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This study was conducted to test the hypothesis that delayed ettringite formation was a cause of the distress shown by a concrete pavement in the Midwest. Another group of investigators had visited the site and obtained core samples of the concrete. The work reported in this paper was done as a supplement to their investigation, using portions of the samples they obtained. Optical microscopy, microanalysis using a scanning electron microscope, wet chemistry, differential scanning calorimetry, and X-ray diffraction were used to examine the concrete. The results showed no distress that could be attributed to delayed ettringite formation. Optical microscopy identified alkali-silica reaction as the primary cause of the distress in portions of the pavement. Ettringite was present in the cracks and air voids, but apparently had been formed opportunistically in the open spaces, and was not associated with any distress. It is possible that frost damage contributed to the distress, but the information and samples available for this study were not sufficient to establish this conclusively. This report is also found on DVD021.
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