Efforts to reduce the corrosion of reinforcing steel in bridge decks has led to the use of a conductive overlay as one type of cathodic protection system. This type of overlay utilizes a conductive aggregate made from coke in a bituminous concrete mix. In preparation for using this system on three bridges on the George Washington Memorial Parkway near McLean, Virginia, a laboratory evaluation was conducted. The Immersion-Compression, Hveem, and Marshall methods of mix design were performed on samples of "coke-breeze" aggregate from two sources to determine the optimum asphalt contents. The results indicated that these three mix design procedures produce large differences in design asphalt contents and sample properties. A test strip placed during construction showed that the Marshall method of compacting samples were the most appropriate for these materials. The resistivity of molded samples of "coke-breeze" asphalt concrete was determined by using soil resistivity techniques. The parameter that showed the most influence on these results was the free carbon content of the coke. The influence of the asphalt content, aggregate gradation, and specimen density was minor unless the carbon content decreased to the 50 percent level or lower. The chemical analysis of these materials showed that the free carbon content may vary considerably for materials obtained at different times from the same source. A recommended gradation band and minimum carbon content (80 percent) were utilized with success in the specifications for the parkway bridges. The Marshall method (50-blow) or equal is recommended for preliminary laboratory evaluation of mixtures. /FHWA/

  • Supplemental Notes:
    • Sponsored by DOT and FHWA.
  • Corporate Authors:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Spelman, S R
  • Publication Date: 1976-5

Media Info

  • Pagination: 80 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00142846
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: FHWA-RD-76- 80 Final Rpt.
  • Files: TRIS, USDOT
  • Created Date: Dec 15 1976 12:00AM