Monitoring of Fluctuations in the Physical Properties of a Class C Fly Ash

Abstract

The "quality" of fly ash produced during 1985 at Ottumwa Generation Station, was evaluated by two different experimental programs. The first consisted of the physical tests specified in ASTM C 311; these results are applicable to the use of fly ash as an admixture to portland cement concrete. The second consisted of monitoring the changes in the physical properties of fly ash pastes; these results would be applicable to the use of fly ash as a grout or a soil base stabilization agent. The physical properties monitored during the testing program were compressive strength, volume stability and setting time. In general, the results obtained from the two testing programs were quite different. When using testing procedures defined by ASTM C 311 the fly ash appeared quite uniform, but results obtained from the fly ash pastes were quite erratic. It was found that compressive strengths of the pastes can vary by a factor of five in rather short periods of time.