Abstract
In order to obtain an insight about the mechanisms of Shrinking Reduction Agent（SRA）in cementitious materials, deuterium（2H or D）quadrupolar echo NMR spectra, deuterium relaxation time τ1, rotational correlation time τc and rotational diffusion coefficient were obtained from white portland cement and D2O mixture at different drying conditions such as RH 11, 33 and 60% for 28days. The result showed that（1）the mobility and diffusivity of water molecules in capillary decreased by adding SRA, however, these decrease might not enough to prevent water molecules in capillary from vaporing and（2）SRA exists more larger pore than large gel pore in Calcium Silicate Hydrate（C-S-H）which is the main component of harden cement paste. Thus, SRA does not exist in inter layer and small gel pore which is smaller pore than large gel pore in C-S-H. The result also support the hypothesis study about the mechanisms of SRA which proposed that SRA support the structure of large gel pore and prevent C-S-H from shrinking.
