Foundry Green Sands as Hydraulic Barriers: Field Study

Abstract

A field study was conducted to determine if the field hydraulic conductivity of barrier layers constructed with foundry green sand is comparable to the hydraulic conductivity measured in the laboratory on laboratory-compacted specimens normally used for testing during design. Three test pads were constructed with foundry green sand. Their field hydraulic conductivity was measured using sealed double ring infiltrometers, two-stage borehole permeameters, and on large block specimens. Additional field hydraulic conductivity tests were conducted on the test pads after exposure to winter weather causing freeze-thaw cycling and summer weather causing desiccation. The field hydraulic conductivity data followed the same trends with bentonite content and liquid limit observed in the laboratory. When the bentonite content is greater than 6% (by weight), the plasticity index is greater than 3, or the liquid limit is greater than 20, the hydraulic conductivity is less than 10\U-7\N cm/s. Testing after winter exposure showed that the field hydraulic conductivity was unaffected by winter weather, even though the test pads underwent up to six freeze-thaw cycles (depending on depth). Similarly, exposing the test pads to summer weather had no measurable effect on the field hydraulic conductivity. The field study validated that foundry sand is a useful industrial by-product that can be beneficially used as a hydraulic barrier material.