History of Epoxy-Coated Steel Reinforcing Bar
For most of the 1900s corrosion of bridge decks was not considered a significant concern. Properly designed and constructed bridges rarely experienced corrosion-related distress. This changed dramatically in the 1950s when highway agencies began applying deicing salts to highways and bridges to keep roadways free of snow and ice. This “bare pavement” policy made roadways safer for the traveling public but resulted in a dramatic increase in deterioration due to corrosion on highways and bridges from chloride penetration. Between 1950 and 1979 annual usage of deicing salts in the United States rose from 1 million tons per year to more 12 million tons per year.
According to the Federal Highway Administration (FHWA), the cost of repairing or replacing structures deteriorated by corrosion is estimated to be more than $20 billion, and is said to be increasing at a rate of $500 million per year. In 1979 the General Accounting Office (GAO) noted that 32 states had more than 160,000 federal-aid system bridges that had moderate to very major corrosion problems.
In response the National Bureau of Standards (now the National Institute for Standards & Technology) initiated tests on various liquid and powdered coatings. These coatings were examined for their corrosion protective qualities, chemical and physical durability, and chloride permeability. Based on the testing, fusion-bonded epoxy coating applied to reinforcing steel was proposed as a way to improve the corrosion resistance of bridge decks.
Epoxy-coated reinforcing steel was first used in a bridge in West Conshohocken, Pennsylvania in 1973. Four spans of this bridge were constructed with epoxy coated steel reinforcing bars (rebar). It was reported in 1987 that at least 41 state transportation departments were using epoxy-coated reinforcing steel as the corrosion-protection system in their concrete decks. Every year over 600,000 ton of epoxy coated rebar is produced in the US and Canada and in 2013, over 80,000 bridges and numerous buildings, wharfs and other structures contain epoxy-coated steel reinforcing bars (rebar).