Abstract
Direct electrical current (DC) is used in several ways for its healing effect in reinforced concrete structures. In long-term application, it is used for cathodic protection (CP), both in preventive and remedial mode. DC applied for a short time is used for electrochemical chloride extraction. In all cases, the DC current induces migration of chlorides from the cathodic reinforcement to the surface anode. The passage of current through wet concrete induces the transport not only of chloride but also of other ions such as hydroxides or calcium and sodium ions. This can cause local concentration changes, dissolution and changes in the microstructure of the cement binder and affect its sorption properties towards chlorides. Thus, concrete after chloride extraction may be less resistant to future chloride penetration. Series of concrete samples based on Portland cement (OPC) and samples containing supplementary materials (micromilled limestone, microsilica) were prepared, treated with DC current and tested for diffusion and migration resistance and microstructural changes afterward. The results showed significant impact of DC treatment on all the properties under study.
