An Innovative Approach to Enhancing Concrete Sustainability: Utilising Unprocessed Steel Slag with Low CaO and High SiO2 Content
Abstract
1. Background
2. Materials and Experimental Procedure
2.1. Steel Slag (SS)
2.2. Cement
2.3. Fine and Coarse Aggregates
2.4. Mix Proportions
2.5. Workability and Density
2.6. Compressive, Tensile, and Flexural Strengths
2.7. Ultrasonic Pulse Velocity (UPV) and Water Absorption (WA)
2.8. Freeze–Thaw (FT)
3. Results and Discussion
3.1. Workability and Density
3.2. Compressive Strength (CS)
3.3. Splitting Tensile Strength (STS)
3.4. Flexural Strength (FS)
3.5. Ultrasonic Pulse Velocity (UPV)
3.6. Water Absorption (WA)
3.7. Freeze–Thaw (FT)
4. Conclusions
- Using LDSS and SSP replacement reduced workability more than replacing HDSS in the concrete mixture; this could be because LDSS’s porose structure and angularity absorb more water than natural coarse aggregate, but this issue is easily resolved with superplasticizer.
- The high density of concrete with high amounts of SS is an advantage for structures such as retaining walls, bases, earthwork blocks, sound insulation, and radiation shields.
- The use of HDSS in concrete resulted in an increase in the mechanical properties. At 20% and 40%, the value of compressive strength was improved by 1.5% and 5.2%, respectively. The trend is similar for other mechanical properties.
- The use of LDSS and SSP in concrete mixtures resulted a decrease in the durability and mechanical performance. At 20% and 40% LDSS, the value of compressive strength was decreased by 8.1% and 7.8%, respectively. The trend is similar for other mechanical and durability properties.
- Due to the very low reactivity of this type of slag, SSP is not recommended to be used in concrete production as a cement replacement material.
- Compared to the control concrete, the freeze–thaw cycles reduced the UPV and compressive strength of concrete with varying types and amounts of SS. The durability is slightly compromised and can be considered lower in all mixes containing SS.
- Using 40% HDSS substitution in concrete led to the best results when the mechanical and durability characteristics of the current investigation were considered. Nonetheless, depending on the application, an acceptable strength for various types and replacement levels can be attained with the appropriate mix design.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
Nomenclature
CS | Compressive Strength |
FS | Flexural Strength |
FT | Freeze–Thaw |
HDSS | High-Density Steel Slag |
IF | Induction Furnace |
LDSS | Low-Density Steel Slag |
SEM | Scanning Electron Microscopy |
SP | Superplasticiser |
SS | Steel Slag |
SSP | Steel Slag Powder |
STS | Splitting Tensile Strength |
UPV | Ultrasonic Pulse Velocity |
WA | Water Absorption |
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Constituent | Composition (%) | Designation (SS) | Property | |||
Cement | SS | Shape | HDSS | Highly angular | ||
SiO2 | 19.83 | 38.73 | LDSS | Highly angular and porosity | ||
Fe2O3 | 2.32 | 25.87 | Surface texture | Rough | ||
CaO | 61.66 | 15.61 | Colour | Light black | ||
Al2O3 | 4.48 | 9.84 | Combustibility | Non-combustible | ||
MgO | 3.14 | 5.21 | ||||
MnO | 0.31 | 2.10 | Specific Gravity | HDSS | 3.1 | |
K2O | 0.68 | 0.83 | LDSS | 2.7 | ||
TiO2 | 0.32 | 0.51 | Water Absorption (%) | HDSS | 3.3 | |
Other | 7.26 | 1.3 | LDSS | 3.9 |
Mix | Mix Code | Cement (kg/m3) | FA (kg/m3) | CA (kg/m3) | SS (%) | SS Type | Water (kg/m3) | SP (%) |
---|---|---|---|---|---|---|---|---|
1 | Control | 400 | 800 | 1200 | 0 | - | 200 | 0.5 |
2 | H20 | 400 | 800 | 960 | 20 | HDSS | 200 | 0.5 |
3 | H40 | 400 | 800 | 720 | 40 | HDSS | 200 | 0.5 |
4 | L20 | 400 | 800 | 960 | 20 | LDSS | 200 | 0.5 |
5 | L40 | 400 | 800 | 720 | 40 | LDSS | 200 | 0.75 |
6 | P20 | 320 | 800 | 1200 | 20 | SSP | 200 | 0.75 |
7 | P40 | 240 | 800 | 1200 | 40 | SSP | 200 | 0.75 |
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Herki, B.M.A.; Ali, A.I.; Smail, Y.S.; Omer, K.M. An Innovative Approach to Enhancing Concrete Sustainability: Utilising Unprocessed Steel Slag with Low CaO and High SiO2 Content. Buildings 2025, 15, 1514. https://doi.org/10.3390/buildings15091514
Herki BMA, Ali AI, Smail YS, Omer KM. An Innovative Approach to Enhancing Concrete Sustainability: Utilising Unprocessed Steel Slag with Low CaO and High SiO2 Content. Buildings. 2025; 15(9):1514. https://doi.org/10.3390/buildings15091514
Chicago/Turabian StyleHerki, Bengin M. A., Ali Ibrahim Ali, Yousif Sadiq Smail, and Karwan Maroof Omer. 2025. "An Innovative Approach to Enhancing Concrete Sustainability: Utilising Unprocessed Steel Slag with Low CaO and High SiO2 Content" Buildings 15, no. 9: 1514. https://doi.org/10.3390/buildings15091514
APA StyleHerki, B. M. A., Ali, A. I., Smail, Y. S., & Omer, K. M. (2025). An Innovative Approach to Enhancing Concrete Sustainability: Utilising Unprocessed Steel Slag with Low CaO and High SiO2 Content. Buildings, 15(9), 1514. https://doi.org/10.3390/buildings15091514