Abstract
In order to improve the durability of concrete structures, silicate-based impregnant have been used, but the chemical interaction mechanism is not clear. Silicate-based impregnant react with calcium hydroxide, which is formed during the process of cement hydration, and form compounds similar to a calcium silicate hydrate (C–S–H). This paper performs reaction experiments by Ca/Si ratio, and solid state nuclear magnetic resonance (NMR) and X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy are conducted for observing chemical changes of cement paste with silicate-based impregnants. Based on the results of XRD, reduction of monosulfate phase was observed as well as the formation of C–S–H (tobermorite-like phase). 29Si and 27Al NMR spectra also correspond with the XRD results. Further, possibility of both Al/Si substitution and formation of a structure close to C-(A)-S-H (C–S–H containing Al) were observed. Therefore, silicate-based impregnant formed not only new C–S–H reacting with calcium hydroxide, but also influenced other hydrates.
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