Evaluation of Fresh Property, Compressive Strength and Environmental Impact of Low-Carbon Geopolymer Based on Ladle Furnace Slag and Soda Residue

In this work, a novel method for the disposal of ladle furnace slag (LFS) and soda residue (SR) was proposed. By applying geopolymer technology, LFS and SR were used as precursors to manufacture a geopolymer with sufficient fresh and mechanical properties that can be used in construction works, such as in non-structural components like lightweight partition walls. The effects of raw material ratios and Na₂O equivalents on the fresh properties, mechanical properties, microstructure and environmental impact of LFS-SR geopolymer (LSG) were analyzed by rheology, compressive strength, XRD, TG/DTG, SEM, and calculation of embodied carbon. The results showed that the compressive strength of LSGs increased when the SR content decreased or Na₂O equivalent increased, and the maximum compressive strength could reach 12.0 MPa at 28 d. The hydration products of LSG were mainly C-(A)-S-H gel, C₃AH₆, and AFt. Notably, the C-(A)-S-H gels formed a stable cross-linked structure, and the extremely fine granular C₃AH₆ further filled the pores. Furthermore, AFt was generated from the interaction between LFS and CaSO₄ rich in SR during the hydration process. The carbon calculation results indicated that the embodied carbon of LSGs was significantly lower than that of traditional cement, and the LSG containing 20% SR and 12% Na₂O equivalent had the highest sustainability. This study proposed strategies for mitigating the environmental hazards of alkaline solid waste and improving its resource utilization, thereby promoting sustainable development in the construction industry.