Enhancing the chloride ion penetration resistance of concrete using metal-organic frameworks

This study focuses on a novel technique to improve the resistance of cement-based concrete to chloride ion penetration by incorporating NH₂-MIL-125(Ti) metal-organic frameworks (MOF) into the mix. The MOF was produced and assessed against its chloride adsorption capacity. Subsequently, it was added to cement-based concrete in proportions of 1 %, 3 %, and 5 %, by cement mass. The effect of incorporating MOF on the concrete resistance to chloride penetration, reaction kinetics, and compressive strength was investigated. The experimental results revealed that the NH₂-MIL-125 (Ti) MOF effectively removed/adsorbed the chloride ions from sodium chloride solutions, with a maximum removal capacity of 31.5 % after 7 days of exposure. Furthermore, the depth and rate of chloride ion penetration into the concrete were reduced as the mass of MOF incorporated into the concrete mix increased. Yet, the efficiency of the MOF to reduce chloride penetration decreased over time, owing to its saturation by continuous exposure to chloride ions. Furthermore, the addition of up to 5 % MOF, by cement mass, had a limited impact (<10 %) on the concrete compressive strength but did not affect the hydration reaction. Owing to its small particle size, MOF strengthened the cement paste by reducing the volume of permeable voids. Such research findings highlight that MOF could be added to cement-based concrete to enhance its resistance to chloride ingress without significantly impacting its compressive strength. This novel approach can effectively impede chloride penetration, thereby delaying corrosion and extending the service life of concrete structures.