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Characterization of C–S–H and C–A–S–H phases by electron microscopy imaging, diffraction, and energy dispersive X‐ray spectroscopy
Author(s) -
Rößler Christiane,
Steiniger Frank,
Ludwig HorstMichael
Publication year - 2017
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.14729
Subject(s) - tobermorite , calcium silicate hydrate , materials science , crystallography , electron diffraction , scanning electron microscope , crystal structure , nanocrystalline material , silicate , electron crystallography , hydrate , diffraction , crystal (programming language) , characterization (materials science) , chemical engineering , cement , chemistry , composite material , nanotechnology , optics , organic chemistry , physics , programming language , engineering , computer science
Improving concrete sustainability by increasing durability requires a detailed knowledge about microstructural properties. Due to the nanoscale nature of hydrate phases that determine concrete properties, microstructural characterization remains a challenge. Analytical electron microscopy offers promising techniques to characterize cement hydrates. In this study, electron microscopy imaging, diffraction, and energy dispersive X‐ray spectroscopic information are combined in order to compare the structural properties of calcium silicate hydrate (C–S–H) and calcium aluminum silicate hydrate (C–A–S–H) phases. Results are shown for 28 days hydrated C–(A)–S–H of portland cement and cement containing ground granulated blast‐furnace slag (GGFBS). Electron diffraction patterns of single fibrous C–S–H and foil‐like C–A–S–H phases reveal a nanocrystalline structure. Also, it is shown by electron diffraction pattern that the crystal structures of C–S–H and C–A–S–H phases are similar. It is confirmed that the crystal structure of 14 Å tobermorite serves as good base for the structure of C–S–H. The electron diffraction patterns of fibrous C–S–H show streaks which indicate stacking faults, proofing that polymerization of silicate chains in C–S–H is limited. Here, we demonstrate for the first time that the dreierketten silicate chains contained in the C–S–H structure are oriented in parallel to the long axis of C–S–H fibers. This finding should be implemented in modeling of crystal growth of C–S–H.