The objective of this study was to investigate the feasibility of using buton natural rock asphalt (BNRA) as a bitumen modifier, to formulate the mix between BNRA and bitumen as a new binder with better physical and mechanical properties, and to evaluate the use of BNRA-modified bitumen (BNRA-MB) as a binder of hot mix asphalt (HMA). In this bitumen penetration grade 60/70 were modified by using BNRA. The bitumen was mixed with 5%, 10%, 15%, 20%, and 25% BNRA by weight of the bitumen at mixing temperature 160°C, mixing time 60 minutes, and mixing stirring speed 800 revolution per minute. BNRA had uniform particle size 75µm. The bitumen mixed with BNRA was called BNRA-modified bitumen (BNRA-MB). To BNRA-MB penetration test at 25°C, softening point test, and specific gravity test were conducted to determine penetration index (PI). In this study, obtained a value of PI is 5%-10% is 0.8-1.1, 15%-20% is 0.6-1.2, and 25% is + 0.9. The results show that all BNRA-MB were susceptible to the changes of temperature, but BNRA-MB with 25% of BNRA content have better PI value that is+ 0.9. Using in stone mastic asphalt (SMA) mixtures resulted in higher Marshall stability, and have higher stiffness compare to the minimum specification requirements. Based on penetration value and the results of Marshall stability BNRA-MB is feasible to be used as modifier of the bitumen, and as a binder for hot-mix asphalt mixtures.

Keyword : Asphalt, Buton, Penetration Index