The potential use of steel slag in refractory concrete

Steel slags are by-products in the steel production industry and can be used for different purposes; e.g. as aggregates in concrete or asphalt, and for blended cements. In the present study the possible use of electric arc furnace slag from carbon steel production in refractory concrete was studied. It was found that slag undergoes a mineralogical transformation of wustite into magnetite when it is heated to temperatures higher than 800 °C, this transformation being accompanied by volumetric expansion, which introduces cracks in the the refractory concrete and drastically worsens its mechanical properties. This transformation is irreversible, so that when slag is heated up to a temperature of 1000 °C prior to its use for refractory concrete, the final products exhibit mechanical properties which are comparable to concrete with conventional refractory aggregate, e.g. bauxite.

Research highlights
► EAF steel slag from carbon steel production is thermally unstable.
► Upon heating above 800 °C wustite decomposes into magnetite.
► Transformation is irreversible.
► If slag is heated up to a temperature of 1000 °C, slag becomes thermally stable.