Abstract
In order to gain more direct insight into nature of water in calcium silicate hydrate（CSH）that is the main component of hardened cement, deuterium（2H or D）quadrupolar echo NMR spectra and deuterium relaxation time T1 and rotational correlation time τc were obtained from white portland cement and D2O mixture with different drying conditions such as no drying and D-drying for 3 days. 2H-NMR spectra show two peaks：a sharp central peak and the outer symmetric peak with horns of about 194kHz. The study on relaxation time T1 and rotational correlation time τc indicates that the signal of central peak contributes the mobile liquid state deuterium with two different components of τc：the faster τc component is like liquid state whereas the slower τc one is restricted. In colloidal model of CSH, about 1.5 nm spherical units of CSH are coagulated to form the globules of about 5nm in diameter as well as and small gel pore of about 3nm in diameter. Further, the globules pack together to form larger structure of CSH and large gel pore of 3-12nm. Deuterium exists in the small gel pore should have stronger interaction between pore wall surfaces. However, deuterium exists in the large gel pore should have weaker interaction between surface of pore walls. Therefore, the D2O with rapid τc corresponds to the large gel pore water while the D2O with slow τc corresponds to the small gel pore water. Furthermore, D-drying enhances the rotational correlation time of mobile deuterium. This can be directly verified the previous study results that the D-dry promotes the deformation of CSH structure and extend gel pore.
T1 and τc of the outer symmetric peak shows that the state of component is rigid. Further, the quadrupole coupling constant（Qcc）of the rigid signal is 258 kHz, and close to Qcc of Na-OD, Ca（OD）2, but Qcc of D2O. Therefore, it can be concluded that the rigid-stare deuterium forms -OD group.
