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36 NOVEMBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 11 C L A S S I C The work on the large slabs established that significant quantities of chloride can be removed from thick concrete slabs using the electrochemical treatment within a reasonable time. However, current densities of at least 54 A/m 2 (5 A/ft 2 ) were required for effective electrochemical treatment. Treatment times of 24 hours appeared adequate to achieve a significant reduction in chloride content. The treatment can be either continuous or intermittent in nature to achieve the same chloride extraction. The removal of chloride was greatest in the concrete over- lying the cathode (rebar). Significant, but lesser reductions in chloride content were also achieved in concrete adjacent to the cathode areas. It was clear that scale up problems with the treatment, from small cylinders to large slabs, were minimal. Bridge Deck Experiments The requirements for a bridge deck for electrochemical chloride removal experiments were that it contain substantial quantities of chloride, but exhibit no evidence of surface spall- ing. With the cooperation of the Ohio Department of Transpor- tation, a number of candidate bridges were visited in the Fall of 1973. The bridges were examined visually for spalling, and electrochemical potential scans were taken to assess corrosion activity of the reinforcing steel. The bridge selected for study was an 8 year old, two lane, steel girder bridge on the southbound lane of U.S. Route No. 33 near Marysville, Ohio (No. UNl-33.1138R). The deck was completely free of surface spalls. As a matter of interest, a similar deck less than 90 m (100 yards) away, constructed at the same time by the same contractor, had about 60% of the surface repaired due to spalling. A 3 x 6 m (10 x 20 ft) area of the selected bridge deck on the west lane was chosen for treatment. Pretreatment Measurements Pretreatment characterization data were obtained in the form of electrochemical potential scans, chloride analyses, delamination detection, and linear polarization electrode readings. FIGURE 3 — Pretreatment potential scan of bridge deck treatment area (April, 1975). FIGURE 4 — Location of cores taken from treatment area, before and after treatment. FIGURE 5 — Chloride extraction hardware in position on bridge deck. FIGURE 6 — Experimental technique used for the electro chemical removal of chloride ions from a PCC bridge deck.