Study on the hydration and moisture transport of white cement containing nanomaterials by using low field nuclear magnetic resonance

In order to characterize the hydration and moisture transport process of white cement containing nano-SiO2 (NS) and nano-Al2O3 (NA), the transverse relaxation time (T-2) spectrum signals of the cement paste and mortars were measured by low field nuclear magnetic resonance (LF-NMR). The effect of NS and NA on the T-2 spectrum, T-2 geometric average values, and porosity of cement paste from 15 min to 72 h of hydration were studied. Moreover, the compressive strength, flexural strength, and pore structure tested by mercury intrusion porosimetry were given. Furthermore, the variation in gel pore and capillary pore of mortar as a function of moisture transport, including drying and moisture absorption (deionized water and 3% NaCl solution) process, was revealed. The results indicate that the induction time of hydration is shorten and the early porosity is reduced by introducing NS and/or NA. In the case of drying, free water evaporates from large pores to small pores, and the water in the gel pore cannot be extracted during drying. With respect to moisture absorption, the incorporation of 1 wt% NS reduces the number of gel pores, the number of capillary pores is decreased by adding 0.5 wt% NS and 0.5 wt% NA, and the mortar containing 0.5 wt% NS and 0.5% NA shows the lowest hygroscopic rate. (C) 2020 Elsevier Ltd. All rights reserved.