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Thermodynamic Stability of Sulfate Ions on Calcium Aluminosilicate Hydrate Microstructure

  • Chenguang Hu (胡晨光)Email author
  • Qingjun Ding
  • Huan Wang
  • Xiaoxin Feng
Cementitious Materials
  • 5 Downloads

Abstract

The thermodynamic stability of sulfate ions on synthesized calcium aluminosilicate hydrate (C-A-S-H) microstructure with different Ca/Si ratios and Al/Si ratios was investigated by XRD, SEM-EDS, 29Si and 27Al nuclear magnetic resonance (NMR) and thermodynamic modeling. The results indicate that sulfate attack leads to both decalcification and dealumination for C-A-S-H gels, and the amount of corrosion products (gypsum and ettringite) decreased gradually with decreasing Ca/Si ratios of C-A-S-H. Sulfate ions can also promote the polymerization degree of C-A-S-H gels, improving its resistance to sulfate attack. Moreover, the 4-coordination aluminum (Al[4]) in C-A-S-H, 5-coordination aluminum (Al[5]), 6-ccordination aluminum (Al[6]) in TAH (third aluminum hydrate) and Al[6] in monosulfate or C-A-H (calcium aluminate hydrate) can be transformed into Al[6] in ettringite by sulfate attack. Furthermore, through thermodynamic calculation, the decrease of Ca/Si ratios and increase of Al/Si ratios can improve the thermodynamic stability of C-A-S-H gels under sulfate attack, which agrees well with the experiment results.

Key words

sulfate attack calcium aluminosilicate hydrate thermodynamic stability microstructure 

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Copyright information

© Wuhan University of Technology and Springer-Verlag GmbH Germany, Part of Springer Nature 2019

Authors and Affiliations

  • Chenguang Hu (胡晨光)
    • 1
    • 2
    Email author
  • Qingjun Ding
    • 3
  • Huan Wang
    • 4
  • Xiaoxin Feng
    • 1
  1. 1.College of Materials Science and EngineeringNorth China University of Science and TechnologyTangshanChina
  2. 2.Hubei Key Laboratory of Roadway Bridge and Structure Engineering (Wuhan University of Technology)WuhanChina
  3. 3.College of Materials Science and EngineeringWuhan University of TechnologyWuhanChina
  4. 4.Hubei Communications Investment Intelligent Detection Co., LtdWuhanChina

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