The results of using minute quantities of secondary chemical additives with an Iowa Class C cementitious fly ash are presented in this paper. Soil stabilization with fly ash conventionally requires the addition of water and lime to initiate pozzolanic reactions with subsequent formation of cementitious products. The glossy (amorphous) phase of Iowa fly ashes accounts for about 75 percent of their composition. They are known to contain significant amounts of calcium, aluminum, and silicon, the building blocks of cementitious compounds. If these elements could be economically liberated, the need to use lime would be reduced or eliminated. Lime is a costly ingredient available only at a few locations in Iowa. Potential additives were selected on the basis of economical considerations and expected reactions, as agents that either initiate chemical attack and dissolution of the glassy phase and seed crystalline compounds. Ammonium phosphate appeared the most promising of the seven additives studied. At 3.0 percent by weight of fly ash, the average 28-day strength for ammonium phosphate-treated samples was 2.5 times that of untreated. Scanning electron microscopy indicated the glassy phase of treated fly ash was being attacked. X-ray diffraction showed formation of cementitious reaction products not present in untreated samples. A rapid means of evaluating early strength gain and setting time properties of fly ash paste is also presented.

Media Info

  • Media Type: Print
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 41-46
  • Monograph Title: Testing and modeling soils and soil stabilizers
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00450713
  • Record Type: Publication
  • ISBN: 0309038073
  • Files: TRIS, TRB
  • Created Date: Feb 28 1986 12:00AM