Using Foundry Sand in Green Infrastructure Construction

Abstract

Foundry sand is a high-quality uniform silica sand that is used to make molds and cores for ferrous and nonferrous metal castings. The metal casting industry annually uses an estimated 100 million tons of foundry sand for production. Over time, foundry sands physically degrade until they are no longer suitable for molds. Consequently, 9 to 10 million tons of sand is discarded each year. However, the discarded foundry sands have remarkably consistent composition and are generally considered a higher quality material than typical bank run or natural sands used in construction. Currently, an estimated 28% of discarded foundry sand is reused, primarily in construction-related applications, while the remaining sand is disposed of in landfills (American Foundry Society 2007). Recycling of foundry sand can save energy, reduce the need to mine virgin materials, and may reduce costs for both producers and end users. Use of foundry sand as a fine aggregate in construction applications offers project managers the ability to enhance green sustainable construction by reducing their carbon footprint, while also qualifying for LEED credits. The U. S. Environmental Protection Agency (EPA) recently estimated that at the current recycling level 20,000 tons of CO2 emissions are prevented while 200 billion BTUs of energy are saved (US EPA 2008). Support for increased reuse of foundry sand has brought together the U.S. EPA, the Federal Highway Administration, the U. S. Department of Agriculture, the Recycled Materials Resource Center (RMRC), state environmental agencies, the foundry industry and end users to develop the tools and resources needed to increase foundry sand recycling to 50% by 2015. This paper provides a comprehensive overview of the engineering and construction properties of foundry sand for use in Portland cement concrete, hot mix asphalt, road subbase layers, embankments, and flowable fill. Recent studies addressing environmental concerns of using foundry sand as a construction material are reviewed. With the goal of advancing use of foundry sand in construction application, references to resources and tools, such as web-based training and a foundry locator map module, are made available.