Experimental Study of Chloride Diffusion Properties of Mortar Mixed with Ion-Exchange Resin

The durability of concrete structures is increasingly being compromised by corrosion of the steel reinforcement resulting from chloride attack. Although mortar containing a nitrite compound is often used in repair work to inhibit corrosion, a harmless and more economical material is sought. The authors investigated adding an ion-exchange resin (IER) to mortar as a possible way to remove chloride from old concrete. IERs, which are widely used in water purification, are capable of exchanging chloride ions in aqueous condition. The anion exchange capacity of an IER in cement solution is experimentally investigated. Then, two chloride diffusion experiments, one involving immersion and drying cycles and the other inverse diffusion from a mortar substrate, are carried out with IER mortar. Chloride profiles are determined by titration and the chlorine distribution is visualized. The results confirm that the IER accelerates chloride diffusion in the mortar as a result of its ability to exchange chloride ions.