Road Performance, Thermal Conductivity, and Temperature Distribution of Steel Slag Rubber Asphalt Surface Layer

The use of steel slag, which is a by-product of the steel manufacture, in the construction of asphalt pavement would contribute to waste reduction and environment protection. Using rubber asphalt at the same time can improve the performance of asphalt mixture. This study investigates the influence of steel slag content on the road performance, thermal conductivity and outdoor temperature distribution of steel slag rubber asphalt mixtures (SSRAM), and calculates the cumulative stress in surface layer. At a certain range of concentration, the steel slag additive improved the deformation resistance and low-temperature cracking resistance of the mixtures. The SSRAM with 40% steel slag content has the best deformation resistance while SSRAM with 60% steel slag content performed well in low-temperature cracking resistance. The thermal conductivity of the SSRAM with different steel slag content (0%, 20%, 40%, 60%, 80%, and 100%) was 1.994, 2.188, 2.239, 2.255, 2.288, and 2.295 W/(m·K), respectively. Measurements of the outdoor temperature distribution further confirmed that steel slag increased the thermal conductivity of the mixtures, thereby increasing the cumulative temperature difference between the top and bottom layers. The temperature stress and temperature-stress ratio of the SSRAM with 40% steel slag were 0.43 MPa and 0.24, while the SSRAM with 100% steel slag were 0.58 MPa and 0.36. The stress and stress ratio were much higher in the SSRAM with 100% steel slag than in the specimen with 40% steel slag. Accordingly, the maximum accumulated temperature stress aggrandized and caused early temperature cracks in the surface layer. The optimum content of steel slag was 40%.