Hindered water motions in hardened cement pastes investigated over broad time and length scales
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hdl:2117/9711
Tipus de documentArticle
Data publicació2009-09-25
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Abstract
We investigated the dynamics of confined water in different hydrated cement pastes with minimized contributions of
capillary water. It was found that the water motions are extremely reduced compared to those of bulk water. The onset of water
mobility, which was modified by the local environment, was investigated with elastic temperature scans using the high-resolution
neutron backscattering instrument SPHERES. Using a Cauchy-Lorenz distribution, the quasi-elastic signal observed in the spectra
obtained by the backscattering spectrometer was analyzed, leading to the identification of rotational motions with relaxation times
of 0.3 ns. Additionally, neutron spin echo (NSE) spectroscopy was used to measure the water diffusion over the local network of
pores. The motions observed in the NSE time scale were characterized by diffusion constants ranging from 0.6 to 1.1 × 10-9 m2 s-1
most likely related to water molecules removed from the interface. In summary, our results indicate that the local diffusion observed
in the gel pores of hardened cement pastes is on the order of that found in deeply supercooled water. Finally, the importance of the
magnetic properties of cement pastes were discussed in relation to the observation of a quasi-elastic signal on the dried sample spectra
measured using the time-of-flight spectrometer.
CitacióBordallo, H. [et al.]. Hindered water motions in hardened cement pastes investigated over broad time and length scales. "ACS applied materials and interfaces", 25 Setembre 2009, vol. 1, núm. 10, p. 2154-2162.
ISSN1944-8244
Versió de l'editorhttp://pubs.acs.org/doi/pdfplus/10.1021/am900332n
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