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Cement–Dispersant Incompatibility due to Ettringite Bridging


  • Chun-Tao Chen,

    Corresponding author
    1. Department of Construction Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC
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    • *Member, The American Ceramic Society.

  • Leslie J. Struble

    1. Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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    • *Member, The American Ceramic Society.

    • **Fellow, The American Ceramic Society.

  • H. Jennings—contributing editor

  • This study was supported by the Center for Advanced Cement-Based Materials (ACBM).

†Author to whom correspondence should be addressed. e-mail:


Sulfonated naphthalene formaldehyde, a common dispersant for portland cement, was found to be incompatible with some cements, the incompatible combinations producing gelation rather than dispersion of cement–water mixtures. The gelation was found to be prevented by the addition of alkali hydroxide or alkali sulfate. The objective of this study was to explore the mechanism behind these incompatibilities. Three hypotheses were tested: ettringite bridging, superplasticizer consumption, and polymer bridging. Results showed that the ettringite formation was responsible for the gelation and that alkali addition inhibited the ettringite formation.