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Atomic and nano-scale characterization of a 50-year-old hydrated C3S paste

  • Author(s): Geng, Guoqing
  • Taylor, Rae
  • Bae, Sungchul
  • Hernández-Cruz, Daniel
  • Kilcoyne, David A
  • Emwas, Abdul-Hamid
  • Monteiro, Paulo JM
  • et al.
Abstract

© 2015 Elsevier Ltd. All rights reserved. This paper investigates the atomic and nano-scale structures of a 50-year-old hydrated alite paste. Imaged by TEM, the outer product C-S-H fibers are composed of particles that are 1.5-2 nm thick and several tens of nanometers long. 29Si NMR shows 47.9% Q1 and 52.1% Q2, with a mean SiO4 tetrahedron chain length (MCL) of 4.18, indicating a limited degree of polymerization after 50 years' hydration. A Scanning Transmission X-ray Microscopy (STXM) study was conducted on this late-age paste and a 1.5 year old hydrated C3S solution. Near Edge X-ray Absorption Fine Structure (NEXAFS) at Ca L3,2-edge indicates that Ca2 + in C-S-H is in an irregular symmetric coordination, which agrees more with the atomic structure of tobermorite than that of jennite. At Si K-edge, multi-scattering phenomenon is sensitive to the degree of polymerization, which has the potential to unveil the structure of the SiO44 - tetrahedron chain.

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