Evaluating Use of Unconventional Fly Ash Sources in Highway Concrete

Supplementary cementitious materials (SCMs) are key ingredients of today’s concrete and have been shown to vastly improve the durability and sustainability and mitigate alkali-silica reactivity of concrete mixtures. While the demand for fly ash (the most commonly used SCM) and other suitable pozzolans continues to increase, the supply of high quality and economically available fly ash has been dwindling or at least become unpredictable. This is partly due to shifting of fuel sources (for example, switching from coal to natural gas) at power plants and partly due to tightening environmental and air pollution regulations, which affect fly ash quality by increasing its carbon, calcium, sulfur, and ammonia contents. Currently, less than 50% of the produced fly ash meet AASHTO M 295 (ASTM C618) requirements for use in concrete. The imbalance between the supply and demand for quality fly ash has resulted in regional and seasonal shortages, which is likely to exacerbate significantly in future. In a recent AASHTO survey, 80% of the respondents indicated issues with fly ash supply. Based on today’s standards and practices, it is estimated that, by the year 2030, the supply of fly ash in the United States meeting AASHTO M 295 (ASTM C618) specifications will be approximately 14 million tons while the demand will exceed 35 million tons. Clearly, transportation agencies and the concrete industry need to identify and evaluate new and unconventional fly ash resources that will maintain the quality and performance of concrete. A vast, largely untapped resource is the fly ash stockpiled over the years in dry storage monofills. Another option is the application of fly ash beneficiation technologies that are easy to implement and do not require high capital investment. The objective of this research is to update AASHTO M 295 (ASTM C618) standard, considering new and unconventional fly ash sources suitable for use in highway concrete.


  • English


  • Status: Proposed
  • Funding: $600000
  • Contract Numbers:

    Project 10-104

  • Sponsor Organizations:

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Jawed, Inam

  • Start Date: 20180619
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01672274
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 10-104
  • Files: TRB, RiP
  • Created Date: Jun 18 2018 3:03PM