Performance Evaluation of Highway Embankment Constructed Using Coal Ash

Abstract

The objective of this project was to assess the environmental and geotechnical performance of two highway embankments constructed using coal combustion fly ash. The environmental work focused on monitoring well water samples from the site before, during, and after construction. In addition, a number of in-situ lysimeter water samples were also tested during and after construction. In each case, water samples were evaluated in terms of their constitutive organic and metal concentrations, as well as their relative bioassay response using a Microtox (trademark) protocol. The geotechnical work included monitoring of ash water content and unit weight during placement, settlement analysis, and in-situ testing of the completed ash fills using the Standard Penetration Test. Analysis of the groundwater and lysimeter water samples indicated that the coal ash had not adversely affected the environmental quality of the 56th Street overpass site. The embankments also performed well from a geotechnical perspective both during and after construction. The only difficulty was the measurement of coal ash water content and unit weight using the nuclear density gauge. The benefits of reusing coal combustion fly ash for highway construction are: 1) low-cost source material for the Indiana Department of Transportation, ii) reduced disposal costs for Indiana utilities, and iii) savings of Indiana landfill capacity.