17O and 29Si MAS NMR study of β– C2S hydration and the structure of calcium-silicate hydrates

Abstract

17O and 29Si MAS and CPMAS NMR spectroscopy has been used to study the mechanism of hydration of β– C 2 S and the structure of calcium silicate hydrates (CSH) formed both during hydration of β– C 2 S and synthesized separately. β– C 2 S was reacted with H 2 17 O at room temperature for up to 100 days. Synthesized CSH was made from silica gel and CaCl 2 solution made with H 2 17 O. All the 17O NMR signal from the reaction products is from 17O originally in the water. The local oxygen environments detected in CSH are SiOCa, 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.