PREPARING SPECIMENS FOR MICROSCOPY

Microscopic examinations of concrete specimens can be compromised because improper and damaging techniques are utilized in preparing the samples. Unless great care is given to preparing specimens, it can be very difficult to know if a simple crack was originally present or created during the sample cutting. Extraction and preparation methods, such as coring, cutting, drying, grinding and polishing, can create altered specimens thereby invalidating test results and skewing research objectives. The authors present multiple and various testing procedures designed to minimize improperly prepared test samples. First, make sure the test specimen truly represents the site in question. Next, select the appropriate blade and saw to reduce any deformation caused by improper cutting. Improper drying will allow outgassing under electron microscopic examination and possibly crack the specimen. The final steps, such as epoxy impregnation, lapping, grinding, polishing and coating must be performed with careful attention to the purpose of the research, equipment available and examination techniques preferred by the researcher.