Manual on Service Life of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements (2006)

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50 Evaluation, Storage, and Preparation of Epoxy-Coated Rebar Cores Pre-Extraction Procedures 1. If the cores are not to be tested within 24 hours of receipt by the laboratory, store them in a freezer below 14˚F. 2. When cores are removed from the freezer, thaw them for a minimum of 24 hours or to room temperature, whichever is earlier. 3. Document the core identification number and date of ini- tial testing on data sheets. 4. Measure the temperature of each core. If the temperature is less than 77˚F, allow further thawing until a minimum temperature of 77˚F is attained. 5. Remove all moisture from the surface of the cores with lint-free, salt-free, absorbent tissues to ensure that the sur- face is dry. 6. Document core information (Figure 11), including diam- eter, height1 (ht), cover over the topmost rebar (C1 and C2),2 and height of concrete below the bottommost rebar (hb). All lengths to be measured to the nearest one-eighth inch. 7. Visually observe the core to identify concrete damage (such as cracking), honeycombing, and evidence of dete- rioration (such as rust staining and delamination). 8. Label the core in multiple locations with the core identifi- cation number. 9. If the core will be used for chloride analysis after the extrac- tion of the rebar, mark the horizons to be powdered every 0.25 inch from the top surface. Also mark the horizon of 5 to 5.25 inches for background chloride information. Extraction of Epoxy-Coated Rebar from the Core 1. Dry saw cut a 0.75-inch-deep groove in two diagonally opposing quadrants (Figure 12). 2. Carefully break the core into two pieces along the sawcuts using a chisel and hammer so as not to damage the epoxy- coated rebars. 3. Carefully remove the epoxy-coated bars from their traces. Bar Selection and Preparation 1. Evaluate no more than two bars from each core. 2. Select the bars to be tested using the following criteria: • If more than two layers of bars are found in a core, only the top two layers shall be selected for evaluation. • If a layer contains more than one bar, one bar shall be randomly selected for evaluation. • Any bars that are not completely extracted (entire cross- section) shall not be tested. 3. With a black permanent marker, paint the top half of one end of each selected bar to designate its orientation in the core. 4. Drill and tap the other end (i.e., the bottom end) of each selected bar. Install a screw and attach a prelabeled tag. When there is more than one bar extracted from the core, the top bar in the mat and the bottom bar should be iden- tified as such. Visual Inspection of Epoxy-Coated Bars 1. Dry the epoxy-coated rebar if necessary by wiping with lint-free, salt-free, absorbent tissues. 2. Record bar size, bar length, deformation pattern, and coat- ing color for each epoxy-coated rebar. 3. Visually observe the condition of the coating and the rein- forcing steel, and rate according to Table 7. If the rating of C H A P T E R 8 Laboratory Evaluation Procedures 1The height of a core may vary from one location to another around the perimeter of the core if both the upper and lower surfaces are not smooth. The maximum core height should be recorded as the maximum height that contains the entire cross-section of the core. 2The concrete cover depth is to be measured from both ends of the topmost bar.

the bar is equal to or greater than 4, no further testing needs to be performed. 4. Record the number of mashed areas, bare areas, and blis- ters for each rebar. Include comments for each rebar as necessary. Holiday Detection 1. Attach the ground wire of the holiday detector to the screw that was previously installed on the rebar. 2. Perform the holiday detection test on all surfaces of each bar in accordance with ASTM 62, “Standard Test Method for Holiday Detection in Pipeline Coatings”—Method A. 3. When recording the number of holidays, distinguish between holidays located in bar ID areas from those not located in bar ID areas.3 Coating Adhesion 1. Measure coating adhesion in accordance with NACE TM0185—Section 5.3.2, “Knife Adhesion Testing,” with three modifications: a. The sample will not be heated in an autoclave. b. Use an “X” shaped groove in place of the “V” groove described. c. Use a modified rating scale. (See Step 5.) 2. Conduct wet adhesion test in three undamaged areas.4 3. If damaged coating areas are identified on the bar, conduct up to three additional wet adhesion tests adjacent to the damaged areas. 4. Record visual observations of the steel beneath the coating. 5. Rate all adhesion test areas according to Table 8. Preparation of Chloride Cores 1. Wear latex gloves to prevent contaminating the core and samples while handling them. 2. Remove the core from protective bag and dry brush the core to remove any dried coring residue attached to the surface. 3. Starting at the top surface, mark 0.25-inch horizons along the length of the core for as many samples as required. A minimum of six horizons must be collected. Mark another horizon between 5 and 5.25 inches for use in determining the background chloride content. 51 C1 ht hb C2 Figure 11. Core information. Table 7. Ratings for epoxy-coated rebars. Figure 12. Sawcut for extraction of bars. sawcuts Rating Description 1 No evidence of corrosion. 2 A number of small, countable corrosion spots. 3 Corrosion area less than 20% of total epoxy-coated rebar surface area. 4 Corrosion area between 20% and 60% of total epoxy-coated rebar surface area. 5 Corrosion area greater than 60% of total epoxy-coated rebar surface area. 3During holiday detection, bare areas will also produce a beep. Areas previ- ously categorized as bare areas will not be counted as holidays. If a holiday is detected over a mashed area, the mashed area will be recategorized as a bare area. If a continuous beep is detected along a bar, then the number of holidays will be considered equal to the length of bar along the test trace divided by the width of sponge. 4The knife adhesion test conducted without drying in a desiccator is termed the “wet adhesion test.”This test measures coating adhesion in an as-is condition. The wet adhesion test must be completed within 24 hours from the time the rebars are extracted from the core.

Setting the Chloride Core 1. There are two ways in which powdered concrete samples from the identified horizons can be obtained. • If a grinding wheel is used (Figure 13), place the core vertically into the vise attached to the drill press. To pre- vent the core from breaking while grinding, it is recom- mended that the core be placed inside a 3-inch-long PVC pipe that has been split down the sides before the core is inserted into the vise. • If a drill bit is used (Figure 14), place the core horizon- tally into the vise attached to the drill press. To help to prevent the core from breaking while grinding, it is rec- ommended that the core be placed inside a 3-inch-long PVC pipe that has been split down the sides before the core is inserted into the vise. 2. Label a single sample bag with the core number, the loca- tion of the core, and the horizon to prevent accidental use of a bag for a different horizon. 3. Wrap a section of aluminum foil around the core below the area to be sampled to catch the powder as it falls. 4. If the drill press used to powder the cores is a variable- speed model, set it at the slowest speed to help contain the powder being created. Powdering the Chloride Core 1. Wear a dust mask to avoid breathing in the dust generated by the powdering process. 2. There are two ways in which chloride cores can be drilled: • If a grinding wheel is used (Figure 15), powder the core down to the desired horizon. Depending on the width of the cutting surface of the grinding disk, several passes along the surface of the core may be required to powder the entire horizon. • If a drill bit is used (Figure 16), set the core so that the drill bit is centered on the median point of the horizon to be powdered. Drill about halfway into the core, then back the bit out and rotate the core so you can make another pass into it. Leave approximately one-eighth inch between bore holes to help prevent the core from breaking. Continue this process until the core has been rotated 360 degrees. Caution: when using this method to powder cores, it is not uncommon for the core to break into many pieces. When marking the horizons, mark the entire circumference and label the horizon 52 Table 8. Ratings for coating adhesion. Rating Description 1 Well-adhered coating that cannot be peeled or lifted from the substrate steel. 3 Coating that can be pried from the substrate steel in small pieces, but cannot be peeled off easily. 5 Coating that can be peeled from the substrate steel easily, without residue. Figure 13. Grinding wheel setup. Figure 14. Drill bit setup.

number (or nominal depth) in several areas so that the core can reassembled if necessary. 3. Carefully remove the foil containing the powdered sample and gently pour the sample into the prelabeled bag. Dis- card the foil to prevent contaminating the next sample. 4. Vacuum the drill press or grinding wheel to remove any dust to prevent contamination of the next sample. 5. Test the chloride samples collected according to AASHTO T 260-94,“Sampling and Testing for Total Chloride Ion in Concrete Raw Materials,” Procedure A—Total Ion or ASTM C 1152, “Standard Test Method for Acid-Soluble Chloride in Mortar and Concrete.” 6. Suggested Equipment: a. Drill press with an attached vise. b. Grinding wheel or 0.25-inch carbide drill bit. c. PVC pipe of appropriate diameter. d. Aluminum foil. e. Dust mask. f. Sealable plastic bags. g. Pen. h. Brush. i. Vacuum. j. Latex gloves. Service Life Model Procedure Preparing Macros for Use in Microsoft Excel 1. The name of the file containing the macros for service life modeling and SI is “Service Life Model 2.0A.” 2. The macros in this file require Microsoft Excel 2003 or a later version. If the file is opened in a version of Excel lower than 2003, one of the macros that controls both the pro- cessing of core data and the calculation of diffusion coef- ficient will not work. 3. Open the file and on the Tools menu click Add-Ins. 4. Make sure that a checkmark is present next to Analysis ToolPak and Analysis ToolPak – VBA. These add-ins are provided with Excel. If they are not checked, click on the box to their left and click OK. Bridge Information Page 1. Click on the Bridge tab at the bottom and open the Bridge sheet. 2. Enter all information on the bridge page in the appropri- ate fields (Figure 17). Enter dates in mm/dd/yyyy format, including the year of construction. 53 Figure 15. Grinding wheel operation. Figure 16. Drill bit operation. Figure 17. Bridge information page. Input Fields

3. If chloride profile samples were collected from the struc- ture at various times (more than 6 months apart), include up to four dates of collection. 4. After all information is entered, click on the Core Process- ing tab and open that page. Core Processing Page 1. To enter data for each chloride profile location, click on the New button. This will clear all information from the sheet. 2. Enter the core ID number or location label in the box fol- lowing Core ID (Figure 18). 3. Click on OK. You will be asked if you want to save this core. 4. Enter Span #, X Location, and Y Location in upper left side of sheet (Figure 19). 5. Move the cursor over to the cell next to Dt. Of Coll: a drop-down menu will appear. Click on the drop-down menu arrow and select the date when the subject core was collected or the location was sampled from the deck. The Date of Construction has already been brought over from the Bridge Information page. The age of the sample at collection will show on the right top of the page after Age. 6. Enter the appropriate data under Nominal Depth and Cl Content (Figure 20). Then entered data will appear in the Chloride Profile – Dc Curve Fit graph to the right of the page. Nominal Depth and Cl Content can be entered in any units. The calculated Dc will be in the same units as the Nominal Depth data. The units of Dc are (unit of Nominal Depth)2/year. 7. Click on Dc in the upper middle of the page (Figure 21). The Apparent Diffusion Coefficient, Sum of Squares (SS), and Coefficient of Correlation (R2) will be calcu- lated and will appear in the appropriate locations. The Best Fit Line will also be calculated and will appear in the Chloride Profile – Dc Curve Fit graph. 8. Click on Save to save all entered and calculated data. 9. Click on New to clear the page and enter the data for the next core or location. 10. To delete a core and its information, simply select the CoreID from the drop-down menu, click OK, and then click Delete. 54 Figure 19. Span, location, and date of collection. Figure 21. Chloride profile—Dc. Figure 20. Nominal depth and Cl content. Figure 18. Core processing page. Input Fields Input Fields Input Fields Click to Calculate Dc

11. To edit a core label, select the CoreID from the drop- down list, then click Edit. A form will open. Type in the new CoreID and click OK. Then click Save. 12. Repeat Steps 1 through 11 until all cores or sampling locations and their data have been entered. 13. Open the Distributions sheet by clicking on the Distri- butions tab. Distributions Page 1. Click on Obtain Co & Dc (Figure 22). This will import that data from the Core Data Sheet. The Core Data Sheet is hidden. 2. Enter, in any order, all cover depth measurements in the Cover column (Figure 23). 3. Place the cursor into any cell that does not have a button. Click on Co (Figure 24). The statistics for Co will be calcu- lated, and a plot showing the distribution of the data and a normal distribution curve for the data will be plotted. 4. Repeat Step 3 for Dc and Cover. 5. Open the Model Results page by clicking on the Model Results tab. Model Results Page 1. Enter the age of the samples in the Age field (Figure 25). If the chloride profiles were collected on different dates, use the weighted average age. 2. In the Reinforcing field, using the drop-down menu, select either Black or Epoxy. 3. Enter the required information in the Model Parameters section (Figure 26). a. Chloride Threshold: Start with 300 ppm or 1.2 pcy. b. Time to propagation: Use 3 to 6 years. Time to propa- gation can be adjusted based on average corrosion rate. Use corrosion rate device manufacturer’s guidelines for time to damage. c. # Of Iterations: Use between 10,000 and 15,000. d. Type of Co: Use the drop-down menu to select either Constant or Linear. If constant is selected, the model will assume that the surface chloride ion concentration remained constant throughout the life of the structure and is equal to that measured at the time of sampling. If Linear is selected, the model assumes that at time = 0, Co = 0, and Co increased to the value at the time of sam- pling linearly. 55 Click to import Data. Input Cover Click to calculate Co Statistics Input Fields Select Linear or Constant Figure 22. Distributions page. Figure 23. Cover depth measurements. Figure 24. Statistics of Co. Figure 25. Model Results page. Figure 26. Model Parameters section.

4. If Epoxy was selected in Reinforcing, then in the blue sec- tion labeled Epoxy Coated Rebar (Figure 27) fill in the fol- lowing information: a. Initial Damage %: Estimated initial damage at the time of the installation of epoxy-coated rebar into concrete. This can be based on allowable damage by the specifications governing during the time of instal- lation. b. Life of ECR: Based on the quantity of damage observed on the epoxy-coated rebars extracted in the cores, esti- mate the life of the epoxy coating assuming that the rate of degradation is linear. This can be calculated as follows: 5. Click on the Model Damage button to obtain the Percent Damage to Age chart and graph. 6. Check to see how the model prediction compares with the actual damage measured during the previous evaluations. If the predictions of the model are not close, vary the Chloride Threshold value and rerun the model. Repeat this step until the predicted values match reasonably well with the actual values. 7. Open the Cl Distribution page (Figure 28) by clicking on the Cl Distribution tab. Life Age(Present Damage Initial Damage)= × − 100 Cl Distribution Page 1. Under the Structure heading, adjacent to Age, fill in the average age that was used in Model Results. 2. The reinforcing type will not matter for this macro. Leave the default value to Black. 3. In the Model Parameters block, fill in the following: a. Chloride Threshold: Use the Chloride Threshold value from the Model Results page. (The predicted damage value had been determined to agree reasonably well with actual damage.) b. Distribution at Age: Enter the age at which the SI is desired. c. # Of Iterations: Use a value between 10,000 to 15,000. d. Type of Co: Use Constant or Linear, whichever was used in the Model Results. 4. Click on the Chloride Distribution button. Adjacent to SI, the calculated index is provided. 5. Save the File with an appropriate name. 6. If a message appears stating that the program cannot close the file because the file is linked to another file, click OK and continue closing the file. 56 Input Field Input Fields Structure Age: 33.81 Reinforcing: Black Model Parameters Chloride Threshold: 700 Distribution at Age: 80 # OfIterations: 12000 Type of Co: Linear Cl Percent Figure 27. Epoxy-Coated Rebar section. Figure 28. Cl Distribution page.