NANOINDENTATION: A COMPLEMENTARY TECHNIQUE FOR MICROSCOPY TO STUDY THE MICROSTRUCTURE OF CONCRETE

摘要

The prediction of macroscopic properties of concrete (mechanical strengths, dimensional variations, resistence to the environmental conditions..) requires, firstly a description of the microstructure, and later a model to link the data obtained at different scales. The informations collected at the microscales, or nanoscales are of "visual" or "textural" type i.e. they are obtained by microscopy (optical or electron), diffraction (X, electron,..) by porosimetry, BET,.... The main difficulty stands in the ability to describe a macroscopic variable of mechanical type with microscopic variables of textural, chemical or mineralogical types. To overcome this problem, we have extended to the cement field, a technique based on the nanoindentation. This technique, well known in metallurgy, electronic and ceramics, allows us to measure the elastic modulus and hardness of the main phases of the concrete (residual clinker, "CSH", aggregates,..) at the micrometric scale (analogous to this obtained by scanning electron microscopy). The present paper describes the method and gives the results obtained for a high performance concrete.