Evaluation the deleterious potential and heating characteristics of basic oxygen furnace slag based on laboratory and in-place investigation during large-scale reutilization

In order to address severe climate change, land occupation and excessive consumption of resources, China as a giant developing country is relentlessly promoting the utilization of basic oxygen furnace slag byproduct. The concerns referred to its large scale reutilization include deleterious potential, and possible problems in aggregate heating. Regarding the concerns, we elaborated a series of tests including toxicity characteristic leaching procedure and differential scanning calorimeter as complements of established researches in literature. The leaching results are consistent with peers' studies that the leachate of slag meets the requirements of laws and regulations in many countries. However toxic metal was detected from in-field waste water in slag aggregate making processor. It indicates the bulk slag in soils should be treated much carefully as it could be a giant pollution to shadow or ground water. The Differential Scanning Calorimeter results show that the enthalpy changes of slag samples from ambient temperature to 200 °C are comparable or less than that of dolerite. Water evaporation and decomposition of gypsum and carbonates contribute to the changes in heat flow. It grants the reliability that slag is a physical stable material in drying drum of asphalt mixture plant. Heating rate tests show that the slag samples with various water contents that are kept in hot oven show negligible discrepancy in the rate of temperature increase in comparison to dolerite. Based on the laboratory test results, an 8-km highway surface layer with basic oxygen furnace slag has been constructed and presents good performance. All the work completed in laboratory and in-place construction indicates that basic oxygen furnace slag is an environment-friendly aggregate if it is well treated. What's more, the bulk slag with less than 3% water content can be used in routine production. The slag based asphalt mixture is able to hold a warmer temperature, and hence granting a longer haul distance than when using dolerite.