Hydration mechanism of sulphoaluminate cement

Abstract

The feasibility of sulphoaluminate cement (SAC) utilization in support mortar was studied. Setting time and strength of as-received sulphoaluminate cement (SAC) paste were examined, hydration kinetics behavior was determined through Isothermal Calorimeter, and hydration mechanism was investigated by X-Ray diffraction analysis (XRD) and field emission scanning electron microscopy analysis (FSEM). Results showed that as-received SAC contained 61% of anhydrous calcium sulfate (3CA·CaSO₄) and dicalcium silicate (C₂S). The strength after 1 day or 3 days grew to 68.6% or 85.7% of that after 28 days respectively, while most of hydration heat was released within 1 day. The emergency of three exothermic peaks at acceleration stage was found and hydration kinetics model was established choosing the terminal time of the first exothermic peak at accelerating stage as the beginning of accelerating stage. XRD analysis suggested that large amount of ettringite (AFt) was produced at early age and FSEM observation revealed that ettringite (AFt) formed in sulphoaluminate cement (SAC) paste was characterized of different morphology which was proved to be caused by different ion concentrations.

Keywords

sulphoaliminate cement / ettringite / hydration kinetics / hydration mechanism

References

[1] Zhou H, Wan Y, Hong Jinxiang Experimental Research on Rubber Plinth Gravitational Grouting Mortar of High Speed Railways[J]. Concrete, 2010 109-111.

[2] Li Dedong Infrared Spectroscopic Study of Sulfoaluminate Cement[J]. Journal of the Chinese Ceramic Society, 1984, 12(1): 119-125.

[3] Han J, Yan Peiyu Influence of Water to Cement Ratio and Lithium Carbonate on Sulphoaluminate Cement Hydration Process[J]. Concrete, 2010, 26: 5-7.

[4] Han J, Yan Peiyu Influence of Lithium Compound on Sulphoaluminate Cement Hydration Process[J]. Journal of the Chinese Ceramic Society, 2010, 38(4): 608-614.

[5] Yuan Runzhang Cementitious Material Science[M], 1996 The Second Edition Wuhan Wuhan University of Technology Press

[6] Knudson T Particale Size Distribution in Cement Hydration[C]. The 7th International Congress on Chemistry of Cement, Paris, 1980

[7] Chen X, Fang K, Yang H, . Hydration Kinetics of Phosphorous Slag-cement Paste[J]. J. Wuhan University of Technology-Mater. Sci. Ed., 2011, 26(1): 142-145.

[8] Wang P, Feng S, Liu Xianping Research Approaches of Cement Hydration Degree and Their Development [J]. Journal of Building Materials, 2005, 8(6): 646-652.

[9] Sakai E, Diamond M, Kondo R Very Early Hydration of Tricaliun Silicate[C]. The 7th International Congress on the Chemistry of Cement, Paris, 1980

[10] Yang H, Jin S, Zong Shaomin The Study of the Hydration Process of and its Thermodynamical Properties[J]. Journal of Shijiazhuang Railway Institute, 1995, 8(1): 75-80.

[11] Peng J, Lou Zonghan Study on the Mechanism of Ettringite Formation[J]. Journal of the Chinese Ceramic Society, 2000, 28(6): 511-515.