Mechanically Activated Iron Tailings as Filler for Asphalt Mastic: High-Temperature Performance and Fatigue Resistance

Iron tailings stockpiling occupies land and poses potential environmental risks. This study compared mastics containing untreated and mechanically activated iron tailings from the same source with limestone mastic at a filler-to-binder mass ratio of 1.0. Particle characterization was combined with rheological testing, linear amplitude sweep testing with viscoelastic continuum damage analysis, and leaching measurements. Grinding for 1.5 h reduced the median particle size from 61.00 to 16.95 μm, a decrease of 72.2%. The activated tailings mastic showed the highest complex modulus and rutting factor. Its non-recoverable creep compliance values were 1.52 and 2.08 kPa−1 at 0.1 and 3.2 kPa, respectively, representing reductions of 34.8% and 27.0% relative to limestone mastic. Predicted fatigue lives were slightly higher than those for untreated tailings and close to those for limestone at the selected strains. No clear evidence of new bond formation was observed, suggesting that the performance improvements were mainly attributable to physical interactions. Measured leachate concentrations were below the reported comparison limits. This same-source comparison links grinding-related particle refinement with mastic performance and provides preliminary leaching evidence to inform the evaluation of iron tailings as an alternative filler.