Chloride binding behavior of CaAl-NO 3 LDHs in simulated concrete solutions under sulfate attack and its influence on the corrosion process of reinforcing steel

Chloride binding tests, electrochemical measurements and microscopic characterizations were performed to systematically explore the Cl- adsorption behavior of co-precipitated CaAl–NO3 LDHs at varying sulfate concentrations and its effects on steel reinforcement corrosion. Under single-chloride conditions, CaAl–NO3 LDHs effectively immobilized Cl- via interlayer anion exchange to form Friedel’s salt, improving chloride binding capacity and delaying steel corrosion initiation. In the presence of sulfate, SO42- preferentially occupies CaAl–NO3 LDHs interlayer sites, suppressing chloride binding and facilitating ettringite (AFt) formation, which in turn weakens the chloride binding capacity of CaAl–NO3 LDHs. Notably, the corrosion evolution of steel reinforcement in the coupled system is decoupled from the chloride binding performance of LDHs, as sulfate hinders the association between oxygen vacancies and chloride ions at the steel surface, postponing corrosion initiation.