Spectral analysis of water dynamics in cement paste by quasi-elastic neutron scattering

Abstract

Quasi-elastic neutron scattering (QENS) is a novel experimental technique for studying the translational dynamics of water in cement paste. In our work, the improved empirical diffusion model has been used to the nonlinear least square fit of the QENS experimental data of cement samples cured for 7, 14 and 30 days, where an energy resolution function R (Q, E) of four Gaussian terms instead of one Gaussian term is utilized during the fitting process. Parameters of the translational dynamics of water in cement paste have been deduced: the number density of immobile water A, the free water index FWI=B1/(A+B1+B2), the full width half maximum of Lorentzian function Γ, the average residence time τ0 between jumps and the self-diffusion coefficient Dt of mobile water. Fitted QENS spectra are more accurate and the dynamics of water in cement paste can be quantitatively explained with these deduced parameters.All this provides a practical and useful method for spectral analysis of QENS on translational dynamics of water in cement.