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34 NOVEMBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 11 C L A S S I C Results of laboratory and on-site tests of removal of NaCl from concrete surrounding reinforcing steel in bridge decks as the result of electroendosmosis are described. Voltages of 100 or more dc impressed on reinforcing steel in con- crete reduced concentration of NaCl near the bars more than 79%; bars were cathodically polarized, and the effect of the NaCl removal persisted for 3 months. The experi- ments involved 100 V dc at current densities up to 100 A/ft 2 for approximately 24 hours. Rebars were positive in a cell comprising the NaCl containing concrete, which was sub - merged in a solution of Ca hydroxide. Platinized Ti anodes were negative. Tests were made with and without ion exchange resin removal of the expelled NaCl. It was con- cluded that this technique was technically feasible, and results of core evaluations and potential tests indicated that rebars stopped corroding after the treatment. D E T E R I O R AT I O N O F ( P O RT L AND CEMENT) CONCRETE bridge decks is a serious problem in many parts of the United States, resulting in high maintenance costs to keep the decks in a safe and serviceable condition. Although deck deteriora- tion can take several forms, such as scaling, cracking, or spall- ing, it is the spalling problem that has become predominant within the last 10 years or so as the major cause of bridge deck maintenance. The increased frequency of spalling of concrete bridge decks appears to be directly related to the increased use of deicing salts (primarily NaCl and CaCl 2 ) in recent years. Chloride ions accelerate the rate of corrosion of the reinforc- ing steel in the concrete. The formation of corrosion products on the steel results in a build-up of stresses in the concrete which is ultimately manifested as spalling of concrete on the deck surface. Assuming that deicing salts will continue to be used, it is obvious that remedial steps must be taken if the problem is not to worsen. Recognizing this, the Federal Highway Admin- istration (FHWA) and other highway agencies have initiated This article is published as originally appeared in MP, Vol. 15, No. 11 (1976). Electrochemical Removal of Chlorides From Concrete Bridge Decks « JOHN E. SLATER, DAVID R. LANKARD, AND PETER J. MORELAND, Battelle, Columbus, Ohio research and field programs to investigate the feasibility of a number of potential solutions to the problem, including (1) polymer impregnation of bridge decks, (2) cathodic protection of reinforcing steel, (3) protection of the reinforcing steel through the use of various coatings, (4) application of imper- meable membranes or coatings to the concrete, and (5) sophisticated rehabilitation procedures involv ing removal of chloride contaminated concrete to below steel levels with sub- sequent protection of the steel (e.g., with epoxy coatings) prior to the placement of new concrete. One means of provid- ing extended service life to existing chloride contaminated concrete decks that has not been adequately researched is the actual removal of the chloride from the concrete. The current program was intended to fill this need. A two phase program was begun at Battelle's Columbus Laboratories during July, 1973, and was completed in Septem- ber, 1975. The initial laboratory phase was intended to evaluate the feasibility of the removal concept and to identify suitable procedures and equipment. This work was followed by a field phase in which the treatment concept developed in the labora- tory was successfully applied to an existing bridge deck in Ohio. « Presented during Corrosion/76, March 22-26, 1976, Houston, Texas. FIGURE 1 — Potentiodynamic polarization curves for titanium, graphite, and platinized titanium in Ca(OH) 2 /NaCl solution.