Characterisation of steel industry slag suitability as raw material for refractory castables

Refractories are inorganic non-metallic materials which are used at high temperatures usually exceeding 1000°C and they should remain chemically and physically stable at high temperatures. Castable refractory materials are needed in all thermal energy intensive industries for example in the construction of the furnaces, kilns, incinerators or reactors. Utilisation of industrial by-products together with innovative processing routes are seen to be key aspects for more sustainable refractories development. Production of high carbon ferrochrome (HCFeCr) produces by-product, ferrochrome (FeCr) slag1. The FeCr slag utilisation has been reported for example in road construction2, brick manufacturing3 and in cement industry4 as a base layer material in road pavements. In the recent studies by Kumar et al. 5,6 the utilisation of FeCr slag as raw material for low cement refractory castables were reported. In study5 refractory castables were prepared using FeCr slag, calcined bauxite, high alumina cement and microsilica as raw materials and in study6 using FeCr slag, calcined bauxite, superfine calcined alumina and high alumina cement as a hydraulic binder. Particle size distribution, phase structure and phase characteristics of the castable mixture are one of the most important factors controlling the properties of the refractory castables. In the current work, the FeCr slag suitability as raw material for refractory castables was studied. FeCr slag sample was analysed by particle size analysis, microstructure and composition studies (SEM+EDS), X-ray-diffraction (XRD) analysis and thermal analysis (TGA/DSC) to find out characteristic properties. Experimental characterisation results were compared to thermodynamic FactSage software simulations of equilibrium phase structures and phase fractions. Presented study is a first part of the research work which eventually aims to the industrial pilot scale demonstration of processing route for refractory castables based on maximal utilisation of secondary raw materials.