IS 18256:2023 and IRC:137-2022: India’s GFRP Rebar Standards

For years, one of the biggest obstacles to the adoption of GFRP rebar in India was the absence of a recognized Indian standard. Engineers, consultants, and project authorities often hesitated to specify Glass Fiber Reinforced Polymer (GFRP) reinforcement because there was no formal code to reference in designs, tenders, or approvals.

That has now changed.

India now has two key standards governing the use of GFRP reinforcement bars:

• IS 18256:2023 → Published by the Bureau of Indian Standards (BIS), covering the material requirements for GFRP rebars.
• IRC:137-2022 → Published by the Indian Roads Congress (IRC), providing design guidelines for using GFRP reinforcement in highway and bridge infrastructure.

In addition, the Ministry of Road Transport and Highways (MoRTH) has endorsed the use of FRP materials in national infrastructure projects, part of a broader set of government guidelines and policy positions that now formally back GFRP in Indian construction. This article explains what these standards cover, how they affect specification and design, and what engineers need to know before using GFRP rebar in construction projects.

Why the Absence of an Indian GFRP Rebar Standard Was a Challenge

Conventional steel is governed by IS 1786, a standard familiar to engineers, contractors, and procurement teams across India.

When a material is backed by a recognized code:

• Consultants can reference it in designs.
• Procurement teams can include it in tenders.
• Approval authorities have a basis for acceptance.
• Contractors know the performance requirements.

For many years, GFRP rebars lacked this regulatory framework in India. Even in projects where corrosion resistance made GFRP a logical choice such as coastal structures, bridges, water treatment facilities, and marine infrastructure, specifiers often avoided it because there was no Indian code to cite.

The introduction of IS 18256:2023 and IRC:137-2022 addresses this issue by providing both material and design standards.

IS 18256:2023 – Indian Standard for GFRP Rebar Material Specifications

IS 18256:2023 establishes the requirements for manufacturing, testing, and supplying Glass Fiber Reinforced Polymer (GFRP) bars for concrete reinforcement.

It serves as the primary reference for manufacturers, consultants, contractors, and project owners.

Scope of IS 18256:2023

The standard applies specifically to:

• Solid round GFRP reinforcement bars
• Glass fiber-based reinforcement systems

It does not cover:

• Carbon Fiber Reinforced Polymer (CFRP) bars
• Aramid Fiber Reinforced Polymer (AFRP) bars

Raw Material Requirements for GFRP Rebars

The standard defines acceptable constituent materials, including:

• Glass fiber types
• Different resin types - Polyester resin systems, Vinyl ester resin systems, Epoxy resin systems

It also specifies minimum fiber content requirements.

A product cannot be classified as compliant solely based on tensile performance. The constituent materials must also meet the requirements defined by the standard.

Mechanical Property Requirements

IS 18256:2023 establishes minimum performance criteria for:

• Tensile Strength: The bar must achieve specified minimum tensile strength values to qualify for structural use.
• Modulus of Elasticity: The standard specifies minimum stiffness requirements to ensure predictable structural performance.
• Ultimate Tensile Strain: Bars must demonstrate adequate strain capacity before failure.
• Transverse Shear Strength: Requirements are included to ensure performance under shear-related stresses.

These values establish the minimum benchmark that compliant GFRP rebars must achieve.

Durability Requirements

Long-term durability is a key focus of the standard.

• Alkali Resistance Testing: Because reinforced concrete creates a highly alkaline environment, GFRP bars must demonstrate resistance to alkali exposure.
• Moisture Absorption Limits: The standard places limits on moisture absorption to maintain long-term performance.
• Surface Bond Requirements: To ensure effective bonding with concrete, bars must include suitable surface treatments such as deformations, sand-coated surfaces, other approved bond-enhancing finishes.

Dimensional Requirements

IS 18256:2023 covers GFRP bars ranging from:

• 6 mm diameter
• Up to 32 mm diameter

The standard also defines acceptable tolerances for:

• Diameter
• Cross-sectional area

These requirements help ensure consistency between specified and supplied material.

Documentation and Certification Requirements

Each production batch must be accompanied by documentation demonstrating compliance.

Typical documentation includes:

• Mill test reports
• Mechanical property test results
• Durability test reports
• Batch traceability records

When specifying GFRP reinforcement bars, engineers should request test reports from NABL-accredited laboratories wherever applicable.

Why GFRP Requires Different Design Rules Than Steel

Steel behaves differently from GFRP.

• Steel Reinforcement: Steel yields before failure, providing visible warning signs such as increased deformation and cracking.
• GFRP: GFRP remains elastic until rupture and does not exhibit yielding.

Because of this difference, design approaches used for steel cannot be directly applied to GFRP-reinforced sections.

IRC:137-2022 accounts for these material characteristics.

Serviceability Often Controls GFRP Design

For many GFRP reinforced concrete structures, serviceability requirements govern design before strength limits are reached.

Key considerations include:

1. Deflection

GFRP generally has a lower modulus of elasticity than steel.

As a result, sections reinforced with GFRP may experience greater deflection under identical loading conditions.

2. Crack Width Control

Crack control remains an important FRP design requirement and must be evaluated according to IRC provisions.

Engineers should perform explicit serviceability checks rather than relying solely on strength calculations.

Environmental Reduction Factor (CE)

One of the most important provisions in IRC:137-2022 is the environmental reduction factor, commonly referred to as CE.

The factor accounts for long-term exposure conditions such as:

• Indoor environments
• Outdoor exposure
• Coastal environments
• Chemical exposure conditions

The design tensile strength used in calculations must be reduced using the applicable factor. Using catalogue tensile strength values directly without applying CE does not comply with the guideline.

Development Length and Lap Splice Requirements

GFRP reinforcement develops bond differently than steel reinforcement.

As a result:

• Development lengths are typically longer.
• Lap splice requirements differ from conventional steel reinforcement.

Designers should use the values provided in IRC:137-2022 rather than adopting values from IS 456.

Concrete Cover Requirements

IRC:137-2022 includes guidance for cover requirements in GFRP-reinforced concrete. Since corrosion of reinforcement is not the primary concern, some applications may permit different cover requirements compared to conventional steel-reinforced sections.

However, designers should always verify cover requirements against the specific exposure classification defined in the guideline.

Applications Covered by IRC:137-2022

The guideline currently addresses:

• Bridge decks
• Culverts
• Retaining walls
• Pavement slabs
• Highway-related reinforced concrete structures

The document does not currently provide design provisions for:

• Building structures
• Prestressed FRP systems
• Seismic design applications

For these situations, designers may need to supplement their design approach using internationally recognized standards.

Comparison of Indian and International GFRP Standards

India's GFRP framework aligns closely with international practices already adopted in North America and other regions.

Standard	Country	Scope
IS 18256:2023	India	GFRP rebar material specification
IRC:137-2022	India	Highway and bridge design guidelines
ASTM D7957	USA	GFRP rebar material specification
ACI 440.1R-15	USA	Design of concrete structures reinforced with FRP
CSA S807	Canada	FRP material specification

Current Gap in Indian GFRP Design Standards

While India now has standards for material specifications and highway infrastructure design, there is currently no BIS design code specifically covering GFRP reinforced buildings.

For building projects, engineers commonly rely on:

• ACI 440.1R-15
• Project-specific design basis reports
• Owner or consultant approval procedures

A dedicated Indian building design standard for GFRP reinforcement is expected in the future.

Specification Checklist for GFRP Projects

When preparing a specification, tender document, or design basis report, consider the following checklist.

1. Identify the Project Type

• Highway and bridge projects: Use IRC:137-2022.
• Building projects: Use ACI 440.1R-15 and document the design methodology.

2. Specify Compliance with IS 18256:2023

Include requirements for:

• Tensile strength
• Modulus of elasticity
• Alkali resistance
• Bar dimensions

3. Request Compliance Documentation

Require:

• Mill test reports
• Third-party laboratory certificates
• Batch traceability records

4. Apply the Environmental Reduction Factor

Determine the exposure class and apply the appropriate CE factor before finalizing design strength values.

5. Use IRC Development Length Requirements

Do not use steel reinforcement development length values from IS 456.

6. Verify Serviceability Performance

Check:

• DeflectionCrack width
• Long-term performance criteria

What These Standards Mean for GFRP Adoption in India

The introduction of IS 18256:2023 and IRC:137-2022 removes one of the most significant barriers to the adoption of GFRP rebar in India.

Engineers now have recognized references for:

• Material specification
• Quality verification
• Structural design
• Tender documentation
• Project approvals

For projects exposed to corrosion risks such as coastal infrastructure, marine structures, water treatment plants, wastewater facilities, and chemically aggressive environments, GFRP bars can now be specified using established Indian standards.

The benefits and limitations of FRP are now something engineers can evaluate against a formal standard, rather than relying only on manufacturer data. The challenge is no longer the absence of codes.

The challenge is ensuring that engineers, consultants, contractors, and project owners are aware that these standards exist and understand how to apply them correctly.

Need IS 18256:2023 Compliant GFRP Rebars?

Tapashri supplies IS 18256:2023 compliant GFRP rebars with supporting test documentation, material certifications, and technical assistance for specification and project compliance.

If you're evaluating GFRP reinforcement for bridges, water infrastructure, coastal construction, or other corrosion-prone structures, our team can help you select the appropriate material and documentation for your project requirements.