U.S. Department of Transportation
Federal Highway Administration
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Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWA-RD-02-082
Date: August 2006
In 1994, the Federal Highway Administration (FHWA) began monitoring test sections of various treatments designed to mitigate distress in portland cement concrete (PCC) pavements that contained aggregates known to be reactive with alkalies. The pavement treatments were part of the Strategic Highway Research Program (SHRP). The test sections were located in California, Nevada, New Mexico, and Delaware. Three pavement sites had suffered some degree of distress due to alkali-silica reaction (ASR) prior to treatment, and one pavement was newly constructed with known reactive aggregates.
The test sections of existing distressed pavement in California were treated with high molecular weight methacrylate (HMWM); the existing pavement sections in Nevada were also treated with HMWM, plus linseed oil, lithium hydroxide, and silane; and the existing pavement sections in Delaware were treated with lithium hydroxide. Various application rates were used at each test section.
The test sections in New Mexico consisted of a newly constructed pavement that contained mineral and chemical admixtures as ASR inhibitors. These were: two rates of addition of lithium hydroxide, a 25 percent replacement of cement with combinations of Class C and Class F fly ashes, and a high-range, water-reducing (HRWR) admixture.
The test sections in all four States were monitored annually for 5 years, from 1994 through 1998. The monitoring was done by Long-Term Pavement Performance (LTPP) visual surveys, faulting measurements, relative humidity testing, petrographic examination, and compressive strength and elastic modulus testing. Falling Weight Deflectometer (FWD) testing also was performed. The FWD results for all four test sites are included in a section near the end of the report.
The standard LTPP visual rating system sometimes had to be modified to accurately describe the differences between test sections. The LTPP criteria only rate the area of map cracking, not its severity. All of the older pavements (Nevada, California, and Delaware) already exhibited nearly 100 percent map cracking at the time of the first survey. Each pavement was in moderate to advanced stages of ASR deterioration before surface treatment. Therefore, additional gradings to rate the severity of map cracking had to be developed for each site. This allowed differences between test sections to be described and quantified.