Investigation into the Bond of Glass Fiber–Reinforced Polymer Stay-in-Place Structural Forms to Concrete for Decking Applications

Glass fiber–reinforced polymer (GFRP) pultruded sections have great potential as structural stay-in-place forms for bridge components, including deck slabs. The bond behavior between cast-in-place concrete and GFRP forms, a key consideration in this type of structure, was studied. Eight concrete slabs cast on GFRP plates were fabricated and tested in bending to investigate and compare various bond systems and GFRP reinforcement ratios. No steel reinforcement was used. Bond systems included adhesively bonded freshly cast concrete on the plate, coarse aggregates bonded to the plate before concrete casting, and GFRP and steel mechanical shear connectors. Adhesive bonding to fresh concrete was the most efficient method. Generally, this method resulted in higher flexural stiffness than mechanically connected systems because no slip occurred in the former, whereas progressive slip occurred in the latter from the onset of concrete cracking. Bond failure eventually occurred within a thin layer of cement mortar that remained adhered to the plate. The hybrid slabs were equivalent in strength and stiffness to conventional steel-reinforced slabs of high reinforcement ratios. In addition, the hybrids had the advantage of simple and quick constructability as well as not being hindered by the limitations of concrete cover or rebar spacing. A general analytical model was developed to predict the full behavior and strength of the slabs and was successfully validated. The model can detect various failure modes, including GFRP plate debonding.