Partial replacement of a traditional raw material by blast furnace slag in developing a sustainable conventional refractory castable of improved physical-mechanical properties

Abstract

Abstract The exponential growth of industrial waste is a problem that has forced the development of clean technologies for their appropriate management. About 0.25 to 0.30 tons of slag is generated per ton of crude steel or pig iron in blast furnaces. In this research, blast furnace slag was recycled to progressively replace the fine fraction of flint clay at 0, 5, 10, 15, and 20 wt.% in laboratory-scale conventional refractory castable samples fired at 120, 850, 1050, and 1400 oC. The physical properties were measured by linear shrinkage, bulk density, apparent porosity, and water absorption. The mechanical behavior was evaluated by cold crushing strength and cold modulus of rupture. Microstructural and mineralogical characteristics were analyzed by scanning electron microscopy and X-ray diffraction, respectively. The incorporation of 10 wt.% of blast furnace slag allowed the development of a slag-containing conventional refractory castable with improved properties compared to those of the reference castable, such as a bulk density of 2.61 g/cm3, percentages of apparent porosity, and water absorption of 10.64 % and 4.08 %, respectively, and mechanical resistance of 94.5 MPa. A denser microstructure via ceramic body s porosity reduction is reached by the anorthite crystallization from a silica-rich liquid phase with CaO contents. This densification mechanism improves mechanical resistance by about 74 %. The anorthite phase and the physical and mechanical characteristics exhibited by the sustainable refractory castable are attractive and suitable for its possible application in the aluminum industry as smelting furnace lining.