Characteristics of steel slag filler and its influence on rheological properties of asphalt mortar

Abstract This paper discusses the feasibility of reusing steel slag as mineral filler in an asphalt mixture. Steel slag aggregate was first crushed and ground into filler with particles smaller than 0.075 mm in size. Then, both the physical and the chemical properties of the steel slag aggregate were characterized. Steel slag filler (SSF) and limestone filler (LF) were characterized by scanning electron microscopy, the aggregate image measurement system, X-ray fluorescence, and X-ray diffraction. The surface characteristics, morphological information, chemical compositions, and crystal structures of the fillers were discussed. Finally, the effect of SSF on the rheological properties of asphalt mortar was investigated via dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. The test results showed that the addition of SSF as mineral filler to asphalt binder enhanced the deformation resistance of the binder but decreased its low-temperature cracking resistance slightly. A slight drop in the creep stiffness occurred when LF was partially replaced with SSF. The results of both the DSR and the BBR tests demonstrated that the use of a combination of SSF and LF as filler could be an effective approach for reusing steel slag as filler in an asphalt mixture. An SSF content lower than 75% by volume is optimal for the combined filler.