U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
|Accelerating Infrastructure Innovations|
Publication Number: FHWA-HRT-07-012
Date: April 2007
Preventing and mitigating alkali-silica reactivity (ASR) in portland cement concrete pavements and structures is the focus of a new $10 million Federal Highway Administration (FHWA) initiative. The 4-year ASR program was established and funded by the 2005 Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU). "This new highway concrete technology program is designed to increase concrete pavement and structure durability and performance and to reduce life cycle costs through the prevention and mitigation of ASR," says Gina Ahlstrom of FHWA's Office of Pavement Technology.
ASR occurs when silica in some aggregates and alkalis in concrete combine with water to form a gel-like substance. As the gel absorbs water and expands, it causes the concrete to crack. Over time, the cracks enable other modes of distress to occur, such as freeze thaw damage or corrosion, causing permanent damage and even structural failure.
FHWA held an ASR Benchmarking Workshop in June 2006 in Chicago, Illinois, to gather stakeholder input on the new ASR program. The 74 participants represented academia, industry, State departments of transportation, FHWA, and other Federal agencies. Workshop attendees discussed the current state of the practice and areas where further development and deployment of ASR prevention, identification, and mitigation techniques are needed. Participants noted, for example, that field identification of ASR is difficult and that there is a lack of understanding of the extent of the problem, as ASR is not included as part of most regular pavement or bridge inspection programs. Inspectors need a test to identify ASR in the field that would be relatively easy, fast, and reliable. Participants noted the need as well for a fast and reliable test method to identify the potential for ASR to occur in concrete mixtures proposed for transportation structures. Workshop participants also stressed the importance of increasing awareness of ASR among agencies and contractors and improving the decisionmaking process for preventing ASR in new construction.
|"The new ASR program will jump start education and awareness of the problem, get new technologies out into the field, and offer the opportunity to extend the life cycle of concrete pavements and structures."|
"The workshop provided a good opportunity to bring stakeholders together and put both the state of the problem regarding ASR and the state of the science for prevention and mitigation on the table," says workshop participant Lizanne Davis of FMC Corporation. "The new ASR program will jump start education and awareness of the problem, get new technologies out into the field, and offer the opportunity to extend the life cycle of concrete pavements and structures."
"The workshop was useful and brought the right group of people together to talk about ASR," adds participant Cecil Jones of the North Carolina Department of Transportation. "This new program offers the opportunity to build on the previous work done by the Strategic Highway Research Program. The implementation aspect of the program will be very important."
The new ASR program focuses on many of the needs identified at the benchmarking workshop. The program will develop rapid test and evaluation protocols for transportation agencies to use in selecting procedures to prevent ASR in new structures and pavements, using materials such as lithium and fly ash. ASR mitigation procedures for existing pavements and structures and procedures to evaluate the condition of pavements and structures afflicted with ASR will also be developed. Work on the protocol development is underway now, with the protocols expected to be ready in 2008. The program will also develop a system for tracking bridges and highway pavements affected by ASR. Technology transfer efforts will include developing informational materials such as training and technical documents and an ASR Web site to display program data and findings.
Another main program focus area is to take technologies into the field. The program will provide funding to States that are interested in field trials or demonstration projects for pavements, bridges, or other highway structures such as median barriers or retaining walls. Projects can utilize technologies that either prevent ASR in new concrete or mitigate ASR in existing concrete.
|Measurements are taken of a structure afflicted with ASR, which can cause permanent damage and structural failure.|
An ASR Stakeholder Technical Working Group (ASR TWG) has been formed to monitor program implementation and provide technical assistance. TWG members represent State transportation agencies, academia, industry, and various Federal agencies. The TWG will hold its first meeting in April.
To learn more about the ASR program or hosting a field evaluation or demonstration project in your State, contact Gina Ahlstrom at FHWA, 202-366-4612 (email: firstname.lastname@example.org). To learn more about the applied research portion of the program, contact Paul Virmani at FHWA, 202-493-3052 (email: email@example.com). The final report on the ASR Benchmarking Workshop is available online at www.fhwa.dot.gov/pavement/concrete/asr.cfm.