Characterisation of Hydrated Cement Pastes by 1H DQF NMR Spectroscopy
Pp. 180-213 (34)
Victor V. Rodin
Abstract
This chapter considers how 1H DQF NMR spectroscopy characterises
hydrated cement pastes. The increase of the DQF NMR signal during cement hydration
has been observed. The mobile single-quantum (SQ) signal was decreasing with
increasing hydration time. The measured DQF NMR signal in hydrated white cement
has been fitted by a sum of two components. The protons of Ca(OH)2 were responsible
for the appearance of the first component. The second component was associated with
the protons of water in the planar C–S–H gel pores. A model of water molecules
movement near the centres of paramagnetic impurities has been considered. The model
was consistent with the level of paramagnetic iron content and experimental data. The
DQF spectra in grey cement pastes have been fitted by a sum of three components.
First two components in grey cement were considered similar to white cement. The
iron-rich phases in grey cements were responsible for an appearance of third
component. The experiments with progressively heating cements showed how water
leaves from cement sample and how the DQF signals of all components changed with
removing water. The behaviour of the DQF signal as function of relative sample mass
was in sympathy with bound component of the solid echo experiment. It was
discovered that the DQF component assigned to the C–S–H water decreases
monotonically, while that associated with the solid Ca(OH)2 first increases before
decreasing.
Keywords:
Ca(OH)2, Creation time, Double-quantum-filter (DQF) NMR,
Evolution time, Fourier transform (FT), Free induction decay (FID), Iron content,
NMR spectra, Residual dipolar interaction (RDI), Spin-lattice relaxation time T1,
Spin-spin relaxation time T2, White and grey cement pastes, Water.
Affiliation:
Institute of Organic Chemistry Johannes Kepler University Linz 4040 Linz, Austria.