# Phase Separation Study on the Storage of Technically Specification Natural Rubber Modified Bitumen
## 4 Conclusions  
Technical specifications for natural rubber (TSNR) as a polymer material for modifying asphalt show satisfactory performance in improving the performance of pen 60/70 asphalt. The most obvious performance improvements are thermal stability, hardness, adhesion, and cohesion. Modified asphalt has lower penetration and a higher soft point than pen 60/70. However, the TSNR-modified asphalt stability evaluation concluded the following:  
1. Modified asphalt with TSNR 8, 10, and 12% without sulfur or with sulfur shows phase separation after storage stability tests at temperatures of 130 \({}^{\circ}\)C and 160 \({}^{\circ}\)C for 48 h, with a more significant difference in soft point than the required 2.2\({}^{\circ}\)C.
2. Adding sulfur additives to the TSNR-modified asphalt mixture does not much help increase its storage stability. However, it increases the softening point of the modified asphalt at the top and bottom. 3. TSNR-modified asphalt with the best storage stability was obtained by adding 10% TSNR without sulfur with the difference in softening point after the storage stability test reaching 11.6 \({}^{\circ}\)C after 48 h of storage and continuing to increase until it reached 13.9 \({}^{\circ}\)C after 72 h of storage. 4. The combination of the fluid flow model with the incompressible Navier-Stokes and phase field equations accurately describes the phase separation in TSNR-modified asphalt, with simulation results showing that asphalt modified with 8, 10, and 12% TSNR is stored optimally at a temperature of 160 \({}^{\circ}\)C for 12 h without stirring. 5. Simulations using the fluid flow model with the incompressible Navier-Stokes and phase field equations show that the phase separation of TSNR-modified asphalt can last up to 96 h.  
Conceptualization, B.I. and A.W. ; methodology, B.I. and A.W. ; software, A.W. and Y.M. ; validation, B.I., A.W., and I.Z. ; formal analysis, N.N. and L.S. ; investigation, A.W. and L.S. ; resources, B.I. ; data curation, L.S. ; writing--original draft preparation, B.I. and A.W. ; writing--review and editing, I.Z. and L.S. ; visualization, Y.M. ; supervision, B.I. ; project administration, B.I. ; funding acquisition, B.I. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Research and Innovation Agency (BRIN) and the Indonesia Endowment Fund for Education Agency (LPDP). Not applicable. The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author. The authors thank the National Research and Innovation Agency (BRIN) and the Indonesia Endowment Fund for Education Agency (LPDP) for funding this research. The authors declare no conflicts of interest. References  
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