TMT vs FGC Rebars: Are Composite Reinforcements the Future of Construction?

Introduction: Is It Time to Rethink Steel?

Steel rebars have been the backbone of reinforced concrete construction for decades. But in environments where moisture, salt, or chemicals speed up corrosion, traditional steel may not be the best long-term choice. In recent years, a new contender has emerged—Fiberglass Composite rebars, also known as GFRP rebars or FGC rebars.

So how do these two materials compare? What are the practical differences in strength, cost, performance, and application? And most importantly, should you consider switching to FGC rebars for your next project?

Let’s break down the facts.

 

What Are TMT and FGC Rebars?

TMT rebars (Thermo-Mechanically Treated) are high-strength steel bars created through a precise process involving heating, quenching, and controlled cooling. The result is a material with a tough, corrosion-resistant outer layer and a soft, ductile core. TMT rebars are the standard in residential buildings, high-rises, bridges, and critical infrastructure.

FGC rebars (Fiberglass Composite Rebars), also called GFRP rebars, are non-metallic reinforcement bars made from glass fibers embedded in a polymer resin. They do not rust, are significantly lighter than steel, and are non-conductive. These properties make them highly suitable for coastal and chemically aggressive environments, as well as structures that demand electrical neutrality—like MRI rooms or substations.

 

Which Rebar Is Stronger—TMT or FGC?

In terms of tensile strength, FGC rebars often outperform steel. While standard TMT rebars typically offer tensile strength around 500 to 600 MPa, FGC rebars can reach 800 to 1000 MPa depending on the grade and manufacturer.

However, strength alone doesn't tell the whole story.

Steel rebars have a much higher modulus of elasticity—approximately 200 GPa, compared to 50 GPa for FGC rebars. This means steel is four times stiffer, providing less deflection under load. In contrast, FGC rebars, although strong, are more flexible and deform more under stress. This requires structural designers to make careful adjustments to account for deflection and anchorage.

 

How Long Do FGC Rebars Last Compared to TMT Steel?

TMT rebars, especially when not properly coated or protected, are susceptible to corrosion in humid or marine environments. Over time, this corrosion leads to rusting, spalling of concrete, and a decrease in load-carrying capacity.

FGC rebars, on the other hand, are completely non-corrosive. They do not rust, react with salts or chemicals, and are resistant to moisture intrusion. Their design life can exceed 50 to 100 years in harsh environments with minimal maintenance—offering a significant advantage in marine and coastal infrastructure.

Read On: Bamboo Reinforcement Bars

How Do FGC Rebars Perform in Fire?

While TMT rebars can withstand high temperatures, making them suitable for fire-prone structures, FGC rebars are more vulnerable under extreme heat. At elevated temperatures, the polymer resin that holds the glass fibers can begin to degrade unless the bars are properly encased or shielded.

Therefore, FGC rebars are not recommended for structures where fire resistance is a critical requirement, unless adequate fireproofing measures are integrated into the design.

 

Weight and Workability: Which Is Easier to Handle?

Steel rebars are heavy, often requiring cranes, hoists, or large labor forces for installation—especially in high-rise or large infrastructure projects.

FGC rebars, by contrast, are about 75 percent lighter than steel. This reduces transportation costs and simplifies on-site handling. They can be easily cut using handheld tools, bent to a degree with pre-molded shapes, and manually lifted into place without the need for heavy machinery. This ease of handling makes them particularly valuable in remote or prefab construction.

 

What Is the Cost Difference Between TMT and FGC Rebars?

Cost remains a key factor in material selection.

• TMT steel rebars generally cost around $500 to $700 per metric ton (₹45,000 to ₹60,000 in India).
• FGC rebars, being composite-based and produced at lower volumes, range between $1,400 to $2,200 per ton (₹1.2 to ₹1.8 lakh per ton).

Although FGC rebars involve a higher upfront investment, they often lead to substantial lifecycle cost savings—especially in projects with high maintenance risks due to corrosion. In corrosive environments, they may completely eliminate the need for rust protection systems, repairs, or concrete patching, justifying the higher initial spend.

 

Are FGC Rebars Approved by Building Codes?

TMT rebars are universally accepted under nearly all national and regional codes, including IS, ASTM, Eurocode, and others.

FGC rebars, however, are still gaining code recognition across the globe. While countries like the United States and Canada have developed specific design guidelines for GFRP rebars (e.g., ACI 440.1R), many regional authorities have yet to formally integrate them into mainstream building codes.

Engineers interested in using FGC rebars should consult local regulatory bodies or follow international guidelines where domestic standards are absent.

 

Where Should Each Type Be Used?

TMT Steel Rebars Are Best For:

• Standard buildings and residential construction
• Fire-prone or earthquake-prone zones
• Projects where ductility and seismic energy absorption are critical
• Structures governed by conventional building codes

FGC Rebars Are Ideal For:

• Marine and offshore structures
• Bridges in saltwater regions
• Foundations in chemically aggressive or acidic soils
• Electrical-sensitive zones like hospitals, substations, and laboratories

Many engineers are now adopting hybrid reinforcement systems, using steel for load-critical elements and FGC rebars for exterior zones, balconies, or underground elements prone to corrosion.

 

What Are the Main Disadvantages of Each Material?

TMT Steel Rebars:

• Can corrode over time without proper coating
• Heavier to handle and transport
• Susceptible to degradation in submerged or highly humid environments

FGC Rebars:

• Lower stiffness requires careful design consideration
• Poor performance in fire unless protected
• Limited approval in some regions
• Brittle failure characteristics without ductile yielding

 

Should You Switch to Composite Rebars?

The answer depends on your project goals and environment.

 
If your structure demands fire resistance, cost efficiency, and ductility, TMT rebars remain the practical choice.

 
But if your project is exposed to corrosive elements, demands low long-term maintenance, and requires non-magnetic or electrically neutral materials, FGC rebars may be the better investment—even at a higher initial cost.

As materials evolve, hybrid reinforcement strategies are becoming more common, blending the strengths of both technologies for safer, longer-lasting, and more efficient structures.

Read More: Types of Rebars for Concrete