Cutting, Bending and Placing GFRP Rebar: Site Rules

For bar sizes, surface types and the purchase scope, start with GFRP rebar and fiberglass reinforcing bars

How to cut fiberglass rebar

Cut with a blade, not a shear. The South Carolina DOT specification allows field cutting only with a high speed cutter, fine blade saw, diamond blade or masonry saw, and prohibits shearing and flame cutting. Bolt cutters and rebar shears crush the end and splinter the fibers, and the damage runs back along the bar beyond what you can see. A diamond blade on a circular saw or angle grinder leaves a clean square end. The DOT specification also makes field cutting conditional on the engineer's permission, so order bars to length where the drawings allow it and treat site cutting as the exception.

• Wear eye protection, gloves, long sleeves and a dust mask or respirator; the dust is glass and cured resin.
• Clamp the bar and cut square. Do not snap a partly cut bar.
• Lightly sand rough ends if needed. Some project specifications require cut ends to be sealed; follow the manufacturer's recommendation for the sealant.
• Replace bars that are cracked, crushed or badly splintered at the cut.

Why you cannot bend fiberglass rebar on site

Field bending of GFRP reinforcement is not allowed, in the words of the DOT specification, and the same prohibition appears in ACI SPEC-440.5-22. A cured GFRP bar is a bundle of continuous glass fibers locked in a thermoset resin. Bending it after cure breaks fibers on the outside of the bend and buckles them on the inside, usually without visible damage, and the bar loses tensile strength where the design needs it most. Heating does not help, because the resin does not soften like steel; it degrades. Hammering, kinking or forcing a bar into position is damage, not fabrication.

Bends are made in the factory before the resin cures. The DOT specification states that if the plans require bent GFRP reinforcement, the bends shall be incorporated during bar manufacturing. ASTM D7957 covers bent shapes and sets minimum inside bend diameters for each bar size, so a factory bend is a specified product with its own test record, not a site improvisation.

How corners, hooks and stirrups are supplied

Because the bar cannot be bent after delivery, every change of direction is ordered as a shape. A slab or footing corner is an L bar or a bent corner bar lapped to the straight bars on each leg. A column or beam cage uses closed or open stirrups formed in the factory. Hooks and standard 90 degree bends are listed by bar size, leg length and inside bend diameter on a bending schedule, exactly as for steel, except that the schedule goes to the manufacturer with the order rather than to a site bending crew. The lap lengths that connect a corner bar to the straight bars come from the design, not from the manufacturer, and the DOT specification requires lapped splices to be made by placing the bars in contact and tying them, without mechanical couplers.

Ties, chairs and spacing

The DOT specification requires ties at all intersections, or at alternate intersections where the spacing is 12 inches or less in each direction, using self-locking plastic straps or soft annealed wire coated with nylon, epoxy or plastic. Plain steel tie wire is avoided because it reintroduces a corroding metal into a system chosen to have none. Supports are plastic bar supports. GFRP is lighter and more flexible than steel of the same size, so chairs need to be closer together to stop the mat bowing, with extra supports at laps, edges, openings and wherever crews walk. Ties should be snug but not tight enough to cut the surface. During the pour, keep a worker watching the mat: pump hoses and foot traffic move light bars more easily than steel.

Storage, handling and damage limits

• Store at least 12 inches above the ground on wood or other soft supports, bundles in a single layer, each bundle clear of the next.
• Cover with opaque plastic or similar to keep ultraviolet light off the bars.
• Do not expose bars to temperatures above 120 °F (49 °C) in storage.
• Lift bundles on multiple supports or a spreader bar; do not drop or drag them. Use non-metallic or padded straps.
• Repair cuts, scratches and abrasions per the manufacturer's method and have the repair accepted before placing. Do not use a bar with damage over 2 percent of its surface area, including repaired areas.
• Keep the surface clean: mud, oil and form release reduce bond to the concrete.

What pultrx supplies

pultrx exports GFRP rebar from the Henan Zhongsheng factory in straight cut lengths and in factory-formed shapes against a bending schedule. The quotation states the surface type, the standard the lot will be certified against, the test values provided with each lot, and the inside bend diameters available by bar size. Ties, chairs and sealant are quoted separately when requested. Site rules in this guide are quoted from public specifications for information; the project specification and the engineer of record govern on site.