Utilization of magnetite tailings as aggregates in asphalt mixtures

Magnetite tailings (MTs) are waste generated from magnetite processing, which not only occupy lots of land, but also result in severe pollution to the surroundings. In this paper, the MTs were used as a substitution of limestone (LMs) aggregate in asphalt mixtures. Water boiling and residual Marshall stability tests were conducted to study asphalt-aggregate interface adhesion, which was improved by hydrated lime (HL). The effects of MTs on high temperature property, low temperature property and water stability property of asphalt mixtures were evaluated respectively through some indexes, such as dynamic stability, splitting strength at low temperature and freeze-thaw splitting strength ratio. In addition, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Infrared spectrometer (IR) and Zeta potential were also adopted to analyze the mechanism. The results show that there are not heavy metal elements and toxic pollution threats in MTs. The HL can improve the asphalt-aggregate interface adhesion and the water stability of the asphalt mixtures with MTs. MTs can improve the high temperature property and slightly decrease splitting strength at low temperature of asphalt mixtures. Freezing-thawing splitting strength ratio increases with the increase of MTs, which is greatly higher 80% requirement in the Chinese specification. Therefore, the asphalt mixtures containing MTs present excellent properties and MTs can be widely used as substitution of natural aggregates in asphalt mixtures for pavement engineering.