Fiberglass (GFRP) rebar is used where steel rebar would rust or where its magnetism or conductivity causes trouble: bridge decks and barrier walls, parking garages, seawalls and docks, water and wastewater plants, tunnel soft-eyes, and rooms around MRI and electrical equipment. In houses and light commercial work it shows up in driveways, exterior slabs, foundations and ICF walls where owners want concrete that will never stain or spall from rusting steel.
The common thread is that GFRP solves a specific problem steel has. This post walks through the main applications, why GFRP is chosen in each one, and the jobs where steel is still the better pick. For the basics of the material itself, see what GFRP rebar is.
Why engineers choose GFRP
Almost every GFRP application traces back to one of four properties:
| Property | What it solves |
|---|---|
| Does not corrode | Salt, seawater and chemicals that destroy steel rebar and spall the concrete |
| Non-magnetic | Interference with sensitive equipment and magnetic fields |
| Non-conductive | Stray currents, induced heating and electrical interference |
| Easily cut by machines | Concrete that must later be cut through, such as tunnel launch walls |
Lighter weight helps handling, but it is rarely the reason GFRP gets specified. The trade-offs, including lower stiffness and factory-only bends, are covered in our post on GFRP pros and cons.
Bridges and highway structures
This is where GFRP use in Canada is most established. De-icing salt is the main enemy of Ontario bridges: chlorides work through the concrete, reach the steel and start corrosion that cracks and spalls decks and barrier walls.
GFRP is used in the elements most exposed to salt:
- Deck top mats, which take salt directly from traffic.
- Barrier walls and parapets, splashed by salty spray from passing vehicles.
The Ministry of Transportation of Ontario lists Grade III GFRP among its premium reinforcement options for these elements, and has its own material and construction specifications for it. Our post on CSA S807, S806 and MTO rules covers what MTO requires.
Parking garages, balconies and exposed slabs
Parking structures are bridges with a roof. Cars carry salty slush in all winter and leave it on the slab, so the same chloride attack happens indoors. GFRP is used in parking decks, ramps and slabs on grade in parking areas to avoid the cycle of corrosion, spalling and repair.
Balconies and other exposed slabs face a similar problem from salt and freeze-thaw. Our post on GFRP for slabs and driveways covers how it is used in flatwork.
Marine and waterfront work
Seawater is one of the harshest environments for steel in concrete. Wharves, seawalls, breakwaters and docks are common GFRP applications. Manufacturers point to the fact that GFRP can resist chloride attack without the cathodic protection or extra concrete cover that steel would need in the same exposure.
Water and wastewater treatment
Treatment plants expose concrete to chlorine, chloramines and, in wastewater, hydrogen sulphide, which forms acids that attack concrete and the steel inside it. GFRP is used in tanks, channels and other plant structures where steel corrosion would shorten the structure's life. The concrete itself still needs a mix designed for the exposure; GFRP takes the corroding steel out of the equation, not the chemistry.
Tunnels: soft-eyes and launch shafts
This is one application where GFRP's weakness becomes a strength. When a tunnel boring machine starts or finishes a drive, it has to cut through the concrete wall of the launch or reception shaft. A section of that wall reinforced with steel would have to be broken out by hand first. A section reinforced with GFRP, called a soft-eye, can be cut by the machine directly because the glass bars are much easier to cut through than steel.
GFRP is also used in diaphragm walls and other temporary or permanent tunnel structures for the same reason.
MRI rooms, substations and electrical facilities
Steel is magnetic and conducts electricity. Around equipment that depends on stable magnetic fields or clean signals, that is a problem. GFRP is used in:
- Hospital MRI rooms and other imaging suites, where steel near the magnet can affect the equipment.
- Electrical substations, where non-magnetic, non-conductive reinforcement avoids electromagnetic interference.
- Toll booths, where embedded steel can degrade the signals of detection and payment equipment.
- Aluminium smelter potrooms, where the huge electrical currents in the process can induce heating in steel reinforcement.
In these jobs, the equipment supplier's requirements usually drive the decision, and the specification will often call for non-metallic ties and supports as well.
Homes and light commercial work
GFRP has moved into residential work, mostly where an owner wants concrete that will never rust:
- Driveways, walkways, garage floors and patios exposed to road salt.
- Foundations and footings. See our post on fiberglass rebar in footings and foundations.
- ICF walls. See GFRP in ICF walls.
- Pool decks and other wet exterior slabs.
There is one important caution. Part 9 of the Ontario Building Code is written around steel reinforcement. Where the code requires rebar, substituting GFRP generally means having an engineer design it rather than relying on the prescriptive tables. Where rebar is optional, such as crack control in many slabs on grade, the choice is more open, but the bar still has to be the right grade and properly supported. Our post on types of fiberglass rebar explains why one GFRP product is not the same as another.
Where steel is still the better choice
GFRP is not a general upgrade. Steel usually wins when:
- The concrete stays dry and indoors. Interior slabs, columns and beams with no salt exposure rarely see corrosion problems with proper cover.
- Bars need changes on site. GFRP cannot be bent once made, so every hook and corner has to be ordered from the factory. Jobs with frequent field changes are easier in steel. See GFRP corners, L-bars and hooks.
- The design depends on steel behaviour. GFRP is less stiff and does not yield, so the design method is different and, for some elements, steel is the simpler and more economical route.
- There is no engineer involved and the work relies on prescriptive Part 9 steel requirements.
Our GFRP vs steel comparison lays out the trade-offs side by side.
Questions to settle before switching to GFRP
If you are weighing GFRP for a job, a few questions sort out most of the decision before anyone prices it:
- What is attacking the concrete? Salt, seawater, chemicals, or nothing in particular. If nothing, steel is usually the answer.
- Does the code require the reinforcement? If so, plan on an engineer designing the GFRP rather than swapping bars one for one.
- Which grade and durability class does the owner or authority require? Bridge and municipal work often has its own specification.
- Can every bend be fixed before ordering? GFRP shapes are made at the factory, so the bar list has to be final.
- Are the ties and supports compatible? Many GFRP specifications call for coated or non-metallic ties and supports. Our post on installing and tying fiberglass rebar covers site handling.
Getting GFRP for your project
Whether your drawings already call for GFRP or you want to compare it with steel for a salt-exposed slab, send them through our quote request form. We supply GFRP rebar alongside steel bar from 10M to 55M, prepare free take-offs and quotes, and deliver across the GTA and Ontario. See our rebar products for the full range.
Frequently asked questions
What is fiberglass rebar used for?
Fiberglass (GFRP) rebar is used where steel would corrode or where its magnetism or conductivity is a problem: bridge decks and barrier walls, parking structures, seawalls and docks, water and wastewater plants, tunnel soft-eyes, MRI rooms and electrical facilities. It is also used in driveways, slabs and foundations where owners want rust-free concrete.
When should you use fiberglass rebar instead of steel?
When corrosion from road salt, seawater or chemicals is the main threat to the structure's life, when the concrete must be non-magnetic or non-conductive, or when the concrete will later be cut through by machinery. For dry interior concrete, steel is usually simpler.
Can fiberglass rebar be used in a house?
Yes, in driveways, exterior slabs, garage floors, foundations and ICF walls, but Part 9 of the Ontario Building Code is written around steel, so using GFRP in place of required reinforcement generally needs an engineer's design. Where the rebar is not required by code, the choice is more open.
Why is fiberglass rebar used in MRI rooms?
GFRP is non-magnetic and does not conduct electricity, so it does not interfere with the magnetic fields and signals of imaging equipment the way steel can. The same properties make it useful around electrical substations and toll booths.
