United States Department of Transportation
i
Performance of Admixtures Intended to Resist Corrosion in Concrete Exposed to a Marine Environment
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2006-12-01
[PDF-1.21 MB]
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Abstract:A study was conducted to evaluate the effects of water/cement ratios, Hawaiian aggregates and various admixtures, which are added to concrete to protect the embedded reinforcing steel from corrosion, on corrosion resistance for reinforced concrete exposed to marine environment. Concrete specimens were proportioned using corrosion-inhibiting admixtures intended to slow the corrosion process. Laboratory specimens were exposed to cyclic ponding to simulate marine conditions, while field panels were located at Pier 38 in Honolulu Harbor. The corrosion-inhibiting admixtures included in this project were categorized into two types. Type 1 intends to reduce the concrete permeability, including Xypex Admix C-2000, latex modifier, fly ash, silica fume and Kryton KIM. Type 2 admixtures intend to raise the threshold value for chloride concentration at which the reinforcement corrosion is initiated, including Darex Corrosion Inhibitor (DCI), Rheocrete CNI, Rheocrete 222+ and FerroGard 901. The focus of this study was on the performance of the field panels after about 3 years of exposure to a marine environment. Relevant properties of the field panels are reported, including half-cell potential readings and chloride concentrations at various depths below the concrete surface. Based on chloride concentrations and half-cell measurements, it was concluded that the control panel with lower water cement ratio (0.35) performed significantly better than the panel with higher water cement ratio (0.40). It was also concluded that concrete using Type 1 admixtures show lower chloride concentrations at various depths from the top of the panel compared with the corresponding control panels. Chloride migration rates were also lower for these panels. Panels using Type 2 admixtures had chloride concentrations that were similar to the corresponding control specimens. The control panel with 0.40 water cement ratio recorded half-cell readings that indicate a high probability of corrosion after 3.4 years field exposure. Panels with Type 1 admixtures recorded significantly lower half-cell potentials, with most in the less than 10% corrosion probability range. Panels with Type 2 admixtures showed varying degrees of corrosion probability.
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