Crystal Growth of [Ca₃Al(OH)₆·12H₂O]₂·(SO₄)₃·2H₂O (Ettringite) Studied Under Microgravity Conditions

Abstract

On parabolic flights, the growth of ettringite, [Ca₃Al(OH)₆·12H₂O]2·(SO₄)₃·2H₂O, a major reaction product of cement with water which forms instantaneously, was crystallized under microgravity conditions and studied. In the experiments, Ca(OH)₂/Al₂(SO₄)₃ solutions were combined and reacted for 10 s, followed by immediate filtration of the suspension and subsequent quenching with acetone. For the ettringite crystals, the size, aspect ratios, quantity and morphology were determined and the results were compared with those from identical experiments performed under terrestric gravity. Under microgravity, generally smaller crystals (l–2.9 µm) precipitated in larger amount than under normal gravity (1–3.5 µm). The aspect ratios of the crystals grown under terrestric or microgravity condition were comparable at about 5.6. It is assumed that the reason for the smaller ettringite crystals is the absence of convection leading to more initial nuclei, but slower crystal growth which is diffusion limited. Apparently, no preference relative to the ion transport to the different faces of the crystals exists. The results contribute to the understanding of the mineralization of inorganic salts under microgravity conditions for which hitherto only a handful of examples were reported.

Keywords

crystallization / ettringite / microgravity / morphology / nucleation

References

[1] Lange A, Plank J. Formation of Nano-Sized Ettringite Crystals Identified as Root Cause for Cement Incompatibility of PCE Superplasticizers[C]. Nanotechnology in Construction-Proceedings of N1COM5, Chicago, 2015

[2] Struble L J. Synthesis and Characterization of Ettringite and Related Phases[C]. 8 International Congress on the Chemistry of Cement, 1986

[3] Lange A, Plank J. A Study on the Cement Compatibility of PCE Superplasticizers[C]. 11 ^th CANMET/ACI Conference on Superplasticizers and Other Chemical Admixtures in Concrete (Proceedings), ACI, Ottawa, 2015

[4] Skoblinskaya N N, Krasilnikov K G, Nikitina L V, et al. Changes in Crystal Structure of Ettringite on Dehydration[J]. Cem. Concr. Res., 1975, 5: 419-431.

[5] Perkins R, Palmer C. Solubility of Ettringite (Ca₆[Al(OH)₆]₂(SO₄)₃ · 26 H₂O) at 5–75 °C[J]. Geochim. Cosmochim. Acta, 1999, 63: 1969-1980.

[6] Wells A F. Structural Inorganic Chemistry, 1984 5th ed Oxford: Oxford University Press. [M]

[7] Yoshioka K, Tazawa E, Kawai K, et al. Adsorption Characteristics of Superplasticizers on Cement Component Minerals[J]. Cem. Concr. Res., 2002, 32: 1507-1513.

[8] McPherson A. Virus and Protein Crystal-Growth on Earth and in Microgravity[J]. J. Phys. D Appl. Phys., 1993, 26: 104-112.

[9] Zhou Y F, Li X Y, Bai S Q, et al. Comparison of Space- and Groundgrown Bi₂Se_0.21Te_2.79 Thermoelectric Crystals[J]. J. Cryst. Growth, 2010, 312: 775-780.

[10] Liu X Y. Effect of Microgravity on Ca Mineral Crystallization and Implications for Osteoporosis in Space[J]. Appl. Phys. Lett., 2001, 79: 3539-3541.

[11] DeLucas L J, Moore K M, Long M M, et al. Protein Crystal Growth in Space, Past and Future[J]. J. Cryst. Growth, 2002, 237: 1646-1650.

[12] Kundrot C E, Judge R A, Pusey M L, et al. Microgravity and Macromolecular Crystallography[J]. Cryst. Growth Des., 2001(1): 87–99

[13] Fontana P, Schefer J, Pettit D. Characterization of Sodium Chloride Crystals Grown in Microgravity[J]. J. Cryst. Growth, 2011, 324: 207-211.

[14] Lundager Madsen H E, Christensson F, Polyak LE, et al. Calcium Phosphate Crystallization under Terrestrial and Microgravity Conditions[J]. J. Cryst. Growth, 1995, 152: 191-202.

[15] Lundager Madsen H E, Christensson F, Chernov A A, et al. Crystallization of Calcium Phosphate in Microgravity[J]. Adv. Space Res., 1995, 16: 65-68.

[16] Sinha A, Gupta A K, Pramanick A K, et al. Mimicking Biomineralization under Microgravity[J]. Mat. Sci. Eng. C, 2009, 29: 779-784.

[17] Goetz-Neunhoeffer F, Neubauer J, Schwesig P. Mineralogical Characteristics of Ettringites Synthesized from Solutions and Suspensions[J]. Cem. Concr. Res., 2006, 36: 65-70.

[18] Hirsch C. Untersuchungen zur Wechselwirkung Zwischen Polymeren Fliessmitteln und Zementen bzw. Mineralphasen der Frühen Zementhydratation[D], 2005 München: München Tech. Univ..

[19] Dalas F, Pourchet S, Rinaldi D, et al. Modification of the Rate of Formation and Surface Area of Ettringite by Polycarboxylate Ether Superplasticizers during Early C₃A-CaSO₄ Hydration[J]. Cem. Concr. Res., 2015, 69: 105-113.

[20] Black L. Raman Spectroscopy of Cementitious Materials[J]. Spectrosc. Prop. Inorg. Organomet. Compd., 2009, 40: 72-127.

[21] Frates R A, Nelson D J, Friedrich C, et al. Formation of Inorganic Precipitates in Microgravity on the STS-40[C]. Proceedings of the Oklahoma Academy of Science, 1996

[22] Okubo T, Tsuchida A, Okuda T, et al. Kinetic Analyses of Colloidal Crystallization in Microgravity-Aircraft Experiments[J]. Coll. Surf. A Physiochem. Eng. Asp., 1999, 153: 515-524.

[23] Frenkel J. A General Theory of Heterophase Fluctuations and Pretransition Phenomena[J]. J. Chem. Phys., 1939, 7: 538-547.

[24] Zeldovich J B. On the Theory of New Phase Formation: Cavitation[J]. Acta Physicochim. URSR, 1943, 18: 120-137.

[25] Vekilov P G. Nucleation[J]. Cryst. Growth Des., 2010, 10: 5007-5019.

[26] Vekilov P G. The Two-step Mechanism of Nucleation of Crystals in Solution[J]. Nanoscale, 2010, 2: 2346-2357.