Using Waste Foundry Sand for Hydraulic Barriers

by Tarek Abichou, (M.ASCE), Dept of Civil and Environ. Engr., University of Wisconsin-Madison, Madison, WI 53706, United States,
Craig H. Benson, (M.ASCE), Dept of Civil and Environ. Engr., University of Wisconsin-Madison, Madison, WI 53706, United States,
Tuncer B. Edil, (M.ASCE), Dept of Civil and Environ. Engr., University of Wisconsin-Madison, Madison, WI 53706, United States,
Brian W. Freber, (M.ASCE), Dept of Civil and Environ. Engr., University of Wisconsin-Madison, Madison, WI 53706, United States,



Document Type: Proceeding Paper

Part of: Recycled Materials in Geotechnical Applications

Abstract: Green sand is a mixture of uniformly graded fine silica sand, bentonite, and organic binders that is used to make molds for castings in gray-iron foundries. Large quantities of waste green sand in the United States are landfilled each year. Because green sand is a sand-bentonite mixture, there is potential for its use in constructing hydraulic barrier layers used in landfill caps. This paper describes a testing program that was conducted to assess the use of green sand from a central Wisconsin foundry as a barrier material. Specimens of the sand were compacted in the laboratory at a variety of water contents and compactive efforts and then permeated in flexible-wall permeameters. Additional tests were conducted to assess how hydraulic conductivity of the compacted sand is affected by environmental stresses such as desiccation and freeze-thaw. Results of the tests were then compared to hydrologic data collected from two final cover test sections constructed with the green sand. The hydraulic conductivity of the green sand is sensitive to the same variables that affect hydraulic conductivity of compacted clays (i.e., compaction water content and compactive effort). However, unlike clays, hydraulic conductivities <10-7 cm/sec can be obtained using a broad range of water contents and compactive efforts, including water contents dry of optimum at lower effort. In addition, the hydraulic conductivity of the sand appears unaffected by freeze-thaw or desiccation. Hydrologic data obtained from the final cover test sections show similar results. Very low percolation rates were obtained, even after exposure to harsh Wisconsin winters and summers. In addition, the barrier layers have hydraulic conductivity similar to that measured in the laboratory.

Subject Headings: Compacted soils | Sandy soils | Sand (hydraulic) | Hydraulic conductivity | Recycling | Hydraulics | Soil water | Water content | Permeability (soil) | Sand (material) | North America | United States | Wisconsin

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