Experiments from the macro to the nanoscale
University of Dresden, Germany
In civil engineering usually tests on a macroscale, on bodies of sizes between meters and centimeters are carried out to discover “material laws” used for structural design. To understand the mechanisms which take place in the material structure and which affect and determine all material properties, additionally tests on smaller scales are normal, e.g. measuring porosimetry of a cementitious material on the microscale. Optical microscopes are not useful. Avoiding sample preparation which would affect the phenomena being investigated, the surface of the sample is relatively rough and the depth of focus actually is insufficient.
New experimental technologies in microscopy were the base for further investigation on the macro- and on the nanoscale. Using an Environmental Scanning Electron Microscope (ESEM) even wet samples without necessity of sample preparation can be observed. This technology allows to develop observation methods for the process of hardening of cement paste. Especially a cement paste containing a polymer dispersion with particle diameters of less than 300 nm (PCC) was a subject of interest in research work.
Having observed the consolidation of PCC-materials it seems likely to try to investigate what happens in a stress state of this material. A miniature testing apparatus was produced which could be put into and used inside the ESEM. Microcrack propagation due to increasing tensile load and crack bridging behaviour of polymer-phase in PCC can be shown. The knowledge about the combined binder effect of both cement and polymer in PCC was highly improved. The contribution contains many impressive pictures taken from the observed samples.
Presentation: invited oral at E-MRS Fall Meeting 2005, Symposium G, by Harald Schorn
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-31 12:17 Revised: 2009-06-07 00:44