THE USE OF BY-PRODUCT PHOSPHOGYPSUM FOR ROAD BASES AND SUBBASES

Phosphogypsum is a chemical by-product of phosphoric acid proceesing plants and consists mainly of calcium sulfate dihydrate. Because of trace impurities, this material has not been used to replace natural gypsum in the housing industry causing domestic stockpiles to accumulate at rates that could produce an inventory of one billion tons by the year 2000. Environmental pressures as well as increased land costs associated with stockpiling phosphogypsum are causing researchers to look for better utilization of this material. One concept involves the use of fly ash or portland cement stabilized by-product phosphogypsum mixtures for construction of road bases and subbases. The results of a study conducted by the Texas Transportation Institute for the Mobil Chemical Company are presented. Phosphogypsum from the Mobil Chemical Company's stockpile in Pasadena, Texas, is used in the study. Use of this locally available material would result in significant energy savings by reducing expensive transportation charges usually incorporated in the cost of conventional construction materials that are presently used in the Houston area. Factors involving strength development such as degree of compaction, stabilizer content, optimum moisture content, and chemical make-up of the phosphogypsum are presented relative to acceptability for use in base courses and subbases. In particular, excellent compressive strengths were obtained so long as compacted dry densities were at least 97 percent of optimum modified Proctor. It was also found that the pH of the phosphogypsum may have a significant effect on the compressive strength. Strengths of mixtures containing highly acidic (pH <3) phosphogypsum were significantly less than those containing a less acidic (pH around 5) material.

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/trr/1984/998/998-008.pdf
• Record URL:
  • https://scholar.google.com/scholar_lookup?title=THE+USE+OF+BY-PRODUCT+PHOSPHOGYPSUM+FOR+ROAD+BASES+AND+SUBBASES&author=C.+Gregory&author=D.+Saylak&author=W.+Ledbetter&publication_year=1984
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• Supplemental Notes:
  • Publication of this paper sponsored by Committee on Energy Consideration in Design and Construction of Transportation Facilities. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Gregory, C A
  • Saylak, D
  • Ledbetter, W B
• Publication Date: 1984

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: pp 47-52
• Monograph Title: Testing and modeling soils and soil stabilizers
• Serial:
  • Transportation Research Record
  • Issue Number: 998
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Calcium sulfates; Compaction; Compressive strength; Fly ash; Gypsum; Moisture content; pH value; Phosphoric acid; Portland cement concrete; Soil stabilization; Subbase (Pavements); Subgrade (Pavements); Waste products (Materials)
• Uncontrolled Terms: Stabilization; Subbase
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00450714
• Record Type: Publication
• ISBN: 0309038073
• Files: TRIS, TRB
• Created Date: Feb 28 1986 12:00AM