Effects of steel slag fillers on the rheological properties of asphalt mastic

The primary objective of this article was to investigate the feasibility of steel slag as fillers, particularly the fillers milled from raw steel slag with different particle size, also the steel slag fillers' effects on rheological properties of asphalt mastics. Four types of fillers were analyzed, including limestone filler (LF) and three steel slag fillers obtained by milling different raw Basic Oxygen Furnace (BOF) steel slags whose original particle sizes were 0-9.5 mm (ASSF, type A Steel Slag Filler), 9.5-13.2 mm (BSSF, type B Steel Slag Filler) and 13.2-26.5 mm (CSSF, type C Steel Slag Filler) separately. Surface characteristics, chemical compositions, phase distributions, thermal properties of fillers were first studied. By applying Bending Beam Rheometer (BBR) at lower temperature and Dynamic Shear Rheometer (DSR) at higher temperature, the rheological properties of asphalt mastics were also investigated. Results show that along with the increase of raw steel slag's particle size, the Fe content in steel slag filler presented a growing trend obviously. Besides that, compared with LF, steel slag fillers have different surface characteristics, chemical compositions, phase distributions and thermal properties. Furthermore, all steel slag fillers presented outstanding rheological properties, which indicated that they can be used as potential materials to replace LF. Moreover, ASSF corresponding mastic owned the best high-temperature rheological properties while BSSF corresponding mastic revealed the most balanced low-temperature rheological properties.