Corrosion of steel in concrete is a major problem in the U. S. infrastructure. Approximately half of the bridges in the interstate highway system are in need of repair, and a significant cause is the corrosion of the embedded steel due to chloride ingress. A similar problem is found in parking structures throughout the northern regions of the United States due to deicing salts brought in from automobiles.
As of now the only commercial means of arresting corrosion without replacing concrete is the application of cathodic protection. Calcium nitrite has been shown to be an effective corrosion inhibitor when admixed into plastic concrete. In this paper an experiment to impregnate a bridge deck and support column with calcium nitrite is discussed.
Two methods were used to impregnate the concrete with calcium nitrite. The first involved drying a bridge deck by heating it above the boiling point of water, and then slowly cooling to ambient temperature to avoid thermal and drying shrinkage cracking. The deck was then successfully impregnated with liquid calcium nitrite.
The column was impregnated by removing delaminated concrete and drilling holes. A calcium nitrite rich latex modified grout was placed in the drill holes and a calcium nitrite rich latex modified concrete was produced to replace the removed concrete. Nitrite migration into the sound concrete left in place is to be measured over time.
Corrosion rates determined by polarization resistance, and corrosion potentials were measured before the above processes were performed. The steel was definitely corroding in some areas and the corrosion behavior is to be monitored over time.