# Phase Separation Study on the Storage of Technically Specification Natural Rubber Modified Bitumen
## 3 Results and Discussion
### Phase Separation Simulation of TSNR-Modified Asphalt
At 48 h of storage (t = 48), the asphalt component fraction increased in the middle and bottom, with asphalt volume fractions ranging from 0.65-0.75%, while the asphalt volume fraction at the top ranged from 0.1-0.3%, indicating that the TSNR volume fraction dominated the top. Up to 72 h of storage (t = 72 h), the final fraction of asphalt components ranged from 0.7-0.9 at the bottom and 0.05-0.2 at the top. However, from the visual in Figure 12, the samples at 48 h and 72 h storage time did not show any significant difference other than the color domain at the top, which was more dominant to blue. Therefore, another data analysis is needed to measure the changes after 48 h.  
Furthermore, the phase separation due to cavitation can be analyzed by measuring the changes in density and viscosity at the top and bottom, as shown in Figures 13 and 14. Figure 13 provides the average density data from various points at the top and bottom of the domain section. The density and viscosity at the top decreased, and the other side increased with the storage time. Figure 13 shows the modified asphalt samples with 8% and 10% TSNR, showing the density difference formed after 12 h of storage. Density changes do not occur spontaneously because the TSNR component requires time for the formation of coalescence and flocculation phenomena until a sufficient density difference is reached for phase separation to occur, which is influenced by gravity, time, and temperature changes. On the other hand, observations on modified asphalt with 12% TSNR revealed that the density difference began to appear at 19 h. This also confirms that phase separation  
Figure 14: TSNR-modified asphalt viscosity simulation results for the top and bottom sections. Figure 13: TSNR-modified asphalt density simulation results for the top and bottom sections. occurs slowly in asphalt modified with 12% TSNR. The density difference formed more slowly than the 8 and 10% TSNR. Many factors influence slow phase separation, including increased TSNR content. Higher TSNR content absorbs asphalt phases like saturates and aromatics. This causes an increase in the viscosity of the asphalt phase, which slows down the rate of separation between components. The simulation results in Figure 13 show that the modified asphalt with 8% TSNR has a greater density difference than the 10 and 12% TSNR. After 12 h of storage, the asphalt modified with 8% TSNR showed a significant decrease in density at the top between 12 and 50 h. The same thing happened to modified asphalt with 10 and 12% TSNR after 24 to 96 h of storage. However, the decrease in density was less than the 8% TSNR content. At the same time, the bottom of all modified asphalt experiences a negligible decrease in density and tends to remain stable. The phase separation rate determines how quickly or slowly the density difference occurs. Based on this analysis, the level of TSNR added to the asphalt influences whether the coalescence and flocculation phenomena are formed sooner or later. It is known that coalescence and flocculation phenomena in modified asphalt are the initial stages that destabilize TSNR and asphalt components [41; 42; 43]. Eventually, the phase compatibility between the components collapses due to the formation of density and viscosity differences. Furthermore, gravity encourages the formation of two-phase flows that move vertically to form the TSNR-rich phase side and the asphalt-rich phase side [6; 53]. Another factor determining how fast or slow gravity affects the movement of phase separation ultimately depends on the viscosity of the modified asphalt mixture. As previously stated, adding TSNR to the modified asphalt increases its viscosity in order to improve mix compatibility. However, the coalescence and flocculation phenomena that occur with storage time influence the viscosity changes at the top and bottom. Figure 14 shows that the viscosity of modified bitumen remained constant during the first 12 h of storage, just as Figure 13 shows that the density did not change.