In this paper a method is described to observe shrinkage microcracks on ‘wet’ specimen cross-sections of cement-based materials with Environmental Scanning Electron Microscopy (ESEM). A sample cooling device which can be used in the ESEM chamber was built to control the relative humidity above a microscope sample. The accuracy of measuring relative humidity is determined to be 5% at a sample temperature of 3°C. A microscope sample preparation method and a pump-down sequence of the ESEM-chamber, both without any drying of the sample, are described. Preliminary results show that in the studied mortar the visibility of shrinkage microcracks on a ‘wet’ specimen cross-section is low due to closure of microcracks by swelling of the cement paste.
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The assistance of Mr. A. S. Elgersma with the construction of the ESEM cooling device is gratefully acknowledged. Financial support was obtained from Delft Interfaculty Research Program ‘Micromechanics for macroscopic lifetime prediction’ (DIOC-10).
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Bisschop, J., Van Mier, J.G.M. Environmental Scanning Electron Microscopy as Tool to Study Shrinkage Microcracks in Cement-Based Materials. MRS Online Proceedings Library 589, 141 (1999). https://doi.org/10.1557/PROC-589-141