Thermodynamic modelling of the reactions of self-healing agents and the chemical binding of aggressive ions in seawater

Conference paper (2021)

Authors

Xintong Wu South China University of Technology, China
Haoliang Huang South China University of Technology, China
Hao Liu South China University of Technology, China
Jie Hu South China University of Technology, China
Jiangxiong Wei South China University of Technology, China
Qijun Yu South China University of Technology, China
Copyright: © 2021 the authors
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Published Date

29-04-2021

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Abstract

In this study, a new concept on self healing of cracks that the ingressive ions in the crack is chemically bound to improve the self-healing efficiency was proposed for cracked cementitious materials in a marine environment. Thermodynamic modeling was performed to determine the appropriate masses and ratio of Ca2+ and Al3+ provided by chemical agents for a good efficiency of self-healing and chemical binding of Cl-, SO4 2-, and Mg2+ ions from sea water. It was found that when CaO-NaAlO2 and CaO-metakaolin are used as self-healing agents, Friedel’s salt, kuzel’s salt, ettringite and hydrotalcite can be formed and, thus, Cl-, SO4 2- and Mg2+ from sea water are chemically bound. Moreover, the volume of phase assemblages becomes larger, which facilitates the self-healing of cracks. For a ratio of 0.3 between the mass of self-healing agent to the mass of sea water, the removal efficiency of Clions for CaO-NaAlO2 agent with a Ca/Al of 5 reaches the maximum value, i.e. 87%, while for CaO-metakaolin agent the removal efficiency of Cl- ions reaches the maximum when the Ca/Al is 3. The chemical binding of Mg2+ and SO4 2- ions is hardly influenced by Ca/Al when it is larger than 2 and the removal efficiency approximates 100%.