## 3 Results and Discussion  
### Rotational Viscosity  
This study investigates the influence of Trinidad Lake Asphalt (TLA) and Crumb Rubber Modifier (CRM) on the viscosity of PG 64-22, a commonly used pure asphalt binder. Viscosity measurements were carried out at two specified temperatures, namely 135 \({}^{\circ}\)C and 180 \({}^{\circ}\)C as seen in Figure 2, to simulate typical circumstances encountered during asphalt mixing and application. The data reveal a clear and noticeable pattern in how different additions affect the viscosity of the binder. The virgin binder, PG 64-22, had the lowest viscosity at both temperatures, serving as a benchmark for comparison. The addition of TLA, known for its high asphaltene content, significantly increased the viscosity of the binder. Specifically, the viscosity of the mixture of PG 64-22 with 10% TLA exhibited a notable rise at both 135 \({}^{\circ}\)C and 180 \({}^{\circ}\)C. There was not much rise in the viscosity values when the concentration of TLA was raised to 20%. The increase in viscosity compared to the virgin binder can be attributed to the elevated content of asphaltene in TLA, which enhances the stiffness and durability of the binder but also poses significant challenges in terms of its workability during the mixing and paving process. Incorporating CRM into the binder also resulted in a substantial increase in its viscosity. CRM, derived from repurposed tires, enhances the elasticity and flexibility of asphalt, improving its resistance to deformation and cracking. Based on the results, the incorporation of 5% CRM into PG 64-22 caused a slight rise in viscosity, whereas the addition of 10% CRM led to a more significant increase. This increase is beneficial for enhancing resistance to rutting but should be approached with care to prevent excessive rigidity. The viscosity increased significantly when both TLA and CRM were combined with the original binder. The incorporation of 10% TLA and 5% CRM into PG 64-22, along with the inclusion of 20% TLA and 5% CRM, led to a collective rise in viscosity. These combinations attained the highest viscosity allowed at 135 \({}^{\circ}\)C and maintained manageable levels at 180 \({}^{\circ}\)C. However, combinations containing 10% CRM, especially PG 64-22 with 10% TLA and 10% CRM, as well as PG 64-22 with 20% TLA and 10% CRM, almost exceeded the viscosity limit at 135 \({}^{\circ}\)C. This indicates potential challenges in the processing and application of these mixtures. These findings highlight the importance of adjusting the quantities of additives to strike a compromise between improved performance characteristics and user-friendliness of the modified binders. The increased viscosity caused by TLA and CRM can enhance the binder's stiffness and capacity to endure deformation, crucial for applications exposed to significant stress. However, exceeding the recommended viscosity limits might pose difficulties in mixing, handling, and compressing the material, reducing the overall quality and  
Figure 2: Viscosity at 135 \({}^{\circ}\)C and 180 \({}^{\circ}\)C of the modified binders at original condition. durability of the pavement. Therefore, future investigations should focus on determining the optimal ratios of additives and potential modifications to maintain viscosity within acceptable limits while achieving desirable performance enhancements. Statistical analysis of viscosity at 135 \({}^{\circ}\)C and 180 \({}^{\circ}\)C, considering different combinations of PG 64-22 asphalt, TLA, and CRM, has yielded noteworthy results as seen in Table 4. At 135 \({}^{\circ}\)C, there are significant variations in viscosity between the base PG 64-22 asphalt and all combinations of PG 64-22 with TLA (10% and 20%) and CRM (5% and 10%), as well as their blends. These changes are statistically significant, demonstrating that both TLA and CRM have a considerable influence on the viscosity of the asphalt at this specific temperature, both separately and combined.