Impact of Unburned Carbon Particles on the Electrical Conductivity of Fly Ash Slurry
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 140, Issue 9
Abstract
Recent stability issues in ash ponds have highlighted the importance of estimation of in situ void ratio or water content of disposed fly ash to assess the field performance and stability of these disposal units. One standard prohibits the use of fly ash with carbon content greater than 6% in concrete, making low-cost methods of quantifying the carbon content of fly ash attractive, especially for applications that might consider mining and reuse of previously disposed fly ash. In this study, electrical conductivity/resistivity measurements were used to measure the in situ carbon content and void ratio of fly ash, with the ultimate goal of quantifying the level of unburned carbon in the material. Because unburned carbon particles are electrically conductive, the resulting media conductivity is a function of carbon content, allowing determination of the carbon content of fly ash as well as the void ratio, or water content, of the soil matrix. The authors found that the measured electrical conductivity generally increased with an increase in carbon content, and the dependency of carbon particle conduction on applied stress increased with an increase in carbon content owing to the increased number of direct contacts between electrically conductive unburned carbon particles. In addition, this study evaluated the effect of pore-water conductivity on media conductivity and carbon particle conduction.
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Acknowledgments
Financial support and ash samples were provided by Southern Company; this support is gratefully acknowledged. The authors thank Dr. Carlos Santamarina, Dr. David Frost, and Dr. Paul Mayne at Georgia Tech, and Mr. Lamar Larrimore at Southern Company for their perceptive comments.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 140 • Issue 9 • September 2014
Copyright
© 2014 American Society of Civil Engineers.
History
Received: Jan 12, 2014
Accepted: May 28, 2014
Published online: Jun 24, 2014
Published in print: Sep 1, 2014
Discussion open until: Nov 24, 2014
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