An existing concrete structure is restored by embedding sacrificial anodes into the concrete layer at spaced positions over the layer and connecting the anodes to the reinforcing members to provide a cathodic protection against corrosion. Each anode is inserted into a drilled hole in the layer of sufficient depth to expose the reinforcement. A steel pin passes through a bore in the cylindrical anode and is attached to the reinforcement by arc welding or by impact so as to hold the anode rigidly within the hole. The hole is filled by a settable filler material. In order to maintain effective current conduction from the anode to the reinforcement through the filler over an extended period to maintain the required protection, there is added a material to hold the pH in a preferred range of the order of 12 to 14 and a deliquescent material to absorb moisture into the filler.