Preparing Specimens for Microscopy
Rachel J. Detwiler; Laura J. Powers; Ulla Hjorth Jakobsen; Wase U. Ahmed; Karen L. Scrivener; and Knut O. Kjellsen
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Optical and electron microscopy are being used more often as investigative tools for research and forensic work in the construction industry. What we see in a microscopic image is actually a combination of the original material from which the specimen was taken, the cumulative effects of all of the procedures required to prepare the specimen for examination, the examination technique itself, and our interpretation of the image. It can be difficult in practice to separate the original material from the artifacts of the preparation technique. For example, were the cracks we see under the microscope originally present in the concrete, or were they induced by the cutting or drying procedures used to prepare the specimen? Ideally, the extraction and preparation techniques should preserve all of the original features of interest such as spatial relationships, mineralogy, and chemistry. In practice, however, coring, cutting, drying, lapping, grinding, and polishing all disturb the concrete specimen in ways that may be detrimental to the outcome of the examination.