Research on thermal conduction of steel slag-modified asphalt mixtures considering aggregate properties

Using an appropriate amount of steel slag as a replacement aggregate can moderately enhance the thermal conductivity of asphalt mixtures. Moreover, accurately understanding how the thermal conductivity of steel slag modified asphalt mixture (S-SMA) affects pavement temperature distribution is crucial for evaluating its snowmelting and deicing performance and advancing green highway construction. This study systematically evaluated the thermal conduction behavior of S-SMA using Scanning electron microscope (SEM), X-ray diffraction (XRD), contact-based heating experiments, microwave irradiation experiments, and discrete element modeling (DEM) incorporating realistic aggregate morphologies. Results showed that, compared with conventional SMA, S-SMA exhibited a 30.0% higher average surface temperature and a maximum temperature increase of 18.7℃ under microwave heating. Contact-based heating revealed that the proportion of high-temperature zones in S-SMA reached 73.1%, compared with only 11.8% in SMA. DEM simulations confirmed that increasing the thermal conductivity coefficient of steel slag from 0.19 to 19 W/(m·K) accelerated uniform temperature formation, with complete homogenization achieved within 1000 s. Moreover, the vertical temperature distribution exhibits a nonlinear decay pattern. As the thermal conductivity of steel slag increases, both the heat transfer rate within the mixture and temperature uniformity are significantly enhanced. These findings demonstrate that incorporating steel slag significantly enhances the heat transfer efficiency of asphalt mixtures but introduces stronger vertical gradients and localized hotspots, offering both performance benefits and challenges for functional pavement design. • Steel slag significantly improves the thermal conduction efficiency of asphalt mixtures, resulting in faster heating rates and higher surface temperatures. • A 3D blue-light scanning system was applied to capture realistic aggregate morphology, enhancing the accuracy of DEM-based thermal conduction simulations. • The steel slag-modified asphalt mixtures show a nonlinear decrease in temperature with increasing height, revealing strong vertical temperature gradients during heating. • Steel slag increases microwave heating efficiency and maximum temperature, but leads to more uneven internal temperature distribution due to localized hot spots.