O-17 AND SI-29 MAS NMR-STUDY OF BETA-C2S HYDRATION AND THE STRUCTURE OF CALCIUM-SILICATE HYDRATES

O-17 and Si-29 MAS and CPMAS NMR spectroscopy has been used to study the mechanism of hydration of beta-C2S and the structure of calcium silicate hydrates (CSH) formed both during hydration of beta-C2S and synthesized separately. beta-C2S was reacted with (H2O)-O-17 at room temperature for up to 100 days. Synthesized CSH was made from silica gel and CaCl2 solution made with (H2O)-O-17. All the O-17 NMR signal from the reaction products is from O-17 originally in the water. The local oxygen environments detected in CSH are Si-O-Ca, Si-O-Si, Ca-OH and possibly Si-OH. Ca-OH sites are also present in Ca(OH)2 accompanying the CSH. The hydration mechanism and CSH structure are discussed.