Investigation of Salt-Releasing Behaviors of Salt-Storing Lignin Fiber and the Performance of Asphalt Mixture

This study investigated a self-developed salt-storing lignin fiber as an anti-icing additive for asphalt pavements. The sustained- salt-release capability and road performance of this material were systematically evaluated. Salt-release kinetics were quantified through conductivity measurements, while morphological changes and salt distribution within the asphalt mortar following freeze–thaw cycles were characterized using scanning electron microscopy with energy-dispersive X-ray spectroscopy. Performance assessments included rutting tests to evaluate high-temperature stability and semicircular bend tests to determine cracking resistance at low and intermediate temperatures, as well as postmoisture damage. Key findings revealed that incorporating a hydrophobic agent enabled the salt-storing fiber to achieve sustained salt release. Freeze–thaw cycling significantly altered the mortar surface morphology, inducing pits, pores, and salt aggregation. Correspondingly, single-cycle conductivity gradually decreased with increasing freeze–thaw cycles. However, by the sixth cycle, the mixture containing 100% salt-storing fiber exhibited an 88.9% higher cumulative conductivity, and the mixture with 100% commercial product (SG) showed a 94.1% higher cumulative conductivity, compared to the mixture with 50% replacement. Increased incorporation of anti-icing material reduced high-temperature performance; dynamic stability declined from 13,676 cycles/mm (0% replacement) to 9,773 cycles/mm (100% salt-storing fiber) and 8,690 cycles/mm (100% commercial product). Low- and intermediate-temperature cracking resistance exhibited nonlinear variation with higher replacement ratios. Following moisture damage, fracture toughness at low temperatures decreased notably with greater anti-icing material content, while fracture energy increased marginally.