MICROSCOPIC OBSERVATION OF CRACKS IN CONCRETE - A NEW SAMPLE PREPARATION TECHNIQUE USING DYE IMPREGNATION

A new technique to prepare concrete sections for microscopic examinati ons is briefly described. The procedure involves the impregnation of a concrete section with a colored dye diluted in an alcohol. After a sh ort impregnation period during which the concrete is constantly kept h umid, the section is polished under water. Contrary to most dye impreg nation techniques, this method does not involve any drying of the samp le. Observations of cracks using optical microscopy can therefore be m ade without concern about drying shrinkage-induced cracking. In additi on to a detailed description of the preparation technique, various exa mples of the application of the method are given. The possibilities of using this dye-impregnation technique in combination with an image-an alysis system are also discussed.