Representative image of foundry waste sand being used as fill material to build a highway embankment. Image Credits: ChatGPT.
In 1996, an unusual road-building experiment in Indiana gave an industrial waste product a second life. The project covered a 275-metre section of the Country Road 37 highway project and was designed to test whether waste sand from a metal foundry could perform as a structural fill material. The 1996 demonstration used waste foundry sand from a ferrous foundry and included both WFS and control sections that were instrumented to monitor their geotechnical and environmental performance, according to Transportation Research Record . Research by the Recycled Materials Resource Center estimated that the Indiana project saved about $145,000 in material costs. From this perspective, the 1996 embankment construction represented a step from laboratory testing to practical application.
Therefore, recycling the material would lessen the need for disposal and provide construction material.
The experiment was more than a laboratory test, according to Purdue e-Pubs . Instead of landfilling used foundry sand, the Indiana Department of Transportation (INDOT) and Purdue University used it to build part of a highway embankment near Butler. Engineers constructed the embankment at full scale and compared the foundry-sand section with sections made using conventional clay borrow and natural sand. The researchers monitored how the materials behaved during and after construction, examining settlement, strength, water movement and other engineering characteristics. Foundry sand is reused in metal casting to make moulds and cores. However, once it is no longer useful in metal casting, large amounts of foundry sand may be treated as waste. The material used in the Indiana case study was supplied by Auburn Foundry Inc. in Auburn, Indiana. Instead of disposing of it, the material’s engineering properties were investigated. The scientists monitored movements within the embankment and changes in the material beneath it. Their observations involved both vertical and lateral deformations, pore water pressure, and penetration resistance. This provided a way of comparing the foundry sand layer with the other two layers of clay and natural sand. These findings were positive from a geotechnical point of view. The foundry sand displayed low internal deformations and high penetration resistance; its overall behaviour was similar to that of natural sand. It was concluded that, from the geotechnical point of view, foundry sand could be successfully used as an embankment material in highway construction projects. Environmental performance was yet another critical factor in the demonstration process. The testing included laboratory and field tests such as bioassays and analysis of metals and other elements, as the groundwater levels were monitored within the embankment area. The results showed that there was migration of some ions from the foundry sand, although concentrations were below the relevant regulatory thresholds. The researchers thus determined that no adverse environmental effects arose from using the material. This was another practical example of why the material deserved further study. The Indiana test did not imply that all foundry waste could be used on roads. Different foundries produce sands with different properties, so testing and quality control are still necessary. The case showed that an industrial waste material could be processed, tested and used in a real highway project to evaluate its performance.
