Reactions of self-healing agents and the chemical binding of aggressive ions in sea water
Thermodynamics and kinetics
Xintong Wu (South China University of Technology)
Haoliang Huang (Guangdong Low Carbon Technologies Engineering Centre for Building Materials, South China University of Technology)
Hao Liu (South China University of Technology)
Jie Hu (South China University of Technology, Guangdong Low Carbon Technologies Engineering Centre for Building Materials)
Jiangxiong Wei (Guangdong Low Carbon Technologies Engineering Centre for Building Materials, South China University of Technology)
Zhengwu Jiang (Tongji University)
Guang Ye (TU Delft - Materials and Environment)
Qijun Yu (Guangdong Low Carbon Technologies Engineering Centre for Building Materials, South China University of Technology)
Barbara Lothenbach (Swiss Federal Laboratories for Materials Science and Technology (Empa))
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Abstract
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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