How FRP Rebars Are Made: Materials and Pultrusion Process Explained

FRP (Fiber Reinforced Polymer) rebars, also known as fiberglass reinforcement bars, are gaining widespread adoption across infrastructure and construction sectors. Their performance begins at the core—with the materials and the precision manufacturing process. GTOFRP™ produces pultruded rebar using high-strength glass fibers and advanced thermosetting resins, creating a product built for durability and consistency.

1. Core Materials: Fiberglass and Resin Matrix

The composition of FRP rebars typically involves:

• Continuous E-glass fibers: These form the load-bearing structure, providing high tensile strength and stiffness.

• Thermosetting resins: Act as the matrix to bond the fibers, resist chemicals, and transfer stress.

Common resin systems include:

Each resin type affects the final properties of the rebar, influencing both mechanical performance and chemical resistance.

2. Pultrusion: Continuous Forming Technology

The pultrusion process is the core of FRP bar manufacturing. It ensures uniformity, high strength, and scalability.

Steps in the pultrusion process:

1. Fiber feed: Glass fiber rovings are pulled from multiple creels.

2. Resin impregnation: Fibers pass through a resin bath (often with additives and pigments).

3. Preforming: The wet fibers are shaped into a circular cross-section.

4. Pultrusion die: The material enters a heated die where curing occurs under pressure.

5. Surface coating: Sand or helically wrapped coatings are added for better concrete bonding.

6. Cutting: The bars are cut into desired lengths—typically in meters or feet.

The result is a pultruded fiberglass rod with consistent diameter, strength, and surface texture.

3. Color Customization and Surface Finish

Unlike steel, fiberglass rebars can be produced in various colors—often based on project requirements or resin systems. For example:

• Green: Vinyl ester-based rebars, common in marine or corrosive applications

• Yellow or orange: Often used in road and safety-marked structures

• Gray or black: For architectural or low-visibility use

Surface treatment options include:

• Sand coating: Improves mechanical bond with concrete

• Helical winding: Enhances anchorage in structural elements

• Plain smooth finish: Used in non-structural or temporary applications

Color is integrated during production, not painted afterward, which ensures lasting visual identification.

4. Quality Control and Production Standards

Consistent quality is essential for structural applications. GTOFRP™ implements the following QC measures:

• Raw material testing: Fiber tensile strength, resin viscosity, glass content ratio

• In-line monitoring: Die temperature, pulling speed, curing cycle

• Post-production checks: Dimensional tolerance, tensile strength, bond stress

• Batch traceability: Unique serial tracking for compliance and logistics

Production conforms to global standards such as ACI 440, ASTM D7957, and CSA S807, ensuring reliability across regions and industries.

5. Sustainable Manufacturing Trends

As the demand for low-carbon and durable construction increases, FRP rebar production is evolving to become greener:

• Low-emission resin systems: With reduced styrene content or bio-based components

• Closed-loop resin baths: Minimizing material waste during impregnation

• Energy-efficient pultrusion lines: Improving throughput with lower energy usage

• Dust and fume extraction: Ensuring worker safety and clean production

Compared to steel rebar, GFRP bar production generates significantly less CO₂ and avoids corrosion-related lifecycle replacements, making it a more sustainable choice for long-term infrastructure.