Workability and Compressive Strength of Steel Slag Powder-Cement-Based Self-Compacting Iron Tailings Mortar

Steel slag and iron tailings are typical industrial solid waste. Their large-scale stockpiling occupies a significant amount of land and has a negative impact on the environment. To respond to the Guiding Opinions on the Comprehensive Utilization of Bulk Solid Waste in the 14th Five Year Plan and expand the use of steel slag powder and iron tailings sand as concrete admixtures and aggregates, this study prepared steel slag powder-cement-based self-compacting iron tailings mortar. The workability index of mortar was determined through two tests: the flow expansion test and the V-shaped funnel test. Additionally, the compressive strength of the mortar was measured using a servo press. The results show that as the replacement rate (Rs) of steel slag powder increases, the flow expansion (e) of the mortar increases, the V-shaped funnel time (Tv) decreases, and the compressive strength (fcu) decreases. Steel slag powders of 300 mesh and 100 mesh show an increase in e by 13.5% and 18.7% and a decrease in Tv by 24.3% and 29.7%, respectively, at Rs=40% compared to Rs=0. The fcu of the three age groups (3 d, 28 d, and 90 d) of the two kinds of steel slag powders decreases by 33.0%, 34.3%, and 20.0% and 43.0%, 40.2%, and 29.3%, respectively. As the replacement rate (Ri) of iron tailings sand increases, e decreases, Tv increases, and fcu first increases and then decreases. Graded iron tailings sand and natural iron tailings sand show a decrease of 14.5% and 31.0% in e and an increase of 31.9% and 52.2% in Tv, respectively, at Ri=40% compared to Ri=0. The Ri corresponding to the peak fcu is 30% and 10%, respectively. Finally, the prediction formulas for compressive strength at the three ages were provided. Validation shows that the predicted compressive strengths agree well with the experimental results, demonstrating the feasibility of the proposed formulas.