GFRP rebar is reinforcing bar made from continuous glass fibres held together in a polymer resin, used in concrete in place of steel. GFRP stands for glass fibre reinforced polymer; on site it is usually just called fiberglass rebar. It does not rust, it is much lighter than steel and it does not conduct electricity, but it is less stiff, it does not yield, and it cannot be bent on site. In Canada the bar is made to CSA S807 and designed with CSA S806 or, for bridges, CSA S6.
What GFRP stands for, and what else it is called
The letters break down simply:
- G: glass. The reinforcing fibres are glass, the same basic material as in fibreglass boats and insulation, but made into long continuous strands.
- F and R: fibre reinforced. The fibres carry the tensile load.
- P: polymer. A resin, usually vinylester or epoxy for construction bar, binds the fibres together and protects them.
You will see the same product called fiberglass rebar, glass FRP, composite rebar or GFRP bar. They all mean the same thing.
FRP is the wider family. CSA S807, the Canadian material standard, covers bars made with glass, carbon, aramid or basalt fibres. Basalt bars (BFRP) and carbon bars (CFRP) exist, but glass is by far the most common in construction, and some owners accept glass only. MTO, for example, accepts glass fibre GFRP on its bridge work but not basalt.
GFRP is not fibre-reinforced concrete. Fibre-reinforced concrete has short chopped fibres (steel, synthetic or glass) mixed into the concrete itself. GFRP rebar is a continuous bar placed in the form like steel rebar. The two do very different jobs; our post on whether fibre concrete replaces rebar explains the difference.
How GFRP rebar is made
Straight GFRP bars are made by pultrusion. Bundles of continuous glass fibres are pulled through a resin bath and then through a heated die that shapes and cures the bar. The bar comes out as a continuous length and is cut to size at the plant.
The surface is finished to bond with concrete. Depending on the manufacturer, that can be a sand coating, a helical wrap, moulded ribs or a combination. The appearance and colour vary from brand to brand, so GFRP from two suppliers can look quite different.
Bent shapes are made at the factory. Because the resin cures into a rigid plastic, a GFRP bar cannot be re-bent once it has set. Corners, L-bars, hooks and stirrups are formed and cured as bent shapes at the plant. That is the single biggest practical difference for anyone ordering it: your bar list has to be right before production. Our posts on GFRP corners, L-bars and hooks and whether you can bend fiberglass rebar go into the details.
How GFRP behaves compared with steel
GFRP is not a stronger or weaker version of steel; it is a different material with a different set of properties.
| Property | GFRP rebar | Steel rebar |
|---|---|---|
| Corrosion | Does not rust | Rusts when chlorides or carbonation reach it |
| Weight | Roughly a quarter to a third of steel for a similar size | 1.570 kg/m for 15M |
| Tensile strength | High, guaranteed values set by grade and size | 400 MPa minimum yield for 400W |
| Stiffness | Much lower (Grade III at least 60 GPa) | About 200 GPa |
| Failure | Stays elastic until it ruptures | Yields and stretches first |
| Electrical and magnetic | Non-conductive, non-magnetic | Conductive and magnetic |
| Bending | Factory bends only | Shop or field bending |
| Heat | Resin softens at relatively low temperatures | Loses strength gradually |
The headline that GFRP is "stronger than steel" compares its ultimate tensile strength with steel's yield strength. In real designs the lower stiffness usually governs: GFRP stretches more under load, so cracks are wider and deflections larger for the same amount of bar. Designers compensate with more bar, closer spacing or deeper sections. Our GFRP vs steel comparison and the post asking is fiberglass rebar stronger than steel cover the numbers.
The Canadian standards behind GFRP
Three CSA standards matter, and they do different jobs:
- CSA S807 is the material specification. It sets the properties, manufacturing and testing requirements for FRP bars and classifies them by fibre type, by grade (based on modulus of elasticity, with Grade III the stiffest) and by durability class.
- CSA S806 covers the design of building structures with FRP.
- CSA S6, the Canadian Highway Bridge Design Code, has a section on fibre-reinforced structures for bridges.
The 2024 Ontario Building Code does not reference S806 or S807, and the prescriptive rebar rules in Part 9 assume steel bar to CSA G30.18. So in a building, GFRP is normally used through an engineer's design submitted as an alternative solution. A bar that meets S807 is not by itself a code-compliant structure; the structure also has to be designed for FRP. Our post on whether fiberglass rebar meets code explains how this works in Ontario, including MTO's requirements on provincial bridges.
Where GFRP rebar is used in Canada
GFRP earns its place where corrosion or electrical and magnetic neutrality matter more than anything else:
- Bridges and highway structures, especially deck top mats and barrier walls exposed to de-icing salt. MTO lists Grade III GFRP among its premium reinforcement options for these elements.
- Parking structures and ramps, where salt brought in by vehicles attacks steel.
- Marine and waterfront work, such as seawalls and docks.
- Facilities that need non-magnetic or non-conductive reinforcement, such as rooms around sensitive electrical or imaging equipment.
- Residential and light commercial work where an owner wants to avoid rust: driveways, exterior slabs, foundations and ICF walls. Here the engineering and code route matters, because Part 9 assumes steel. See our posts on GFRP for slabs and driveways, GFRP in footings and foundations and GFRP in ICF walls.
For ordinary interior concrete that stays dry, steel is usually simpler and the default. Our post on GFRP pros and cons weighs where the switch is worth it.
Sizes, weights and ordering
GFRP is identified in CSA S807 by a designated diameter and a nominal area, not by the M sizes used for steel. Some suppliers still label GFRP bars "10M" or "15M", but those labels do not guarantee the same area as steel bar of the same name. Order GFRP by the size, area and grade shown on the drawings, and check the supplier's datasheet. Our GFRP sizes and weights post covers the common sizes.
When ordering, expect to provide:
- The grade (for example, Grade III) and any durability class or resin requirement in the specification.
- A complete bar list, with every bent shape detailed, since nothing can be bent on site.
- Accessories that suit the bar, such as coated, stainless or plastic ties and non-metallic chairs where the specification requires them.
Lead times for bent shapes are usually longer than for steel, because they are made to order. Our guide to buying GFRP rebar in Ontario covers specifications, lengths and lead times.
Getting GFRP for your project
We supply GFRP rebar alongside steel bar, so a job that uses fiberglass in the exposed elements and steel everywhere else can come from one bar list. If your engineer has specified GFRP, or you want the two options priced side by side, send us your drawings for a free take-off and quote. You can see what we supply on our rebar products page.
Frequently asked questions
What does GFRP rebar stand for?
GFRP stands for glass fibre reinforced polymer (glass fiber reinforced polymer in US spelling). It is a reinforcing bar made of continuous glass fibres bound in a resin, used in concrete in place of steel bar.
Is GFRP rebar the same as fiberglass rebar?
Yes. Fiberglass rebar, GFRP bar and glass FRP rebar all mean the same product. FRP is the wider family, which also includes bars made with basalt, carbon or aramid fibres.
Does GFRP rebar rust?
No. GFRP contains no steel, so it does not rust and is not attacked by chlorides from road salt or seawater the way steel is. That corrosion resistance is the main reason it is specified.
Is GFRP rebar allowed under the Ontario Building Code?
The 2024 OBC does not reference the Canadian FRP standards, and its prescriptive Part 9 rules assume steel bar. In buildings, GFRP is normally used through an engineer's design to CSA S806, accepted by the building department as an alternative solution.
Can GFRP rebar be bent on site?
No. GFRP bends are made at the factory before the resin cures. Once cured, the bar cannot be re-bent, so corners, hooks and stirrups have to be ordered as bent shapes.
