Leaching Characteristics of Heavy Metals from Asphalt Mixture with Basic Oxygen Furnace Slag as Aggregate

Basic oxygen furnace (BOF) slag, which has good mechanical properties, can be recycled as pavement materials. However, BOF slag contains several kinds of heavy metals. Batch leaching tests are usually conducted to investigate the leaching characteristics of asphalt mixture with BOF slag, which has a few limitations. In this article, the leaching characteristics of heavy metals were investigated through the column leaching test device self-designed in the laboratory. The factors that influence the leaching of heavy metals were evaluated. The experimental results indicate that high-basicity BOF slag that has high content of free calcium oxide (f-CaO) can effectively inhibit the leaching of heavy metals from asphalt mixture. Copper and nickel have no leaching risk in neutral and weakly acidic conditions. However, zinc and lead in asphalt mixture with medium-basicity BOF slag have a risk of causing environmental implication in long-term leaching process. Moreover, covering of asphalt inhibits the leaching of f-CaO and hinders the contact between heavy metals and the leachant at the same time. The conclusions of this article provide a theoretical basis for the green application of BOF slag as an asphalt pavement material.