National Academies Press: OpenBook

Nondestructive Testing to Identify Concrete Bridge Deck Deterioration (2012)

Chapter: Chapter 5 - Approach to Validation Testing

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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 39
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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
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Page 41
Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 41
Page 42
Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 42
Page 43
Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 43
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Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 44
Page 45
Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 45
Page 46
Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 46
Page 47
Suggested Citation:"Chapter 5 - Approach to Validation Testing." National Academies of Sciences, Engineering, and Medicine. 2012. Nondestructive Testing to Identify Concrete Bridge Deck Deterioration. Washington, DC: The National Academies Press. doi: 10.17226/22771.
×
Page 47

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34 C h a p t e r 5 High-speed NDT technologies such as ground-penetrating radar, infrared thermography, and impact echo scanning have been increasingly used in recent years for bridge deck condition assessment. Still, these technologies have not been widely adapted or accepted for two main reasons: (1) high- way agencies are not fully aware of the capabilities and limita- tions of these methods or how they should best be used, and (2) some agencies have had less-than-positive experiences with NDT techniques, perhaps because of unrealistic expec- tations and improper use of these technologies. Therefore, a plan to evaluate the most promising technologies, both in the field under actual, production-level conditions and in the laboratory under controlled conditions, was developed for the second phase of the project. The performance factors of highest importance during the laboratory validation were accuracy and precision. The parameters of the highest impor- tance in the field validation were speed of evaluation, includ- ing data collection and analysis; ease of use; precision; and cost. The following sections describe the validation testing, a task designed to evaluate the performance of candidate NDT technologies. Field Validation testing Field validation was conducted on the Route 15 bridge over I-66 in Haymarket, Virginia. Bridge selection and organiza- tion of testing were done in collaboration with the FHWA’s Long-Term Bridge Performance (LTBP) Program, Virginia Department of Transportation, and Virginia Transportation Research Council. This bridge was selected because it had gone through a rigorous evaluation using both destructive and nondestructive means, visual inspection, and full-scale loading as a part of the LTBP activities. The instrumentation and monitoring of this particular bridge within the LTBP Program commenced in September 2009, which provided a wealth of information about the bridge condition. The Hay- market Bridge is a two-span concrete deck on a steel girder structure and was constructed in 1979. The bridge has a 15° skew. The reinforced concrete deck is about 8 in. thick, with clearly visible deterioration on its surface (Figure 5.1). In August 2010, the SHRP 2 research team released elec- tronic announcements regarding the validation testing of 10 nondestructive testing technologies. This was done via targeted e-mails to industry vendors, manufacturers, and research centers, along with postings to the TRB, the Ameri- can Society for Nondestructive Testing, and SHRP 2 websites. On receipt of invitee responses, the SHRP 2 team provided each respondent with a detailed description of the planned valida- tion testing to be conducted. The descriptions included test- ing objectives, activity scope, participant and research team responsibilities, and result reporting methods. The final team comprised eight non-SHRP 2 project participants and two groups from the institutions of the SHRP 2 project team, but not the members of the project team. Thus 10 groups in total were involved in the validation testing. The participating teams in alphabetical order are as follows: 1. FHWA, Turner–Fairbank Highway Research Center (Dr. Ralf Arndt); 2. Germann Instruments; 3. IDS, Italy; 4. NDT Corporation; 5. Olson Engineering; 6. Rutgers University, CAIT; 7. 3D-RADAR, Norway; 8. University of Illinois (Dr. John Popovics); 9. The University of Texas at Austin (Dr. Jinying Zhu); and 10. The University of Texas at El Paso, CTIS. Henceforth, each participant will be referred to by assigned numbers from the research teams. The technologies participating in the validation testing included ground-penetrating radar, impact echo, surface wave testing, impulse response, half-cell potential, electrical Approach to Validation Testing

35 resistivity, galvanostatic pulse measurement, infrared thermo- graphy, ultrasonic pulse echo, and chain dragging and ham- mer sounding. Some of the technologies were represented by multiple participants, each using a different system. Testing was conducted on a 1,008 ft2 (84-ft × 12-ft) area, extending over parts of the shoulder and travel lane (Fig- ure 5.2). A 2-ft by 2-ft rectangular grid was marked on the deck using washable paint. A blue, washable spray paint was used to mark the grid, rather than the commonly used white paint, to facilitate better imaging for infrared thermogra- phy. The origin of the test grid was located 24 ft from the north expansion joint and 3 ft from the west parapet wall. The grid had 301 test points. The grid schematic is depicted in Figure 5.3, and a part of the grid is shown in Figure 5.4. The participants were required to collect data on the grid points. However, they were also permitted to collect addi- tional data, within the allocated time period, after obtaining the required test location data. Eight locations were marked on the deck for vertical crack evaluation for those partici- pants who were engaged in their characterization. To evalu- ate technology repeatability, all participants were required to repeat measurements three times along the middle line (Line D). Detailed testing plan instructions were provided to all par- ticipants both before the testing and at the bridge site. These instructions clearly delineated evaluation objectives, testing methods, results to be reported, elements of comparative Figure 5.1. Side view of Route 15 bridge over I-66 in Haymarket, Virginia. Testing Area Parking Area Figure 5.2. Route 15 bridge over I-66 in Haymarket, Virginia. Figure 5.3. Grid schematic with marked locations of vertical cracks (green squares) and extracted cores (red circles).

36 evaluation, and technology ranking information. Figures 5.5 to 5.11 illustrate data collection by different participants. After testing had been completed, eight cores were removed from the deck by a local contractor. These cores were used to provide ground truth. Four of the cores were taken at the vertical crack locations evaluated by the participating teams (Figure 5.12). Images of eight cores removed from the deck are shown in Figure 5.13. All four defects of interest—delamination, cor- rosion, vertical crack, and concrete deterioration—can be observed in the cores. Laboratory Validation testing The laboratory validation testing commenced in December 2010 at El Paso, Texas. Two test decks were prepared for the validation testing. The first test deck was a newly fabricated Figure 5.4. Test grid. Figure 5.5. Impact echo: (left) Germann Instruments; (right) NDT Corporation. Figure 5.6. Impulse response (left): Germann Instruments. Ground-penetrating radar (right): 3D-RADAR.

37 Figure 5.7. Ground-penetrating radar: IDS. Figure 5.8. Air-coupled ultrasonic surface wave: University of Texas at Austin. concrete deck with simulated defects, and the other test deck was removed from a bridge on I-10 in El Paso. The two test decks were embedded in the ground at a site near the main campus of the University of Texas at El Paso. Fabricated Bridge Deck The fabricated bridge deck was 20 ft long, 8 ft wide, and about 8.5 in. thick and supported by three 1.5-ft-wide prestressed girders retrieved from a Texas Department of Transportation (Texas DOT) project (Figure 5.14). Class S concrete mix, as per Texas DOT Specification 421.4, was adapted for deck con- struction. This mix requires a minimum 28-day compressive strength of 4,000 psi and has been widely used in bridge deck construction in Texas DOT projects. To simulate an actual con- crete bridge deck, the slab was finished with a rough top surface. Water curing was applied to the slab for 7 days after concrete placement. The 28-day compressive strength and modulus of the mix were more than 5,000 psi and 4,000 ksi, respectively. The deck was built with two mats of uncoated steel rein- forcement. Each of the reinforcement mats consisted of No. 5 steel bars spaced at 8 in. in the transverse direction and spaced at 10 in. in the longitudinal direction. The top and bottom concrete covers of the deck were 2.5 to 3 in. and 2 in. thick, respectively. Nine artificially delaminated areas, two pieces of corroded reinforcement mats, and four vertical cracks were built in the deck. In addition, a natural crack was observed in the deck about 2 weeks after construction.

38 Figure 5.9. Half-cell potential (left) and electrical resistivity (right): Rutgers University. Figure 5.10. Impact echo and surface waves (left) and galvanostatic pulse measurement (right): Olson Engineering.

39 Figure 5.15 depicts an overview of the approximate distri- bution of the as-built defects in this deck. The information about each defect is summarized in Table 5.1. In Figure 5.15 and Table 5.1, DL denotes delaminations and CK denotes vertical cracks. Ideally, corrosion should be built on the original steel bars used for the enforcement for HCP and ER testing. However, because of the fund restriction and time limitation, it is practi- cally impossible to build accelerated corrosion of 2 to 3 ft long on each 20-ft or 8-ft-long regular steel bar. Instead, thirty two 30-in.-long steel bars were pretreated in a manual way similar to the practice of ASTM B-117 [Standard Practice for Operat- ing Salt Spray (Fog) Apparatus]. One-half of these bars were treated for 2 months and another one-half for 3 months. They were then used to build two sets of corrosion mats. The two sets of corrosion mats were merged parallel to one another and electrically connected to the normal reinforcement bars at one end of the fabricated deck (Figure 5.16). To inspect the behavior of the materials used to simulate delaminations and to check the status of rebar corrosion, four cores (C1, C2, C3, and C4) were extracted from the deck at the locations shown in Figure 5.17 after all validation tests had been completed. Images of the four cores from the fabricated deck are shown in Figure 5.18. Cores C1, C2, and C3 reflect three different levels of delamination. Core C4 shows the status of the corroded bar 8 months after placement; that is, red corrosion (Fe2O3; also see Figure 5.16) turned to black Figure 5.11. Infrared thermography (left): FHWA. Ground-penetrating radar (right): NDT Corporation. Figure 5.12. Vertical crack and core locations. (text continues on page 43)

40 (a) (c) (e) (b) (d) (f) Figure 5.13. Cores 1 (a), 2 (b), 3 (c), 4 (d), 5 (e and f). (continued on next page)

41 (g) (h) (i) (j) Figure 5.13. (continued) Cores 6 (g and h), 7 (i), and 8 (j).

42 Figure 5.14. Fabricated slab: (a) schematic and (b) curing. (a) (b) Shallow Delamination Shallow Severe Delamination Vertical Cracking Deep Delamination Corroded Rebar 8 ft 24"x 24" 12"x 12" 12"x 12" 24"x 24" 12 " x 24 " 20 ft 24"x 24" 24"x 24" 24"x 24" In ta ct A re a 24 " x 48 " Figure 5.15. Overview of defect distributions in fabricated slab.

43 Table 5.1. Detailed Information of Defects in Fabricated Concrete Deck Defect Type Code Size (in.) Depth (in.) Description Delamination DL1 12 × 12 2.5–3.0 Soft and high-strength, thin (about 1 mm) foam DL2, DL3 24 × 24 2.5–3.0 DL4 12 × 12 2.5–3.0 Soft and high-strength, thick (about 2 mm) foam DL5, DL6 24 × 24 2.5–3.0 DL7 24 × 24 6–6.5 Soft and high-strength, thin (about 1 mm) foam DL8 24 × 48 6–6.5 DL9 12 × 24 2.5–3.0 Very thin (about 0.3 mm), soft polyester fabric Vertical crack CK1, CK2 12 (length) 2.5 Soft thin cardboard CK3 12 (length) 3.0 Soft thick cardboard with void CK4 12 (length) 6.0 CK5 13 (length) 2.5–3.0 Natural, fine cracka Rebar corrosion 30 in. × 30 in. (each mat) 2.5 and 6.5 (midpoints) 1- to 2-mm deep corrosion a It extended to the edge of the deck, and its depth is measurable. Red Corrosion (Fe2O3) Figure 5.16. Setup of the corroded steel bar mat in the fabricated deck. corrosion (Fe3O4). The mechanism for this change is un- clear in this situation. Recovered Bridge Deck A 9-ft by 14-ft section was removed from a distressed highway bridge along Interstate 10 near El Paso, Texas. The bridge deck consisted of arch-type concrete overlaid by a 4–in.-thick, hot- mix asphalt surface (Figure 5.19). The arch-type concrete showed continuous cracks at the bottom of each arch. After all validation tests had been completed, seven cores were taken from the deck (Figure 5.20). These cores indicate that the deck is seriously delaminated and cracked, which seemed to be stress-induced by traffic loading, because almost no corrosion was observed from the cores. Shallow Delamination Shallow Very Thin Delamination Shallow Severe Delamination Deep Delamination Vertical Cracking Rebar Corrosion Test Lines and Points Core Location 8 ft 20 ft 1 11 1715139753 DL8 DL9 C3 C4 C1 C2 Figure 5.17. Locations of coring on fabricated deck. (continued from page 39)

44 Corroded Rebar in Core: Black Corrosion (Fe3O4) C4 C3 Very Thin Delaminaon Delaminaon Thick Delaminaon C2C1 Delaminaon Figure 5.18. Cores from fabricated bridge deck. Arch Bridge Deck Removed Section Crack at Arch Bottom Figure 5.19. Bridge with arch deck.

45 Figure 5.20. Cores from recovered bridge deck. A B C D E 1 2 3 4 5 6 7 8 D2 C3 D4 On line D (on arch). Location of coring on the recovered bridge deck. On line C (between arches). On line B (on arch). B1 B2 B3 B6

46 Preparation for Validation Testing To facilitate testing, compacted soil shoulders and ramps were built surrounding the fabricated slab, so that the sur- face was vehicle accessible, as shown in Figure 5.21. Similarly, the recovered bridge deck was placed into the soil ground. The hot-mix asphalt surface was removed from the deck before testing to eliminate any potential effect on the measurements. For the fabricated bridge deck, the grid test points were 1 ft apart, although the test points were 1.5 ft apart for the recov- ered bridge deck. All the field validation testing participants took part in the laboratory testing as well. The participants were asked to sub- mit the results no later than 2 weeks after conducting their tests. Figures 5.22 to 5.25 illustrate data collection by different participants. Figure 5.22. Air-coupled impact echo (left): University of Illinois. Impact echo (right): NDT Corporation. Figure 5.21. Fabricated bridge deck (top) and recov- ered bridge deck (bottom) in place for testing.

47 Figure 5.25. Infrared thermography (left): FHWA. Ultrasonic surface waves (right): Rutgers University. Figure 5.23. Impact echo (left): Olson Engineering. Impact echo (right): Rutgers University. Figure 5.24. Air-coupled impact echo (left): University of Texas at Austin. Ground-penetrating radar (right): Rutgers University.

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TRB’s second Strategic Highway Research Program (SHRP 2) Report S2-R06A-RR-1: Nondestructive Testing to Identify Concrete Bridge Deck Deterioration identifies nondestructive testing technologies for detecting and characterizing common forms of deterioration in concrete bridge decks.

The report also documents the validation of promising technologies, and grades and ranks the technologies based on results of the validations.

The main product of this project will be an electronic repository for practitioners, known as the NDToolbox, which provides information regarding recommended technologies for the detection of a particular deterioration.

An e-book version of this report is available for purchase at Amazon, iTunes, and Google

As part of the project that developed SHRP 2 Report S2-R06A-RR-1, a series of videos were produced that show various nondestructive testing technologies being demonstrated by teams from industry and academia. Technologies highlighted in the videos include electrical resistivity (Rutgers); galvanostatic pulse measurement (Olson Engineering); ground penetrating radar (3D Radar, IDS-Italy, NDT Corp, Aladdin System, Olson Engineering/IDS, and Rutgers); half-cell potential (Rutgers); impact echo (University of Illinois, NDT Corp, Olson Engineering, Rutgers, University of Texas at Austin, and Germann Instruments); impulse response (Germann Instruments); infrared thermography (FHWA and the University of Texas at El Paso); ultrasonic pulse echo (University of Texas at El Paso); and ultrasonic surface waves (Rutgers).

Renewal Project R06A is one of seven follow-on projects to SHRP Renewal Project R06 that produced SHRP 2 Report S2-R06-RW: A Plan for Developing High-Speed, Nondestructive Testing Procedures for Both Design Evaluation and Construction Inspection, which examines existing and emerging nondestructive evaluation technologies and their current state of implementation to satisfy the NDE needs for highway renewal.

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