Durability of Bridge Deck with FRP Stay-in-Place Structural Forms under Freeze-Thaw Cycles

This study examines the effect of aggressive freeze-thaw (FT) cyclic exposure on strength and integrity of bridge decks built using glass fiber-reinforced polymer (GFRP) stay-in-place (SIP) structural forms that completely replace the bottom rebar layers. The concern has been whether entrapped moisture may cause frost-jacking of the form, negatively impacting deck integrity. Eleven scaled deck specimens were built, each using two flat GFRP plates with T-shape ribs running normal to girders. Both plates spanned the gap between girders and were spliced by overlapping, directly under the load. The study simulated the following surface treatments of the form: no treatment at all, adhesive bond to freshly cast concrete, and coarse aggregates bonded to the forms. Also, unbonded and bonded lap splices of the forms were tested. The decks were subjected to three cracking load cycles before being saturated and subjected to up to 300 FT cycles at $+5$ to $-18°\mathrm{C}$ core temperatures. Freezing was in air while thawing was by water. Some specimens were thawed without being submerged and one specimen had perforated forms for drainage. Specimens of various splice and surface treatments survived the 300 FT cycles. Subsequent testing showed no reduction in ultimate load or stiffness, relative to control specimens, despite the 23% reduction in tensile strength and 11% in modulus of GFRP coupons exposed to the 300 FT cycles. This is because failure of the decks was governed by concrete punching shear. Decks with untreated forms and unbonded splices showed 21% lower capacity than treated and bonded ones, even without any FT exposure, but this lower capacity was still 3.9 times higher than the equivalent design truck service load at this scale.