Raman spectra of single-phase calcium-silicate hydrate (C-S-H) samples with C/S ratios between 0.88 and 1.45 are consistent with a defect tobermorite model for the structure of these materials, in agreement with previously published nuclear magnetic resonance (NMR) spectroscopic data for the same samples. The Raman spectra of C-S-H samples with C/S ratios <1.0 are very similar to those of 14 angstrom tobermorite. Those of C-S-H samples with C/S ratios ≥1.0 show substantial concentrations of both Q1 and Q2 Si sites and indicate the possible presence of jennite-like environments. Raman spectroscopy, like infrared and NMR, is a probe of local structure on the atomic nearest neighbor and next-nearest neighbor scale, and thus provides significantly different information than diffraction methods. The Raman spectra of the C-S-H have a rich structure and contain peaks for Si-O stretching, Si-O-Si bending, internal deformation of the Si-O tetrahedra and Ca-O polyhedra, and characteristic peaks at lower frequencies. The spectra of jennite and 14angstrom tobermorite are quite similar, confirming the result from NMR spectroscopy that jennite has dominantly Q2 polymerization. The Raman spectra of 11angstrom and 14angstrom tobermorite are also similar, although our sample of 11angstrom tobermorite has a significant concentration of Q3 Si sites, which indicates cross-linking of the chains.
ASJC Scopus subject areas
- Ceramics and Composites
- Industrial and Manufacturing Engineering