Investigation of Cement-Fly-Ash Concrete Mixtures for Underground Conduit Construction

Concrete mixes that are especially applicable to underground conduit-line construction are evaluated. Concretes in-herently release free lime which, in sufficient concentration, is corrosive to lead cable sheaths. Varying amounts of fly ash were used in trial concrete mixes, and the resulting reduction in free lime release was measured. A calcium lignosulfonate type of dispersing agent was added to some mixes, and concrete thermal resistivities for various mixes are reported. The effects of extremely wet and dry conditions, as limiting cases for thermal resistivity, are shown.