Study of calcium silicate hydrates by solid state high resolution ²⁹Si nuclear magnetic resonance

Synthetic calcium silicate hydrates were hydrothermally prepared at temperatures between 100 and 200°C. Preparations of tobermorite, xonotlite, hillebrandite, gyrolite, kilchoanite, calciochondrodite, α-dicalcium silicate hydrate and tricalcium silicate hydrate were characterized by X-ray diffraction, scanning electron microscopy and infra-red spectroscopy. The products were examined by high resolution solid state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. Spectra for tobermorite, xonotlite, hillebrandite and tricalcium silicate hydrate have previously been reported, hut spectra for gyrolite, kilchoanite, calciochondrodite and α-dicalcium silicate hydrate are reported for the first time. NM R spectra reveal information about phase structure suggesting that some of the postulated crystal structures are incorrect. NMR spectroscopy shows promise as a means of identifying constituent phases of the silicate matrix in autoclaved cement pastes.