Glass Fiber Reinforcing Bars Being Evaluated by KDOT

Reinforcing steel corrosion is one of the main enemies of bridge decks. When steel corrodes, or rusts, it expands to many times its original volume, cracking the concrete around it and creating a vulnerable point of entry for salt-laden runoff water to access

Exposed Rebar

the steel. This accelerates the corrosion process and ultimately leads to weakening of the bridge deck, potholes, undesirable patches, lane closures and more.

In their continuing effort to mitigate bridge deck cracking, KDOT has partnered with GBA to evaluate a new way to reinforce bridge decks: glass fiber reinforced polymer rebar (GFRP).

Being an inert non-corrosive material, the GFRP is not expected to react to de-icing salts that typically corrode reinforcing steel. To test this, GBA designed twin bridge decks — one with GFRP and one with standard epoxy-coated reinforcing steel rebar.

Glass Fiber Reinforcing Bars

The bridges are on I-635 over State Avenue in Kansas City, Kansas. Both the north bound and south bound bridges will be completely re-decked within the next two years. The south bound bridge will get GFRP, while the northbound bridge will be reinforced conventionally.

As the bridge decks age and are subjected to truck loading and corrosive runoff water, KDOT will be able to draw conclusions about the long-term durability of the GFRP. In addition to the deck replacement, plans were also provided for girder strengthening, approach slab replacement, and detailed traffic management. 

While the initial construction bid increased approximately one percent due to the GFRP, it is anticipated the life cycle cost of the project will more than gain that amount back due to reduced maintenance costs.