Reactions of self-healing agents and the chemical binding of aggressive ions in sea water: Thermodynamics and kinetics

摘要

New self-healing agents that can chemically bind seawater ions invading cracked cementitious materials were proposed. The potential of self-healing and binding of seawater ions were investigated by thermodynamic modeling. It was found that CaO-NaAlO2 and CaO-metakaolin agents can have Cl-, SO42- and Mg2+ chemically bound by reacting with sea water to form Friedel's salt, Kuzel's salt, ettringite and hydrotalcite. The removal of Cl- from seawater firstly increased and then decreased with the increase of Ca/Al molar ratio in both agents, while the removal of Mg2+ and SO42- were hardly influenced and approximated 100%. Because NaAlO2 dissolves and releases Al(OH)(4)(-) rapidly, precipitates binding Cl-, SO42- and Mg2+ were formed fast. In comparison, the reaction of metakaolin binding aggressive ions occurred after 3 days. Because of the faster reaction and the capacity to make [Cl-]/[OH-] lower in the solution, CaO-NaAlO2 would be more efficient for self-healing and mitigating reinforcement corrossion than CaO-metakaolin.

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