¹⁷ O MAS NMR Investigation of the Structure of Calcium Silicate Hydrate Gel

Abstract

This paper presents the results of a systematic investigation of the structure of hydrothermally synthesized calcium silicate hydrate gel using 17 O 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 H 2 O. The compositional variation of the relative intensities of the signal for different sites measured by 17 O NMR is consistent with that calculated from 29 Si 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.