kept moist the water may be held in place by means of a tank temporarily fixed to the concrete for example by bolts usually the primary purpose of the process in the present invention is to remove chloride ions and such a process would be normally referred to as a desalination process however there will also be processes where the primary purpose is to effect an increase in the alkalinity of the concrete such a process would normally be called realkalization and where the concrete contains chloride ions and these migrate to the anode with the risk of their being discharged as gas such processes are intended to be within the scope of the present invention since some removal of chloride takes place however when alkali metal carbonates are employed in realkalization normally this would be as a solution in contact with the surface and the external anode it is preferred not to use the chlorine scavengers of the invention because of the risk of precipitating calcium carbonate or barium carbonate and the formation of sodium hydroxide leading to a loss of chlorine scavenging ability when no alkali metal carbonate is employed for example when treating concrete prone to the alkali silica reaction then the chlorine scavengers of the present invention may with advantage be used the calcium or barium hydroxide scavenger reacts with chlorine to substantially reduce the mount of chlorine liberated and the term scavenger.