CHARACTERIZATION OF C-A-S-H GEL FORMED IN C-A-S-H/N-A-S-H GEL BLENDS

Abstract

This paper reports on the phase transformation of C-A-S-H/N-A-S-H blends and the structural characterization of C-A-S-H and zeolites formed in this process. C-A-S-H/N-A-S-H blend gels were prepared with different Si/Al and Ca/Si ratios and characterized by X-ray diffraction （XRD）, fourier transform infrared spectroscopy （FT-IR） and magic angle spinning nuclear magnetic resonance （MAS NMR）. The results showed that when the Al content in the blend gels was high, zeolite with a high Si/Al composition ratio is formed, and when Ca is added, C-A-S-H is formed immediately after gel mixing, but then the zeolite phase is gradually formed. On the other hand, when Al content in the blend gel was low, C-A-S-H became the main phase even with a small addition of Ca. Furthermore, FT-IR spectra may provide insight into the formation behavior of C-A-S-H and the relationship between the Ca/Si ratio and the amount of Al in solid solution in C-A-S-H.