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Title: Alkali-carbonate reaction in concrete from Chickamauga Dam powerhouse
Authors: Luke, Wilbur I.
Keywords: Alkali-aggregate reactions
Concrete testing
Chickamauga Dam (Tenn.)
Publisher: U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)
Series/Report no.: Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; no.6-659.
Description: Miscellaneous paper
Abstract: Petrographic examination of eight cores from three concrete areas in the Chickamauga Dam powerhouse indicated that an expansive reaction between dolomitic limestone particles present in the coarse aggregate and alkalies present in the cement paste may be responsible, at least in part, for the difficulty that the TVA has had in holding generating equipment in line. The reaction, involving dedolomitization of certain types of carbonate rock by cement alkalies, has been described by Hadley, and Swenson and Gillot. In this investigation direct evidence that the reaction had taken place was found in thin sections of the concrete. The evidence was supported in directly by length change measurements (expansion) of concrete specimen made from the cores and exposed to laboratory conditions conducive to the reaction. Thin-section studies indicated that the concrete from wet and damp areas in the powerhouse had reacted more than that from dry areas, which suggests that the concrete in the wet and damp areas had expanded more than the concrete in the dry areas. However, even though an expansive reaction was evident in the cores, the relative amount of coarse aggregate involved was small when total amount of aggregate is considered. The reaction had not progressed sufficiently to cause the concrete to crack, since no evidence of cracking of any sort was seen either in the cores or in thin sections made from the cores.
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