ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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 indirectly by length-change measurements expansion of concrete specimens made from the cores and exposed to laboratory conditions conducive to the reaction.