Key Takeaways & Executive Findings
- •• GBFS releases active Si4+ and Al3+ to synergistically activate Ca2+ from steel slag, promoting C-S-H gel and ettringite formation, and optimizing microstructure. • At 30% GBFS content, C-S-H content increases by 40.8%, large pores decrease by 68.7%, and 90-day compressive strength quintuples compared to baseline. • Desulfurization gypsum accelerates silicate hydration, but excessive addition (>16%) causes AFt expansion-induced microcracks and strength loss. • Optimal synergistic system (8% DG + 30% GBFS) yields peak heat release rate of 0.92 mW/g and cumulative heat of 240 J/g, enabling high-content SS backfill materials.
Abstract
In the steel slag-based mine backfill cementitious material systems, the hydration reaction mechanisms and synergistic effects of steel slag (SS), granulated blast furnace slag (GBFS), and desulfurization gypsum (DG) are crucial for performance optimization and regulation. However, existing studies have yet to fully reveal the underlying synergistic mechanisms, which limits the application and promotion of high SS content in mine backfill and low-carbon building materials. This study systematically explores the synergistic effects between various solid wastes and their regulation of the hydration process in the SS-based cementitious system through multi-scale characterization techniques. The results show that GBFS, by releasing active Si4+ and Al3+, triggers a synergistic activation effect with Ca2+ provided by SS, promoting the formation of C-S-H gel and ettringite, significantly optimizing the hardened paste microstructure. When the GBFS content reaches 30%, the C-S-H content increases by 40.8%, the pore size distribution improves, the proportion of large pores decreases by 68.7%, and the 90-day compressive strength increases to 5 times that of the baseline group. The sulfate activation effect of DG accelerates the hydration of silicate minerals, but excessive incorporation (>16%) can lead to microcracks caused by the expansion of AFt crystals, resulting in a strength reduction. Under the synergistic effect of 8% DG and 30% GBFS, the hydration reaction is most intense, with the peak heat release rate reaching 0.92 mW/g and the cumulative heat release amount being 240 J/g. By constructing a “SS-GBFS-DG-cement” quaternary synergistic system (mass ratio range: SS:GBFS:cement:DG=(50–62):(20–40):10:(8–12)), the matching of active components in high-content SS systems was optimized, significantly improving microstructural defects and meeting engineering application requirements. This study provides a theoretical basis for the component design and performance regulation of high-content SS-based cementitious materials.
1. Introduction
With the acceleration of global industrialization, the scale of mining operations continues to expand, and the application of filling mining methods, which are crucial for ensuring the safety of mineral extraction, improving resource recovery rates, and reducing surface subsidence, is growing increasingly important [1–3]. However, traditional cement-based filling materials face urgent challenges regarding high energy consumption, high emissions, and high costs [4,5]. Steel slag, due to its rich mineral composition and potential self-cementing properties, has become an ideal substitute for cement. By leveraging the synergistic hydration effect between SS and various solid waste components, and through rational mix design, cementitious materials that meet the performance requirements for mining can be prepared, significantly reducing mine backfill costs and CO2 emissions [6,7]. This also provides experimental data and theoretical support for the development of new low-carbon cementitious materials such as SS, accelerating its large-scale utilization in mining engineering and low-carbon building materials.
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Jianshuai Hao, Zihan Zhou, Zhonghui Chen, Yanjun Shen, Kuizhen Fang, Fei Tang, Lingfei Zhang (2025). Synergistic mechanisms of steel slag, granulated blast furnace slag, and desulfurization gypsum in high-content steel slag-based cementitious backfill materials. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.05.007
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Frequently Asked Questions
What are the synergistic mechanisms between steel slag, granulated blast furnace slag, and desulfurization gypsum in backfill materials?
GBFS releases active Si4+ and Al3+ that react with Ca2+ from steel slag to form C-S-H gel and ettringite, enhancing microstructure. Desulfurization gypsum provides sulfate to accelerate silicate hydration, but excessive amounts cause expansion and microcracks.
How does the addition of granulated blast furnace slag affect the performance of steel slag-based backfill materials?
At 30% GBFS content, C-S-H content increases by 40.8%, large pores decrease by 68.7%, and 90-day compressive strength becomes five times higher than baseline, significantly improving mechanical properties.
What is the optimal dosage of desulfurization gypsum in the synergistic system?
The optimal dosage is 8% DG combined with 30% GBFS, which yields the most intense hydration reaction with peak heat release rate of 0.92 mW/g and cumulative heat of 240 J/g. Excessive DG (>16%) leads to strength reduction due to AFt expansion.
What is the recommended mix design for high-content steel slag-based cementitious backfill materials?
The recommended mass ratio range is SS:GBFS:cement:DG = (50–62):(20–40):10:(8–12), which optimizes active component matching and meets engineering requirements.
How does this research contribute to low-carbon building materials?
By utilizing industrial solid wastes like steel slag, GBFS, and DG, the study reduces cement consumption and CO2 emissions, providing a theoretical basis for sustainable backfill materials in mining and construction.
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