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37 NACE INTERNATIONAL: VOL. 56, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2017 Electrochemical Removal of Chlorides From Concrete Bridge Decks Potential Scans. Prior to electrochemical treatment of the selected area, a number of potential scans were made of the deck (November, 1973; August, 1974; and April, 1975). Mea- surements were made on a 1 foot grid in general accordance with the technique described by Stratfull 2 using Cu/CuSO 4 as the reference cell. It has been established that steel showing a potential more negative than about -0.35 volt is undergoing active corrosion. Over the 17 month measurement, the active region of the treatment area increased from 18 to 55%. Figure 3 shows the potential profile of the test section of the deck just prior to the electrochemical treatment (April, 1975). Chloride Analyses. A number of cores were removed from the test area of the deck over the 18 month period preceding the electrochemical treatment. The location of the cores on the deck are shown in Figure 4. The average chloride content as a function of depth of concrete is shown in Table 1. An increase in chloride content at all levels in the deck was noted over the 17 month observation. This increase was approxi mately 0.10% (4 lbs/yd) at the 0 to 1 inch level, 0.05% (2 lbs/yd 3 ) at the 1 to 2 inch level, and 0.01% (0.5 lb/yd 3 ) at the 2 to 3 inch level. Just prior to electrochemical treatment, the chloride content of the top inch of deck concrete exceeded 0.40% (15 lb/yd 3 ) while the 1 to 2 inch level contained 0.10 to 0.26% (4 to 10 lbs/yd 3 ). The rather large specimen to specimen variation in mea- sured chloride observed when duplicate cores were taken pre- cluded speculation on the differences in chloride content between the high and low corrosion activity areas of the deck. Delamination Detection. The selected area of the bridge deck was examined for delamination by maintenance person- nel of the Ohio Department of Transportation in April, 1975, prior to electrochemical treatment. The method used was that of a sounding rod. There was no evidence of any delamination despite significant areas of high corrosion activity. Electrochemical Treatment of the Deck Following the pretreatment characterization, electrochemi- cal removal experiments on the bridge deck were begun on April 7, 1975. The 19 m 2 (200 ft 2 ) area treated was broken down into five, 3.7 m 2 (40 ft 2 ) sections (Figure 4), which were treated individually. In each sub area, deep wood ponding frames which con- tained four 0.76 x 1.2 m (2.5 x 4 ft) compartments were used to hold the ion exchange resins. The frames were sealed to the bridge deck surface (previously swept) with construction caulking compound. (2) Weights were placed on the frame to prevent movement, and to aid in maintaining a leakproof seal. The electrolyte solution of saturated Ca(OH) 2 was placed in the ponding frame to a depth of 13 to 25 mm (0.5 to 1.0 inch). Dowex 2-X8 ion exchange resin in the OH – form was slurried into the electrolyte to a depth of 6 to 10 mm (1/4 to 3/8 inch). It was rather difficult to maintain a homogeneous dispersion of the resin in the electrolyte. A 0.7 x 1.2 m (2-1/4 x 4 ft) platinized titanium anode was then placed in each of the four compartments within the pond- ing frame. The anodes were supported about 12 mm (1/2 inch) (2) DAP Caulking Compound, DAP, Inc., Dayton, Ohio.