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

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44 This chapter presents detailed procedures for field testing and sampling methodologies. The procedures have been prepared primarily for bridge deck application, but they can easily be applied to other superstructure members. Grid Stationing 1. For safety and coordination with traffic control patterns, mark grids in the direction of traffic flow. In the field, it is often more convenient to have a separate grid for each set of lane closures. If only one lane can be closed at a time, then a separate grid is marked for each lane. Sometimes only one span is closed and the grid can be established only for that span. All grids can later be combined in the laboratory to provide a single point of reference for the entire structure. 2. Identify the span numbering scheme from the bridge drawings and start at Span 1 in the direction of traffic. 3. Number the lanes from right to left in each direction. If only one lane exists in each direction, then mark it as Lane 1 in each direction. 4. Locate the origin (0, 0), which is the starting point for the grid at the intersection of the rightmost edge of the right- most lane (facing in the direction of traffic) of the closed section. 5. Mark the X-axis in the longitudinal direction and the Y-axis in the transverse direction. Generally, a grid spacing of either 2 feet or 5 feet is used. 6. Suggested Equipment (Figure 5): a. 100-foot, reel-type tape measure or land wheel. A rope or a string marked at regular intervals can also be used. b. Lumber crayon (keel) or spray paint. Visual Survey 1. Conduct the visual survey in accordance with ACI 201.1R- 92, “Guide for Making a Condition Survey of Concrete in Service.” 2. Sketch the surface view of the concrete element to be sur- veyed. 3. Record dimensions of areas. 4. Sketch location of observed typical deterioration (spalls, patches, cracks, scaling, rust staining, and efflorescence) and note severity of each. 5. Photograph the structure such that the overall condition and any items of interest are documented. 6. Suggested Equipment: a. Tape measure. b. Camera. Delamination Survey 1. Perform the delamination survey in accordance with ASTM D-4580-86, “Standard Practice for Measuring Delaminations in Concrete Bridge Decks by Sounding.” 2. Using a hammer, chain drag (Figure 6), or chain, perform a delamination survey in the subject area (Figure 7). Other nondestructive equipment can also be used (see Chapter 3). 3. Mark delaminated areas with a lumber crayon (keel) using simple geometric shapes such as a square, a rectangle, and a triangle. Because it is very time consuming to identify the exact shape of the delamination and transfer it to a draw- ing, simple shapes are used. However, the use of the shapes must be consistent throughout the survey. 4. Record dimensions of delaminated areas and any areas that have been patched by either concrete or asphalt. 5. Determine the percentage of delaminated area as follows: where X = total delaminated area A = total surface area of the concrete element 6. Suggested Equipment: a. Hammer/chain/chain drag. Delam X A % = 100 C H A P T E R 7 Field Evaluation Procedures

45 b. Lumber crayon (keel). c. Tape measure. Cover Depth Measurements 1. With a covermeter, determine and mark on the surface of the deck the location and direction of the reinforcing steel in the areas to be tested. 2. A minimum of 30 measurements per span are generally required. Of the 30 measurements, 5 measurements need to be actual depths measured (see Steps 3, 4, and 5), and the balance of 25 can be obtained directly from the cov- ermeter and then correlated. 3. Using a hammer drill and a 0.75-inch drill bit, drill a hole to expose the reinforcing steel. A core drill can be used in the place of a hammer drill. Use a 1- or 2-inch core bit to expose the reinforcing steel. 4. Clean out all dust and debris (including water if a core drill was used) from the excavation using a wet-dry vacuum. 5. Measure the cover depth as shown in Figure 8. 6. Patch the excavation upon completing all testing on the exposed steel. 7. Suggested Equipment: a. Covermeter. b. Lumber crayon (keel). c. Generator. d. Hammer drill or a core drill. e. 0.75-inch hammer bit or a 1- or 2-inch core bit. f. Wet-dry vacuum. g. Tape measure. Continuity Testing—Direct Current Method 1. Using a covermeter, locate and mark the required num- ber of transverse and longitudinal reinforcing bars on Figure 5. Equipment for grid marking. Figure 6. Chain Drag.

each span of the deck. Of each reinforcing bar type, at least five bars should be tested in each span. If there is rebar already exposed from other tests or in spalled areas, this rebar could also be used instead of excavating new areas. 2. To expose a bar, use a hammer drill with a 0.75-inch drill bit. Drill down until the rebar is exposed. 3. Select one exposed rebar to be the ground location. 4. At the ground location, drill into the rebar and set a self- tapping screw, making sure that there is a tight fit. Use an alligator clip attached to the test lead to make connection with the screw in the rebar. 5. At the other exposed rebars, clean the surface of the bar to a bright metal with a wire brush, emery cloth, or file. Cleaning may not be necessary if a hammer drill was used to expose the bar. 6. Set the multimeter to read resistance. Ensure that the range automatically selected by the meter produces a res- olution of 0.1 Ω or less. 7. Use one short test lead to connect to the rebar for testing and one long test lead to connect to the rebar designated as the ground. 8. Zero the multimeter and check the battery according to the manufacturer’s instructions. Check and record the resistance of all test leads, including any length of wire necessary to reach all test locations. 9. Attach the long test lead from the positive terminal of the multimeter to the ground location. 10. Attach the short test lead from the negative (i.e., com- mon) terminal of the multimeter to the rebar to be tested. 11. Read and record the resistance in ohms. Reverse the leads at the meter, and read and record the resistance again. 12. Set the multimeter to read voltage. Ensure that the range automatically selected by the meter produces a resolution of 0.001 V. Read and record the voltage difference between the two points. 13. Subtract the lead resistance obtained in Step 8 from both resistance values obtained in Step 11. If the resultant resistance values are both less than 1 Ω (or less than 1 Ω apart) and the voltage difference is no more than 0.001 V, the two points are electrically continuous. 14. Repeat this process for each exposed rebar using the same ground. When continuity of rails and other embedded metals in the concrete element have to be ascertained, the same procedure can be used. Use the rebar designated as the ground and the rail or the embedded metal as the test point. 15. If the direct current (DC) method shows different results when the leads are reversed or estimates negative resist- ance, the measurement may have been impacted by cor- rosion or stray current in the concrete element. Disconnect the multimeter and replace it with a soil resistance meter that reads alternating current (AC) (Fig- ure 9). Connect the two leads to the soil resistance meter, and balance the bridge to determine the resistance between the ground and the test rebar. If the AC resist- ance is less than 1 Ω, then the rebars are considered to be continuous. 46 Figure 7. Chain dragging in progress. Figure 8. Cover depth. C concrete surface rebar C = clear concrete cover concrete surface rebar C 3/4 inch

47 16. When epoxy-coated reinforcing steel is encountered dur- ing evaluation of a structure, expect discontinuity between reinforcing steel. 17. Patch all test locations (unless the area will be used in another test). 18. Suggested Equipment: a. Multimeter. b. Soil resistance meter. c. Lead wires. d. Probe wires. e. Alligator clips. f. Hammer. g. Chisel. h. Wire reel. i. Rechargeable drill. j. Steel-tapping bits. k. Self-tapping screws (to match the size of the tapping bit). l. Screwdriver. m. Covermeter. n. Lumber crayon (keel). o. Hammer drill. p. 0.75-inch hammer bit. q. Extension cord. r. Generator. s. Wet-dry vacuum. Core Sampling—Chloride Ion Distribution 1. Perform core extraction in accordance with ASTM C42/C42M-99,“Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete.” 2. The area(s) to be sampled should be free from any defects, such as spalls, delaminations, and patches (unless testing patch material). Sample areas may be placed adja- cent to defective areas, but not in them. 3. Using a covermeter, locate and mark all reinforcing steel in the area where the core(s) will be collected. 4. Mark the depth of the core to be taken plus 1 inch on the outside of the core bit (2-inch diameter). 5. Locate the core bit so as to avoid any reinforcing steel in the core. 6. Drill down to the desired depth (Figure 10). 7. Place the tip of the chisel in the gap between the core and the deck concrete. Gently hammer on the head of the chisel until the core breaks at the bottom. It helps to tap on the chisel a couple of times and then move the chisel to another location around the core. 8. If a delamination is observed in the core, take the core at another location. Delamination in the core can be veri- fied by checking for a crack in the original concrete at the level of the break in the core. 9. Immediately upon extraction, label each core with Bridge #, Lane #, and Span # and X, Y coordinate of the sample. 10. Pack the core in a sealable plastic bag, and record all of the information from Step 9 on the outside of it. 11. Clean out the slurry/water from the excavation using a wet-dry vacuum. 12. Patch all test locations. 13. Suggested Equipment: a. Core drill. b. 2-inch core bit. c. Generator. d. Covermeter. e. Lumber crayon (keel). f. Hammer. g. Chisel. h. Wet-dry vacuum. i. Sealable plastic bags. Figure 9. Multimeter and AC soil meter. Figure 10. Core drilling.

Core Sampling—Epoxy-Coated Rebar 1. Perform core extraction in accordance with ASTM C42/C42M-99,“Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete.” 2. The area(s) to be sampled should be free from any defects, such as spalls, delaminations, and patches (unless testing patch material). Sample areas may be placed adja- cent to defective areas, but not in them. 3. Using a covermeter, locate and mark all reinforcing steel in the area where the core(s) will be taken. The sample will be taken at the intersection of two rebars in the top mat of reinforcement. 4. Mark the depth of the core to be taken on the outside of the core bit (4-inch diameter). 5. Drill down to the desired depth. 6. Place the chisel in the cut grove, and gently hammer while moving the chisel along the grove until the core breaks loose. 7. If a delamination is observed in the core, take the core at another location. Delamination in the core can be veri- fied by checking for a crack in the original concrete at the level of the break in the core. 8. Immediately upon extraction, label each core with Bridge #, Lane #, and Span # and X, Y coordinate of the sample. 9. Wrap the core in wet burlap, pack it in a sealable plastic bag, and record all of the information from Step 8 on the outside of it. 10. If the core is not to be tested within 24 hours of receipt by the laboratory, it shall be stored in a freezer below 14°F. 11. Clean out the slurry/water from the excavation using a wet-dry vacuum. 12. Patch all test locations. 13. Suggested Equipment: a. Core drill. b. 4-inch core bit. c. Generator. d. Covermeter. e. Lumber crayon (keel). f. Hammer. g. Chisel. h. Wet-dry vacuum. i. Sealable plastic bags. j. Burlap. Core Sampling—Petrographic Core Extraction 1. Perform core extraction in accordance with ASTM C42/C42M-99,“Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete.” 2. The area(s) to be sampled should be free from any defects, such as spalls, delaminations, and patches (unless testing patch material). Sample areas may be placed adja- cent to defective areas, but not in them. 3. Using a covermeter, locate and mark all reinforcing steel in the area where the core(s) will be taken. 4. Mark 5 inches on the outside of a 4-inch diameter core bit. 5. Locate the core drill such as to avoid any reinforcing steel. 6. Drill down to the desired depth. 7. Place the chisel in the cut grove, and gently hammer while moving the chisel along the grove until the core breaks loose. 8. If a delamination is observed in the core, take the core at another location. Delamination in the core can be veri- fied by checking for a crack in the original concrete at the level of the break in the core. 9. Immediately upon extraction, label each core with Bridge #, Lane #, and Span # and X, Y coordinate of the sample. 10. Store the core in a sealable plastic bag, and record all of the information from Step 9 on the outside of it. 11. Clean out the slurry/water from the excavation using a wet-dry vacuum. 12. Patch all test locations. 13. Suggested Equipment: a. Core drill. b. 4-inch core bit. c. Generator. d. Covermeter. e. Lumber crayon (keel). f. Hammer. g. Chisel. h. Wet-dry vacuum. i. Sealable plastic bags. j. Pen. k. Tape measure. Corrosion Potential Survey 1. Perform the corrosion potential survey in accordance with ASTM C-876, “Standard Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete.” 2. A corrosion potential survey should be performed only after an area has been tested for continuity and found to be continuous, after a delamination survey has been con- ducted, and after the delaminations have been marked on the surface. 3. Either mark a 2-foot × 2-foot grid on the surface or use tape measure, rope, or string with marks on a 2-foot inter- val as a guide in both the longitudinal and the transverse directions. 48

49 4. Fill a copper-copper sulfate half-cell with copper sulfate solution in accordance with the manufacturer’s instructions. 5. Select one exposed rebar that is ground installed for another test or expose a rebar to be the ground location (see Continuity Testing—Direct Current Method). 6. At the ground location, drill into the rebar and set a self- tapping screw, making sure that it is a tight fit. Use an alli- gator clip attached to the test lead to make connection with the screw in the rebar. 7. Connect the half-cell by a test lead to the negative termi- nal of your multimeter. 8. Connect the positive terminal on the multimeter by a test lead to the ground connection on the rebar. Please note that test leads should not exceed 500 linear feet for a test lead wire thinner than American Wire Gage (AWG) 24. 9. Spray with water all locations where half-cell potential measurement is to be made. Let the water soak in for a few minutes prior to making the measurement. 10. Set the multimeter to read in volts. 11. Begin your survey and record all readings to the nearest 0.001 V. Measurements should not be made in delami- nated or spalled areas. 12. Suggested Equipment: a. Multimeter (with a 10-MΩ input impedance). b. Copper-copper sulfate half-cell. c. Copper sulfate solution. d. Test leads. e. Alligator clips. f. Wire reel. g. Rechargeable drill. h. Steel-tapping bits. i. Self-tapping screws. j. Screwdriver. k. Covermeter. l. Lumber crayon (keel). m. Measuring tape. n. Hammer drill. o. 0.75-inch hammer bit. p. Extension cord. q. Generator. Corrosion Rate Measurement Survey 1. Select the rebar on which the corrosion rate measure- ment will be performed. 2. If all the steel is continuous, use the ground used for con- tinuity testing or the half-cell potential measurement. 3. If steel is not continuous, install a ground on the bar to be tested. 4. If a ground has to be installed on the rebar to be tested, expose the rebar 18 inches away from the test location by drilling with a 0.75-inch drill bit. 5. At the ground location, drill into the rebar and set a self- tapping screw, making sure that it is a tight fit. Use an alli- gator clip attached to the test lead to make connection with the screw in the rebar. 6. Follow the manufacturer’s instructions to use the corro- sion rate measurement device. The procedure for con- ducting the corrosion rate measurement depends on the device. Carbonation Testing 1. Choose a test for measuring carbonation depth. All avail- able tests require 0.15% solution of Phenolphthalein in ethanol to be sprayed onto dry, freshly cut concrete. 2. In the field, find an area where the reinforcing steel has just been exposed for clear concrete cover measurement or electrical continuity testing. 3. In the laboratory, slice a core into two parts along its lon- gitudinal axis. 4. Remove any dust from the surface of the area to be tested with a lint-free, salt-free, dry tissue paper. 5. Spray Phenolphthalein solution onto the cut surface. The indicator will exhibit a pink color on uncarbonated con- crete and no color on carbonated concrete. 6. Measure and record the depth of carbonation in inches. 7. Suggested Equipment: a. 0.15% solution of Phenolphthalein in ethanol. b. Measuring tape or ruler. c. Drill with a drill bit to expose fresh concrete in the field. d. Concrete saw to slice the core in the laboratory. e. Lint-free, salt-free tissue paper. Patching Excavated Areas 1. Patch all excavated areas with high-quality, dry, bagged concrete mix having a maximum aggregate size of 0.5 inch to 1 inch. 2. Suggested Equipment: a. Dry, bagged concrete mix. b. Mixing bucket. c. Trowel. d. Water.