ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 58, (4) 269 - 274 (2014)

Song Fei, Yu Zhenglei, Yang Fengling, Liu Yunfei, Lu Yinong
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China

Keywords: Belite-calcium sulphoaluminate, Hydration, Stratlingite, Calcium hemicarboaluminate hydrate

Belite-calcium sulphoaluminate (BCSA) cement is a promising low-CO2 alternative to ordinary Portland cement. With high water cement ratio, phase compositions of the BCSA pastes at different curing ages were investigated via X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Large amounts of water accelerated the hydration reaction significantly and substantial ettringite (C63.H32, AFt) was generated in the early stages. With the carbonation of AFt in the later stages, lots of strätlingite (C2ASH8) and calcium hemicarboaluminate hydrate (C40.5H12, Hc) formed after curing age of 28 days. The microstructure of C2ASH8 and Hc in the BCSA pastes were observed and confirmed via a scanning electron microscope (SEM) and an energy dispersive X-ray spectrometer (EDS). The results indicated that C2ASH8 was thick hexagonal plate product and Hc was thin sheet-like product. C2ASH8 and Hc would stack together respectively in the later stages of hydration. In addition, spherical aluminum hydroxide (AH3) and rod-like AFt were also observed.

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