A Calcined Mg/Al LDHs Strategy for High-Performance Steel Slag Cementitious Composites

Due to the low hydration activity of steel slag, its mechanical properties are insufficient, which limits its strategic application in steel slag based cementitious composite. In this study, the promoting effect of calcined layered double hydroxide (CLDH) on the hydration process, mechanical properties, and microstructure of high-volume steel slag cementitious materials was systematically investigated. The results showed that the addition of CLDH significantly optimized the material’s performance. When the mass fraction of steel slag was 70 wt% and the CLDH dosage was 2.0 wt%, the 7-day compressive strength reached 42.5 MPa, indicating an increase of 23.9% compared with the control group. Microscopic characterization suggested that CLDH slightly enhanced the hydration reaction of steel slag and increased the generation of hydration products through the nucleation effect. The addition of CLDH demonstrated a change in the composition of C-(A)-S-H to a higher Al/Ca ratio. Meanwhile, the lamellar structure of CLDH effectively filled the pores and promoted the densification of the matrix. This research provides valuable insights for the high-value utilization of steel slag and the design of high-performance cementitious materials.