## 4 Results and Discussion
### G-R Index Results
The 4% animal bone ash shows the best balance between stiffness and flexibility, remaining in the no block cracking region at 25 \({}^{\circ}\)C, though it becomes prone to cracking at 15 \({}^{\circ}\)C under higher stress. The 5% animal bone ash offers more structural integrity but leads to more pronounced stiffness, especially at low temperatures, with a significant risk of cracking under stress. The 6% animal bone ash provides the most rigidity, increasing the risk of block cracking even at higher temperatures under high stress. Therefore, while animal bone ash is effective in enhancing stiffness, higher concentrations make the bitumen more susceptible to cracking, particularly in colder climates and under high-stress conditions. In the WCO 3% sample (Figure 4a), the bitumen shows significant susceptibility to block cracking, especially at lower temperatures (15 \({}^{\circ}\)C) and higher stress levels (G-R = 600 kPa). The plot shifts toward the block cracking region as the stress increases, indicating that the bitumen becomes stiffer and more prone to cracking. At higher temperatures (25 \({}^{\circ}\)C), the material remains largely within the no block cracking region, though under high stress, it starts moving toward the damage zone. This behavior suggests that while WCO 3% improves flexibility somewhat, the bitumen remains vulnerable to block cracking under extreme conditions, particularly at low temperatures and high stress. In the WCO 4% sample (Figure 4b), the performance improves slightly compared to WCO 3%. At 15 \({}^{\circ}\)C, the bitumen still shows some stiffness, but it stays closer to the no block cracking region than WCO 3%. The increased concentration of WCO allows for better flexibility, as indicated by the higher phase shift angle (8), but under high stress (G-R = 600 kPa), the material still begins to approach the block cracking region. At 25 \({}^{\circ}\)C, the bitumen exhibits better flexibility, remaining in the no block cracking region for a longer range, even under high stress. This indicates that WCO 4% offers a balance between flexibility and stiffness, making it more suitable for varying temperature conditions than WCO 3%. The WCO 5% sample (Figure 4c) demonstrates the best performance among the three concentrations. At 15 \({}^{\circ}\)C, the bitumen remains more flexible, as indicated by the higher phase shift angle, and avoids the block cracking region even under high stress. The plot stays closer to the no block cracking region compared to the other samples, showing that the higher concentration of WCO helps maintain elasticity at lower temperatures. At 25 \({}^{\circ}\)C, WCO 5% performs exceptionally well, remaining in the no block cracking region across the entire range of stress and temperature. The bitumen's increased flexibility with 5% WCO reduces the risk of entering the damage zone, making it the most resilient sample in terms of handling both temperature extremes and stress conditions. In summary, the progression from WCO 3% to WCO 5% illustrates a clear improvement in the bitumen's ability to resist block cracking. WCO 3% shows limited flexibility, especially at lower temperatures, and becomes prone to block cracking under high stress. WCO 4% offers better performance, providing a balance between stiffness and flexibility, but it still shows some vulnerability to cracking under extreme stress. WCO 5% delivers the best performance, with the bitumen maintaining flexibility and avoiding block cracking across both temperature settings and stress levels. This indicates that increasing the concentration of WCO enhances the bitumen's ability to deform without cracking, especially in high-stress or low-temperature environments, making WCO 5% the most effective concentration for improving bitumen performance  
To conclude, unmodified bitumen displays significant stiffness and a high propensity for block cracking, especially at lower temperatures and under elevated stress.