Beneficial use of Foundry By-Products in Highway Construction

Abstract

U.S. industries annually generate millions of metric tons of solid by-products, and most of these materials have been landfilled at considerable cost since the inception of modern environmental regulations in the late 1970s and early 1980s. Recently there has been a shift in societal attitudes resulting in strong interest in developing beneficial re-use markets for industrial by-products. As a result, environmental regulations have changed and beneficial re-use of industrial by-products is now permissible in a variety of applications. Blast furnace slag, fly ash, bottom ash, boiler slag, reclaimed pavement materials, coal waste, and many other industrial by-products have been or are in the process of being beneficially used as construction materials. The transportation, construction, and environmental industries have the greatest potential for re-use because they use vast quantities of earthen materials annually. Replacement of natural soils, aggregates, and cements with solid industrial by-products is highly desirable. In some cases, a by-product is inferior to traditional earthen materials, but its lower cost makes it an attractive alternative if adequate performance can be obtained. In other cases, a by-product may have attributes superior to those of traditional earthen materials. Select materials are also added to industrial by-products to generate a material with well-controlled and superior properties. This paper describes beneficial reuse applications in the gray iron foundry industry that has been investigated at the University of Wisconsin-Madison. These applications include embankments, retaining walls, sub-base, flowable fills, barrier layers, and HMA mixtures.