Hydration and microstructure of nano-clay cement material in ion erosion solution

The influence of nano-clay (NC) content on the hydration and microstructure of cement grouting material was investigated under sodium chloride solution. Five different NC cement pastes were prepared and studied by means of FT-IR, TG-DTG and SEM analysis. The results indicated that NC promoted the formation of the hydrate ettringite (AFt), and made the AFt transform from loose acicular into cylindrical shape of staggered reticulated skeleton structure. Besides, with the increase of NC content, calcium silicate hydrate (C-S-H) gel increased and the calcium hydroxide (CH) decreased, NC obviously reduced the porosity and made an increasingly dense microstructure. However, when the content of NC is more than 3 wt%, the hydration process is inhibited, and the effect of ion erosion resistance is still better than without NC. The results of compressive strength and chloride ion diffusion coefficient are better verified by microstructure. (C) 2019 Elsevier B.V. All rights reserved.