Microscopic observation of cracks in concrete — A new sample preparation technique using dye impregnation

Abstract

A new technique to prepare concrete sections for microscopic examinations is briefly described. The procedure involves the impregnation of a concrete section with a colored dye diluted in an alcohol. After a short impregnation period during which the concrete is constantly kept humid, the section is polished under water. Contrary to most dye impregnation techniques, this method does not involve any drying of the sample. Observations of cracks using optical microscopy can therefore be made without concern about drying shrinkageinduced cracking. In addition to a detailed description of the preparation technique, various examples of the application of the method are given. The possibilities of using this dye-impregnation technique in combination with an image-analysis system are also discussed.