Green Castable Using Steelmaking Slags: A Sustainable Product for Refractory Applications

Continuous focus on capacity growth and increase in productivity by the manufacturing sector has led to the generation of a huge quantity of solid waste as by-product and depletion of the natural resources including refractories. The present study focuses on a sustainable approach to develop a low-cost castable intended for low-temperature applications by utilizing steelmaking slags as the raw materials. Firstly, the ladle slag generated after the secondary steelmaking process was used in the range of 50–70% as a complete source of CaO to develop a calcium-aluminate cement. The slag was used as a 100% replacement of limestone and partial replacement of Al2O3 source in the cement. Thus, it was possible to eliminate the CO2 emission associated with dissociation of limestone during the clinker making process. The castable was prepared using primary steelmaking slag as the aggregate and developed slag cement as the binder. CA and CA2 were formed as the primary phases in the slag cement, with Gehlenite, C12A7, and ‘Q’ phases as the secondary phases. Slag cement with 60% slag content exhibited superior strength as compared to commercial calcium-aluminate cement of medium purity. Further, the 110 °C and 1000 °C crushing strengths were found to be better for slag cement-added castable than the commercial cement-added one. Thus, it was possible to develop a green castable by using by-products of the steelmaking process that would not only help in reducing the carbon footprint, but also reduce the manufacturing cost and address the environmental concerns.