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54 NOVEMBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 11 CHEMICAL TREATMENT a saturated copper/copper sulfate (Cu/ CuSO 4 ) electrode (CSE). Observations of the slabs used in the OS-1 study found that the average time for corrosion initiation was five cycles with a standard deviation (SD) of 1.5 cycles. One cycle is four weeks long (two weeks of ponding and two weeks of dr ying ). At this point in the testing phase, OS-1 was applied to the surface of five of the corroding slabs, which were labeled as "treated." Two coats of OS-1 were applied to the slabs, with each coat applied at a coverage rate of 200 ft 2 /gal. TABLE 1. PROPERTIES OF CONCRETES USED TO EVALUATE OS-1 AND OS-2 Property Value OS-1 OS-2 Plastic Properties Slump (ASTM C143) 13 3.5 in (889 mm) 3.75 in (953 mm) Unit Weight (ASTM C138) 14 143.8 Air Content (ASTM C231) 15 6.0% 4.6% Setting Time (ASTM C403) 16 4.9 h 6.3 h 4.3 h 5.6 h Hardened Properties Background Chloride Content (ASTM C1152) 248 ppm 218 ppm Mat-to-Mat Resistance 10.4 Ω 11.8 Ω Electrical Resistivity 4,453 Ω·cm 3,670 Ω·cm Compressive Strength (ASTM C39 17 ) 1-day/3-day 1,803 psi (12.43 MPa) 3,910 psi (26.96 MPa) 7-days 4,320 psi (29.79 MPa) 4,370 psi (30.13 MPa) 28-days 5,150 psi (35.51 MPa) 5,360 psi (36.96 MPa) 56-days (calculated/actual) 6,080 psi (41.92 MPa) 5,670 psi (39.09 MPa) 90-days (calculated/actual) 6,560 psi (45.23 MPa) 6,080 psi (41.92 MPa) Chloride Ion Resistance ASTM C1202 18 ASTM C1760 19 (Equivalent ASTM C1202 value) 28 days/36 days 5,549 C 25.5 mS/m (4,640 C) 90 days 5,300 C 22.4 mS/m (4,070 C) 180 days 3,690 C 17.1 mS/m (3,110 C) 365 days 3,590 C 14.1 mS/m (2,620 C) TABLE 2. CONCRETE AVERAGE VALUES OF CHLORIDE AT THE REBAR DEPTH (1 IN) FOR OS-1 Value Control/Untreated (ppm in Concrete) Treated (ppm in Concrete) Cycle 5 End of Test Cycle 5 End of Test Average 1,712 3,730 1,572 2,652 SD 148 169 155 136 Relative humidity (RH) readings of the control slabs indicated they essentially remained saturated from time of treat- ment, whereas the RH decreased initially in the slabs treated with OS-1 and then gradu- ally increased . Although the RH of the treated slabs was lower than the RH of the control slabs, the RH value was still in a region that would support corrosion. 9 The average chloride content at the level of the reinforcing bars (1-in depth) was determined at the time the OS-1 was applied and at the end of testing, and is shown in Table 2. At the time of OS-1 appli- cation, the chloride values were not signifi- cantly different in the control and treated slabs. However, over time, as additional chlorides were being introduced into the slabs by ponding with NaCl, the increase in chloride ion penetration was much higher for the untreated slabs compared to the treated slabs. This indicated that OS-1 was efficient at keeping the majority of chlo- rides from penetrating into the concrete. Macrocell current was constantly moni- tored for each slab. Just prior to the appli- cation of OS-1, the average macrocell cur- rent measured was 9,097 C, well beyond the M-82 protocol's minimum value of 5,000 C for application of the treatment. Hence, at the end of the study, considerable rust and corrosion on the bars was expected for the treated as well as untreated slabs. The effectiveness of the treatment can be determined by comparing the inte- grated macrocell current after the treat- ment was applied, as shown in Figure 2. The change in slope of the macrocell cur- rent curve shows that after treatment with O S - 1 , t h e i n t e g ra t e d c u r re n t f o r t h e untreated slabs increased at a much faster rate than the treated slabs. The 95% confi- dence limits are the dashed lines. The crack length and area were mea- sured after the test. Both crack length and area decreased by over a factor of three for the treated slabs compared to the untreated slabs. 9 The slabs also were cut and the rebar removed to examine the corrosion activity at the rebar. Visual examination indicated that 46.4% of the area at the top of the rebar was corroding in the untreated slabs com- pared to 24.6% in the treated slabs. It must be not ed that signs of corrosion were expected on the rebar from the treated slabs as corrosion was induced before treatment. The corroded area for the bars in the treated slabs was significantly less than for the control slabs, indicating that corrosion was mitigated by the application of OS-1. 9