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Federal Highway Administration > Publications > Research > Structures > Long-Term Performance of Epoxy-Coated Reinforcing Steel in Heavy Salt-Contaminated Concrete

Publication Number: FHWA-HRT-04-090
Date: JUNE 2004

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Chapter 3. RESULTS AND DISCUSSION

Short-Circuit Potential and Macrocell Current Density

Tables 6 through 8 summarize the last electrochemical test data, grouped by type of test slab, that were collected in December 2002 just before the autopsy of the slabs. The data include SCP, OCP, macrocell current, AC resistance, and impedance modulus at 0.1 Hz. Figures 5 through 16 summarize the changes of mean SCP and mean macrocell current density with time for the slabs having different configurations. The elapsed time in the figures was calculated from the day when the slabs were placed in the outdoor test yard. It was noted that when test slabs had suffered from corrosion-induced physical damage, the data listed in tables 6, 7, and 8 did not represent actual condition of the reinforcing bars in those slabs.

Test slabs containing black bars in both mats

Each of the black bar test samples had cracking and delamination of the concrete cover after 96-week SE testing and before placing the slabs outdoors. Therefore, the SCP and microcell currents measured after cracking are not indicative of the true difference in performance, because the corrosion rate and potentials (SCP) drop after cracking and delamination of the concrete cover occurs. The straight, non-bent black bars had an average corrosion current density of about 2.4 mu symbolA/cm2 (15.5 mu symbolA/in.2) during the 96-week SE testing. Upon outdoor exposure, the black bar samples averaged somewhat less than 1.5 mu symbolA/cm2 (9.7 mu symbolA/in.2). This same effect may be present for some of the other poorly performing ECR samples with large damaged areas, precracks, and bending damage.

Test slabs containing ECRs in the top mat and black bars in the bottom mat

Test slabs containing ECRs performed better, especially the ones with smaller initial defect size (0.004 percent), than the black bar control slabs because ECRs exhibited lower macrocell current and more positive SCP over the test period than those of the black bar counterparts. Macrocell current density of the black bars became negative in every category after 1,600 days (see figures 6, 8, and 10). Negative current readings indicated reversal of macrocell current between original anode (top mat) and original cathode (bottom mat) at the time of measurement. Such current reversal was caused by corroding bottom mat cathode steel first instead of usual corrosion initiation at the top mat bars. This situation was possible when chloride reached the black bars in the bottom mat and subsequently initiated the active corrosion there, while top mat ECRs were able to suppress corrosion. As discussed later, chloride concentration at some bottom bar depths was found to far exceed the chloride threshold for corrosion initiation of black bars (250 to 300 ppm).

Test slabs containing ECRs in both mats and stainless steel

Figures 11 and 12 show variations of mean SCP and macrocell current density with time for the slabs containing either ECRs in both mats or stainless steel. There were three test slabs containing stainless steel bars in the top mat or in both mats, and two of them were precracked. Because of the small number of slabs, the stainless steel slabs were treated as one variable, even though some contained cracks and/or black bottom bars. Each pair of ECRs in the top and bottom mats contained the same coating damage (0.004 or 0.5 percent), and every slab contained two pairs of ECRs with each of the two coating defect areas. While the 0.5 percent damaged ECRs exhibited more negative potentials compared to the others (ECRs with 0.004 percent coating defect and stainless steel) during most of the exposure time, all of the mean macrocell current density data remained very small throughout the test period. Mean macrocell current density of stainless steel bars with black bottom steel became negative at around 1,600 days due to active corrosion in the bottom black mat. Furthermore, when ECR was used in both mats, the coating defect size did not make a noticeable difference in macrocell current density output, which approached that of stainless steel bars. This observation suggests that using ECRs in both mats in northern bridge decks is likely to give very high corrosion resistance in corrosive environments under deicing salt applications, and may approach an equivalent corrosion resistance to that offered by stainless steel bars.

Effect of precrack

The effect of having precracks on SCP and macrocell current density can be seen in figures 13 and 14, which show the change of mean SCP and mean macrocell current density with time for the slabs containing straight black bars and straight ECRs, respectively. All the top bars were connected to black bottom bars. In general, mean SCP and macrocell current density data for black bars and top mat ECRs behaved similarly in precracked and uncracked concrete during the outdoor weathering test period. The presence of the precrack influenced the time-to-corrosion initiation during the initial 96 weeks of SE testing more than after long-term outdoor exposure.

Effect of bent ECR

Figures 15 and 16 show the change of mean SCP and mean macrocell current density with time for straight and bent ECRs in uncracked concrete, respectively. Test slabs containing ECRs in both mats exhibited the most negative mean SCP among three groups, however, the performance between the groups was not largely different. When bent ECRs were connected to the black bottom bars, they produced the highest mean macrocell current density and were followed closely by the straight ECRs coupled with black bottom bars. In contrast, test slabs containing straight ECRs in both mats exhibited insignificant mean macrocell current density throughout the entire exposure period.

Further data analysis related to slab configuration and bar type

Table 9 summarizes the mean values of the test data presented in figures 5 through 12 according to four bar types (black, stainless steel, ECR with 0.5 percent initial coating damage, and ECR with 0.004 percent initial coating damage) and five slab configurations (straight top-black bottom-uncracked, straight top-ECR bottom-uncracked, straight top-black bottom-precracked, bent top-black bottom-uncracked, and stainless steel bars in uncracked).

The SCP and macrocell current density data listed in table 9 also are presented in figures 17 and 18, respectively. As shown in figure 17, black and stainless steel bars exhibited the most negative and positive mean SCP, respectively. Mean SCP of the black bars moved in the negative direction when slabs contained precracks and bent bars. When coating defect size decreased from 0.5 to 0.004 percent, the mean SCP became more positive (lower corrosion tendency). As observed in figures 5 through 16, mean macrocell current density varied significantly depending on slab configuration and bar type. This trend is summarized in figure 18. The black bars produced the highest mean macrocell current density among various combinations of test variables regardless of slab configuration, i.e., presence of crack and bar shape (bent vs. straight).

To illustrate relative significance of slab configuration and bar type on the mean macrocell current density, figure 19 presents the ratios of macrocell current density data shown in table 9 and figure 18 by dividing them by the highest average value (1.3 mu symbolA/cm2 (8.4 mu symbolA/in.2)) of the black bent bar-black bottom-uncracked concrete slabs. The stainless steel bars exhibited negligible mean macrocell current density which was only 1 percent of the highest black bar case. For straight ECRs, the mean macrocell current density was influenced by the size of the initial coating damage and whether the bottom mat bar was coated or uncoated. When straight ECRs in the top mat were coupled with black bars in the bottom mat, the size of coating defect became a factor for controlling macrocell current density. In the case of straight top ECRs containing 0.004 percent of initial coating defect coupled with black bottom bars, mean macrocell current density was 7 to 21 percent of the highest black bar case, depending on the presence of precracks. If straight top ECRs contained 0.5 percent initial coating defect, the current values increased to more than 40 percent of the highest black bar case, regardless of whether the slab had a precrack. For bent ECRs, even ones containing 0.004 percent coating damage produced noticeable macrocell current density when they were connected to black bottom bars, such that mean macrocell current density increased to 38 and 49 percent of the highest black bar case, regardless of initial coating defect size. If top mat ECRs were connected to ECRs in the bottom mats in uncracked concrete, the effect of coating damage on macrocell current density was minor, and the ratio decreased to no greater than 2 percent of the highest black bar data. They behaved similarly to stainless steel bars.

Figure 20 shows the effect of coating defect size on macrocell current density for ECRs in top mat only and ECRs in both mats cases. A regression analysis shows a well-defined relationship, indicating that defect size makes a significant influence on the ECRs coupled with black bottom bars, but the coating size effect is diminished when ECRs are used in both mats.

Effect of coating type

Table 10 lists mean SCP and mean macrocell current density data per coating type. The same data are presented in figures 21 and 22. Because of a large variation among different coating types, mean macrocell current density is presented in two scales: a linear scale in figure 22(a) and a logarithmic scale in figure 22(b). Performance differences are difficult to interpret from the SCP data in figure 21. Generally, coatings C and F had the worst SCP data, while coatings A, D, and E had the best SCP data. It can be seen in figure 22 that mean macrocell current density varied significantly by coating type, which could be related to coating quality, but such variation disappeared when ECRs were used in both mats. Coatings A and D performed well in all configurations, while coatings C and F had generally poor performance (except for the case of ECRs in both mats).

Statistical Analysis of Test Data

A statistical analysis was conducted to calculate sample mean (Symbol: Variable x with a line over it indicating mean.) and sample standard deviation (s) for SCP, macrocell current density, AC resistance, and impedance modulus at 0.1 Hz data. Then, the results were used to determine the 95 percent confidence interval for the unknown population mean (mu symbol). The 95 percent confidence interval for mu symbol means that researchers are 95 percent confident that the unknown mu symbol is within this interval for a variable. Statistical analysis was performed for the variables classified by combinations of slab configuration and bar type, and the final results are provided in figures 23 through 26.

Figure 23 shows the distribution of mu symbol for the SCP data categorized by 12 combinations of test variables. The mu symbol's are evenly distributed among different variables. The stainless steel bars and bent black bars exhibited the most positive and most negative SCP mean values, respectively.

Figure 24 shows distribution of mu symbol's for the macrocell current density data categorized by 12 combinations of test variables. As noted in earlier sections, use of stainless steel bars and ECRs containing 0.004 percent initial coating damage produced the least current density. When ECRs having 0.5 percent initial coating defect are used in both mats, the macrocell current density slightly increased from zero. These are followed by straight ECRs containing 0.004 percent coating defects in the top mat only and other top mat only ECR cases. The black bar cases yielded the highest mean values.

High coating resistance and impedance is characteristic of a quality, corrosion-resistant coating. Figures 25 and 26 show distribution of mu symbol's for AC resistance measured between the two mats and impedance modulus at 0.1 Hz of top mat bar, respectively. Impedance modulus data exhibited larger variations and higher absolute values than did the AC resistance test data. The four highest upper limits of mu symbol's were achieved by ECRs containing 0.004 percent coating defect. However, the lowest limit of mu symbol's was near zero resistance for most combinations of test variables.

Autopsy Results

Researchers began test slab autopsies by making a 1.3-cm (0.5-inch) deep groove along the bottom side of the slabs at two locations (figure 27) using a gas-powered saw. A test slab was split into several fragments by using a chisel and hammer. Embedded bars were then carefully extracted using a small chisel and hammer (figure 28). Researchers exercised caution when removing ECRs to avoid coating damage.

Figure 29 shows a photograph of a top mat straight ECR that performed well throughout the severe testing regime. The ECR and concrete/bar interface appearance was excellent, with no sign of corrosion. Figure 30 shows a severely corroded, straight, top mat ECR. Figures 31 and 32 show photographs of well and poorly performing bent ECRs, respectively, both from the top mat.

Closeup examination of the extracted ECRs revealed four different coating conditions, which are shown in figure 33. When the ECR performed well, the exposed coating looked new with a glossy texture (figure 33(a)). It was observed that when the epoxy coating reaches the advanced stage of deterioration due to corrosion, the coating exhibits numerous hairline cracks (figure 33(b)) and then blisters (figure 33(c)). Accumulation of multiple rust layers beneath disbonded coating was also a common corrosion morphology observed on severely corroded ECRs (figure 33(d)). The disbonded coating mentioned above was defined as a permanently separated coating from substrate upon knife adhesion test performed several days after the ECRs were excavated. Therefore, it was different from temporary adhesion loss, which can recover fully or partially with time.

Figures 34 and 35 show photographs of a severely corroded straight black bar and a poorly performed bent black, respectively. Figure 36 shows a photograph of a broken test slab fragment, which exhibited active corrosion in the bottom black bar mat.

All of the extracted bars, including those in the bottom mat, were carefully documented, cleaned, and examined according to the autopsy procedure described. Figures 37 and 38 show photographs of autopsied bars taken after they were cleaned. The bars shown in figure 37 were removed from slab #18, which contained ECRs in the top mat only. While one top ECR (the second bar from the top in the photograph) exhibited localized coating disbondment originated from corrosion at the smaller artificial coating defects (0.004 percent), the other top ECR (the first bar from the top in the photograph) experienced severe corrosion, again initiated at the larger artificial coating defects (0.5 percent), such that the epoxy coating could be peeled off completely.

The bars shown in figure 38 were removed from slab #10, which contained ECRs in both mats. While one top ECR (the second bar from top in the photograph) exhibited virtually no reduction in adhesion even at the smaller artificial coating defects (0.004 percent), the other top mat ECR (the first bar from top in the photograph) experienced moderate corrosion that initiated at the larger artificial coating defects (0.5 percent), such that epoxy coating could be peeled off locally around the initial defects. The ECRs extracted from the bottom mat were corrosion-free and had minimal adhesion loss. The photographs of individual autopsied bars are included in appendix A.

Tables 11 and 12 summarize the findings of the autopsied ECRs in terms of the number of final defects, coating thickness, exterior physical appearance, knife adhesion, and degree of adhesion loss. Final defects were classified as bare area, mashed area (mechanical damage), coating crack, and holiday. The number of final coating defects on the autopsied ECRs was very large on some poorly performing bars, while others maintained good coating continuity. The coating cracks as shown in figure 33 were the most frequent form of coating deterioration. When the coating defects were too excessive to count individual defects, an arbitrary number of 100 was assigned to quantify the worst condition in the subsequent data analysis.

Figures 39 through 42 present the 95 percent confidence intervals for mu symbol of the data provided in tables 11 and 12. Each plot was constructed for 10 combinations of test variables. It is statistically significant that the ECRs removed from the bottom mat of the ECR top-ECR bottom slabs exhibited the least number of final defects (figure 39) and the best appearance (figure 40). The bottom mat ECRs extracted from these slabs also exhibited the strongest knife adhesion (figure 41) and the least amount of coating disbondment (figure 42). Their performance was followed by the top mat straight ECRs containing 0.004 and 0.5 percent coating defects, respectively. Conditions of top mat ECRs that were removed from the ECR top-ECR bottom slabs were not particularly different from those of the top mat only cases. Based on macrocell current density data and autopsy results, the excellent performance of test slabs containing ECRs in both mats should be attributed to the fact that the presence of ECR in the bottom mat suppresses the corrosion activity by minimizing the cathodic reaction (oxygen reduction through consuming electrons). In general, bent ECRs, when coupled with black bottom bars, performed the worst of all materials tested.

Chloride Analysis

Tables 6 through 8 list the water-soluble chloride data for every bar in the top mat. Based on the reversal of macrocell current and the high level of chloride in the top mat, some slabs were selected for additional chloride analysis at the bottom mat. To estimate the total chloride, limited acid-soluble chloride analysis also was conducted, with the selected powder samples representing various concentrations of water-soluble chloride. Figure 43 shows a result of the regression analysis demonstrating a relationship between water-soluble vs. acid-soluble chloride concentration. Regression analysis of the experimental chloride data indicates that the water-soluble chloride concentration of the concrete is approximately 89 percent of the total (acid-soluble) chloride concentration. Coarse aggregates used in this project came from Eau Claire, WI. Because these aggregates did not contain chlorides, the acid-soluble (total chlorides) and water-soluble (free chlorides) test results were similar.

Figure 44 shows the 95 percent confidence intervals for mu symbol for 10 combinations of test variables. It is interesting to note that water-soluble chloride concentration in the top mat containing black bars was far lower than the rest. This is likely due to the fact that the slabs containing black bars were cracked and delaminated after the 96-week SE testing and before being placed outdoors. Rainwater passing through the cracks and delaminations likely dissolved some of the free chloride ions in the concrete near the top mat of steel. Compounding of the free chloride in the black bar rust products also may have occurred.


Figure 5. Short-circuit potential change with time (straight top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure. Graph. This chart plots the short circuit potential change for straight top black and ECR uncracked concrete. The vertical axis is short-circuit potential ranging from -0.7 to 0.00, and the horizontal axis is time in days ranging from 0 to 2000. The key contains black circles that are the black mean, green squares that are the ECR mean with 0.004 percent damage and red triangles that are the ECR mean with 0.5 percent damage. The black mean ranges from -0.56 at 100 days and ascends to -0.3 at 1900 days. The red ECR mean varies between -0.42 at 100 days holding steady to end on -0.3 at 1900 days. The green ECR mean varies between -0.25 at 100 days and descends to -0.4 at 1900 days.
Figure 5. Short-circuit potential change with time (straight top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure

Figure 6. Macrocell current density change with time (straight top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure. Graph. This chart plots the macrocell current density for straight top black and ECR uncracked concrete. The vertical axis is macrocell current density ranging from -1.5 to 3.0, and the horizontal axis is time in days ranging from 0 to 2000. The key contains black circles that are the black mean, green squares that are the ECR mean with 0.004 percent damage and red triangles that are the ECR mean with 0.5 percent damage. The black mean ranges from 2.75 at 100 days and descends to -1.25 at 1900 days. The red ECR mean varies between 0.25 at 100 days and varies between 1.5 and 0 ending on 0.5 at 1900 days. The green ECR mean is a steady line that starts at 0.0 and ends on 0.5 at 1900 days.
Figure 6. Macrocell current density change with time (straight top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure

Figure 7. Short-circuit potential change with time (straight top (black and ECR)-black bottom-cracked concrete) during outdoor exposure. Graph. This chart plots the short circuit potential change for straight top black and ECR cracked concrete. The vertical axis is short-circuit potential ranging from -0.8 to 0.00, and the horizontal axis is time in days ranging from 0 to 2000. The key contains black circles that are the black mean, green squares that are the ECR mean with 0.004 percent damage and red triangles are the ECR mean with 0.5 percent damage. The black mean ranges from -0.5 at 100 days, dips to -0.78, and ascends to -0.4 at 1900 days. The red ECR mean varies between -0.45 at 100 days and ascends to -0.3 and ends at -0.4 at 1900 days. The green ECR mean varies between -0.3 at 100 days, ascends to -0.2 and ends at -0.38 at 1900 days.

Figure 7. Short-circuit potential change with time (straight top (black and ECR)-black bottom-cracked concrete) during outdoor exposure

Figure 8. Macrocell current density change with time (straight top (black and ECR)-black bottom-cracked concrete) during outdoor exposure. Graph. This chart plots the macrocell current density for straight top black and ECR cracked concrete. The vertical axis is macrocell current density ranging from -2.0 to 4.0, and the horizontal axis is time in days ranging from 0 to 2000. The key contains black circles that are the black mean, green squares that are the ECR mean with 0.004 percent damage and red triangles that are the ECR mean with 0.5 percent damage. The black mean ranges from 0.5 at 100 days and descends to -1.25 at 1900 days. The red ECR mean varies between 0.5 at 100 days, ascends to 2.6 at 800 days and ends on -2.5 at 1900 days. The green ECR mean is a steady line that starts at 2.5 and ends on 0.0 at 1900 days.
Figure 8. Macrocell current density change with time (straight top (black and ECR)-black bottom-cracked concrete) during outdoor exposure

Figure 9. Short-circuit potential change with time (bent top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure. Graph. This chart plots the short circuit potential change for bent top black and ECR uncracked concrete. The vertical axis is short-circuit potential ranging from -0.7 to 0.00, and the horizontal axis is time in days ranging from 0 to 2000. The key contains black circles that are the black mean, green squares that are the ECR mean with 0.004 percent damage and red triangles that are the ECR mean with 0.5 percent damage. The black mean ranges from -0.65 at 100 days and ascends to -0.3 at 1900 days. The red ECR mean varies between -0.45 at 100 days and ascends to -0.25 at 1900 days. The green ECR mean is a steady line between -0.35 at 100 days and ends on -0.28 at 1900 days.
Figure 9. Short-circuit potential change with time (bent top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure

Figure 10. Macrocell current density change with time (bent top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure. Graph. This chart plots the macrocell current density for bent top black and ECR uncracked concrete. The vertical axis is macrocell current density ranging from -2.0 to 4.0, and the horizontal axis is time in days ranging from 0 to 2000. The key contains black circles that are the black mean, green squares that are the ECR mean with 0.004 percent damage and red triangles that are the ECR mean with 0.5 percent damage. The black mean ranges from 3.2 at 100 days and descends erratically to -1.4 at 1900 days. The red ECR mean varies between 0.7 at 100 days, ascends to 1.1 at 900 days and ends at -0.5 at 1900 days. The green ECR mean starts at 0.5, ascends to 1.75 at 600 days and ends on 0.7 at 1900 days.
Figure 10. Macrocell current density change with time (bent top (black and ECR)-black bottom-uncracked concrete) during outdoor exposure

Figure 11. Short-circuit potential change with time (stainless steel and ECR in both mats-uncracked concrete). Graph. This chart plots the short circuit potential change for stainless steel and ECR in uncracked concrete. The vertical axis is short-circuit potential ranging from -0.7 to 0.00, and the horizontal axis is time in days ranging from 0 to 2000. The key contains blue circles that are the stainless steel, green squares that are the ECR mean with 0.004 percent damage and red triangles that are the ECR mean with 0.5 percent damage. The blue stainless steel circles ranges from -0.22 at 100 days rising to a peaks of 0.12 and descending to -0.28 at 1900 days. The red ECR mean starts at -0.6 and rises to -0.35 at 1900 days. The green ECR mean starts at -0.23 and descends in an erratic pattern to -0.29 at 1900 days.
Figure 11. Short-circuit potential change with time (stainless steel and ECR in both mats-uncracked concrete)

Figure 12. Macrocell current density change with time (stainless steel and ECR in both mats-uncracked concrete). Graph. This chart plots the macrocell current density for stainless steel and ECR uncracked concrete. The vertical axis is macrocell current density ranging from -0.05 to 0.20, and the horizontal axis is time in days ranging from 0 to 2000. The key contains blue circles that are the stainless steel, green squares that are the ECR mean with 0.004 percent damage and red triangles that are the ECR mean with 0.5 percent damage. The blue stainless steel circles make a steady line that ranges from 0.01 to -0.01 at 1900 days. The red ECR mean starts high at 0.17 and descends to a steady line that ends on 0.00 at 1900 days. The green ECR mean is a steady line that starts at 0.01 and ends on 0.00 at 1900 days.
Figure 12. Macrocell current density change with time (stainless steel and ECR in both mats-uncracked concrete)

Figure 13. Mean short-circuit potential change with time (uncracked vs. precracked concrete). Graph. This chart plots the short circuit potential change for uncracked versus precracked concrete. The vertical axis is short-circuit potential ranging from -0.700 to 0.000, and the horizontal axis is time in days ranging from 0 to 2000. The key contains solid black circles that represent uncracked straight black top and bottom, open black circles that are precracked straight black top and bottom, green solid squares that are the uncracked straight ECR top with black bottom and open green squares that are the precracked straight ECR top with black bottom. The solid black circle values start at -0.580 and ascend erratically to a high of -0.180 at 1500 days and end at -0.300. The open black circle line starts near -0.500 and ascends in a similar configuration ending at -0.400. The solid green square line starts at -0.330, ascends to -0.200 and levels out to -0.300 at 1900 days. The open green squares start at -0.390 and follow a similar pattern to end at -0.330 at 1900 days.
Figure 13. Mean short-circuit potential change with time (uncracked vs. precracked concrete)

Figure 14. Mean macrocell current density change with time (uncracked vs. precracked concrete). Graph. This chart plots the mean macrocell current density for uncracked versus precracked concrete. The vertical axis is macrocell current density ranging from -1.5 to 3.0, and the horizontal axis is time in days ranging from 0 to 2000. The key contains solid black circles that represent uncracked straight black top and bottom, open black circles that are precracked straight black top and bottom, green solid squares that are the uncracked straight ECR top with black bottom and open green squares that are the precracked straight ECR top with black bottom. The solid black circle values start at 2.7 and descend erratically to -1.2 at 1900 days. The open black circle line starts at 0.6 and ascends erratically until it drops to -0.4 at 1900 days. Both the uncracked and precracked straight ECRs plot similarly, starting at 0.4 and diverting only at the last point when the uncracked reading is 0.5 and the cracked reading is 0.2.
Figure 14. Mean macrocell current density change with time (uncracked vs. precracked concrete)

Figure 15. Mean short-circuit potential change with time (straight vs. bent ECRs in uncracked concrete). Graph. This chart plots the short circuit potential change for uncracked concrete for straight ECR, bent ECR and straight ECR in both mats. The vertical axis is short-circuit potential ranging from -0.600 to 0.000, and the horizontal axis is time in days ranging from 0 to 2000. The key contains green squares that are the straight ECR top with the black bottom, red triangles that are bent ECR top with the black bottom and blue squares that are the straight ECRs in both mats. The green squares start at -0.340, ascend to -0.200 and end at -0.300 at 1900 days. The red triangles start at -0.400 and gradually ascend to -0.220. The blue squares start at -0.420 and ascend erratically to -0.330 at 1900 days.
Figure 15. Mean short-circuit potential change with time (straight vs. bent ECRs in uncracked concrete)

Figure 16. Mean macrocell current density change with time (straight vs. bent ECRs in uncracked concrete). Graph. This chart plots the mean macrocell current density for uncracked concrete for straight ECR, bent ECR and straight ECR in both mats. The vertical axis is macrocell current density ranging from 0.0 to 1.2, and the horizontal axis is time in days ranging from 0 to 2000. The key contains green squares that are the straight ECR top with the black bottom, red triangles that are bent ECR top with the black bottom and blue squares that are the straight ECRs in both mats. The green squares start at 0.4 and ascend and descend erratically ending at 0.5. The red triangles start at 0.6 and ascend and descend erratically ending at 0.5. The blue squares start at 0.1 and track a straight line along the 0.0 value until 1900 days.
Figure 16. Mean macrocell current density change with time (straight vs. bent ECRs in uncracked concrete)

Figure 17. Mean short-circuit potential data classified by bar type (from table 9). Graph. This bar chart shows the short circuit potential change by bar type. The vertical axis is short-circuit potential ranging from -0.500 to 0.000, and the horizontal axis is the various color-coded bar types. The key identifies them as straight top-black bottom-uncracked (lavender) straight top-black bottom-precracked (yellow), stainless steel (red), straight top-ECR bottom, uncracked (magenta) and bent top-black bottom-uncracked (light blue). Under the black category, the lavender bar reads -0.413, the yellow bar -0.447, and the light blue bar is -0.469. The red bar stainless steel reading is -0.196. The ECR with 0.004 damage readings are: -1.274 for the lavender bar, -0.272 for the magenta bar, -0.353 for the yellow bar and -0.319 for the light blue bar. For the ECR with 0.5 percent damage the readings are: -0.341 for the lavender bar, -0456 for the magenta bar, -0.382 for the yellow bar and -0.354 for the pale blue bar.
Figure 17. Mean short-circuit potential data classified by bar type (from table 9)

Figure 18. Mean macrocell current density data classified by bar type (from table 9). Graph. This bar chart shows the mean macrocell current density by bar type. The vertical axis is macrocell current density ranging from 0.0 to 1.5, and the horizontal axis is the various color-coded bar types. The key identifies them as straight top-black bottom-uncracked (lavender) straight top-black bottom-precracked (yellow), stainless steel (red), straight top-ECR bottom, uncracked (green) and bent top-black bottom-uncracked (light blue). Under the black category, the lavender bar reads 1.24, the yellow bar 1.24, and the light blue bar is 1.30. The red bar stainless steel reading hardly registers at 0.01. The ECR with 0.004 damage readings are: 0.09 for the lavender bar, 0.01 for the green bar, 0.27 for the yellow bar and 0.64 for the light blue bar. For the ECR with 0.5 percent damage the readings are: 0.60 for the lavender bar, 0.02 for the green bar, 0.53 for the yellow bar and 0.49 for the pale blue bar.
Figure 18. Mean macrocell current density data classified by bar type (from table 9)

Figure 19. Relative ratio of macrocell current density per slab configuration. Graph. This bar chart shows the ratio of macrocell current density by the various slab configurations. The vertical axis is the ratio ranging from 0.0 to 1.0, and the horizontal axis lists the categories. The key identifies the black as black, the ECR (0.004 percent damage) as left to right green cross-hatching and the ECR (0.5 percent damage) as right to left green cross-hatching and the stainless steel is blue. In the straight top-black bottom-uncracked category, the black reading is 0.95, and the green cross-hatched values are 0.07 and 0.46. In the straight top-black bottom-precracked category, the black reading is 0.95, and the green cross-hatched values are 0.21 and 0.41. In the bent top-black bottom-uncracked category, the black reading is 1.00 and the green cross-hatched values are 0.49 and 0.38. For the straight top-ECR bottom-uncracked category, the black reading is negligible at 0.01 and the green ECR (0.5 percent damage) value is 0.02. In the last category, the stainless steel reading is 0.01.
Figure 19. Relative ratio of macrocell current density per slab configuration

Figure 20. Relationship between macrocell current density versus initial artificial coating defects. Graph. This line graph shows the relationship between the microcell current density and initial coating defects. The vertical axis is microcell current density ranging from 0.0 to 1.4, while the horizontal axis is the reciprocal of the initial coating damage in percent ranging from 0.01 to 1000. The key shows a blue circle for the ECR in the top mat only and a green square for the ECR in both mats. The blue line is the log connecting the blue circles and the green line is the log connecting the green squares. The formulae listed for the two situations are Y (ECR in top mat only) equals -0.1053LN times X plus 0.7914 with R squared equaling 0.94 and Y (ECR in both mats) equals -0.0055LN times X plus 0.0376 with R squared equaling 1.0. The blue line descends from 1.3 to 0.2, and the green line is level near 0.0 starting at 0.5 and ending at 400.
Figure 20. Relationship between macrocell current density versus initial artificial coating defects

Figure 21. Short-circuit potential data classified by coating type. Graph. The bar chart shows short-circuit potential data by coating types. The vertical scale is short-circuit potential ranging from -0.600 to 0.000, while the horizontal scale is the coating categories. The key identifies them as straight top-black bottom-uncracked (lavender) straight top-black bottom-precracked (yellow), straight top-ECR bottom, uncracked (green) and bent top-black bottom-uncracked (light blue). Under all ECRs combined, the lavender bar reads -0.29, the green bar -0.372, the yellow bar -0.355, and the light blue bar is -0.328. For coating A, the readings are -0.272 for the lavender bar, -0.250 for the green bar, -0.303 for the yellow bar, and -0.377 for the light blue bar. For coating B, the readings are -0.217 for the lavender bar, -0.415 for the green bar, -0.350 for the yellow bar, and -0.282 for the pale blue bar. For coating C, the readings are -0.450 for the lavender bar, -0.554 for the green bar, -0.346 for the yellow bar, and -0.430 for the light blue bar. For coating D, the readings are -0.149 for the lavender bar, -0.293 for the green bar, -0.209 for the yellow bar, and -0.193 for the pale blue bar. For coating E, the readings are -0.301 for the lavender bar, -0.303 for the green bar, -0.427 for the yellow bar, and -0.211 for the light blue bar. For coating F, the readings are -0.387 for the lavender bar, -0.288 for the green bar, -0.505 for the yellow bar, and -0.452 for the pale blue bar.
Figure 21. Short-circuit potential data classified by coating type

Figure 22(A). Macrocell current density data classified by coating type (linear scale). Graph. The bar chart shows macrocell current density data by coating types. The vertical scale is macrocell current density ranging from 0.0 to 2.0, while the horizontal scale is the coating categories. The key identifies them as straight top-black bottom-uncracked (lavender) straight top-black bottom-precracked (yellow), straight top-ECR bottom, uncracked (green), and bent top-black bottom-uncracked (light blue). Under all ECRs combined, the lavender bar reads 0.35, the green bar is 0.01, the yellow bar is 0.40, and the light blue bar is 0.57. For coating A, the readings are 0.02 for the lavender bar, 0.01 for the green bar, 0.02 for the yellow bar, and 0.13 for the light blue bar. For coating B, the readings are 0.25 for the lavender bar, 0.01 for the green bar, 0.46 for the yellow bar, and 0.28 for the pale blue bar. For coating C, the readings are 0.87 for the lavender bar, 0.01 for the green bar, 0.77 for the yellow bar, and 1.94 for the light blue bar. For coating D, the readings are 0.02 for the lavender bar, 0.04 for the green bar, 0.03 for the yellow bar, and 0.02 for the pale blue bar. For coating E, the readings are 0.28 for the lavender bar, 0.01 for the green bar, 0.19 for the yellow bar, and 0.03 for the light blue bar. For coating F, the readings are 0.59 for the lavender bar, 0.01 for the green bar, 0.55 for the yellow bar, and 1.00 for the pale blue bar.
Figure 22(a). Macrocell current density data classified by coating type (linear scale)

Figure 22(B). Macrocell current density data classified by coating type (logarithmic scale). Graph. The bar chart shows macrocell current density data by coating types using a logarithmic scale. The vertical scale is macrocell current density ranging from 0.001 to 10,000, while the horizontal scale is the coating categories. The key identifies them as straight top-black bottom-uncracked (lavender) straight top-black bottom-precracked (yellow), straight top-ECR bottom, uncracked (green) and bent top-black bottom-uncracked (light blue). Under all ECRs combined, the lavender bar reads 0.35, the green bar is 0.01, the yellow bar is 0.40, and the light blue bar is 0.57. For coating A, the readings are 0.02 for the lavender bar, 0.01 for the green bar, 0.02 for the yellow bar, and 0.13 for the light blue bar. For coating B, the readings are 0.25 for the lavender bar, 0.01 for the green bar, 0.46 for the yellow bar, and 0.28 for the pale blue bar. For coating C, the readings are 0.87 for the lavender bar, 0.01 for the green bar, 0.77 for the yellow bar, and 1.94 for the light blue bar. For coating D, the readings are 0.02 for the lavender bar, 0.04 for the green bar, 0.03 for the yellow bar, and 0.02 for the pale blue bar. For coating E, the readings are 0.28 for the lavender bar, 0.01 for the green bar, 0.19 for the yellow bar, and 0.03 for the light blue bar. For coating F, the readings are 0.59 for the lavender bar, 0.01 for the green bar, 0.55 for the yellow bar, and 1.00 for the pale blue bar.
Figure 22(b). Macrocell current density data classified by coating type (logarithmic scale)

Figure 23. Ninety-five percent confidence intervals for short-circuit potential data. Graph. This bar graph shows the ninety-five percent confidence intervals with short-circuit potential on the horizontal scale, ranging from -0.650 to -0.200. The categories listed below are the vertical axis. ECR top and bottom with 0.5 percent damage ranges from -0.525 to -0.475. Bent black top ranges from -0.600 to -0.525. Black top in precracked concrete ranges from -0.550 to -0.475. Black top ranges from -0.525 to nearly -0.450. ECR top (0.5 percent damage) in precracked concrete ranges from -0.475 to -0.425. Bent ECR top (0.5 percent damage) ranges from -0.425 to -0.375. ECR top (0.004 percent damage) in precracked concrete ranges from -0.450 to -0.380, ECR top (0.5 percent damage) ranges from -0.425 to -0.375. Bent ECR top (0.004 percent damage) ranges from -0.420 to -0.350. Both the ECR top (0.004 percent damage) and the ECR top and bottom with 0.004 percent damage have the same ranges of -0.375 to -0.310. The stainless steel top and bottom reading ranges from -0.250 to -0.210.
Figure 23. Ninety five percent confidence intervals for short-circuit potential data

Figure 24. Ninety-five percent confidence intervals for macrocell current density data. Graph. This bar graph shows the ninety-five percent confidence intervals with macrocell current density on the horizontal scale, ranging from 0.0 to 1.8. The categories listed below are the vertical axis. Bent black top ranges from 0.9 to 1.7. Both black top in precracked concrete and black top range from 0.9 to 1.5. Bent ECR top (0.004 percent damage) ranges from 0.4 to 0.8. ECR top (0.5 percent damage) ranges from 0.4 to 0.7. ECR top (0.5 percent damage) in precracked concrete ranges from 0.4 to 0.6. Bent ECR top (0.5 percent damage) ranges from 0.3 to 0.6. ECR top (0.004 percent damage) in precracked concrete ranges from 0.1 to 0.4. ECR top (0.004 percent damage) ranges from 0.0 to 0.1. Both stainless steel and ECR top and bottom (0.004 percent damage) have readings of 0.0.
Figure 24. Ninety five percent confidence intervals for macrocell current density data

Figure 25. Ninety-five percent confidence intervals for AC resistance data. Graph. This bar graph shows the 95 percent confidence intervals for AC resistance on the horizontal scale, ranging from 1.0E plus 00 to 1.0E plus 08. The categories listed below are the vertical axis. Black top and bottom falls near 1.0E plus 02. Stainless steel falls between 1.0E plus 02 and 1.0E plus 03. ECR top (0.5 percent damage), bent ECR top (0.5 percent damage) and ECR top (0.5 percent damage) in precracked concrete all range from 1.0E plus 00 to between 1.0E plus 03 and 1.0E plus 04. ECR top and bottom (0.5 percent damage) ranges from 1.0E plus 03 to near 1.0E plus 05. ECR top (0.004 percent damage) in precracked concrete, bent ECR top (0.004 percent damage) and ECR top (0.004 percent damage) all range between 1.0E plus 00 and 1.0E plus 06. ECR top and bottom (0.004 percent damage) ranges from near 1.0E plus 05 to more than 1.0E plus 07.
Figure 25. Ninety five percent confidence intervals for AC resistance data

Figure 26. Ninety-five percent confidence intervals for impedance modulus data. Graph. This bar graph shows the 95 percent confidence intervals for impedance modulus at 0.1 Hertz (ohm) on the horizontal scale ranging from 1.0E plus 00 to 1.0E plus 08. The categories are the vertical axis. Black top and bottom ranges from 1.0E plus 00 to almost 1.0E plus 03. Stainless steel falls between 1.0E plus 02 and the midpoint of 1.0E plus 04. ECR top (0.5 percent damage), bent ECR top (0.5 percent damage), ECR top (0.5 percent damage) in precracked concrete, and ECR top and bottom (0.5 percent damage) all range from 1.0E plus 00 to around 1.0E plus 04, ECR top (0.004 percent damage) in precracked concrete, bent ECR top (0.004 percent damage), ECR top (0.004 percent damage), and ECR top and bottom (0.004 percent damage) all range from 1.0E plus 00 to between 1.0E plus 06 and 1.0E plus 07.
Figure 26. Ninety five percent confidence intervals for impedance modulus data

Figure 27. Cutting a test slab with a gas-powered saw. Photo. This picture shows a man outdoors working with five slabs on a wooden pallet. He is wearing a protective mask and is cutting a test slab through the top with a gas-powered rotary saw.
Figure 27. Cutting a test slab with a gas-powered saw

Figure 28. Extraction of embedded reinforcing bars. Photo. This picture shows a man indoors crouching on the floor. He is wearing protective kneepads, gloves, a mask and a face shield. He is using a hand-held sledgehammer to break apart the concrete to extract the reinforcing bars.
Figure 28. Extraction of embedded reinforcing bars

Figure 29. Typical condition of ECR with good corrosion resistance (slab #7-top right bar). Photo. The picture shows an ECR concrete slab with one green bar at the top and two extracted channels and one green bar with no evidence of discoloration or corrosion. The sample label is 7B-T.
Figure 29. Typical condition of ECR with good corrosion resistance (slab #7—top right bar)

Figure 30. Typical condition of ECR with poor performance (slab #30-top right bar). Photo. The picture shows an ECR concrete slab with a severely corroded ECR. The concrete interface shown above the ECR sample is completely covered with corrosion product. The ECR is mottled green with some rust and discolored spots and is separated from the concrete. The label reads 30B-T.
Figure 30. Typical condition of ECR with poor performance (slab #30—top right bar)

Figure 31. Typical condition of a bent ECR with good performance (slab #1-top left bar). Photo. The picture shows a bent gold-colored ECR labeled 1A-T extracted from a concrete slab. The concrete and bar are in good condition with no evidence of discoloration or corrosion.
Figure 31. Typical condition of a bent ECR with good performance (slab #1—top left bar)

Figure 32. Typical condition of a bent ECR with poor performance. Photo. The picture shows a closeup of a corroded bent ECR. The bar is olive green with discoloration and rust spots. The concrete below is discolored dark brown from the corrosion.
Figure 32. Typical condition of a bent ECR with poor performance

Figure 33. Closeup views of ECRs exhibiting various conditions: (A) an intact ECR; (B) an ECR containing hairline cracks; (C) an ECR containing blisters and hairline coating cracks; and (D) a delaminated ECR revealing severely corroded substrate. Photos. Photo (A) shows an intact ECR bar that is pure green and shiny. Photo (B) shows an ECR coating with hairline cracks. The surface color has changed to mottled green and rust and the cracks are black wavy lines. Photo (C) is a closeup of an ECR bar that shows coating blisters and hairline cracks that are rust and brown color compared to the green coating. Photo (D) is a delaminated ECR that has lost a majority of its green color so that the rusty and brown corrosion shows on the substrate.

Figure 33. Closeup views of ECRs exhibiting various conditions:
(a) an intact ECR; (b) an ECR containing hairline coating cracks;
(c) an ECR containing coating blisters and hairline coating cracks; and
(d) a delaminated ECR revealing severely corroded substrate

Figure 34. Typical condition of black bars in the top mat. Photo. The photo shows two severely corroded black bars in the top map. They exhibit significant section loss due to corrosion and their interface with concrete show thick rust layer covered the entire contact surface.

Figure 34. Typical condition of black bars in the top mat

Figure 35. Typical condition of bent black bars in the top mat (slab #23-top right bar). Photo. The picture shows an extracted bent black bar labeled 23A-T from the top map. It is severely corroded.

Figure 35. Typical condition of black bent bars in the top mat (slab #23—top right bar)

Figure 36. Corroded bottom mat (slab #19). Photo. The corroded bottom mat shows four grooves that held bars designated B1, B2, B3 and B4. Two top mat ECRs labeled 19B and 19A had been connected to these bars in the bottom mat. The grooves as well as the area around them are discolored and covered with corrosion products.

Figure 36. Corroded bottom mat (slab #19)

Figure 37. Photograph of autopsied bars extracted from slab #18 (ECR top-black bar bottom). Photo. The picture shows typical condition of poorly performed ECRs along with four bottom mat black bars. They were extracted from slab number eighteen. The top one is the most corroded, the second one has a few corrosion spots, the third, fourth and fifth still have some original color and shine and the bottom bar has some corrosion on the left and some shine on the right.

Figure 37. Photograph of autopsied bars extracted from slab #18 (ECR top-black bar bottom)

Figure 38. Photograph of autopsied bars extracted from slab #10 (ECRs in both mats). Photo. The bars in this photo show typical condition of well performing ECRs in the top mat. Four bottom mat ECRs are also shown at the bottom of the photo. They retain original green coating. The top bar is the most delaminated with some rust spots showing. The second bar up from the bottom shows four intentional coating defects.

Figure 38. Photograph of autopsied bars extracted from slab #10 (ECRs in both mats)

Figure 39. Ninety-five percent confidence intervals for number of final defects. Graph. This bar graph shows the 95 percent confidence intervals with number of defects ranging from 0 to 100 on the horizontal scale and the categories below on the vertical axis. Bent ECR top (0.5 percent damage) ranges from 20 to 99. Bent ECR top (0.004 percent damage) ranges from 0 to 99. ECR top (0.5 percent damage) ranges from 20 to 99. ECR top and bottom (0.5 percent damage) with top ECR ranges from 3 to 85. ECR top (0.5 percent damage) in precracked concrete ranges from 12 to 85. ECR top (0.004 percent damage) ranges from 0 to 62. ECR top and bottom (0.004 percent damage) with top ECR ranges from 0 to 60. ECR top (0.004 percent damage) in precracked concrete ranges from 0 to 57. ECR top and bottom (0.5 percent damage) with bottom ECR ranges from 0 to 5. ECR top and bottom (0.004 percent damage) with bottom ECR ranges from 1 to 3.

Figure 39. Ninety five percent confidence intervals for number of final defects

Figure 40. Ninety-five percent confidence intervals for ECR rating data. Graph. This bar graph shows the 95 percent confidence intervals for ECR rating data with the ECR condition ranging from 0 to 5 on the horizontal scale and the categories below on the vertical axis. Bent ECR top (0.5 percent damage) ranges from 3.6 to 5. ECR top (0.5 percent damage) in precracked concrete ranges from 3.5 to 5. ECR top (0.5 percent damage) ranges from 2.3 to 5. ECR top (0.004 percent damage) ranges from 0.9 to 5. Bent ECR top (0.004 percent damage) ranges from 3 to 4.8. ECR top and bottom (0.5 percent damage) with top ECR ranges from 2 to 4.8. ECR top (0.004 percent damage) in precracked concrete ranges from 1.5 to 4.5. ECR top and bottom (0.004 percent damage) with top ECR ranges from 0.8 to 3.8. ECR top and bottom (0.5 percent damage) with bottom ECR ranges from 1.3 to 2. ECR top and bottom (0.004 percent damage) with bottom ECR ranges from 1.2 to 2.

Figure 40. Ninety five percent confidence intervals for ECR rating data

Figure 41. Ninety-five percent confidence intervals for knife adhesion data. Graph. This bar graph shows the 95 percent confidence intervals with knife adhesions ranging from 0 to 5 on the horizontal scale and the categories below on the vertical axis. Bent ECR top (0.004 percent damage) ranges from 3 to 5. Bent ECR top (0.5 percent damage) is 5. ECR top (0.5 percent damage) in precracked concrete ranges from 3 to 5. ECR top (0.004 percent damage) in precracked concrete ranges from 2 to 5. ECR top and bottom (0.5 percent damage) with top ECR is 5. ECR top (0.5 percent damage) is 5. ECR top (0.004 percent damage) ranges from 1 to 5. ECR top and bottom (0.004 percent damage) with top ECR ranges from 0.8 to 4.8. ECR top and bottom (0.5 percent damage) with bottom ECR ranges from 1.3 to 2.9. ECR top and bottom (0.004 percent damage) with bottom ECR ranges from 1.2 to 2.2.

Figure 41. Ninety five percent confidence intervals for knife adhesion data

Figure 42. Ninety-five percent confidence intervals for extent of disbondment data. Graph. This bar graph shows the 95 percent confidence intervals with disbondment in percent ranging from 0 to 100 on the horizontal scale and the categories below on the vertical axis. Bent ECR top (0.5 percent damage) ranges from 30 to 99. ECR top (0.5 percent damage) in precracked concrete ranges from 55 to 99. ECR top and bottom (0.5 percent damage) with top ECR ranges from 70 to 99. ECR top (0.5 percent damage) ranges from 51 to 99. Bent ECR top (0.004 percent damage) ranges from 5 to 90. ECR top (0.004 percent damage) in precracked concrete ranges from 0 to 72. ECR top and bottom (0.004 percent damage) with top ECR ranges from 0 to 55. ECR top (0.004 percent damage) ranges from 0 to 32. ECR top and bottom (0.5 percent damage) with bottom ECR ranges from 0 to 6. ECR top and bottom (0.004 percent damage) with bottom ECR is 0.

Figure 42. Ninety five percent confidence intervals for extent of disbondment data


Figure 43. Relationship between water-soluble versus acid-soluble chloride data. Graph. The scatter diagram shows the acid-soluble chloride content on the vertical scale ranging from 0 to 1.2 and the water-soluble chloride content on the horizontal scale, also ranging form 0 to 1.2. Y equals 1.1249X plus 0.0113, and R squared equals 0.9176. The blue line ascends above the line of equality with most of the points falling in the lower left quadrant between 0 and 0.6.

Figure 43. Relationship between water-soluble versus acid-soluble chloride data

Figure 44. Ninety-five percent confidence intervals for water-soluble chloride data at top bar depth. Graph. This bar graph shows the 95 percent confidence intervals for water soluble chloride with chloride concentration in parts per million ranging from 0 to 9,000 on the horizontal scale, and the categories below are the vertical axis. ECR top (0.004 percent damage) ranges from 3200 to 8200. ECR top (0.5 percent damage) in precracked concrete ranges from 3000 to 7500. ECR top (0.004 percent damage) in precracked concrete ranges from 2000 to 5800. Stainless steel ranges from 3300 to 5600. Bent ECR top (0.004 percent damage) ranges from 2800 to 5500. ECR top and bottom (0.5 percent damage) ranges from 3000 to 5200. ECR top and bottom (0.004 percent damage) ranges from 2000 to 5000. Bent ECR top (0.5 percent damage) ranges from 2800 to 3800. Black top and black bottom ranges from 1000 to 1500.

Figure 44. Ninety five percent confidence intervals for water-soluble chloride data at top bar depth


 

Table 6. Electrochemical and chloride data for test slabs containing ECR in top mat only
Slab Configuration Final Data Upon Termination Chloride Concentration (ppm)
Test Group Slab ID Coating Type Top Bar ID ECR Artificial Defect Size (Percent) SCP
(V vs. CSE)
I (uA) OCP
(V vs. CSE)
AC Resistance (Ohm) Impedance at 0.1 Hz
(Ohm)
Top Mat Bottom Mat
Water-Soluble Acid-Soluble Water-Soluble Acid-Soluble
Straight ECR Top +
Black Bottom
Uncracked Concrete
3 C 3A 0.5 -0.403 114.1 -0.430 1.6E+02 5.1E+01 1,880      
3B 0.004 -0.576 132.8 -0.635 2.8E+02 2.1E+02 4,300      
6 B 6A 0.5 -0.239 67.6 -0.320 4.4E+02 3.0E+02 3,590      
6B 0.004 -0.125 0.023 -0.308 3.2E+05 1.3E+06 4,880      
15 D 15A 0.004 -0.064 0.0003 -0.166 2.2E+05 2.1E+06 3,660      
15B 0.5 -0.136 0.339 -0.155 3.7E+03 1.6E+04 3,800      
18 F 18A 0.5 -0.429 157.4 -0.479 1.8E+02 1.9E+03 5,830      
18B 0.004 -0.489 26.9 -0.583 1.1E+03 1.0E+02 9,190      
24 A 24A 0.5 -0.228 17.8 -0.396 2.2E+03 4.3E+03 4,100 4,690    
24B 0.004 -0.161 0.002 -0.140 6.8E+05 1.2E+07 4,810      
28 E 28A 0.004 -0.360 234.8 -0.597 5.2E+02 1.7E+03 8,330      
28B 0.5 -0.392 8.5 -0.454 7.4E+02 1.9E+03 2,480      
Straight ECR Top +
Black Bottom In
precracked Concrete
7 A 7A 0.5 -0.384 -5.6 -0.443 2.1E+03 3.3E+03 4,080   1,680  
7B 0.004 -0.335 .0-224 -0.399 1.4E+05 2.2E+06 2,570      
13 C 13A 0.5 -0.174 1.2 -0.240 3.8E+03 2.8E+04 3,900      
13B 0.004 -0.082 0.003 -0.152 1.9E+05 5.7E+05 2,400      
14 E 14A 0.004 -0.334 0.518 -0.474 3.0E+04 1.4E+05 5,270      
14B 0.5 -0.337 13.5 -0.396 5.5E+02 6.1E+02 5,350      
19 F 19A 0.004 -0.471 23.8 -0.502 4.6E+02 1.2E+03 8,060      
19B 0.5 -0.520 350 -0.572 1.6E+02 7.9E+01 9,550 10,610    
21 D 21A 0.5 -0.152 0.002 -0.233 1.2E+04 6.7E+04 2,520      
21B 0.004 -0.140 0.678 -0.173 9.4E+04 4.3E+05 3,500      
25 B 25A 0.004 -0.431 -0.752 -0.383 3.8E+03 4.9E+04 3,650   1,610  
25B 0.5 -0.508 122.3 -0.555 2.0E+02 1.6E+02 7,400 9,270    
30 C 30A 0.004 -0.489 -0.548 -0.512 2.6E+02 1.2E+02 2,740 3,750    
30B 0.5 -0.613 -100.7 -0.573 1.2E+02 7.4E+01 4,570   4,990 4,950
Bent ECR Top +
Black Bottom
Uncracked Concrete
1 D 1A 0.5 -0.157 1.3 -0.210 4.6E+03 3.6E+04 3,670 2,620    
1B 0.004 -0.115 0.002 -0.106 5.2E+05 1.2E+06 5,090   30  
4 C 4A 0.5 -0.467 246.5 -0.524 2.0E+02 1.0E+02 2,850      
4B 0.004 -0.433 320.5 -0.489 1.8E+02 7.5E+01 2,740   840 490
8 F 8A 0.004 -0.385 248.6 -0.449 2.8E+02 9.7E+01 4,920      
8B 0.5 -0.235 50.2 -0.297 4.4E+02 2.2E+02 3,590      
11 B 11A 0.5 -0.312 15.2 -0.403 7.0E+02 1.0E+03 3,640      
11B 0.004 -0.150 1.0 -0.316 5.2E+03 2.8E+04 5,080 4,720    
22 A 22A 0.004 -0.433 51.4 -0.590 1.0E+03 1.5E+03 5,040      
22B 0.5 -0.274 18.7 -0.318 5.9E+02 1.2E+03 3,130 3,880    
31 E 31A 0.5 -0.130 2.6 -0.213 4.2E+03 3.2E+04 2,710      
31B 0.004 -0.146 0.0002 -0.087 > 1100000 5.7E+06 2,450 3,660    

 

 

Table 7. Electrochemical and chloride data for test slabs containing ECR in both mats
Slab Configuration Final Data Upon Termination Chloride Concentration (ppm)
Test Group Slab ID Coating Type Top Bar ID ECR Artificial Defect Size (Percent) SCP
(V vs. CSE)
I (uA) OCP
(V vs. CSE)
AC Resistance (Ohm) Impedance at 0.1 Hz
(Ohm)
Top Mat Bottom Mat
Water-Soluble Acid-Soluble Water-Soluble Acid-Soluble
Straight Top ECR +
Bottom ECR in
Uncracked Concrete
2 F 2A 0.004 0.004 -0.173 0.003 -0.145 8.6E+05 1.7E+06 3,490      
2B 0.5 0.5 -0.305 -2.3 -0.264 1.5E+03 1.8E+03 3,430 4,890 5,560 6,140
9 B 9A 0.5 0.5 -0.459 0.134 -0.418 3.8E+03 2.1E+03 4,880 6,250    
9B 0.004 0.004 -0.459 -0.008 -0.388 3.3E+05 6.5E+04 3,720   110  
10 A 10A 0.5 0.5 -0.181 0.009 -0.186 6.2E+03 4.9E+04 4,520 6,470    
10B 0.004 0.004 -0.174 0.000001 -0.165 > 1.1E+06 1.7E+06 4,180   20  
12 C 12A 0.5 0.5 -0.521 1.4 -0.561 2.6E+03 1.8E+02 3,510   < 30 70
12B 0.004 0.004 -0.562 0.013 -0.590 1.5E+05 1.2E+02 4,300      
17 D 17A 0.004 0.004 -0.262 -0.00004 -0.313 6.4E+05 9.8E+05 5,370 5,720 < 800  
17B 0.5 0.5 -0.275 0.008 -0.333 8.4E+03 9.7E+04 5,870      
29 E 29A 0.004 0.004 -0.060 0.00005 -0.075 5.6E+05 4.9E+07 3,590      
29B 0.5 0.5 -0.389 0.146 -0.394 3.0E+03 2.7E+03

3,160

     

 

 

Table 8. Electrochemical and chloride data for test slabs containing black and stainless steel bars
Test Group Slab ID Slab Configuration Final Data Upon Termination Chloride Concentration (ppm)
Bar ID Top
Mat
Bent / Straight Bottom Mat Precrack
(Yes/ No)

SCP
(V vs. CSE)

I (uA) OCP
(V vs. CSE)
AC Resistance
(Ohm)
Impedance at 0.1 Hz
(Ohm)
Top Mat Bottom Mat
Water-Soluble Acid-Soluble Water-Soluble Acid-Soluble
Black Top + Black Bottom 5 5A Black S Black N -0.284 -83.6 -0.278 2.5E+02 1.4E+03 1,470      
5B S N -0.307 -260.1 -0.320 2.4E+02 7.5E+01 1,290   2,170 3,170
23 23A Black B Black N -0.334 -177.2 -0.348 1.9E+02 4.6E+01 1,670      
23B B N -0.257 -225.4 -0.235 2.1E+02 6.5E+01 1,190   1,360 2,130
20 20A Black S Black Y -0.360 -102.9 -0.324 3.1E+02 1.7E+02 1,210   2,290 2,940
20B S Y -0.439 0.0002 -0.302 2.5E+02 1.4E+02 1,170 800    
Stainless Steel 16 16A Stainless Steel B Black N -0.361 -6.8 -0.257 8.7E+02 8.7E+02 5,280   2,610 1,890
16B B N -0.446 -7.8 -0.243 3.9E+02 1.2E+03 4,310      
26 26A Stainless Steel S Black N -0.147 0.023 -0.152 5.6E+02 2.7E+01 5,770      
26B S Y -0.197 0.06 -0.183 5.2E+02 4.9E+03 3,300      
27 27A Stainless Steel S Stainless Steel Y -0.230 -0.005 -0.239 5.4E+02 2.6E+03 3,330      
27B S N -0.240 0.0003 -0.169 5.4E+02 1.9E+03 5,280      

 

Table 9. Electrochemical test data classified by bar type

Data

Material

Slab Configuration

Straight Top -
Black Bottom -
Uncracked

Straight Top -
ECR Bottom -
Uncracked

Straight Top -
Black Bottom -
Precracked

Bent Top -
Black Bottom -
Uncracked

Stainless Steel

Short-Circuit Potential
(V vs. CSE)

Black

-0.413

 

-0.447

-0.469

 

Stainless Steel

       

-0.196

ECR with 0.004%
Initial Coating Damage

-0.274

-0.272

-0.353

-0.319

 

ECR with 0.5%
Initial Coating Damage

-0.341

-0.456

-0.382

-0.354

 

Macrocell Current Density
(uA/cm2)

Black

1.239

 

1.240

1.304

 

Stainless Steel

       

0.009

ECR with 0.004%
Initial Coating Damage

0.085

0.007

0.268

0.644

 

ECR with 0.5%
Initial Coating Damage

0.595

0.021

0.531

0.491

 

 

Table 10. Electrochemical test data classified by coating type
Data Material Slab Configuration
Straight Top -
Black Bottom -
Uncracked
Straight Top -
ECR Bottom -
Uncracked
Straight Top -
Black Bottom -
Precracked
Bent Top -
Black Bottom -
Uncracked
Short-Circuit Potential
(V vs. SCE)
All ECRs
Combined
-0.291 -0.372 -0.355 -0.328
Coating A -0.272 -0.250 -0.303 -0.377
Coating B -0.217 -0.415 -0.350 -0.282
Coating C -0.450 -0.554 -0.346 -0.430
Coating D -0.149 -0.293 -0.209 -0.193
Coating E -0.301 -0.303 -0.427 -0.211
Coating F -0.387 -0.288 -0.505 -0.452
Macrocell Current Density
(uA/cm2)
All ECRs
Combined
0.350 0.014 0.399 0.568
Coating A 0.023 0.007 0.025 0.133
Coating B 0.253 0.009 0.461 0.279
Coating C 0.871 0.011 0.770 1.940
Coating D 0.016 0.039 0.025 0.024
Coating E 0.279 0.008 0.192 0.033
Coating F 0.595 0.011 0.547 0.996

 

Table 11. Characterization of autopsied ECRs tested in the top mat
Test Group Slab ID Coating Type Characterization of Epoxy-Coated Reinforcing Bars
Top Bar ID Artificial Defect Size (Percent) Number of Final Defects Coating Thickness
(mils)
Exterior Condition
(1: excellent - 5: worst)
Knife Adhesion
(1: strongest - 5: weakest)
Adhesion Loss
(Percent)
Bare Area Mashed Area Coating Crack Holiday Total Mean STDEV
Straight Top ECR +
Black Bottom in
Uncracked Concrete
3 C 3A 0.5 7 0 100 0 100 13.9 3.5 5 5 100
3B 0.004 0 0 100 2 100 8.4 1.8 5 5 30
6 B 6A 0.5 2 0 100 0 100 17.4 2.9 5 5 100
6B 0.004 0 1 0 4 5 11.6 1.3 1 1 0
15 D 15A 0.004 0 0 0 2 2 11.8 0.5 1 1 0
15B 0.5 2 0 0 0 2 13.0 0.8 1 5 26
18 F 18A 0.5 7 0 100 0 100 14.6 3.1 5 5 100
18B 0.004 3 0 16 0 19 9.1 1.4 5 5 32
24 A 24A 0.5 2 0 16 1 19 9.4 1.8 4 5 85
24B 0.004 4 0 0 0 4 7.6 0.6 2 2 0
28 E 28A 0.004 0 1 18 0 19     4 5 33
28B 0.5 3 0 100 0 100     4 5 95
Straight ECR Top +
Black Bottom in
precracked Concrete
7 A 7A 0.5 2 2 28 2 34 10.6 2.5 4 5 100
7B 0.004 0 0 3 3 6 9.1 1.2 3 5 23
13 C 13A 0.5 2 0 1 1 4 10.4 1.5 3 1 46
13B 0.004 0 2 0 3 5 9.4 1.2 1 1 0
14 E 14A 0.004 0 1 0 2 3 9.1 1.1 2 3 2
14B 0.5 8 2 26 4 40 12.1 5.3 5 5 61
19 F 19A 0.004 1 0 23 2 26 14.7 2.8 5 5 56
19B 0.5 17 0 100 0 100 17.5 3.3 5 5 100
21 D 21A 0.5 2 2 10 0 14 14.1 2.0 4 5 60
21B 0.004 0 0 0 1 1 14.6 1.0 2 2 0
25 B 25A 0.004 2 3 23 4 32 9.1 1.9 4 5 74
25B 0.5 10 7 46 2 65 15.7 3.5 5 5 100
30 C 30A 0.004 4 0 100 0 100 18.5 4.7 5 5 100
30B 0.5 2 0 100 0 100 18.4 4.9 5 5 100
Bent Top ECR +
Black Bottom in
Uncracked Concrete
1 D 1A 0.5 3 4 0 0 7 14.3 1.2 3 5 50
1B 0.004 1 1 0 0 2 15.4 1.3 3 2 0
4 C 4A 0.5 6 0 100 0 100 10.7 3.3 5 5 50
4B 0.004 5 0 100 0 100 13.0 4.3 5 5 68
8 F 8A 0.004 13 0 100 0 100 15.5 3.5 5 5 100
8B 0.5 3 0 100 0 100 19.7 5.6 5 5 100
11 B 11A 0.5 4 0 61 0 65 16.0 3.3 5 5 100
11B 0.004 0 1 4 6 11 10.9 1.5 3 5 56
22 A 22A 0.004 0 2 100 0 100 10.3 1.1 4 5 73
22B 0.5 5 0 100 0 100 11.4 1.9 5 5 100
31 E 31A 0.5 11 9 2 2 24 7.1 1.7 5 5 18
31B 0.004 7 5 2 2 16 7.2 1.9 4 4 4

 

Table 12. Characterization of autopsied ECRs tested in both mats
Test Group Slab ID Coating Type Characterization of Epoxy-Coated Reinforcing Bars
Bar ID Artifical Defect Size
(Percent)
Number of Final Defects Coating Thickness
(mils)
Exterior Condition
(1: excellent - 5: worst)
Knife Adhesion
(1: strongest - 5: weakest)
Adhesion Loss
(Percent)
Bare Area Mashed Area Coating Crack Holiday Total Mean STDEV
Straight ECR Top +
Bottom ECR in
Uncracked Concrete
2 F 2A-Top 0.004 2 0 1 0 3 10.6 1.8 2 3 3
2B-Top 0.5 8 0 71 2 81 13.2 2.5 5 5 100
2A-Bottom 1 0.004 3 0 1 2 6 9.2 3.0 1 3 0
2A-Bottom 2 0.004 7 1 0 1 9 13.3 2.0 1 2 0
2B-Bottom 1 0.5 2 2 1 0 5 9.3 0.6 1 5 22
2B-Bottom 2 0.5 8 2 2 0 12 8.2 0.9 2 4 5
9 B 9A-Top 0.5 2 0 39 4 45 11.5 1.6 3 5 96
9B-Top 0.004 0 0 0 3 3 9.7 1.0 2 5 19
9A-Bottom 1 0.5 2 0 0 0 2 10.9 1.0 1 1 0
9A-Bottom 2 0.5 0 0 0 4 4 10.4 0.6 2 1 0
9B-Bottom 1 0.004 0 2 1 2 5 10.4 0.7 1 1 0
9B-Bottom 2 0.004 2 0 0 0 2 10.7 0.7 1 1 0
10 A 10A-Top 0.5 3 0 4 0 7 8.8 1.1 2 5 61
10B-Top 0.004 0 4 0 4 8 7.9 0.9 2 1 0
10A-Bottom 1 0.5 2 0 0 0 2 7.5 0.8 1 2 0
10A-Bottom 2 0.5 2 0 0 0 2 8.2 1.0 2 3 0
10B-Bottom 1 0.004 2 1 0 4 7 8.3 0.8 3 1 0
10B-Bottom 2 0.004 0 0 0 4 4 8.2 0.7 2 3 0
12 C 12A-Top 0.5 7 3 100 0 100 9.7 2.4 5 5 90
12B-Top 0.004 9 0 100 0 100 9.7 2.4 5 5 90
12A-Bottom 1 0.5 2 1 0 0 3 8.3 1.1 1 1 0
12A-Bottom 2 0.5 1 6 2 0 9 8.2 1.0 3 2 0
12B-Bottom 1 0.004 0 0 0 4 4 8.7 2.4 1 1 0
12B-Bottom 2 0.004 0 0 0 3 3 8.5 0.8 2 2 0
17 D 17A-Top 0.004 1 0 0 1 2 12.8 0.9 2 2 0
17B-Top 0.5 2 0 0 0 2 13.0 0.8 2 5 13
17A-Bottom 1 0.004 0 0 0 4 4 14.5 1.0 2 1 0
17A-Bottom 2 0.004 0 0 0 4 4 13.7 0.8 2 2 0
17B-Bottom 1 0.5 2 0 0 0 2 14.3 0.9 2 1 0
17B-Bottom 2 0.5 2 0 0 1 3 13.1 1.1 2 2 0
29 E 29A-Top 0.004 0 0 0 3 3 8.4 1.9 1 1 0
29B-Top 0.5 6 2 32 1 41 7.9 0.9 4 5 75
29A-Bottom 1 0.004 1 0 0 4 5 8.1 0.9 2 2 0
29A-Bottom 2 0.004 4 0 0 0 4 9.9 1.3 2 1 0
29B-Bottom 1 0.5 3 0 0 0 3 8.9 0.8 2 1 0
29B-Bottom 2 0.5 2 5 0 0 7 7.9 1.0 2 3 4

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