Development of Calcined Clays as Pozzolanic Additions in Portland Cement Concrete Mixtures

A number of clay sources in the state of Florida were characterized in this study. It was determined that field material contains a substantial portion of sand, approximately 65-80%, which needs to be beneficially processed before the material can be used as a pozzolan. The clay fraction met the chemical oxide composition requirements of ASTM C618. All samples had a sum of SiO2, Al2O3, and Fe2O3 oxides above 70%, and their SO3 content was below 4%. Additionally, the clay fraction had a high kaolinite content, 70-90%, which indicates a good potential of producing a high-quality pozzolanic material on calcination. It was determined that complete dehydroxylation of all the clay samples occurred at 600˚C and that further heating to 800˚C did not increase the amorphous content of the calcined clays. Pozzolanic activity of the material calcined at 600˚C was evaluated by compressive strength testing at 7 and 28 days at a replacement level of 10%. The results showed that the Florida clays obtained can be calcined for use in portland cement concrete materials, and are capable of yielding strength indices meeting the requirements of ASTM C618 at a 10% replacement level, and are, therefore, suitable for use in concrete as Class N natural pozzolans.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 91p

Subject/Index Terms

Filing Info

  • Accession Number: 01687186
  • Record Type: Publication
  • Contract Numbers: BDV25-977-38
  • Created Date: Nov 9 2018 12:07PM