Nano- and Microstructure of Cement Stone with and without Fibers

摘要

The visualization of structures resulting from processes that take place in the scale of a few nanometers is important when studying the properties of concrete and mortar. Electron microscopy is in principle capable of acquiring images of structural constituents at this size. Unfortunately, studies using conventional electron microscopes are subject to serious limitations. For this reason 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 wet micro- and nano- world of cement-based materials. It is even possible to carry out sophisticated observations of hydration processes in complicated multi-phase systems, such as Portland cement. This article describes investigations of the phase development during the hydration of OPC with and without fiber-like reinforcements including carbon na notubes (CNT) from the induction to the final period. The results of the hydration process without fibers are summarized in a scheme for a new model of ordinary Portland cement hydration. ESEM investigations were supported by the calculation of saturation factors from ion concentration in the pore fluid.