Field evaluation performance of subbases constructed with industrial byproducts

Abstract

Alternative methods for providing a stable platform over soft subgrades were evaluated using a 1.4-km section along a Wisconsin state highway that incorporated twelve test sections to evaluate nine different stabilization alternatives. A variety of industrial by-products and geosynthetics were evaluated for stabilization. The industrial by-products included foundry slag, foundry sand, bottom ash, and fly ash as subbase layer materials. The geosynthetics included geocells, a non-woven geotextile, a woven geotextile, a drainage geocomposite, and a geogrid. The same pavement structure was used for all test sections except for the subbase layer, which varied depending on the properties of the alternative material being used. All test sections were designed to have approximately the same structural number as the conventional pavement structure used for the highway, which included a subbase of granular excavated rock. Observations made during and after construction indicate that all sections provided adequate support for the construction equipment and that no distress is evident in any part of the highway. Each of the alternative stabilization methods, except a subbase prepared with foundry sand, appear to provide equivalent or greater stiffness than that provided by the control section constructed with excavated rock. However, the foundry sand subbase is also providing adequate support. Analysis of leachate collected from the base of the test sections shows that the by-products discharge contaminants of concern at very low concentrations.