Specimen Preparation for Scanning Electron Microscopy.
Specimen Preparation for Scanning Electron Microscopy.
(1520 K)
Stutzman, P. E.; Clifton, J. R.
Cement Microscopy, 21st International Conference.
Proceedings. April 25-29, 1999, Las Vegas, NV, Jany,
L.; Nisperos, A., Editor(s)(s), 10-22 pp, 1999.
Keywords:
microscopy; cementitious materials; cements; concretes;
mortar; x ray imaging; portland cement
Abstract:
Microscopy plays an important role in the examination of
cementitious materials. Optical and electron-optical
techniques allow examination of microstructural details
with sub-micrometer definition. The increased
application of scanning electron microscopy in cement
and concrete investigations has brought attention to
differences in preparation techniques. The success of
these investigations is, in part, influenced by the type
and quality of specimen preparation. In particular,
backscattered electron and X-ray imaging modes are
influenced by the specimen surface characteristics, with
the ideal surface being highly polished. Saw-cut
surfaces that have not been epoxy-impregnated, nor
polished, are not representative of the true
microstructure, and are difficult to examine and
interpret without bias. Sawing creates a series of
fractures, which are enhanced with subsequent drying
shrinkage. Particulate matter from the sawing is also
deposited on the surface. These effects combine to
present a surface that is not well suited for any type
of microscopy and that is substantially different from
the true concrete microstructure. Polished
epoxy-impregnated surfaces are relatively simple to
prepare and allow the researcher to avoid the
above-mentioned difficulties. Claims that this procedure
alters, or 'smears', the microstructure have not been
substantiated. Procedures developed in our laboratory
for preparation of polished sections of clinker,
cements, and hardened portland cement concrete
preparations are presented here.
