Dr. Eric R. Giannini, RJ Lee Group’s expert in concrete durability, test method development, and nondestructive testing, has co-authored a new publication in Journal of Advanced Concrete Technology. The article is titled “Monitoring Alkali-Silica Reaction Significance in Nuclear Concrete Structural Members.”
This paper provides an overview of ongoing research sponsored by the US Department of Energy’s Light Water Reactor Sustainability Program. The issue of alkali-silica reaction (ASR) in concrete nuclear power plant structures has been of considerable interest in recent years, following its detection in plant structures in the United States, Canada, and Japan. Although only two plants are currently under construction in the United States today, the vast majority of plants are over 30 years old, and either have renewed or will seek renewal of their initial 40-year operating licenses, permitting them to operate to an age of 60, or even 80 years 1 (Kurtis et al. 2017). This extended service life comes with increased potential for a variety of concrete distresses, including ASR.
The effects of ASR on concrete structures in general have been extensively studied, and this project seeks to address critical knowledge gaps related to certain nuclear power plant structures. Many of these structures are very thick and lack through-thickness shear reinforcement (though they are generally well-reinforced and confined in the in-plane direction. This has the effect of focusing the expansion caused by ASR in the out-of-plane (thickness) direction, while substantially limiting any expansion in the in-plane directions that would be visible for inspection. As a result, there are questions regarding both the residual shear capacity, given that the unreinforced direction sustains the greatest expansion and damage from ASR, and the ability of power plant owners to detect the presence of ASR, given that indications of distress on the visible surface may considerably lag the development of distress in the interior of the concrete.
The research discussed in this paper takes place at the University of Tennessee Knoxville and will seek to address these questions two phases of experiments on three large-scale specimens. I was engaged to provide support with specimen design and fabrication, mostly with regards to designing reactive and non-reactive concrete mixtures, and the practicalities of avoiding thermal issues with casting such massive concrete elements in the summer. The latter required nearly 10,000 pounds of ice to keep the fresh concrete temperatures below 70°F. Following successful fabrication, the specimens are being conditioned in an environmental chamber to accelerate the development of ASR, and extensively monitored using multiple techniques to advance our understanding of how to detect ASR in similar structures. After approximately two years of conditioning and monitoring, the specimens will be destructively tested to evaluate the impact of ASR on their residual shear capacity.
A video produced by the University of Tennessee-Knoxville with further information on the project can be found here: https://youtu.be/hwynrQY42Xs
To read the paper in its entirety, please click here.
1.) Kurtis, Kimberly E., Yunping Xi, Michał A. Glinicki, John L. Provis, Eric R. Giannini, and Tengfei Fu. “Can we design concrete to survive nuclear environments?” Concrete International 39(11) (2017): 29-35.