27 March 2018 Detecting alkali-silica reaction in thick concrete structures using linear array ultrasound
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Commercial nuclear power plants (NPPs) depend heavily on concrete structures, making the long-term performance of these structures crucial for safe operation, especially with license period extensions to 60 years and possibly beyond. Alkali-silica reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, noncrystalline silica (aggregates). In the presence of water, an expansive gel is formed within the aggregates, which results in microcracks in aggregates and adjacent cement paste. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, flexural stiffness, shear strength, and tensile strength. Currently, no nondestructive evaluation methods have proven effective in identifying ASR before surface cracks form. ASR is identified visibly or by petrographic analysis. Although ASR definitely impacts concrete material properties, the performance of concrete structures exhibiting ASR depends on whether or not the concrete is unconfined or confined with reinforcing bars. Confinement by reinforcing bars restrainsthe expansion of ASR-affected concrete, similar to prestressing, thus improving the performance of a structure. Additionally, there is no direct correlation between the mechanical properties of concrete sample cores and the in-situ properties of the concrete. The University of Tennessee–Knoxville, Oak Ridge National Laboratory, and a consortium of universities have developed an accelerated ASR experiment. Three large concrete specimens, representative of NPP infrastructure, were constructed containing both embedded and surface instruments. This paper presents preliminary analysis of these specimens using a frequency-banded synthetic aperture focusing technique.
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N. Dianne Bull Ezell, N. Dianne Bull Ezell, Austin Albright, Austin Albright, Dwight Clayton, Dwight Clayton, Hector Santos-Villalobos, Hector Santos-Villalobos, } "Detecting alkali-silica reaction in thick concrete structures using linear array ultrasound", Proc. SPIE 10599, Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, Civil Infrastructure, and Transportation XII, 1059906 (27 March 2018); doi: 10.1117/12.2295604; https://doi.org/10.1117/12.2295604

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