United States Department of Transportation
i
Recommendations for Extension in Service Life of ASR-Affected Concrete
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2024-08-01
[PDF-3.07 MB]
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Edition:Final Report (August 2020–August 2024)
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Abstract:Alkali–silica reaction (ASR), a chemical reaction occurring in concrete between reactive siliceous minerals in some aggregates and alkalis in the concrete pore solution, can produce an expansive gel that, in the presence of sufficient moisture, can lead to expansion and cracking. This not only decreases mechanical properties but also increases permeability and, as a result, increases potential for degradation by other aggressive agents. Common methods to mitigate damage or repair of affected concrete include surface coatings and external confinement. New approaches that claim to better extend the service life of ASR-affected concrete are being used in the field but have not yet been systematically evaluated. In this report, laboratory-cast concrete and field concrete—both affected by ASR—were repaired to examine the performance of a range of existing and emerging repair materials. Laboratory-cast samples were repaired with silane- and nanosilica-based coatings, and others were confined with fiber-reinforced ultra-high performance concrete (UHPC). In the field, cracked concrete traffic (i.e., Jersey) barriers were repaired with flexible caulk and surface-treated with silanes and slurries. The efficacy of each is being monitored through measurements of expansion and crack growth. Recommendations for repair of ASR-affected transportation infrastructure are made, depending on the initial level of ASR-damage. These recommendations begin with silanes for mild to moderate conditions and increase in repair potential to the most rigorous recommendations of structural confinement.
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