Evaluation of Corrosion Inhibitors

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CAIT project no.: FHWA NJ 2001 023

Fiscal Year: 1996/1997

Status: Final

Rutgers-CAIT Author(s): P.N. Balaguru

External Author(s): Carey Younger, Robert Baker



Corrosion of reinforcement is a global problem that has been studied extensively. The use of good quality concrete and corrosion inhibitors seems to be an economical, effective, and logical solution, especially for new structures. A number of laboratory studies are available on the performance of various corrosion inhibiting admixtures. But studies on concrete used in the field are rare. A new bypass constructed by the New Jersey Department of Transportation provided a unique opportunity to evaluate the admixtures in the field. Five new bridge decks were used to evaluate four corrosion inhibiting admixtures.

The concrete used in the four bridge decks had one of the following admixtures: DCI – S, XYPEX C- 1000, Rheocrete 222+, Ferrogard901. All the admixtures are commercially available and used in the field. The fifth deck was used as a control. All the decks with admixtures had black steel where as the control deck had epoxy coated bars. Extra black steel bars were placed on the control deck.

Both laboratory and field tests methods were used to evaluate the admixtures. The uniqueness of the study stems from the use of field concrete, obtained as the concrete for the individual bridge decks were placed. In addition to cylinder strength tests, minidecks were prepared for accelerated corrosion testing. The bridge decks were instrumented for long term corrosion monitoring. Tests to measure corrosion rate, corrosion potential, air permeability, and electrical resistance were used to determine the performance of the individual admixtures.

The evaluation produced an overall best performing admixture though the differences in the overall performance of the admixtures were not significant. The admixtures were ranked from best to worst in corrosion protection for each test.

In terms of scientific observations, xypex provides a denser concrete. If the concrete can be kept free of cracks this product will minimize the ingress of liquids reducing corrosion. The other three provides a protection to reinforcement by providing a barrier, reducing the effect of chlorides or both. In order to distinguish the differences the study should continue as explained in the following recommendation section.