Corrosion — The Enemy Within

This article describes how the corrosion of reinforcing steel in concrete bridges degrades bridge decks and other superstructure elements, in addition to substructures, by causing embedded steel to expand, which causes cracks in concrete, leads to rough riding surfaces at best, and structural failure at worst. Fortunately, many tools exist in the bridge owner’s “toolbox” of fixes to slow or halt corrosion in its tracks. Corrosion prevention can be built into a bridge or applied retroactively. Pavement deicing techniques and materials also can moderate chloride-induced corrosion. Research continues to produce new options for the owner and designer to consider. Here’s a look at some of those changes and options. Bridge corrosion results from the reaction between the steel and its environment. Steel is refined from iron ore, but the moment it is produced it begins to corrode, primarily to oxide compounds, on its way to a less-refined state. Steel bridges can also suffer greatly from corrosion, and they usually are well protected by a variety of high-performance bridge coatings. But in recent decades, the proliferation of steel-reinforced concrete bridges, constructed of pre-stressed or post-tensioned elements including girders, piers, pier caps and decks has focused a tremendous amount of attention on preventing corrosion of steel within concrete.