Synergistic anti-corrosion of self-healing microcapsule hybridized by MgAl LDHs-NO2: A combined experimental and DFT approach

Abstract

The anti-corrosion of the steel bar is greatly reduced by the coupling effect of matrix microcracks and chlorides. To realize the synergistic anti-corrosion of cement-based materials through self-healing, chlorine binding and corrosion inhibition, the self-healing microcapsule was hybridized by MgAl LDHs-NO₂. The agglomeration of LDHs and the synergistic anti-corrosion of cement-based materials have been effectively solved by this work. The anti-corrosion properties and mechanism of microcapsules were revealed by experiments and DFT calculations. The results demonstrated that the microcapsules were well dispersed. The average particle sizes of SM, HM10 and HM20 were 91.24, 126.52 and 143.94 μm, respectively. The appropriate dosage of microcapsules optimizes the internal pores of mortar and improves the compactness and resistance to chloride ion penetration of cement-based materials. The highest impermeability recovery ratio and healing ratio of cement-based materials doped with microcapsules were 112.46 % and 23.28 %, respectively. The chlorine binding capacity of the cement paste was increased by 22.5 % and 40.2 % for 3 % and 6 % microcapsule dosage, respectively. The highest protection efficiency of electrochemical samples mixed with microcapsules was 97.84 %. The anti-corrosion property was improved by the synergistic effect of hybridized microcapsules with the core-wall structure. The electron charge recombination of LDHs-NO₂@EC hybridized microcapsule was confirmed by XPS characterization and DFT calculation, and Bader charge analysis showed that LDHs-NO₂ migrated out of the electron charge is 2.12 e⁻. The LDHs-NO₂ component of the wall showed persistent and targeted anti-corrosion effect. The microcapsule is triggered by the extended microcrack, and the matrix microcrack is healed by the generated polymer.