Use of Concrete Admixtures to Provide Long-Term Durability From Steel Corrosion

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Title: Use of Concrete Admixtures to Provide Long-Term Durability From Steel Corrosion

Author(s): N. S. Berke and l. R. Roberts

Publication: Special Publication

Volume: 119

Issue:

Appears on pages(s): 383-404

Keywords: admixtures; air entrainment; calcium compounds; chlorides; concrete durability; corrosion resistance; freeze-thaw durability; diffusion; high-strength concretes; permeability; plasticizers; reinforced concrete; reinforcing steels; silica fume; Material

Date: 9/1/1989

Abstract:
Steel is used widely in reinforced concrete for its structural properties and because the alkaline environment normally protects the steel from corrosion. However, this alkalinity does not protect steel in the presence of chloride ions. Furthermore, in environments subjected to freezing and thawing, durability can also be affected severely. The corrosion resistance of embedded metals can be improved by the use of concrete admixtures. Calcium nitrite improves corrosion resistance by promoting passivity of metals in concrete. Superplasticizers reduce chloride ingress by allowing the use of lower water-cement ratios. Microsilica (silica fume) substantially increases concrete resistivities as well as lowering permeability to chloride. In this paper it is demonstrated how various combinations of these admixtures improve the corrosion resistance of steel in concrete, while giving greatly improved strengths, necessary freeze-thaw resistance, and handling properties conducive to rapid placement and consolidation.