O-17 MAS NMR investigation of the structure of calcium silicate hydrate gel

This paper presents the results of a systematic investigation of the structure of hydrothermally synthesized calcium silicate hydrate gel using O-17 MAS NMR at 11.7 T and MAS frequencies up to 12 kHz. The results support the previously proposed defect-tobermorite structural model for C-S-H. At least six O-sites have been identified, two NBO, BO, Ca-OH, Si-OH, and H2O, The compositional variation of the relative intensities of the signal for different sites measured by O-17 NMR is consistent with that calculated from Si-29 NMR results for the same samples, The chemical shifts of the NBO and BO sites become more deshielded (more positive) with increasing C/S ratio.