What is a Fiber-Reinforced Polymer (FRP)?

Definition

A fiber-reinforced polymer (FRP) is a composite material that holds strong fibers in a polymer resin. The fibers give strength and stiffness. The resin binds the fibers together. Glass, carbon, aramid and basalt are common fibers. Epoxy, vinyl ester and polyester are common resins.

FRP in concrete

FRP reinforcement is an alternative to reinforcing steel in concrete structures where steel corrodes. FHWA lists these properties of FRP reinforcement:

• Advantages: high longitudinal strength, no corrosion, nonmagnetic, high fatigue endurance, and low thermal and electric conductivity. The density is about one-fifth to one-fourth that of steel.
• Disadvantages: high cost, no yielding before brittle rupture, low transverse strength, and low modulus of elasticity. Ultraviolet radiation can damage it. Fire damage depends on the resin and the concrete cover.

An FHWA study modeled continuously reinforced concrete pavement. It used a modulus of 40 GPa for glass FRP (GFRP) rebar and 200 GPa for steel rebar. These are model inputs, not standard values. The study found lower concrete stress with GFRP rebar because of its lower modulus.

FRP is also bonded to the surface of an existing concrete member as supplemental reinforcement. ACI 440.2R-17 is the ACI guide for these systems. ACI 440.1R-15 is the ACI guide for FRP bars in new concrete.

FRP on airfields

FAA AC 150/5300-13B says not to use magnetic materials, such as reinforcing steel, in a compass calibration pad. It allows non-metallic dowels, for example fiberglass. It does not name FRP rebar. AC 150/5370-10H lists fiberglass pipe, made of glass-fiber reinforced thermosetting resin, in its specification for storm drain and culvert pipe.