Molecular silicate and aluminate species in anhydrous and hydrated cements.

The compositions and molecular structures of anhydrous and hydrated cements are established by using advanced solid-state nuclear magnetic resonance (NMR) spectroscopy methods to distinguish among different molecular species and changes that occur as a result of cement hydration and setting. One- and two-dimensional (2D) solid-state 29Si and 27Al magic-angle spinning NMR methodologies, including T1-relaxation-time- and chemical-shift-anisotropy-filtered measurements and the use of very high magnetic fields (19 T), allow resonances from different silicate and aluminate moieties to be resolved and assigned in complicated spectra. Single-pulse 29Si and 27Al NMR spectra are correlated with X-ray fluorescence results to quantify the different crystalline and disordered silicate and aluminate species in anhydrous and hydrated cements. 2D 29Si{1H} and 27Al{1H} heteronuclear correlation NMR spectra of hydrated cements establish interactions between water and hydroxyl moieties with distinct 27Al and 29Si species. ...