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Primary Topic: Materials-Concrete
Description: This study consists of continued field evaluations of treatments to four pavements suffering from distress due to alkali-silica reaction (ASR). One set of treatments was evaluated on existing pavements in Delaware, California, and Nevada that already showed ASR-related distress. Two of the existing pavements were located in relatively dry environments, while the third (in Delaware) was located in a moderately wet environment. The fourth site, in New Mexico, consisted of treatments on newly constructed pavements built with known reactive aggregates. At the Nevada site, the pavement was treated with methacrylate (HMM), silane, linseed oil, or lithium hydroxide. The Delaware site used only lithium hydroxide, while the California site used only methacrylate. The test sections in New Mexico consisted of pavement that contained admixtures as ASR inhibitors. There were two rates of addition of lithium hydroxide, a 25 percent replacement of cement with combinations of Class C and F fly ashes, and a high-range water reducer (HRWR). This evaluation showed that, unfortunately, none of the treatments were significantly beneficial to pavements with moderate to advanced ASR damage. The methacrylate sealer was effective when applied to a bridge deck and extended the pavement service life 3 to 5 years or more when applied in two to three coats. The results indicate that, regardless of the treatment, upward moisture migration from the subgrade to the bottom of the pavement is sufficient to support continued ASR even in dry desert climates. Preliminary results from the New Mexico test sites show that Class F ash, LOMAR (HRWA), or blended Class C and Class F ash may improve resistance to ASR distress. However, Class C ash can make deterioration much worse. Careful selection of the fly ash is necessary when attempting to mitigate known reactive aggregate. Continued monitoring of this test site is recommended.
FHWA Publication Number: FHWA-RD-02-082
Publication Year: 2006
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