Part of the problem with deteriorating bridge decks is the attack of salts on reinforcing steel. If we repair the bad concrete how can we be sure there is no salt that has penetrated the good concrete where it may attack the steel at a later time?
This is a problem that is under current study at Battelle's Columbus Laboratories under a Federal Highway Administration contract. A two-step chloride neutralizing technique is being investigated. In the first step a water reservoir is provided under the deck from which water will be transported upward through the concrete by capillary action. The water will carry the salts to the surface and leave them there when it evaporates. In the second step an electrochemical process is used to remove chloride ions from the concrete surface. Negatively charged chloride ions are caused to migrate toward positive charges on the surface where they react with ion exchange resins. The chloride-containing resin can then be removed. A report on the effectiveness of the method is expected later.