Dynamic behaviors of water contained in calcium-silicate-hydrate gel at different temperatures studied by quasi-elastic neutron scattering spectroscopy

• Published in: Chinese physics B 2016-10, Vol.25 (10), p.271-278
• Main Author: 易洲 邓沛娜 张丽丽 李华
• Format: Article
• Language: English
• Subjects: C-S-H gel pastes; dynamics of water; empirical diffusion model; quasi-elastic neutron scattering spectra
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/25/10/106401

The dynamic behaviors of water contained in calcium-silicate-hydrate（C-S-H） gel with different water content values from 10%to 30%（by weight）,are studied by using an empirical diffusion model（EDM） to analyze the experimental data of quasi-elastic neutron scattering（QENS） spectra at measured temperatures ranging from 230 K to 280 K.In the study,the experimental QENS spectra with the whole Q-range are considered.Several important parameters including the bound/immobile water elastic coefficient A,the bound water index BWI,the Lorentzian with a half-width at half-maximum（HWHM） Γ1（Q） and Γ2（Q）,the self-diffusion coefficients Dt1 and Dt2 of water molecules,the average residence times τ01and τ02,and the proton mean squared displacement（MSD）（u2） are obtained.The results show that the QENS spectra can be fitted very well not only for small Q（≤1 A1） but also for large Q.The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI.The distinction between bound/immobile and mobile water,which includes confined water and ultra-confined water,can be seen by the fitted MSD.All the MSD tend to be the smallest value below 0.25 A2（the MSD of bound/immobile water） as the Q increases to 1.9 A1 no matter what the temperature and water content are.Furthermore,by the abrupt changes of the fitted values of Dt1,τ01,and Γ1（Q）,a crossover temperature at 250 K,namely the liquid-to-crystal-like transition temperature,can be identified for confined water in large gel pores（LGPs） and/or small gel pores（SGPs） contained in the C-S-H gel sample with 30% water content.