Abstract

Corrosion of steel in reinforced concrete bridges is a major concern for the structural integrity, long-term durability, and maintenance of the highway infrastructure. The corrosion mechanisms vary greatly due to the multitude of engineered highway systems with the varying exposure environments, chemistry, and construction materials. Of the many engineering systems in the highway infrastructure, corrosion of reinforcing steel in bridge substructures has been critical. It is therefore highly advantageous to evaluate the performances of implemented corrosion control measures. Five bridges in Florida utilizing various corrosion mitigation strategies were revisited in 2021 to provide a prospective of their corrosion durability after several decades of service. The assessment compared plain to epoxy coated rebar, use of fly ash, and the use of concrete coatings. The presence of flyash in concrete mix designs allow for slower chloride diffusion rates. The presence of concrete surface coatings can allow lower chloride surface concentrations to develop. Bridge service life assessment should not account for chloride ion diffusivity alone as it was shown that elevated initial chloride concentrations can facilitate corrosion conditions. The barrier provided by epoxy-coated rebar can extend the time to initial concrete degradation caused by corrosion, but corrosion can still develop on the coated reinforcing steel.

Introduction

Corrosion of steel in reinforced concrete bridges is a major concern for the structural integrity, long-term durability, and maintenance of the highway infrastructure. Statistics from a national study in 2002 indicated that approximately 15% of the national bridge inventory is structurally deficient because of corrosion and the national annual direct cost exceeded $8 billion.1 In the state of Florida, the typical design life expectation for the >6,000 bridges in the state highway infrastructure exceed 75 years. However, approximately half of the bridges are in aggressive marine service where corrosion can be pervasive. The corrosion mechanisms vary greatly due to the multitude of engineered highway systems with the varying exposure environments, chemistry, and construction materials. Even though much research and recommendations have been made by the state transportation departments and technical organizations such as NACE and ACI 2-3 to promote corrosion durability of highway bridge infrastructures, history and current maintenance needs remind owners of the need to continue to improve designs to control corrosion and to develop tools to assess future performance and maintenance needs.

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