With the support of the Iowa Fly Ash Affiliates, research on reclaimed fly ash for use as a construction material has been ongoing since 1991. The material exhibits engineering properties similar to those of soft limestone or sandstone and a lightweight aggregate. It is unique in that it is rich in calcium, silica, and aluminum and exhibits pozzolanic properties (i.e., gains strength over time) when used untreated or when a calcium activator is added. Reclaimed Class C fly ashes have been successfully used as a base material on a variety of construction projects in southern and western Iowa. Many of the soil types encountered for highway projects are unsuitable soils under the current Iowa Department of Transportation specifications. The bulk of the remaining soils are Class 10 soils. Select soils for use directly under the pavement are often difficult to find on a project, and in many instances are economically unavailable. This was the case for a 4.43-mi (7.13-km) grading (STP-S-90(22)-SE-90) and paving project in Wapello County. They supported the use of reclaimed fly ash for a portion of the project. Construction of about 3 mi (4.8 km) of the project was accomplished using 10 in. (25 cm) of reclaimed fly ash as a select fill beneath the portland cement concrete (PCC) slab. The remaining 1 mi (1.6 km) was constructed according to the original design to be used as a control section for performance monitoring. The project was graded during the summers of 1998 and 1999. Paving was completed in the fall of 1999. This paper presents the results of laboratory and field testing during construction.


  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 147-150

Subject/Index Terms

Filing Info

  • Accession Number: 00793287
  • Record Type: Publication
  • ISBN: 0965231046
  • Files: TRIS
  • Created Date: May 25 2000 12:00AM