FRP rebar installation follows a similar process to steel rebar placement but requires specific handling practices due to differences in material properties. GFRP bars are lighter, cannot be bent on site after manufacturing, and require non-metallic tie wire or plastic clips for assembly. Following the correct installation procedure ensures the reinforcement performs as designed throughout the structure's service life.
This guide covers the complete process - from cutting and handling on site to tying, placing, and concreting over GFRP bars.
Before installation, ensure the following are available on site:
Before cutting any bars, confirm the following from the structural engineer's drawing:
GFRP bars cannot be bent on site. If a bent bar is required - for hooks, stirrups, or cranked bars - it must be ordered pre-bent from the manufacturer. Attempting to bend GFRP bars on site will damage the fibres and compromise structural performance.
Use an angle grinder with a diamond or abrasive blade, or a circular saw with a diamond blade, to cut GFRP bars to the lengths specified on the drawing. A standard hacksaw can be used for smaller diameters but is slower.
Always cut in a well-ventilated area and wear a dust mask and eye protection. GFRP cutting generates fine glass fibre particles that are an irritant if inhaled or if they contact eyes or skin. Wear long sleeves and gloves when handling cut bars.
After cutting, lightly sand or file the cut end to remove any sharp fibre protrusions before handling.
Place plastic bar chairs on the formwork or blinding concrete at the spacing required to achieve the specified concrete cover. Cover depth for GFRP bars is typically specified at 20-40mm depending on the exposure class and structural element - confirm from the project specification.
Use only plastic or fibreglass bar chairs. Metal chairs can create a corrosion path to the reinforcement and defeat the purpose of using non-metallic GFRP bars.
Place the first layer of bars on the chairs at the spacing marked on the formwork. Tie intersections using plastic tie wire or plastic clips. Do not use standard galvanised or black steel tie wire - it will corrode and can cause surface staining on the finished concrete.
At lap splice locations, overlap bars by the length specified on the structural drawing. GFRP lap lengths are typically longer than equivalent steel laps due to the different bond characteristics of the material - this will be explicitly noted in the structural specification.
Place the second layer of bars perpendicular to the first, on top of the tied bottom layer. Use plastic spacers or bar chairs between layers where the structural drawing specifies a gap between reinforcement layers.
Tie all intersections and check that bar spacing matches the structural drawing before proceeding. Once concrete is poured, corrections cannot be made.
Before ordering concrete, carry out a final check:
GFRP bars are compatible with standard Portland cement concrete mixes. No special mix design is required for most applications. Pour and vibrate concrete as per standard practice - GFRP bars are unaffected by internal vibration when the vibrator is not placed in direct contact with the bars.
Do not use external form vibrators directly against formwork adjacent to GFRP bars without confirming with the structural engineer, as vibration frequency can affect bar position in thin sections.
FRP rebar installation is straightforward when the key differences from steel are understood - no site bending, plastic tying accessories only, and longer lap lengths. Following the structural specification carefully and using the correct tools ensures GFRP bars perform as designed and deliver their full corrosion-free service life benefit.
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