United States Department of Transportation
i
Concrete Performance in Aggressive Salt and Deicing Environments
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2018-12-01
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[PDF-5.15 MB]
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Edition:Final Report 01/01/2017 - 12/31/2018
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Abstract:Roadside concrete parapets, barriers as well as bridge decks across the State of Idaho are exposed to deicing chemicals and salt brine used for ice and snow control in the winter. As such, signs of durability damage have manifested in some of such concrete infrastructure. The main objectives of this project were to evaluate current Idaho Transportation Department (ITD) concrete mixtures’ durability against freeze-thaw (F–T) and wetting–drying (W–D) cycling. Salt brine, mag bud converse, freeze guard plus, and mag chloride are four types of deicers that are currently used during winter times in the state of Idaho across the six districts. The commonly used chemical is the salt brine, made by dissolution of rock salt at 23.3% concentration. Furthermore, when possible recommended strategies were proposed to improve the durability of ITD mixtures. Eight concrete mixtures from five of ITD districts were reproduced using their local aggregates and based on the corresponding field test results obtained from the respective district. The fresh properties of unit weight, entrained air, slump and the super air meter (SAM) were measured after batching. All mixtures were tested and evaluated by surface resistivity test, deicing scaling test, rapid F-T cycling test, continuous soaking, petrographic analysis, and acid soluble chloride test when exposed to Salt brine, mag bud converse, freeze guard plus, and mag chloride. The structural mixtures with no SCMs showed severe scaling, while other mixtures showed moderate scaling, and consequently two alternative structural mixtures were proposed. The proposed mixtures containing silica fume and class C-Fly ash were evaluated under the same testing matrix used in the original mixtures. The major findings recommend modifying the ITD concrete mixtures to include SCMs in a ternary fashion, since the ternary mixtures showed outstanding durability against the high concentrations of chemical deicers. Mix design optimization is required before the ternary mixes are ready for implementation.
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