Mechanical and Bond-Slip Properties of Steel-Fiber-Reinforced Geopolymer Recycled-Aggregate Concrete
Abstract
1. Introduction
2. Experimental Program
2.1. Materials
2.2. Specimen Design and Preparation
2.3. Test Procedure and Loading Setup
3. Results and Analysis
3.1. Workability
3.2. Compressive Strength
3.3. Splitting Tensile and Flexural Strength
3.4. Bond-Slip
3.4.1. Failure Modes
3.4.2. Bond-Slip Curves
4. Bayesian Theory-Based Prediction Model for Bond Strength of SFGRC
4.1. Bayesian Method
4.2. Database
4.3. Probabilistic Model Development
4.4. Model Validation
5. Conclusions
- (1)
- The dry apparent density of steel-fiber geopolymer recycled-aggregate concrete (SFGRC) ranges from 1856 kg/m3 to 2004 kg/m3. The slump value of the concrete is between 121 and 177 mm, and its fluidity decreases with the increase in the amount of recycled aggregate and steel fiber.
- (2)
- As the content of recycled aggregates increases, the compressive strength of SFGRC decreases by 41.5%, but the tensile-compressive ratio increases by 18–22%. When the volume fraction of steel fibers increases from 0% to 1.5%, the splitting tensile strength increases by 10.99–158.79%, and the flexural strength increases by 36.97–113.80%. The dry apparent density of the material is 10–15% lower than that of traditional concrete, but the workability decreases with the increase of recycled aggregates and fiber content.
- (3)
- The bond strength between the SFGRC and steel bars is 14.82–17.57 MPa. When the anchorage length increases from 5d to 10d, the bond strength decreases by 11.3%, and the ultimate slip amount is 0.30–0.38 mm. The failure mode is dominated by steel bar pull-out. The porous structure of recycled aggregates improves the bond strength through the mechanical interlocking effect, but an excessively long anchorage length will lead to non-uniform stress distribution.
- (4)
- Based on 123 sets of test data, a Bayesian probability model is established. The predicted mean ratio of bond strength is 1.14, and the coefficient of variation is 2.61. It is verified that the model can accurately predict the bond strength of SFGRC, providing strong theoretical support and data reference for subsequent engineering applications and further research.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Material | SiO2 | Al2O3 | Fe2O3 | CaO | MgO | SO3 | K2O | Na2O |
---|---|---|---|---|---|---|---|---|
Class I Low-Calcium Fly Ash | 51.494 | 37.186 | 3.515 | 2.793 | 0.414 | 0.831 | 1.109 | 1.145 |
S95-Grade Slag | 32.083 | 15.134 | 0.466 | 38.610 | 8.454 | 2.502 | 0.426 | 0.493 |
SF88-Grade Silica Fume | 90.442 | 0.805 | 3.555 | 0.632 | 1.044 | 1.336 | 0.949 | 0.292 |
Material | Particle Size (mm) | Bulk Density (kg/m3) | Apparent Density (kg/m3) | Water Absorption (%) | Crushing Index (%) |
---|---|---|---|---|---|
Recycled Coarse Aggregate | 4.75~16.00 | 1250 | 2250 | 8.3 | 18.2 |
Recycled Fine Aggregate | 0.15~4.75 | 1130 | 2650 | 11.2 | 14.1 |
Fiber Type | Density (kg/m3) | Length (mm) | Diameter (mm) | Aspect Ratio | Elastic Modulus (GPa) | Tensile Strength (MPa) |
---|---|---|---|---|---|---|
Hooked-End Steel Fiber | 7800 | 35 | 0.5 | 65 | 200 | 1100 |
Grade | Diameter (mm) | Yield Strength (MPa) | Ultimate Strength (MPa) | Elastic Modulus (MPa) |
---|---|---|---|---|
HRB400 | 16 | 451.3 | 634.9 | 1.94 × 105 |
Mixtures | Slag | Fly Ash | Silica Fume | Recycled Fine Aggregate | Recycled Coarse Aggregate | Steel Fiber | NaOH Solution | Na2SiO3 Solution | Water | Water-Reducing Admixture |
---|---|---|---|---|---|---|---|---|---|---|
SFGRC-1 | 420 | 210 | 70 | 530 | 675 | 39 | 54 | 209 | 88 | 7 |
SFGRC-2 | 337 | 169 | 56 | 635 | 810 | 39 | 44 | 167 | 70 | 5.5 |
SFGRC-3 | 420 | 210 | 70 | 530 | 675 | 0 | 54 | 209 | 67 | 7 |
SFGRC-4 | 420 | 210 | 70 | 530 | 675 | 77 | 54 | 209 | 67 | 7 |
SFGRC-5 | 420 | 210 | 70 | 530 | 675 | 116 | 54 | 209 | 67 | 7 |
Mixtures | la/mm | la/d | c/mm |
---|---|---|---|
SFGRC-80 | 80 | 5 | 92 |
SFGRC-120 | 120 | 7.5 | 92 |
SFGRC-160 | 160 | 10 | 92 |
Mixtures | Slump (mm) | ρd /(kg/m3) | fcu,3d /MPa | fcu,7d /MPa | fcu,28d /MPa | fts /MPa | ff /MPa |
---|---|---|---|---|---|---|---|
SFGRC-1 | 156 | 1947 | 28.18 | 32.08 | 43.13 | 3.27 | 3.77 |
SFGRC-2 | 146 | 1889 | 20.69 | 26.39 | 25.23 | 2.35 | 2.62 |
SFGRC-3 | 177 | 1856 | 24.82 | 31.10 | 34.57 | 1.82 | 2.92 |
SFGRC-4 | 137 | 1959 | 26.06 | 30.15 | 39.83 | 4.28 | 4.80 |
SFGRC-5 | 121 | 2004 | 27.98 | 33.54 | 40.10 | 4.71 | 5.93 |
Mixtures | Ultimate Load Fu/kN | Ultimate Bond Strength τu/MPa | Ultimate Slip su/mm | Steel Stress τs/MPa | Failure Mode |
---|---|---|---|---|---|
SFGRC-80-2 | 70.61 | 17.57 | 0.38 | 348.07 | Pull-out |
SFGRC-120-2 | 93.93 | 15.58 | 0.34 | 484.17 | Pull-out after yielding |
SFGRC-160-2 | 119.13 | 14.82 | 0.30 | 595.69 | Pull-out after yielding |
Reference | Number | Compressive Strength fcu/MPa | Cover Thickness c/d | Anchorage Length l/mm | Rebar Diameter d/mm | Recycled Aggregate Replacement Ratio R | Fiber Content F | τu /MPa |
---|---|---|---|---|---|---|---|---|
Zheng Yongqian [18] | 51 | 20.6~78.8 | 2.63~5.75 | 1d~8d | 12~22 | 0~100 | 0 | 10.45~32.54 |
Zhang Haiyan [23] | 8 | 45.3~48.1 | 8.6 | 5d~12d | 16 | 0 | 0 | 9.8~23.9 |
Li Guanghui [24] | 9 | 24.6~41.8 | 8.3 | 3.5d | 6 | 0 | 0 | 0.72~4.29 |
Xiao Jianzhuang [18] | 17 | 36.1~48.1 | 2.27~7.0 | 5d~9d | 10~25 | 0 | 0 | 10.91~19.71 |
Seshu [25] | 20 | 26~61.2 | 4.19 | 2d~5d | 16 | 0~100 | 0 | 13.53~30.13 |
Abdulrahman [26] | 9 | 24~43.2 | 2.6~4.5 | 5d | 10~16 | 0 | 0 | 9.9~22.1 |
Le [27] | 9 | 20.3~41.1 | 1.19~5.75 | 5d~8.33d | 12~20 | 0 | 0 | 6.01~15.4 |
Yang [28] | 20 | 32.5~154.5 | 1.61~8.875 | 3d | 8~14 | 0 | 2.5% | 4.75~35.44 |
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Ji, J.; Zhang, Z.; Zhang, Y.; Liu, X. Mechanical and Bond-Slip Properties of Steel-Fiber-Reinforced Geopolymer Recycled-Aggregate Concrete. Buildings 2025, 15, 2179. https://doi.org/10.3390/buildings15132179
Ji J, Zhang Z, Zhang Y, Liu X. Mechanical and Bond-Slip Properties of Steel-Fiber-Reinforced Geopolymer Recycled-Aggregate Concrete. Buildings. 2025; 15(13):2179. https://doi.org/10.3390/buildings15132179
Chicago/Turabian StyleJi, Jianhua, Zening Zhang, Yi Zhang, and Xi Liu. 2025. "Mechanical and Bond-Slip Properties of Steel-Fiber-Reinforced Geopolymer Recycled-Aggregate Concrete" Buildings 15, no. 13: 2179. https://doi.org/10.3390/buildings15132179
APA StyleJi, J., Zhang, Z., Zhang, Y., & Liu, X. (2025). Mechanical and Bond-Slip Properties of Steel-Fiber-Reinforced Geopolymer Recycled-Aggregate Concrete. Buildings, 15(13), 2179. https://doi.org/10.3390/buildings15132179