Feasibility of high titanium heavy slag used as aggregates for asphalt mixtures

High titanium heavy slag (HTHS) is a typical solid waste produced in the iron production process of vanadium titanomagnetite. The feasibility of using the HTHS as coarse aggregates in the two gradations of AC-13 and AC-20 asphalt mixtures mixed with base asphalt and SBS modified asphalt binders was discussed in this paper. Firstly, the physical and chemical properties of HTHS were tested. Then, asphalt mixtures with limestone coarse aggregate were replaced by HTHS at five rates of 0% (control), 25%, 50%, 75% and 100% were designed and made by Marshall method. Twenty types of asphalt mixtures was discussed by their different volume properties, and the volume properties of asphalt mixtures under the optimal asphalt content (OAC) were further verified. Finally, selected properties of asphalt mixtures under the optimum asphalt content were tested. Results showed that 1) HTHS had low activity and good stability, the mechanical properties met the requirements of coarse aggregates for asphalt mixtures; 2) With the increased replacing rate of HTHS, the OAC and asphalt absorbed by aggregate (Pba) of 20 asphalt mixtures increased simply due to the porous structure of HTHS; 3) The rough, hard surface of HTHS improved the mechanical anchoring force between aggregates and increased the Marshall stability and rutting resistance of asphalt mixtures. However, with the increased replacing rate of HTHS, the Marshall residual stability, freeze-thaw splitting strength ratio and maximum tensile strain at low temperature decreased.