Maria C. Hicks

Predicting long-term durability of steel reinforced concrete with calcium nitrite corrosion inhibitor

Abstract Steel reinforced concrete is one of the most durable and cost effective construction materials, but it can suffer in high chloride environments from corrosion due to chloride induced breakdown of the normal passive layer protecting the steel. One way of protecting embedded steel reinforcement from chloride induced corrosion is by the addition of corrosion inhibiting admixtures. The most widely used corrosion inhibiting admixture is calcium nitrite, due to its excellent inhibitor properties and its benign effect on concrete properties. One advantage to calcium nitrite is that its protection mechanism is well defined. In this paper data are presented that show the levels of chloride to which given levels of calcium nitrite will protect. Furthermore, it will be shown that once corrosion initiates, the rates are lower with calcium nitrite present. Finally, it is demonstrated how these results can be used by the design engineer in an integrated durability model to produce reinforced concrete structures with durabilities in excess of 50–100 years.

Corrosion of steel in cracked concrete

Abstract Corrosion of steel in concrete is studied typically in uncracked concrete. In the field, however, concrete often has cracks that extend to the reinforcing steel. Electrochemical corrosion ...

Predicting Chloride Profiles in Concrete

Abstract Laboratory studies were undertaken to compare chloride (Cl−) profile data to predictions obtained using ASTM C 1202 of Cl− diffusion into concrete. The effective diffusion coefficients (Deff) derived can be used to determine long-term Cl− profiles of concrete structures. Equations relating Deff with resistivity and permeability of concrete were developed. One- and two- dimensional models were used to determine Cl− profiles of Cl− ions entering concrete in structures such as square piles and decks.

Predicting times to corrosion from field and laboratory chloride data

Corrosion of steel in concrete is one of the major causes of the premature failure of steel reinforced concrete. In marine and deicing salt environments the ingress of chloride is the primary cause for the breakdown of passivity and the onset of severe corrosion. In this paper, we show how to develop effective diffusion coefficients for chloride ingress based on chloride profiles from several marine structures. Predictions of the times to reach chloride levels associated with initiation of severe corrosion are made. Chloride profiles using effective diffusion coefficients determined in other studies are given for bridge decks and parking structures. There are significant benefits of increased concrete cover and the use of corrosion inhibitors in increasing the time to corrosion. Finally, comparisons of Standard Test Method for Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration (ASTM C 1202) coulomb values with effective diffusion coefficients, determined from field and laboratory studies, indicate that effective diffusion coefficients for low permeability concretes can be estimated using simple modifications of this test method. Thus, we demonstrate that knowledge of the chloride profile is useful to assess the future performance of existing structures that are not undergoing active corrosion, and in predicting the time to corrosion initiation of new structures.

Reply to Discussion: Corrosion of Steel in Cracked Concrete

Abstract This work replies to a discussion by D.B. McDonald of “Corrosion of Steel in Cracked Concrete,” which was published in Corrosion 50, 6 (1994): pp. 419–421. The original work by N.S. Berke,...