Geotechnical Properties of Fly and Bottom Ash Mixtures for Use in Highway Embankments

Class F fly ash and bottom ash are the solid residue byproducts produced by coal-burning electric utilities. They are usually disposed of together as a waste in utility disposal sites with a typical disposal rate of 80% fly ash and 20% bottom ash. Direct use of these materials in construction projects consuming large volumes of materials, such as highway embankment construction, not only provides a promising solution to the disposal problem, but also an economic alternative to the use of traditional materials. Representative samples of class F fly and bottom ash were collected from two utility power plants in Indiana and tested for their mechanical properties (compaction, permeability, strength, stiffness, and compressibility). Three mixtures of fly and bottom ash with different mixture ratios (i.e., 50, 75, and 100% fly ash content by weight) were prepared for testing. Test results indicated that ash mixtures compare favorably with conventional granular materials.