HIGH STRENGTH PHOSPHATE CEMENT USING INDUSTRIAL BYPRODUCT ASHES

During the authors' efforts to stabilize contaminated ashes in the U.S. Department of Energy's (DOE's) complex by a novel chemically bonded phosphate ceramic, they formulated a high strength concrete made of benign ashes (such as fly ash and coal bottom ash) that may be useful for specialized applications in the construction industry. It is formed by a room temperature process in which MgO is reacted with a solution of one of the soluble hydrophosphates to form a dense matrix. Any ash or slag may be incorporated during the reaction. The slurry formed by mixing these components for 15-30 minutes is a pourable, low viscosity paste. Once it is left undisturbed, it sets into a hard mass in about 45 minutes with a small amount of heat evolution. Its density ranges between 1.7 g/cc to 2.0 g/cc; open porosity is <5%. For a typical ash loading of 60 wt. %, it has a strength of about 12,000 psi. The microstructure of the concrete is glass-crystalline. This product is not very sensitive to the ash composition. Unlike in portland cement, it is unaffected by the unburnt carbon in the ash or to any Cl ions, and thus a wide variety of combustion products may be incorporated to develop this product. The material cost is generally 50% higher than portland cement, but processing advantages, such as faster setting, setting in cold environment, and self binding characteristics may off-set some of the costs; or improved properties may justify slightly higher costs for specialized product development.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 542-553

Subject/Index Terms

Filing Info

  • Accession Number: 00778480
  • Record Type: Publication
  • ISBN: 0784404194
  • Files: TRIS
  • Created Date: Nov 27 1999 12:00AM