The objectives of this investigation were to study the factors contributing to the blistering of asphalt overlays on highways in Mississippi and determine if the problem can be prevented or the damage minimized. Gas chromatographic analyses of samples taken from blisters revealed the presence of CH4 and large amounts of CO2. Microbial populations in the degraded materials ranged from 1,000 to 10,000 organisms/gram. Chemical analyses of the sand and gravel materials used in the asphalt highway mixes, and the soils native to these areas experiencing problems, revealed the presence of both inorganic nitrogen and inorganic phosphorus. Using a microbial bioassay technique it was shown that sufficient nitrogen and phosphorus were available in these materials to support microbial growth and gas production. The microflora in degraded asphalt mix was shown to produce CO2, H2, CH4, N2O, N2 and H2S. CO2 and CH4 were shown to dissolve in the asphalt overlay material in quantities sufficient to cause blistering of the overlay material when released. Washing the asphalt mix ingredients with an acid to remove N and P inhibited microbial activity. Incorporation of lime into the asphalt mix was even more effective in halting microbial activity and gas production.

  • Supplemental Notes:
    • Mississippi No. PR-1(19), Part II, State Study No. 84.
  • Corporate Authors:

    Mississippi State University, Mississippi State

    Department of Biological Sciences, P.O. Drawer GY
    Mississippi State, MS  United States  39762

    Mississippi State Highway Department

    P.O. Box 1850
    Jackson, MI  United States  39215

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Brown, L R
    • Darnell, T R
  • Publication Date: 1986-1

Media Info

  • Features: References;
  • Pagination: 43 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00457075
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: MSHD-RD-86-84
  • Created Date: Aug 27 2004 9:38PM