From metallurgical waste to sustainable refractory binder: hydraulic performance of vanadium-bearing slags

Circular economy principles can create value while minimising the production of waste and its associated environmental impact. Vanadium-bearing slags originate from specific alloy production, forming alumina-vanadium or ferrovanadium alloys (used for automotive, jet engine, and airframe industries). This study assesses the feasibility of valorising vanadium-bearing slags (vanadium content <1 wt.%) as eco-friendly alternatives to commercial calcium aluminate cement. Two vanadium-bearing slags, Slag 1 and Slag 2, coming from basic-oxygen furnace and electric arc furnace respectively, are comprehensively characterised and their performance is compared with commercial cements Secar71 and CMA72. Slag 2 showed minimal hydraulic activity due to its large content of inert MgAl 2 O 4 phase. Slag 1, rich in CaAl 2 O 4 and CaAl 4 O 7 phases, exhibited high reactivity with water, rate of hydration and strength. Its hydration behaviour and strength development are comparable to Secar71. The results revealed that vanadium content did not compromise hydration or mechanical performance. This study offers a strategic framework for predicting slag hydraulic performance and reveals vanadium-bearing slags with high CaAl 2 O 4 and CaAl 4 O 7 contents as potential alternatives to calcium aluminate cement in sustainable refractory materials.