# Phase Separation Study on the Storage of Technically Specification Natural Rubber Modified Bitumen
## 3 Results and Discussion
In addition, the higher penetration at either the top or bottom of the modified asphalt can be indicated as the accumulation of TSNR-rich phase in one part of the modified asphalt mixture, which is an indication of phase separation between components [4; 9; 13]. Penetration indicates the softness and consistency of the asphalt and the ability to resist shear force failure. Penetration is also used to test temperature sensitivity, asphalt diffusion, and rheology. Based on the evaluation, the penetration of the modified asphalt increased as the TSNR content increased, with the difference between the top and bottom penetration values smaller than 1 mm. The small difference in penetration between the top and bottom shows that the TSNR-modified asphalt made does not indicate phase separation before the storage stability test, so all samples are declared feasible to proceed to the next stage, namely, the storage stability test. Softening Point of Technically Specified Natural Rubber (TSNR)-Modified Asphalt before Storage Stability Test  
Figure 3 shows how modifying asphalt with TSNR-type natural rubber increases the softening point and TSNR content. The increase in softening point ranges between 25 and 45%, with the highest softening point of 72.2 \({}^{\circ}\)C at 12% TSNR. The increase in softening  
Figure 2: Illustration of TSNR swelling. point correlates with the decrease in asphalt penetration, which is influenced by the ratio of asphaltene to maltene [4]. The ratio of asphaltene and maltene is linearly influenced by the diffusion of maltene fraction into TSNR. The diffused maltene fraction in TSNR results in volume expansion (swelling) of TSNR [40; 44]. Swelling of TSNR by the maltene fraction increases the asphaltene ratio and makes the asphalt harder [41]. The increase in asphalt hardness indicates that the asphalt mixture's average weight and molecular density also increase [29; 49]. Finally, the phenomena that occur increase the cohesion and adhesion properties of asphalt after modification in preventing rutting and susceptibility to temperature variations [50]. Using natural rubber as an asphalt mixture can increase resistance, flexural modulus, and service life. The difference between the lower and upper softening points (T\({}_{\text{Bottom}}\)-T\({}_{\text{Top}}\)) of TSNR-modified asphalt mixtures can be used to evaluate storage stability by ASTM D7173. TSNR-modified asphalt can have good storage stability if the TSNR phase does not experience degradation or segregation in the production, storage, or application process [29]. Storage stability is influenced by the compatibility between the constituent components, namely, asphalt and TSNR [39; 41]. The better the compatibility of the two components, the smaller the segregation that occurs, characterized by the difference in the softening point between the top and bottom, which is less than 2.2 \({}^{\circ}\). Figure 3 also illustrates the difference in softening point between T\({}_{\text{Bottom}}\) and T\({}_{\text{Top}}\) of modified asphalt before the storage stability test. The difference in softening point (T\({}_{\text{Bottom}}\)-T\({}_{\text{Top}}\)) increased as the asphalt's TSNR content increased. The greatest difference in softening point was 1.8 \({}^{\circ}\)C at 12% TSNR. The difference in softening point obtained by adding 8-12% TSNR was less than the ASTM 5976 specification of 2.2 \({}^{\circ}\)C. As a result, all samples were identified as stable TSNR-modified asphalt mixtures.