Self-Healing Mechanisms of Cement-Based Materials Including Different Ion Complexing Agents

This study explores the impact of four ion complexing agents on the self-healing behavior of cement-based materials, to elucidate the self-healing mechanisms of cement-based materials including various ion complexing agents. The selected ion complexing agents include sodium hexametaphosphate, tetrasodium ethylenediaminetetraacetate, tetrasodium glutamate diacetate, and pentasodium diethylenetriamine pentaacetate. First, the complexing performance of ion complexing agents is assessed based on calcium complexing capacity and constancy of calcium complex. Then, the self-healing performance of specimens is evaluated through the recovery of compressive strength and water absorption properties. The self-healing abilities of cracks are studied by microscopic observation, while the analysis of the self-healing products is conducted by thermogravimetric testing. The experimental results indicated the four ion complexing agents improved the self-healing behavior of cement-based materials to varying degrees. The variations in the improvement of different ion complexing agents on self-healing behavior were attributed to various complexing performances, including the calcium complexing capacity and constancy of calcium chelates. A complexing performance indicator, Ci, was proposed to comprehensively evaluate the complexing performance of ion complexing agents, based on the ratio of calcium complexing capacity and constancy of calcium complex. The complexing performance indicators, Ci, of four ion complexing agents were positively correlated with their improvement in self-healing behavior. The thermodynamic and kinetic analysis of the self-healing reaction of ion complexing agents revealed that the ion complexing agents with higher calcium complexing capacity and lower constancy of the calcium complex were more effective in enhancing the self-healing performance of cement-based materials.