Fiberglass Rebar vs Steel Rebar Strength: Which Is Stronger?

When selecting reinforcement materials for concrete, strength is a top priority. Two commonly compared options are fiberglass rebar (also known as GFRP) and steel rebar. This article explores the tensile strength, shear strength, and long-term durability of both materials to help contractors and engineers make informed decisions.

1. Tensile Strength: Comparable but Different

Steel rebar has been the industry standard for decades, boasting high tensile strength, usually around 500–600 MPa. However, fiberglass rebar has caught up, offering tensile strengths of 600–1000 MPa, depending on the formulation and manufacturer.

Key Insight: Although fiberglass rebar often has higher tensile strength, it exhibits linear elastic behavior up to failure without yielding, unlike steel which deforms plastically before breaking.

2. Shear and Bending Strength

Steel has superior shear strength and ductility, making it more forgiving under impact or extreme load conditions. Fiberglass rebar, while strong, is brittle in nature and not suitable for applications where high shear or dynamic load impact is expected.

3. Durability and Environmental Resistance

One of the key advantages of fiberglass rebar is its resistance to corrosion. Unlike steel, it does not rust, making it ideal for marine structures, bridges, and chemical plants.

• Steel Rebar: Prone to corrosion if not properly coated.

• GFRP Rebar: Maintains integrity in high-moisture, salt-rich, or acidic environments.

4. Creep and Fatigue

Fiberglass rebar performs well under static loads, but under continuous loading (creep) or repetitive loading (fatigue), its performance may vary depending on the resin matrix used.

5. Which Is Stronger?

In terms of raw tensile strength, GFRP often surpasses steel. However, if ductility, impact resistance, and overall robustness under varying loads are considered, steel remains the preferred choice for many structural applications.

6. Conclusion

• Choose fiberglass rebar for corrosive environments, lightweight design, and long-term durability.

• Choose steel rebar for dynamic loads, structural redundancy, and applications requiring ductility.