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53 NACE INTERNATIONAL: VOL. 56, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2017 Chloride-Induced Corrosion Specimens For each OS product tested, 10 concrete test slabs were fabricated with dimensions of 40-in (1.02 m) wide by 40-in long by 5.5-in (140-mm) thick. The test slabs had six lon- gitudinal #4 (0.5-in [13-mm] diameter) rebar, spaced 5-in (127-mm) apart, that spanned the entire slab. The concrete cover over the top of the bars was 1-in (25-mm) thick. Each slab contained welded-wire fab- ric (WWF), with wire spacing of 6 by 6 in (152 by 152 mm) and W4/W4 wire diame- ter, as the bottom layer of steel. The WWF represented a bottom mat of steel with a l arge sur fac e area that c oul d prov i d e catho dic current to th e top b ars and thereby accelerate the corrosion process, as would occur with a bottom mat of rein- forcing bars. To facilitate measurements of individ- ual rebar, all bars were electrically inter- connected to the bottom mat through indi- vidual 1-Ω resistors inside a junction box mounted on the front face of the slab. The macrocell current was equal to the voltage drop across the resistor (divided by the 1-Ω resistance). Each test slab had a 2-in (51- mm) tall by 1-in wide lip located around the perimeter of the test slab to facilitate pond- ing of a 5% sodium chloride (NaCl) solu- tion. The test slab configuration is shown in Figure 1. The concrete was designed as an ASTM C150 7 Type I/II ordinary Portland cement, with a 0.50 w/c ratio and coarse and fine aggregates meeting ASTM C33. 8 The con- crete mixture proportions are listed in Berke, et al., 9 and Table 1 provides the con- crete properties. After casting, the concrete slabs were cured under wet burlap and plastic for one week and then dried in a temperature- controlled warehouse environment for an additional 21 days. The slabs were then cyclically ponded with a 5% NaCl solution for 14 days and allowed to dry for 14 days. Corrosion measurements were performed at the end of each wet/dry cycle (one cycle equaled 28 days). Measurements consisted of corrosion potentials to produce a poten- tial map, and macrocell currents between FIGURE 1 Corrosion test slab configuration. each top bar, the bottom mat, and other bars. The OS-1 and OS-2 corrosion inhibitors were applied to the concrete by spray appli- cation at a net coverage rate of 100 ft 2 /gal (2.5 m 2 /L). This was achieved by applying two coats at 200 ft 2 /gal (5 m 2 /L) for each coat. Chloride penetration was determined using ASTM C1152 10 on cores extracted from a designated area on each of the con- crete slabs. Profiles were measured at cor- rosion initiation, just prior to application of the OS inhibitors, and at the end of testing. The macrocell current between each top reinforcing bar and the bottom WWF was determined at the end of each ponding cycle by reading the voltage drop across the 1-Ω resistors that connected each compo- nent to a common bus bar. The area of one top reinforcing bar was ~57 in 2 (36,776 mm 2 ) (#4 bar, with a 36-in [914-mm] length exposed). The degree of corrosion was assessed using the guidelines in the M-82 protocol. Carbonation-Induced Corrosion The carbonation corrosion testing was conducted using beams with th e sam e dimensions noted in ASTM G109, 11 with a reduced concrete cover of 0.5-in over the top reinforcing bar and the standard 1-in concrete cover for the bottom bars. A w/c ratio of 0.6 facilitated carbonation. 12 Spec- im ens were stripp ed from th e covered mol d s on e d ay aft er castin g and th en moist-cured for seven days. Upon the com- pletion of moist-curing, the specimens were put in a room at 100 °F (38 °C) for one week to accelerat e dr ying. Th e b eams were th en placed in a C O 2 chamber to carbonate. 12 Corrosion testing was done per ASTM G 1 0 9 , e xc e p t th a t p o t a b l e t a p w a t e r replaced the chloride solution and the 100-Ω resistor was changed to a 10-Ω resis- tor. One cycle consisted of two weeks of ponding and two weeks of drying. Corro- sion potentials and macrocell currents were measured according to ASTM G109. Results M-82 Protocol Test Results for OS-1 and OS-2 The time to corrosion in M-82 is defined as the time to 0.03 mA and corrosion poten- tials (E corr ) more negative than –300 mV vs.