Experimental Study of Comparison between GFRP and Steel bars

Abstract

This experimental study investigates the viability and performance of replacing traditional steel reinforcement with Glass Fiber Reinforced Polymer (GFRP) bars in concrete structures. With the increasing demand for sustainable and durable infrastructure, the construction industry seeks alternatives to steel reinforcement due to its susceptibility to corrosion and associated maintenance costs. GFRP bars offer a promising alternative due to their non-corrosive nature, high tensile strength, and light weight. The experimental program involves casting concrete specimens with varying percentages of GFRP bars as a substitute for steel reinforcement. Mechanical properties such as tensile strength, flexural strength, and bond strength between GFRP bars and concrete are evaluated and compared with conventional steel-reinforced concrete. The results indicate that GFRP-reinforced concrete exhibits comparable or even superior mechanical properties compared to traditional steel-reinforced concrete. The tensile strength of GFRP bars matches or exceeds that of steel, ensuring adequate structural performance. Moreover, the non- corrosive nature of GFRP bars eliminates the risk of corrosion-induced deterioration, leading to longer service life and reduced maintenance costs. Furthermore, the bond strength between GFRP bars and concrete is found to be satisfactory, indicating effective load transfer between the reinforcement and the surrounding concrete matrix. In conclusion, the experimental study supports the feasibility and effectiveness of replacing steel reinforcement with GFRP bars in concrete structures. This alternative offers numerous advantages including enhanced durability, reduced maintenance requirements, and increased sustainability, making it a promising solution for modern construction practices seeking to address both structural and environmental concerns.

Introduction

Concrete is strong in compression but weak in tension, traditionally reinforced with steel. However, due to corrosion and fatigue issues, Fiber-Reinforced Polymer (FRP) bars—especially Glass FRP (GFRP)—are emerging as a superior alternative. These non-metallic bars offer corrosion resistance, high tensile strength, and lightweight advantages, making them ideal for aggressive environments.

Key Advantages of FRP/GFRP Bars:

• 3x higher tensile strength than steel

• Lightweight and non-corrosive

• Resistant to fatigue, chemical attack, and chloride penetration

• Longer service life and reduced maintenance

• Better damage tolerance than epoxy-coated steel

Limitations:

• Higher initial cost (though decreasing)

• Lower stiffness and brittle failure behavior

• Poor fire resistance

• Limited long-term performance data compared to steel

• Less ductility than steel

Applications:

• Reinforcing concrete beams, slabs, and columns

• Structural strengthening and retrofitting (e.g., CFRP wraps for seismic upgrades)

• Use in foundations, ground anchors, water tanks, and corrosive environments

• Repair of heat-damaged structures using CNT-modified CFRP

Literature Insights:

• Multiple studies confirm GFRP’s comparable or superior performance to steel under proper design.

• Optimal reinforcement ratios are critical—too low causes rupture; too high leads to compression failure.

• GFRP performance depends on bar diameter, fiber orientation, and matrix bonding.

• Finite element and deep learning models help predict performance, but limitations exist in capturing bond-slip and micro-cracks.

Manufacturing Process (Pultrusion):

A continuous process involving:

1. Fiber feeding and guiding

2. Resin impregnation

3. Preforming and shaping

4. Curing in a heated die

5. Pulling and cutting to length

Scope for Future Research:

1. Mechanical Testing under varied loading (static, dynamic, fatigue)

2. Durability Studies across harsh environmental conditions

3. Fire Resistance Evaluation and performance during high-temperature exposure

Conclusion

1) FRP bars, including CFRP and AFRP, enhance the design and reliability of concrete structures, improving safety and failure mode prediction, especially regarding shear and bond failure. 2) Locally produced GFRP bars perform similarly to commercial ones, showing promise in terms of fiber volume fraction, tensile strength, and elastic modulus for concrete reinforcement. 3) Failure modes of GFRP reinforced concrete depend on the reinforcement ratio, with excessive reinforcement leading to compression failure, while insufficient reinforcement causes GFRP rupture. 4) Due to FRP’s lower modulus of elasticity, FRP-reinforced concrete structures tend to show smaller deflections and strains compared to steel-reinforced ones. 5) For optimal performance, the reinforcement ratio should be balanced. Too high or too low a ratio can cause issues such as GFRP rupture or compression failure. 6) GFRP bars show superior mechanical properties, including higher tensile strength and yield strain compared to traditional steel rebars, offering corrosion resistance and good flexural strength. 7) GFRP rebars offer significant cost savings (up to 30%) compared to steel, while maintaining superior shear and tensile strengths, making them ideal for modern construction. 8) Using CFRP jackets for retrofitting damaged concrete columns significantly improves their strength, ductility, and seismic resistance, particularly in cases of prior damage. 9) The incorporation of alkali-resistant glass fibers enhances the durability of concrete, improving resistance to acid attacks and reducing bleeding, especially in high-grade concrete. 10) The interaction between GFRP bars and concrete can significantly impact performance, with surface coatings like sand-coating improving bond performance and crack control in GFRP-reinforced beams. These studies highlight the growing importance and application of advanced composite materials like GFRP and CFRP in enhancing the performance and durability of reinforced concrete structures.

References

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Copyright

Copyright © 2025 Mr. Tejas Suresh Tayade, Dr. B. H. Shinde. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.