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From page 12...
... 12 Controlled Evaluation of NDT Techniques Test Slabs and Pavement Sections for Controlled Testing This chapter provides brief information about the test slabs and pavement sections. More detailed information about the design and construction of the slabs and pavement sections is presented in Volume 3, Chapter 1.
From page 13...
... 13 Figure 3.1. Design of two HMA slabs for controlled laboratory evaluation.
From page 14...
... 14 at each of the following locations. The pipe was filled with water to apply hydrostatic pressure to inject water into the delaminated layer interfaces.
From page 15...
... 15 primary state DOT applications of GPR were for measurement of pavement thickness (ASTM D 4748-06) , bridge deck delamination, and depth of reinforcing steel (Maser and Puccinelli 2009; Maser 2005)
From page 16...
... 16 coverage with multiple paths from the array of transmitters and receivers. The MIRA's disadvantage is that it is a groundcoupled system that is deployed at a relatively low (walking)
From page 17...
... 17 3d-Radar systems were evaluated on November 8–9, 2009, and the MALA system was tested on November 22, 2009. The second round of testing took place on March 7–8, 2010, for all the systems.
From page 18...
... 18 pavement surface with a wooden support beam. The alignment of the data lines was visually maintained by the vehicle driver by using spacing markers painted on the pavement surface every 100 ft.
From page 19...
... 19 The GPR data for each system were analyzed by using a timedepth slice technique, which is a representation of the reflection activity in a horizontal plane at a particular time and depth interval. Time-depth slice data obtained for each GPR system in Sections 4, 5, 6, and 7 (Figure 3.9)
From page 20...
... 20 3d-Radar slice at 3" Figure 3.9. GPR time-depth slices for Sections 4, 5, 6, and 7.
From page 21...
... 21 are required, including a minimum temperature difference of 0.5°C and a wind velocity of less than 30 mph (ASTM D4788-03)
From page 22...
... 22 lens, but this lens was not available at the time of testing. The primary difference between the two cameras is size.
From page 23...
... 23 and tire marks, rather than subsurface features. In general, the IR image anomalies did not clearly correlate with the known subsurface defects placed in the test sections.
From page 24...
... 24 receivers and the source. The source strikes the pavement surface and generates stress waves that are detected by the receivers.
From page 25...
... 25 Test Date October 2009 Test location (ft) > 17.5 22.5 27.5 32.5 37.5 42.5 47.5 52.5 57.5 62.5 Test Line 1 > 0.1 0.2 0.2 0.2 0.1 0.4 0.9 0.6 0.5 Test Line 2 > 0.2 0.3 0.2 0.1 0.1 0.9 0.8 0.9 0.9 1.0 Test Line 3 > 0.2 0.2 0.2 0.3 0.5 1.0 1.0 0.7 1.0 0.8 Test Line 4 > 0.4 0.2 0.1 0.1 0.1 0.8 1.0 0.9 0.9 0.9 Pavement Surface Temperature (F)
From page 26...
... 26 Scanning iE/SaSW and MiSW dEvicES Figures 3.16 and 3.17 show examples of detailed results of the scanning IE test in the form of resonant frequencies during the second round of testing on Sections 1, 2, 9, and 10. The resonant frequency shown in the figures is directly related to the pavement structure's thickness.
From page 27...
... 27 to 200,000 Hz) wave propagation–based test methods, such as the PSPA, the scanning IE/SASW device, and the MISW device.
From page 28...
... 28 FWD is an impact load device that applies a single-impulse transient load of approximately 25- to 30-ms duration. With this trailer-mounted device, a dynamic force is applied to the pavement surface by dropping a weight onto a set of rubber cushions.
From page 29...
... 29 delaminated areas simulated with baghouse dust because of the texture provided by the baghouse dust. On the basis of field testing results, the LWD does not appear to be able to show differences in deflection between the various sections.
From page 30...
... 30 used in Phase 1 to rank the evaluated NDT techniques. Nine factors were rated on a scale of 1 (low)
From page 31...
... 31 Table 3.1. Summary of Findings from Controlled Laboratory and Field Evaluation Factor GPR Mechanical Wave Deflection Measurement GSSI 3d-Radar MALA MISW IE PSPA LWD FWD Detection of stripping Good Good Good Poor Fair Fair Fair Poor Detection of debonding Fair Poor Poor Poor Fair Fair Poor Poor Potential for implementing Fair to good Good Good Fair Fair Good Good Good Equipment availability Not multichannel Not FCC-approved Available Limited Limited Available Available Available Current application Used in United States Used outside United States Used in United States Limited use in United States Limited use in United States Used in United States Used in United States Used in United States Cost ($)
From page 32...
... 32 equipment improvement, uncontrolled field testing did not begin until winter 2010 for the GPR technique and began in spring 2011 for the mechanical wave technique. Weather conditions were not suitable for field testing in Maine and Washington State.
From page 33...
... 33 domain, where the spectrum is divided into frequency intervals, or "bins." The algorithm computes the energy contained in every bin and then sorts the obtained values. The value that will be finally extracted is relative to only one bin, which is selected by the user.
From page 34...
... 34 interpretation of the GPR data by using the depth slice at 4.7 in.
From page 35...
... 35 Table 3.3. GPR versus Core Information for Florida I-75 Site Core Distance (ft)
From page 36...
... 36 antenna, particularly visible close to the surface. Suspicions are that this behavior is due to the resonant frequency of the vehicle suspension; that is, the antenna vibrates together with the vehicle and produces small undulations in the data.
From page 37...
... 37 changed to a clamping attachment that can slide across the towing assembly bar, allowing endless measurement configuration possibilities. Lift bails were added to the towing assembly to allow the transducer wheels to be picked up off the pavement surface to back the system up or to reposition the truck with greater ease.
From page 38...
... 38 0.5 ft. The interpretation of the scanning SASW results agrees well with the as-built condition, which is delamination at a 5-in.
From page 39...
... 39 IE/SASW system was able to detect the 5-in.-deep delaminations but not the shallower 2-in.-deep delaminations. This was most likely a result of the current system's difficulty in exciting high frequencies in asphalt mixtures at higher temperatures; this was due to asphalt's temperature-dependent elastic moduli.
From page 40...
... 40 • 3,100 to 3,285 ft. This section had relatively high surface wave velocities throughout the cross section and was considered one of the best areas of the test site.
From page 41...
... 41 the core samples that were removed from the pavement all showed signs of delamination. Thus, there was no comparison for data measured with the LWD.
From page 42...
... 42 Section break D3 0 0.5 11 12 13 14 21 22 23 24 31 32 33 34 41 42 43 44 51 52 53 54 61 62 63 64 1 1.5 2 2.5 3 3.5 4 4.5 Core Hole Location D ef le ct io n (m ils ) D2 D1-average D1 Figure 3.28.

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