indirect tension (IDT) test and semicircular bending (SCB) test] to evaluate the proposed indicator. The findings of this study demonstrated that ${\mathrm{Weibull}}_{\mathrm{CRI}}$ results are sensitive to the variation in binder content and binder performance grade (PG) and were in good agreement with expected cracking resistance based on the composition of the studied mixes. In addition, ${\mathrm{Weibull}}_{\mathrm{CRI}}$ had low variability and provided a good statistical grouping of mix resistance to cracking. The study recommended IDT to determine ${\mathrm{Weibull}}_{\mathrm{CRI}}$ in order to assess asphalt mix resistance to cracking.

Various monotonic cracking resistance assessment tests and indicators of asphalt mixes have their own merits; however, they provide illogical interpretations of mix resistance to cracking under different air void (AV) contents. This study aims to investigate and address the limitations of the monotonic tests and indicators in evaluating the cracking resistance of asphalt mixes with different AV contents. The results show that the shape of the load-displacement curve, curve basic elements, and monotonic indicators are significantly sensitive to variation in AV content. However, the currently proposed correction ratios could not address this dependency of cracking assessment on AV content. This study therefore proposes and evaluates a new approach and correction ratios for monotonic tests and performance indicators. The results demonstrate that the newly proposed correction ratios could normalize the effect of AV content on the examined performance assessment indicators.