Apparent Contact Angle and Water Entry Head Measurements for Organo-Silane Modified Sand and Coal Fly Ash
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 144, Issue 6
Abstract
Organo-silane (OS) surface modification chemically alters the surface of silica-based materials such as soils and industrial byproducts, rendering them hydrophobic. Such modification offers the potential to transform porous media with relatively high hydraulic conductivity into a water-repellent barrier to infiltration. This paper reports on experimentally observed relationships between dry density, apparent contact angle, and water entry head for Ottawa sand and a Class-F coal fly ash (CFA). Modification with two different OS products resulted in maximum apparent contact angles of approximately 120° and 140° for sand and CFA, respectively. Both products and materials exhibited an asymptotic relationship such that increasing OS dosages beyond a threshold level yielded diminishing increases in contact angle. The water entry head was found to range from 0 to 14 cm of water and 0 to 542 cm of water for OS-modified sand and OS-modified CFA, respectively. Positive correlations were established between dry density, apparent contact angle, and water entry head. Soil hydrophobicity was found to have a negligible effect on saturated hydraulic conductivity; the governing parameter for infiltration control is water entry head. The Washburn equation was found to provide reasonable estimates of experimentally observed water entry head, especially at large values of apparent contact angle. These results suggest that designing with water repellency is a plausible concept for infiltration control.
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Acknowledgments
SWCC testing was performed by Dr. Alexandra Wayllace under the direction of Professor Ning Lu at the Colorado School of Mines (CSM)/USGS Geotechnical Testing Laboratory using the recently developed transient water release and imbibition method (TRIM) (Wayllace and Lu 2012). Funding for the work presented here was received from the Energy Production and Infrastructure Center at the University of North Carolina at Charlotte and from the Environmental Research and Education Foundation in Raleigh, North Carolina.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 144 • Issue 6 • June 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Apr 4, 2017
Accepted: Dec 2, 2017
Published online: Mar 30, 2018
Published in print: Jun 1, 2018
Discussion open until: Aug 30, 2018
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