Lawrence Berkeley National Laboratory
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.
Published Web Locationhttps://doi.org/10.1016/j.cemconres.2015.06.010
© 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.