Reclaimed Hydrated Fly Ash As a Geomaterial

Abstract

To effectively use recycled geomaterials in earthwork and pavement base/subgrade construction, engineering properties, design values, proper construction practices, and long-term behavior must be known. Recent experience in Iowa reveals that reclaimed hydrated fly ash (HFA) can be designed and constructed to meet performance objectives as demonstrated by three field test projects where HFA materials were used in construction of structural pavement base layers. In addition to construction operations and field performance monitoring, this paper summarizes HFA engineering properties determined from laboratory tests including: compaction characteristics, shear strength parameter values, hydraulic conductivity, freeze–thaw durability, and microstructural features. Results are also presented for HFA materials activated with high calcium stabilizers including hydrated lime, cement kiln dust, Class C fly ash, and atmospheric fluidized bed combustion residue. Successful use of these materials follows 10 years of research and field performance monitoring in Iowa.