## 3 Results and Discussion  
### Physical Properties  
Figure 2 and Table 4 demonstrate how different amounts of TLA and SIS affect the viscosity of PG64-22 asphalt binder at two important temperatures, 135 \({}^{\circ}\)C and 180 \({}^{\circ}\)C. Viscosity plays a crucial role in evaluating the ease of use and effectiveness of asphalt binders, especially in the presence of elevated temperatures during pavement construction and usage. The red arrow on the graph represents a viscosity limit of 3000 cP. This limit is crucial for maintaining the workability of the binder while also providing enough stiffness to resist deformation.  
The PG64-22 binder has a viscosity of 755 cP at 135 \({}^{\circ}\)C and 285 cP at 180 \({}^{\circ}\)C, which falls within the acceptable range for workability and handling. Upon the addition of TLA to the binder, a discernible increase in viscosity is noted. More precisely, the introduction of 10% TLA increases the viscosity to 855 cP at a temperature of 135 \({}^{\circ}\)C and 305 cP at a temperature of 180 \({}^{\circ}\)C. On the other hand, when 20% TLA is added, the viscosities become 866 cP and 311 cP at the same respective temperatures. The observed increases indicate that the addition of TLA causes a slight increase in the rigidity of the binder, enhancing its ability to resist deformation while not significantly affecting its ease of use.  
However, the addition of SIS to the TLA-modified binders results in a more noticeable increase in viscosity, emphasizing its important role in improving binder stiffness and performance. As an example, when 10% TLA and 5% SIS are combined, the resulting viscosity is 1775 cP at 135 \({}^{\circ}\)C and 575 cP at 180 \({}^{\circ}\)C. The significant increase in value indicates that the addition of SIS improves the elasticity of the binder, thereby increasing its ability to withstand permanent deformation. This characteristic is particularly important for achieving optimal performance at high temperatures.  
As the levels of TLA and SIS increase, the viscosity consistently increases. Specifically, when the mixture contains 20% TLA and 5% SIS, the viscosity is 2212.5 cP at 135 \({}^{\circ}\)C and 787.5 cP at 180 \({}^{\circ}\)C. As long as these values stay below the 300 cP limit, it shows that the binder can still be worked with. However, the increased stiffness indicates better ability to withstand rutting and deformation, which is crucial for ensuring that the pavement remains durable over time, especially when subjected to heavy traffic loads.  
However, when the content of SIS is increased to 10%, the viscosity that is obtained exceeds the threshold of 3000 cP, especially at a temperature of 135 \({}^{\circ}\)C. At this temperature, viscosities of 3812.5 cP (with 10% TLA) and 4975 cP (with 20% TLA) are observed. Although high viscosities suggest excellent resistance to deformation at high temperatures, they can also present difficulties in handling and applying the binder, as it may become excessively rigid for efficient mixing and compaction.  
To summarize, the use of SIS is essential for enhancing the performance of TLA-modified PG64-22 binders, specifically by improving stiffness and elasticity. These properties are crucial for withstanding deformation under high temperatures. Nevertheless, it is crucial to carefully balance the trade-off between enhanced performance and reduced workability. To achieve the desired pavement performance while maintaining workability during construction, it is important to determine the optimal concentrations of SIS and TLA. Having a proper balance is crucial in order to fully optimize the advantages of SIS in improving the durability and ability to withstand stress of pavements.  
Figure 2: Viscosity at 135 \({}^{\circ}\)C and 180 \({}^{\circ}\)C of the modified binders in original condition.