Among the most promising methods of combating steel rebar corrosion in concrete parking decks, bridge decks and other areas is the use of fusion-bonded epoxy-coated rebars in new construction and in repair. The chief danger to uncoated steel bars in northern and coastal states is from corrosion that occurs after calcium chloride or sodium chloride seeps into the concrete. The sources of these chlorides are deicers or seawater spray. Many concrete parking ramps and bridge decks constructed as recently as 5 to 10 years ago are deteriorating to the point where major repair or replacement is already necessary. The problem results in millions of dollars worth of damage each year.
The use of a fusion-bonded epoxy coating on rebars is considered by many engineers to be among the most effective techniques for combating corrosion though it has been in use for only a few years. A parking deck constructed in Minnesota consists of a structural steel deck and a ground-level slab within an area that measures approximately 215 by 240 feet. The cast-in-place upper deck, supported by steel framing, is divided into quarters with good slope for drainage. A low-slump mix was used with a high cement content (588 pounds per cubic yard). Special care was taken in selecting the aggregate. This mix contained 6 to 8 percent air, and a retarder was used to delay set over steel beams to eliminate minor cracking. The concrete was placed by pump. After curing, a minimum of two coats of sealer was applied. Central to the design was the use of rebars with a fusion-bonded epoxy coating. The 6-inch-thick composite deck slab allowed use of 2 inches of concrete cover over both top and bottom bars, compared with the 3/4 inch of cover often used on earlier parking decks.
The cost differential for the epoxy coating would be approximately 3.6 percent of the total cost, whereas conservative estimates of replacement costs are many times the estimated cost of using the coated rebars initially.