Study on the Performance of Asphalt Mixtures Incorporating Phase Change Materials and Sustained Release Deicing Salts

To improve the winter snow-melting and temperature-regulating performance of asphalt mixtures, a low-temperature phase change material (LPCM) was prepared by melt blending polyethylene glycol 400 (PEG400) with expanded graphite at a mass ratio of 9:1. The prepared LPCM and sustained-release deicing salt were incorporated into SMA-13 asphalt mixtures. Five mixtures were designed, including a control mixture, an LPCM-modified mixture, a salt-modified mixture, and two mixtures containing both additives at different dosages. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the materials. The combined effects were evaluated through laboratory ice-melting tests, temperature–time measurements, natural snowfall observations, and pavement performance tests. The results showed that the melting and crystallization enthalpies of LPCM were 91.1 and 88.1J/g, respectively. Physical adsorption and mixing were the dominant mechanisms during the preparation and modification processes. Compared with the control mixture, the mixtures containing LPCM reached 0℃ for the first time 6–24min later. The minimum temperature of the high-salt composite mixture increased by 1.7℃, while its average cooling rate decreased by 9.1%. The delayed cooling helps maintain a liquid phase and favorable wetting conditions at the ice–pavement interface. These conditions facilitate the continuous dissolution and migration of chloride salts from the carrier, allowing thermal regulation and freezing-point depression to act in a complementary manner. The high-salt composite mixture achieved a relative ice-melting capacity of 0.34 g/cm² after 3h, representing a 21.4% increase over the mixture containing the same salt dosage alone. During the first 6 h of outdoor observation, its average snow-melting rate, calculated from changes in snow layer thickness, reached 0.079 mm/min. This was 26.7% higher than that of the control mixture, indicating improved ice-melting and snow-removal performance. The low-salt composite mixture exhibited a dynamic stability of 4755times/mm and a flexural tensile strain of 3571με. Its residual Marshall stability and tensile strength ratio (TSR) were 93.0% and 90.2%, respectively. Increasing the salt dosage further enhanced ice-melting and snow-removal performance but reduced rutting resistance and moisture stability. The combined incorporation of LPCM and sustained-release deicing salt provides both cooling mitigation and ice–pavement interface regulation. The low-salt composite mixture achieves a favorable balance between winter functional performance and pavement performance.