Chemical, rheological and aging characteristic properties of Xinjiang rock asphalt-modified bitumen

Abstract

Recently, rock asphalt has been widely used to modify bitumen binder; however, limited studies have been conducted to comprehensively evaluate the chemical, rheological and aging characteristics of bitumen modified with Xinjiang rock asphalt (XRA) from China. In this study, base bitumen (K64) was added with 0%, 8%, 12%, 16% and 20% XRA by mass respectively to prepare different modified binder, and rolling thin-film oven (RTFO) and pressure aging vessel (PAV) tests were performed to simulate short-term and long-term aging, respectively. The evolution of the chemical and rheological characteristics of the binders before and after aging were monitored with Fourier transform infrared (FTIR), rotational viscosity, dynamic shear oscillatory, frequency sweep, multiple stress creep recovery (MSCR) and bending beam rheometer (BBR) tests. Furthermore, several empirical indexes were tracked with softening point, ductility and penetration tests. The FTIR results indicated that with the introduction of the XRA modifier, the carbonyl functional group of the binders was reduced after aging, and the carbonyl index was more stable than the sulfoxide index to characterize the aging extent of the XRA-modified bitumen binders. Moreover, the rheological and empirical indexes suggested that the XRA could reduce excessive plastic deformations at high temperatures and broaden the final performance grade (PG) of the binder, while a high XRA addition ratio could compromise the low-temperature stress relaxation properties of the bitumen. Additionally, principal component analysis (PCA) suggested that ten parameters employed in this paper (such as stiffness, PG grade, percent recovery and etc.) have similarity and can be explained by two variables: PG grade and carbonyl index. Generally, based on the above evaluations and selection sort algorithm, 12% XRA was the optimum dose for modifying K64 to exhibit the best performance.