Evaluation of the Effect of MgO and P 2 O 5 on the Performance of Steel Slag as a Cementitious Material

The annual output of steelmaking slag has exceeded 150 million tons. Mass accumulations of slag damage the environment and hinder sustainable development. Preparing cementing materials in the powder form is a promising solution for the large-scale utilization of slag. Our study focused on the effects of MgO and P 2 O 5 on the grindability, soundness, and cementitious activity of steelmaking slags. Experimental results showed that by increasing the P 2 O 5 content in basic oxygen furnace slag from 0.5% to 3%, the free CaO content, grindability index, and early strength decreased from 6.82% to 5.35%, 0.78 to 0.72, and 29.3 MPa to 21.0 MPa, respectively, and the later strength increased from 42.8 MPa to 46.5 MPa. For electric arc furnace slag, the free CaO content, grindability index, and early and later strengths decreased from 4.0% to 1.9%, 0.75 to ~ 0.6, 29.5 MPa to 23.6 MPa, and 31.2 MPa to 27.5 MPa, respectively. The increase in the MgO content insignificantly influenced the grindability of the slag, but led to a deterioration in the soundness and cementitious characteristics of the slag powders. These results provide guidance for optimizing the chemical composition of steel slag during steelmaking to improve its use in cementing materials and thereby alleviate slag pollution and carbon dioxide emissions caused by cement production.