Field demonstration of highway embankment constructed using waste foundry sand

Barry Kirk Partridge, Purdue University

Abstract

Considerable savings is available to the metal casting industry through development of reuse applications for waste foundry sand (WFS). Furthermore, generators frequently are willing to provide WFS to reusers at no cost. Laboratory investigations have indicated that WFS from ferrous foundries can provide the necessary engineering properties for a highway embankment and that the MicrotoxTM bioassay test can be used to screen the ‘toxicity’ of WFS to prevent a negative environmental impact. In 1996, the Indiana Department of Transportation (INDOT) and Purdue University constructed a demonstration embankment using WFS. WFS and control embankments were instrumented to monitor geotechnical and environmental performance. Stockpile and job site ‘grab’ WFS samples were also tested. Geotechnical results indicate that WFS can perform well as a structural fill with strength and deformation characteristics comparable to natural sand, but cannot be considered as freely draining. Environmental testing consisted of MicrotoxTM and Nitrotox bioassays, ion chromatography, and inductively coupled plasma spectrophotometer testing for metals. Bioassay results indicate the WFS have not resulted in inhibitions (toxicity) higher than those expected from natural sands. Ion migration from the WFS into the foundry sand lysimeter was found, supporting bioassay data, but at concentrations below reuse regulatory criteria. Metal concentrations were generally below Indiana regulatory reuse Type III criteria and typically below Drinking Water Standards. Where metal concentrations in the wells exceeded regulatory criteria, exceedences appeared in both up- and down-gradient wells suggesting background metal concentrations as opposed to significant leaching from the WFS. The WFS did not result in a negative environmental impact on the site. State environmental regulatory agencies were the most frequently identified source of barriers to the beneficial reuse of WFS and reuse is further compounded by the lack of decision-based scientific tools such as life-cycle or risk-based analysis methods. The resultant liability exposure from state and federal regulations was the prevailing concern expressed by Departments of Transportation (DOTs) when considering using a regulated waste such as WFS. Furthermore, foundries often lack an organizational commitment to the reuse of its WFS as evidenced by the lack of both product quality control and a marketing strategy.

Degree

Ph.D.

Advisors

Alleman, Purdue University.

Subject Area

Environmental engineering|Civil engineering|Geotechnology|Transportation

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