Field demonstration of highway embankment construction using waste foundry sand

Considerable savings are available to the metal casting industry through the development of reuse applications for waste foundry sand (WFS). Departments of Transportation (DOTs) that are facing increased pressure to reuse waste materials may also save from using low-cost WFS as a source material in transportation construction. In 1996, the Indiana Department of Transportation (INDOT) and Purdue University constructed a demonstration embankment using WFS from a ferrous foundry. WFS and control embankments were instrumented to monitor geotechnical and environmental performance during and after construction. Stockpile WFS samples were also tested. The geotechnical performance of the WFS was comparable to that of natural sand, with small internal deformations and a high-standard penetration resistance. However, the WFS had a hydraulic conductivity considerably lower than that of natural sand and cannot be considered as freely draining. Minor problems were encountered during construction due to foreign objects and dust in the WFS. Environmental testing consisted of Microtox^TM and Nitrotox bioassays, ion chromatography, and inductively coupled plasma testing for metals. Bioassay results indicate the WFS has not resulted in inhibitions (toxicity) higher than those expected from natural sands. Ion migration from the WFS into the foundry sand lysimeter and down-gradient wells was found but at concentrations below regulatory reuse criteria. Metal concentrations also were below regulatory reuse criteria and typically below drinking water standards. The WFS did not result in a negative environmental impact at the site.