Evaluation of microstructural features of Buton rock asphalt components and rheological properties of pure natural asphalt modified asphalt

Abstract

Buton rock asphalt (BRA) is a natural asphalt composed of pure natural asphalt (PNA) and BRA minerals. This study observed the microstructures of BRA components by atomic force microscopy (AFM) and scanning electron microscopy (SEM) and evaluated the rheological properties of PNA-modified asphalt using dynamic shear rheological (DSR) tests, bending beam rheological (BBR) tests, and Brookfield rotary viscosity tests. The road performances of BRA-modified mixtures were also measured to characterize the influence of the BRA additive on the asphalt mixtures. Bee phase structures were not observed in the AFM image of the PNA microstructure. SEM images showed that the surface topography of BRA minerals was fluffy and rough, while that of limestone mineral powder was dense and smooth. The DSR and BBR tests gave the asphalt modified with 10%–15% PNA a performance grade of 64–22. Given the low-temperature performance, the blending ratio of PNA in the base asphalt should not be more than 15%. The shear strength, ratio of freeze-thaw splitting strengths, and fatigue life of the BRA mixture were higher than those of the base asphalt and styrene–butadiene–styrene control mixtures. Overall, the performance of BRA-modified asphalt mixture was significantly improved from that of the base asphalt.