Laboratory evaluation of warm mix asphalt Mixtures containing electric arc furnace steel slag

Conservation of natural resources, optimization of energy use, and minimization of environmental pollution are among the core goals of sustainable development that should be duly considered in the development of national infrastructures, including roads and highways. In the case of asphalt mixtures, these goals can be achieved by the reduction of mixing temperature and the use of recycled materials instead of natural aggregates. This study investigated the mechanical properties of asphalt mixtures containing Electric Arc Furnace Slags(EAFS), which were used as partial replacement for coarse aggregates, and also Sasobit, which was used as an additive for Warm Mix Asphalt (WMA) mixtures. This replacement was performed in, 0, 25, 50, and 75% of natural Coarse limestone (>4.75 mm). In WMA specimens, Sasobit was also added at a concentration of 3% by weight of bitumen. After investigating the properties of aggregates and slags, the Marshall method was used to determine the optimum bitumen content of 8 asphalt mixtures (4 HMA+ 4 WMA) with different slag contents. The results of the Marshall Mix Design method showed that because of the high porosity of slags, slag-containing mixtures have a higher optimum bitumen content. Overall, 120 specimens with optimum bitumen content were prepared with a Superpave Gyratory Compactor (SGC). To assess mechanical properties, these specimens were subjected to Indirect Tensile Strength (ITS) test, resilient modulus test at 25°C and 40°C, and dynamic creep test at 40°C and 55°C. The results of these tests showed an improvement in the mechanical properties of the mixtures containing Sasobit and EAF slags. This improvement can be attributed to the increased stiffness resulting from the use of Sasobit, better interlocking of slags, and better adhesion of slags to bitumen.