Abstract

Transport processes between aqueous solutions and cement-based materials are a key component of reactions which lead to a reduction of durability. The transport processes within capillary pores are already well established as opposed to the influence of the pore system on the nanoscale. To determine the potential impact of the gel pores of the calcium silicate hydrate on material properties, a realistic picture of the entire pore structure is fundamental.

However, due to the materials complexity and sensitivity, most analytical techniques have individual shortcomings and provide only a limited understanding of the system. In order to gain a more comprehensive understanding of the nanostructure of cement-based systems, a new approach using scanning transmission electron microscopy with focused ion beam prepared lamellas was developped.

The challenge of this approach was the vulnerability of the material, in particular regarding the high content of instable hydrate mineral phases. Using this approach, it was possible to image the structure on the nanoscale including the pore system with a high depth of field and showing the connectivity of the CSH's gel pores. This is discussed with results of other common investigation techinques for nanoporous systems, such as gas sorption and mercury intrusion porosimetry with regard to material performance aspects.

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