Effect of Si-based reductive modifying auxiliary on the recovery of iron and the cementitious reactivity of modified EAF slag

Si sludge was used as reductive modifying auxiliary during the iron component in the electric arc furnace (EAF) slag was reduced by carbon. The reduction behavior of the iron component in the EAF slag and the relationship between the mineral structure and the cementitious reactivity of the secondary slag were explored. The results show that the Si sludge can effectively reduce the iron-containing compounds in the slag. When the amount of Si sludge added is greater than 10 wt.%, the iron recovery rate exceeded 92% when reduced at 1773 K for 30 min. Si sludge has a modifying effect on EAF slag. When the amount of Si sludge is low (<10 wt.%), the content of cementitious components in the modified EAF slag is reduced, and low-activity merwinite crystals are precipitated in the slag, which reduces the cementitious reactivity. When Si sludge addition is greater than 10 wt.%, the amorphous phase content and reaction activity in the modified slag increased. The 28d compressive strength of the secondary slag with sludge addition of 14 wt.% reached 45.7 MPa.