Crack Prevention Program, Hiwassee Dam

As completed, Hiwassee Dam, a Tennessee Valley Authority (TVA) structure in western North Carolina, with a height of 322 ft from the lowest rock foundation to the roadway, was the highest overflow gravity dam. Its concrete, manufactured from the local graywacke rock, had to be placed largely during the warm summer months. To insure that the dam would be impervious to the passage of water and its surface would be weather-resistant, it was important that the mass should be free from major cracks. This required a concrete with a gradual temperature rise, one that would harden slowly, and one that would permit considerable expansion before its ultimate strength was reached.