Case Study: Hot-dip galvanized rebar: A major component in the new Gov. Mario M. Cuomo Bridge

Until 2017 the Tappan Zee Bridge was a vital crossing of the Hudson River, located just north of New York City and considered integral to the major metropolitan area. At the time it was built in 1955, bridges were estimated to last 50 years. By the 2000s the aging bridge was deteriorating and deemed past its expiration date. 

As the owner of the bridge, the New York State Thruway Authority (NYSTA) started constructing a replacement in 2013 with the goal of creating a 100-year, seismically resilient bridge featuring forward-thinking technology and materials that would enable them to maintain the bridge with minimally invasive techniques. The new bridge, named the Gov. Mario M. Cuomo Bridge, utilized hot-dip galvanized (HDG) A767 Class 1 rebar.

Considered state of the art by many, the bridge attracted considerable national attention during construction. The massive I Lift NY Super Crane, which can lift the equivalent of 12 Statues of Liberty at once, was the star of the show. Meanwhile, the bridge’s backbone, HDG rebar, was hiding under the surface— literally. Approximately every 6 inches of the bridge contains hot-dip galvanized rebar, which NYSTA has used in bridge projects requiring concrete since 1995.

“The major cause of deterioration of any reinforced concrete is when water, especially salt-laden water, gets into the concrete and starts to deteriorate the bar and it deteriorates the concrete,” said Paul Provost, now-retired bridge inspector and senior structural engineer for the NYSTA with more than 30 years of experience. “With galvanized rebar, that is not the case.” 

“So far [on any bridge utilizing HDG rebar since 1995], NYSTA, generally speaking, hasn’t had to do any maintenance related to those items or the galvanized rebar,” said Provost. “The galvanized coating is mechanical so it bonds to the rebar. It’s more durable. Zinc is a metal that doesn’t expand when it deteriorates. The goal is to eliminate maintenance in the future or reduce it as much as we can and to put work out there that is going to last as long as possible.”