Investigation of bond in concrete of GFRP and steel hybrid rebar

Fiber reinforced polymer (FRP) rebar is a great alternative to the conventional steel reinforcing bar because of its corrosion-free characteristics and high strength. This study introduces a newly developed hybrid FRP rebar which is composed of a conventional steel rebar inside and glass fiber reinforced polymer (GFRP) on the outer surface. The developed hybrid rebar takes advantage of overcoming the low elastic modulus from their composite action and durability as the outer GFRP surface resists corrosion. In addition, this hybrid GFRP rebar is also cost-effective. This study investigated the bonding characteristics between the newly developed hybrid FRP rebar and concrete. A direct pull-out test was conducted following the KS F 2441 testing method. In the test result, the bond strength and slip relationship were investigated for test variables. The rebar outer diameter was 16 mm, and inside steel rebar diameters were 10 and 13 mm with varying thickness of GFRP.