The visualisation of structures resulting from processes taking place at a few nanometers is immensely important when studying the properties of concrete and mortar. Electron microscopy is in principle capable to obtain images of structural constituents in this size. Unfortunately, studies with conventional electron microscopes are subject to serious limitations: the specimens must be high-vacuum-stable or correspondingly prepared and the specimen must generally be electrically conductive or be made conductive by a coating of the surface. For these reasons an Environmental Scanning Electron Microscope with Field Emission Gun (ESEM-FEG) in different operating modes has been used to investigate wet materials in their native state. These methods provide deep insights into the moist micro and nano world. It even makes it possible to carry out sophisticated observations of hydration processes in complicated multi-phase systems, such as Portland cement.
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