Valorization of the steel industry slag and by-products as raw material asset for innovative refractories

The European steel industry generated in 2012 about 21.4 million tons of slag of which about 24% was landfilled. Landfilling of the huge amount of materials poses a severe environmental problem in Europe. Utilization of... [ view full abstract ]

The European steel industry generated in 2012 about 21.4 million tons of slag of which about 24% was landfilled. Landfilling of the huge amount of materials poses a severe environmental problem in Europe. Utilization of currently landfilled waste is a target of growing interest towards circular economy and closing the loop. Insulating refractory materials are needed in all thermal energy intensive industries for example in the construction of the furnaces, kilns, incinerators, or reactors. The relevant properties of certain slags and industrial by-products to withstand high temperatures make them possible raw material candidates when manufacturing novel refractory materials. In the presented study, exploitation potentiality of ferrochrome slag and other by-product as raw material asset for refractory materials has been studied. The goal was to maximize the use of secondary raw materials in refractory materials with mechanical and chemical resistance up to 1200°C in gaseous atmosphere. Recipes were formulated based on raw material characterization results and theoretical calculations including optimal particle packing calculations. Mortar pieces were prepared according to standard EN 196-1. Mechanical properties of the refractory specimens were evaluated based on their cold crushing strength. In addition, specimens were characterized in terms of physical and thermo-physical properties: density, porosity, thermal conductivity, thermal diffusivity and heat capacity and compared to commercially available refractory material. The cold compressive strengths reaching the values of 70-90 MPa were observed for the mortars heat-treated at 1200°C being comparable level to commercial reference. Thermal conductivity values of the mortars were at the level of 1.8-2.2 W/K∙m, which indicates good heat insulating capability showing values even below that of reference material.