United States Department of Transportation
i
Evaluation of Chemical Solutions to Concrete Durability Problems
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2021-06-01
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[PDF-13.48 MB]
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Edition:January 2016–August 2020
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Abstract:The reinforced concrete infrastructure in Texas has been plagued by various durability-related issues over the years, including deterioration from alkali-silica reaction (ASR), delayed ettringite formation (DEF), and corrosion of reinforcing steel. For many of these durability problems, fly ash has been the remedy of choice; however, with changes in fly ash quality and quantity spurred by new emissions standards and changes in fuel sources, concern has arisen that fly ash may not be as available or effective in the future. Thus, there exists a need to evaluate other solutions to reinforced concrete durability problems besides the traditional use of fly ash. This need formed the basis for the research described in this report. A range of materials were tested, including corrosion inhibitors (calcium nitrite, calcium nitrate, others), ASR and/or DEF inhibitors (lithium nitrate), integral water repellants, nanoparticles (silica and dispersible calcium silicate hydrates (C-S-H)), and gypsum as an additive to improve sulfate resistance of Class C fly ash. These materials were tested under a comprehensive laboratory testing program, with tests including heat of hydration, strength, electrical resistivity, corrosion potential, chloride diffusivity, sorptivity, and expansion (due to ASR, DEF, or sulfate attack). Corresponding field specimens were stored at three different outdoor sites in Texas and evaluated for ASR and/or DEF, as well as for corrosion potential (marine site). Lastly, the research team performed a forensic evaluation of a bridge deck in Amarillo, focusing on possible causes of cracking and remedies for future decks. Several products evaluated in this project showed some potential for improved durability and increased service lives for concrete infrastructure. Although there was no single product that was able to improve all durability aspects (like Class F fly ash), there may be opportunities for some of the products to be used in targeted applications to address specific durability requirements.
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