Chloride Ingress into Concrete in Saturated and Cyclic Wetting and Drying Environments

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Title: Chloride Ingress into Concrete in Saturated and Cyclic Wetting and Drying Environments

Author(s): B. D. Miller and M. A. Miltenberger

Publication: Special Publication

Volume: 221

Issue:

Appears on pages(s): 471-482

Keywords: chloride ingress; cyclic wetting and drying; silane sealer; sorption

Date: 5/1/2004

Abstract:
Chloride ingress into concrete is commonly modeled using Fick's second law of diffusion. The common form of Fick's second law was derived for the boundary condition of one surface being in contact with a reservoir of constant concentration, such as the submerged portion of a marine seawall. However, in structures exposed to cyclic wetting and drying, this constant concentration boundary condition is not satisfied. Essentially, in cyclic exposures the surface concentration is not constant, but increases as a function of time. Chloride ingress occurs through sorption and diffusion in such exposures, but solely through diffusion in saturated environments. This paper compares the difference between chloride ingress in concrete exposed to cyclic wetting and drying environments with that of submerged concrete. This multi-year evaluation consisted of six different concrete mixtures, five of which contained different supplementary cementing materials. In addition, each concrete mixture was tested with and without a surface applied silane sealer. The results of these evaluations illustrate the relative rates of chloride ingress in the different environments and the effectiveness of supplementary cementing materials when combined with a silane sealer to reduce chloride ingress in cyclic exposures.