Investigation of the Temporal Evolution of Translational Dynamics of Water Molecules in Hydrated Calcium Aluminate Pastes

We investigated the translational dynamics of water molecules in the hydrated aluminate and aluminum-ferrite pastes (C(3)A and C(4)AF), two main components of the Ordinary Portland Cement (OPC), using the incoherent quasi-elastic neutron scattering (QENS) technique. We used a high-resolution disk chopper spectrometer (DCS) at the Center For Neutron Research (NCNR) in NIST, with incident monochromatic neutrons of wavelength, lambda = 9 Angstrom, resulting in an energy resolution of 20 mueV, covering a Q-range from 0.31 to 1.22 Angstrom(-1). QENS spectra have been analyzed with a translational "relaxing cage model" previously developed by us.' We were able to extract time evolution of three characteristic parameters of the setting pastes: p, beta and tau, describing the fraction of the bound water (p) and relaxation behavior of the glassy water (beta and tau) present in the aluminate pastes during the last stage of the reaction kinetics. These parameters, obtained for the first time for CA and C4AF, show striking difference from that obtained in previous experiments for calcium silicate pastes (C2S and C3S).