Parameter Optimization and Durability Performance of Alkali-Activated and Carbonated Steel Slag Soil Blocks
Abstract
:1. Introduction
2. Experiment Methods
2.1. Materials
2.2. Mix Design and Sample Preparation
2.3. Curing Regimes
2.4. Test Methods
2.4.1. Compressive Strength
2.4.2. Scanning Electron Microscopy
2.4.3. Freeze-Thaw Cycling
2.4.4. Dry-Wet Cycling
2.4.5. Micro-CT Analysis
3. Optimization of Parameters
3.1. Alkaline Activator
3.2. Steel Slag Content
3.3. Liquid/Solid Ratio
3.4. Forming Pressure
4. Performance Evaluation Based on Optimized Parameters
4.1. Compressive Strength
4.2. SEM
4.3. Freeze-Thaw Cycling
4.3.1. Mass Change
4.3.2. Compressive Strength
4.3.3. Micro-CT Analysis
4.4. Wet-Dry Cycling
4.4.1. Mass Change
4.4.2. Compressive Strength
4.4.3. Micro-CT Analysis
5. Conclusions and Future Perspectives
- The optimal manufacturing parameters for steel slag soil blocks include a sodium silicate with a Na2O concentration of 6%, steel slag content of 30%, liquid/solid ratio of 0.18, and forming pressure of 10 MPa, resulting in the highest compressive strength of 14.46 MPa.
- The combination of alkali activation and carbonation can further promote the development by reaching a maximum compressive strength of 17.4 MPa, where the most compact microstructure, characterized by a honeycomb-like C-(A)-S-H gel and a substantial presence of well-crystallized, triangular-shaped aragonite can be found in the SEM image.
- Freeze-thaw and wet-dry cycling tests indicate that the blocks perform poorer after carbonation, likely due to the transformation of C-(A)-S-H gel into calcium carbonate, which has relatively weaker cementitious properties and causes cracks and surface detachment.
- Micro-CT analysis revealed distinct internal cracking patterns, with freeze-thaw cycles producing a ring-like pattern and wet-dry cycles generating diagonally distributed cracks. In contrast, the reference OPC group exhibited the highest degree of compactness, with no cracks observed under either cycling condition.
- Long-term durability remains a critical challenge. Future research should focus on enhancing material durability by establishing a clear relationship between durability degradation and carbonation products, thereby guiding adjustments to the carbonation process (e.g., optimizing carbonation duration and CO2 concentration). Alternatively, improvements can be achieved through optimized mix design, such as fiber incorporation, chemical additives, or other material modifications.
- Additionally, careful selection of application scenarios is crucial. The primary objective is to recycle and repurpose solid waste materials. In line with this goal, the AAC group may be more suitable for non-structural components with relatively lower durability requirements, such as curbstones and landscaping blocks.
- To ensure a balance between material performance, environmental impact, and economic feasibility, future studies could incorporate life cycle assessment (LCA) and life cycle cost analysis (LCCA) to provide a more comprehensive evaluation.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Moisture Content | Unit Weight (kN/m3) | Specific Gravity | Void Ratio | Liquid Limit | Plastic Limit | Cohesive Strength (kPa) | Internal Friction Angle (◦) |
---|---|---|---|---|---|---|---|
ω0 | γ | Gs | e0 | ωl | ωp | c | φ |
45.0% | 17.2 | 2.73 | 1.3% | 43.2% | 23.6% | 13.7 | 9.4 |
Group No. and Testing Variables | Steel Slag Content (% of Soil) | OPC Content (% of Soil) | Type of Activator 1 | L/S Ratio | Forming Pressure (MPa) | ||
---|---|---|---|---|---|---|---|
NA (%) | MgO (%) | NS (%) | |||||
Group A: alkaline activator and Na2O concentration | 15 | 3/6/9 | - | - | 0.18 | 10 | |
15 | - | 3/6/9 | - | 0.18 | 10 | ||
15 | - | - | 3/6/9 | 0.18 | 10 | ||
Group B: steel slag content | 15 | - | - | 6 | 0.18 | 10 | |
30 | - | - | 6 | 0.18 | 10 | ||
45 | - | - | 6 | 0.18 | 10 | ||
Group C: liquid/solid ratio and Na2O concentration | 30 | - | - | 2/4/6/8 | 0.18 | 10 | |
30 | - | - | 2/4/6/8 | 0.20 | 10 | ||
30 | - | - | 2/4/6/8 | 0.22 | 10 | ||
Group D: forming pressure | 30 | - | - | 6 | 0.18 | 5 | |
30 | - | - | 6 | 0.18 | 10 | ||
30 | - | - | 6 | 0.18 | 15 | ||
Group E: control group of OPC block | - | 30 | - | - | - | 0.18 | 10 |
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Li, L.; Li, H.; Cui, Y.; Zhang, S. Parameter Optimization and Durability Performance of Alkali-Activated and Carbonated Steel Slag Soil Blocks. Materials 2025, 18, 1596. https://doi.org/10.3390/ma18071596
Li L, Li H, Cui Y, Zhang S. Parameter Optimization and Durability Performance of Alkali-Activated and Carbonated Steel Slag Soil Blocks. Materials. 2025; 18(7):1596. https://doi.org/10.3390/ma18071596
Chicago/Turabian StyleLi, Lufan, Haodong Li, Yunliang Cui, and Shimin Zhang. 2025. "Parameter Optimization and Durability Performance of Alkali-Activated and Carbonated Steel Slag Soil Blocks" Materials 18, no. 7: 1596. https://doi.org/10.3390/ma18071596
APA StyleLi, L., Li, H., Cui, Y., & Zhang, S. (2025). Parameter Optimization and Durability Performance of Alkali-Activated and Carbonated Steel Slag Soil Blocks. Materials, 18(7), 1596. https://doi.org/10.3390/ma18071596