Ladle metallurgy stainless steel slag as a raw material in Ordinary Portland Cement production: a possibility for industrial symbiosis

Ladle metallurgy (LM) slag is generated during the refining process step in stainless steel making. In view of its very fine particle size, due to the transformation of β- to γ-C2S, and the Cr content, the slag is challenging in terms of handling and disposal and is used in only few applications. The current work explores the utilisation of the LM's fine fraction in Ordinary Portland Cement (OPC) clinker production. Three sets of samples containing LM slag, in 0 wt% (OPC - reference), 6 wt% (OPC6) and 14 wt% (OPC14), were investigated. The sintering temperature was 1450 °C with 40 min soaking time. The clinkers containing LM slag, showed a slight increase in C3S and a decrease in C3A and C4AF. The formation of the C3S initiated at a lower temperature probably due to the presence of F and C2S. Longer setting times were found for OPC6 and OPC14. The compressive strength results were found to be comparable at 2 d (22-25 MPa), 7 d (36-38 MPa) and 28 d (44 MPa) of curing, falling into 42.5R CEM I category. The emission of kgCO2/t of clinker during production, is estimated to decrease at least 12% for OPC14. A processing step for the pre-treatment of the slag is also presented, aiming to reduce the initial Cr content.