Dehydration Characteristics of C-S-H with Ca/Si Ratio 1.0 Prepared Via Precipitation

Abstract

Calcium silicate hydrate (C-S-H) with Ca/Si ratio 1.0 was prepared via precipitation in solution and heated at various temperatures to investigate its dehydration behavior. The dehydration, structural collapse and recrystallization characteristics of C-S-H and its microstructural change during heating process were investigated by XRD, SEM, Raman and TG-DSC techniques. C-S-H gradually lost non-evaporable water upon heating, about 50% and 80% non-evaporable water was removed below 200 and 400 °C, respectively, and the rest was removed up to about 1 000 °C. At 400 °C, dehydrated C-S-H exhibited the increasing disordering of calcium/silicon environment and the decreasing symmetrical bending vibration of Si-O-Si of Q ² silicate chains. At 650 °C non-bridging oxygen atoms (O_non) attached to silicon were almost removed, and significant structural change occurred, and at 815 °C C-S-H dehydrated to wollastonite.

Keywords

C-S-H / heat / dehydration / structure / morphology

References

[1] Cong X D, Kirkpatrick R J. 29Si and 17O NMR Investigation of the Structure of Some Crystalline Calcium Silicate Hydrates[J]. Advanced Cement Based Materials, 1996, 3: 133-143.

[2] Taylor H F W. Cement Chemistry, 1997 London: Thomas Telford Publishing.

[3] Kantro D L, Brunauer S, Weise C H. Development of Surface in the Hydration of Calcium Silicates. II. Extension of Investigations to Earlier and Later Stages of Hydration[J]. The Journal of Physical Chemistry, 1962, 66: 1804-1809.

[4] Okada Y, Ishida H, Mitsuda T. 29Si NMR Spectroscopy of Silicate Anion in Hydrothermally Formed C-S-H[J]. Journal of the American Ceramic Society, 1994, 77(3): 765-768.

[5] Cong X D, Kirkpatrick R J. 29Si MAS NMR Study of the Structure of Calcium Silicate Hydrate[J]. Advanced Cement Based Materials, 1996, 3(3): 144-156.

[6] Komarneni S, Roy D M, Fyfe C A, et al. Naturally Occurring 1.4 nm Tobermorite and Synthetic Jennite: Characterization by 27Al and 29Si MAS NMR Spectroscopy and Cation Exchange Properties[J]. Cement and Concrete Research, 1987, 17(6): 891-895.

[7] Grutzeck M W, Larosa T J, Kwan S. Characteristic of C-S-H gels[C]. Proceedings of the 10th International Congress on the Chemistry of Cement, vol.II, 1997 Sweden: Gothenburg.

[8] Zhong B Q, Yang N R, Ikeda Y S H K. Study on the Formation of β-C2S by Hydrothermal Synthesis of C-S-H Dehydration Using 29Si-NMR and TMS-GC[J]. Journal of the Chinese Ceramic Society, 1994, 22(6): 566-572.

[9] Cong X D, Kirkpatrick R J. Effects of the Temperature and Relative Humidity on the Structure of C-S-H Gel[J]. Cement and Concrete Research, 1995, 25(6): 1237-1245.

[10] Alonso C, Fernandez L. Dehydration and Rehydration Processes of Cement Paste Exposed to High Temperature Environments[J]. Journal of Materials Science, 2004, 39: 3015-3024.

[11] Matsuyama H, Young J F. Synthesis of Calcium Silicate Hydrate/Polymer Complexes: Part I. Anionic and Nonionic Polymers[J]. Journal of Materials Science, 1999, 14(8): 3379-3388.

[12] He Y J, Zhao X G L L N, et al. Effect of C/S Ratio on Morphology and Structure of Hydrothermally Synthesized Calcium Silicate Hydrate[J]. Journal of Wuhan University of Technology-Materials Science Edition, 2011, 26(4): 770-773.

[13] He Y J, Lu L N, Leslie J, et al. Effect of Calcium-silicon Ratio on Microstructure and Nanostructure of Calcium Silicate Hydrate Synthesized by Reaction of Fumed Silica and Calcium Oxide at Room Temperature[J]. Materials and Structures, 2014, 47: 311-322.

[14] Yoshihiko O, Kaori S, ZHONG B Q, et al. Formation Processes of β-C2S by the Decomposition of Hydrothermally Prepared C-S-H with Ca(OH)2[J]. Journal of the American Ceramic Society, 1994, 77(5): 1319-1323.

[15] Kirkpatrick R J, Yarger J L, Mcmillan P F, et al. Raman Spectroscopy of C-S-H, Tobermorite, and Jennite[J]. Advanced Cement Based Materials, 1997, 5: 93-99.

[16] Krassimir G, Peter S, Leon B, et al. Structural Features of C-S-H(I) and Its Carbonation in Air-A Raman Spectroscopic Study. Part I: Fresh Phases[J]. Journal of the American Ceramic Society, 2007, 90(3): 900-907.

[17] Kamitsos E I, Kapoutsis J A J H, et al. Vibrational Study of the Role of Trivalent Ions in Sodium Trisilicate Glass[J]. Journal of Non-Crystalline Solids, 1994, 171: 31-45.

[18] Mcmillan P, Piriou B. Raman Spectroscopic Studies of Silicate and Related Glass Structure: A Review[J]. Bulletin De Mineralogie, 1983, 106: 57-75.

[19] Mcmillan P. Structural Studies of Silicate Glasses and Melts-Applications and Limitations of Raman Spectroscopy[J]. American Mineralogist, 1984, 69: 622-644.

[20] Wu Y Q, Jiang G C, You J L, et al. Theoretical Study of the Local Structure and Raman Spectra of CaO-SiO₂ Binary Melts[J]. The Journal of Chemical Physics, 2004, 121(16): 7883-7895.

[21] Stade H, Widker W. Zum Aufbau Schlecht Geordneter Calciumhydrogensilicate. I. Bildung und Eigenschaften Einer Schlecht Geordneten Calciumhydrogendisilicatphase[J]. Zeitschrift für anorganische und allgemeine Chemie, 1980, 466: 55-70.

[22] Swamy V, Dubrovinsky L S, Tutti F. High-Temperature Raman Spectra and Thermal Expansion of Wollastonite[J]. Journal of the American Ceramic Society, 1997, 80(9): 2237-2247.