GFRP rebar
Glass fiber reinforced polymer bar used instead of steel where corrosion is the dominant concern. It does not rust and is roughly a quarter the weight of steel.
What does gfrp rebar mean?
GFRP has high tensile strength but much lower stiffness than steel and no yielding behavior, so it fails suddenly rather than deforming first. That means designs using it are not simple substitutions of steel; member behavior and serviceability are calculated differently. It cannot be field bent, so all bends are ordered from the manufacturer.
In practice
It appears in marine structures, salt-heavy bridge decks, and anywhere magnetic transparency matters, such as MRI suite slabs.