Laboratory investigation of modified asphalt containing buton rock asphalt or ash from buton rock asphalt

Buton rock asphalt (BRA)-modified asphalt has been extensively applied in the pavement because of its excellent aging resistance and high-temperature stability. The research on the overall behavior of BRA-modified asphalt has been relatively comprehensive. However, the main components in rock asphalt contain not only pure asphalt but also a large amount of ash. Their respective roles in asphalt modification still need to be clarified. This study analyzed rock asphalt's morphological changes and dissolution characteristics after heating. Then, the road performance of BRA ash-modified asphalt and BRA-modified asphalt was revealed. Finally, the contribution of pure asphalt and BRA ash to neat asphalt for elevated temperature properties was analyzed quantitatively. The microstructure of BRA and BRA ash was observed. Furthermore, the Fourier transform infrared spectroscopy (FTIR) results of pure asphalt, BRA and BRA-modified asphalt was analyzed. The test consequences demonstrate that the pure asphalt in BRA is not directly compatible with the neat asphalt. The appearance of BRA is soft honeycomb, and pure asphalt is tightly wrapped in mineral particles. BRA is mainly modified by physical miscibility, thus significantly improving the elevated temperature property of neat asphalt. But it will weaken the cryogenic property of neat asphalt. With the increase in BRA content, this effect is more pronounced. Both ash and pure asphalt play a vital role in modifying neat asphalt. With the temperature rise, the weight of ash in conversion gradually increases, and the weight of pure asphalt gradually declines. The weight of ash enhanced with the rise of BRA content, and the weight of pure aspahlt also increased gradually. The average contribution rate of ash to improve the rutting index is 45.57%, and the average contribution rate of neat asphalt to the rutting index advancement is 54.43%.