1、Designation: D6087 08 (Reapproved 2015)1Standard Test Method forEvaluating Asphalt-Covered Concrete Bridge Decks UsingGround Penetrating Radar1This standard is issued under the fixed designation D6087; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTERemoved converted inch-pound units editorially in June 2015.1. Scope1.1 This test method cover
3、s several ground penetratingradar (GPR) evaluation procedures that can be used to evaluatethe condition of concrete bridge decks overlaid with asphalticconcrete wearing surfaces. These procedures can also be usedfor bridge decks overlaid with portland cement concrete andfor bridge decks without an o
4、verlay. Specifically, this testmethod predicts the presence or absence of concrete or rebardeterioration at or above the level of the top layer of reinforc-ing bar.1.2 Deterioration in concrete bridge decks is manifested bythe corrosion of embedded reinforcement or the decompositionof concrete, or b
5、oth. The most serious form of deterioration isthat which is caused by corrosion of embedded reinforcement.Corrosion may be initiated by deicing salts, used for snow andice control in the winter months, penetrating the concrete. Inarid climates, the corrosion can be initiated by chloride ionscontaine
6、d in the mix ingredients. Deterioration may also beinitiated by the intrusion of water and aggravated by subse-quent freeze/thaw cycles causing damage to the concrete andsubsequent debonding of the reinforcing steel with the sur-rounding compromised concrete.1.2.1 As the reinforcing steel corrodes,
7、it expands andcreates a crack or subsurface fracture plane in the concrete ator just above the level of the reinforcement. The fracture plane,or delamination, may be localized or may extend over asubstantial area, especially if the concrete cover to the rein-forcement is small. It is not uncommon fo
8、r more than onedelamination to occur on different planes between the concretesurface and the reinforcing steel. Delaminations are not visibleon the concrete surface. However, if repairs are not made, thedelaminations progress to open spalls and, with continuedcorrosion, eventually affect the structu
9、ral integrity of the deck.1.2.2 The portion of concrete contaminated with excessivechlorides is generally structurally deficient compared withnon-contaminated concrete. Additionally, the chloride-contaminated concrete provides a pathway for the chloride ionsto initiate corrosion of the reinforcing s
10、teel. It is therefore ofparticular interest in bridge deck condition investigations tolocate not only the areas of active reinforcement corrosion, butalso areas of chloride-contaminated and otherwise deterioratedconcrete.1.3 This test method may not be suitable for evaluatingbridges with delaminatio
11、ns that are localized over the diameterof the reinforcement, or for those bridges that have cathodicprotection (coke breeze as cathode) installed on the bridge orfor which a conductive aggregate has been used in the asphalt(that is, blast furnace slag). This is because metals are perfectreflectors o
12、f electromagnetic waves, since the wave imped-ances for metals are zero.1.4 A precision and bias statement has not been developedat this time. Therefore, this standard should not be used foracceptance or rejection of a material for purchasing purposes.1.5 The values stated in SI units are to be rega
13、rded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determi
14、ne the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 5.2. Summary of Test Method2.1 The data collection equipment consists of a short-pulseGPR device, data acquisition device, recording device, anddata processing and interpretation equ
15、ipment. The user makesrepeated passes with the data collection equipment in adirection parallel or perpendicular to the centerline across abridge deck at specified locations. Bridge deck condition isquantified based on the data obtained.1This test method is under the jurisdiction of ASTM Committee D
16、04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.32 onBridges and Structures.Current edition approved June 1, 2015. Published July 2015. Originally approvedin 1997. Last previous edition approved in 2008 as D6087 08. DOI: 10.1520/D6087-08R15E01.Copyright ASTM Inter
17、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Significance and Use3.1 This test method provides information on the conditionof concrete bridge decks overlaid with asphaltic concretewithout necessitating removal of the overlay, or other destruc-tive
18、procedures.3.2 This test method also provides information on thecondition of bridge decks without overlays and with portlandcement concrete overlays.3.3 A systematic approach to bridge deck rehabilitationrequires considerable data on the condition of the decks. In thepast, data has been collected us
19、ing the traditional methods ofvisual inspection supplemented by physical testing and coring.Such methods have proven to be tedious, expensive, and oflimited accuracy. Consequently, GPR provides a mechanism torapidly survey bridges in an efficient, non-destructive manner.3.4 Information on the condit
20、ion of asphalt-covered con-crete bridge decks is needed to estimate bridge deck conditionfor maintenance and rehabilitation, to provide cost-effectiveinformation necessary for rehabilitation contracts.3.5 GPR is currently the only non-destructive method thatcan evaluate bridge deck condition on brid
21、ge decks containingan asphalt overlay.4. Apparatus4.1 GPR SystemThere are two categories of GPR systems,depending on the type of antenna utilized for data collection.4.1.1 GPR systems using air-launched horn antennas withcenter frequencies 1 GHz and greater. The equipment mayconsist of an air-couple
22、d, short-pulse monostatic or bistaticantenna(s) with sufficient center frequency to provide theaccurate measurement ofa5cmthick asphalt pavement.4.1.2 GPR systems using ground-coupled antennas withcentral frequencies greater than 1 GHz.4.2 Data Acquisition SystemA data acquisition system,consisting
23、of equipment for gathering GPR data at the mini-mum data rates specified in 4.1.1 and 4.1.2.The system shall becapable of accurately acquiring GPR data with a minimum of60-dB dynamic range.4.3 Distance Measurement SystemA distance measure-ment system consisting of a fifth-wheel or appropriate distan
24、cemeasurement instrument (DMI) with accuracy of 6100mm/km and a resolution of 25 mm.NOTE 1Fig. 1 shows a functional block diagram for multiple GPRsand support equipment.5. Hazards5.1 During operation of the GPR system, observe themanufacturers safety directions at all times. When conductinginspectio
25、ns, ensure that appropriate traffic protection is utilizedin accordance with accepted standards.5.2 Electromagnetic emissions from the GPR apparatus, ifthe system is improperly operated, could potentially interferewith commercial communications, especially if the antenna isnot properly oriented towa
26、rd the ground. Ensure that all suchemissions from the system comply with Part 15 of the FederalCommunications Commission (FCC) Regulations.6. Procedure6.1 Conditions for Testing:6.1.1 If soil, aggregate, or other particulate debris is presenton the bridge deck surface, clean the bridge deck.6.1.2 Te
27、st the bridge deck in a surface dry condition.6.2 System Performance ComplianceThe system shouldbe calibrated and performance verified in accordance with themanufacturers recommendations and specifications. The fol-lowing information is included for reference only and describesFIG. 1 Block Diagram o
28、f GPR and Support EquipmentD6087 08 (2015)12typical calibration procedures for different types of systems.Compliance with the following procedures is not required andthe manufacturers calibration procedure takes preference. Forair-launched antennas, this test shall consist of the following:6.2.1 Sig
29、nal-to-Noise Ratio:6.2.1.1 Signal-to-Noise Ratio TestPosition the antenna atits far field distance approximately equal to maximum dimen-sion of antenna aperture above a square metal plate with awidth of 4 antenna aperture, minimum. Turn on the GPR unitand allow to operate for a 20-min warm-up period
30、 or the timerecommended by the manufacturer. After warming up the unit,record 100 waveforms. Then evaluate the recorded waveformfor signal-to-noise ratio. The signal-to-noise ratio is describedby the following equation:Signal Level Amp!Noise Level An!.20 26.0 dB! (1)6.2.1.2 This will be performed on
31、 each of the 100 wave-forms and the average signal-to-noise value of the 100 wave-forms will be taken as the “signal-to-noise of the system.”Noise voltage (An) is defined as the maximum amplitudeoccurring between metal plate reflection and region up to 50 %of the time window after the metal plate re
32、flection, normallyused with the antenna (that is, 1.0 GHz/20 ns: 10 ns.). Thesignal level (Amp) is defined as the amplitude of the echo fromthe metal plate.6.2.1.3 The signal-to-noise ratio test results for the GPR unitshould be greater than or equal to 20 (+26.0 dB).6.2.2 Signal Stability:6.2.2.1 S
33、ignal Stability TestUse the same test configura-tion as described in the signal-to-noise ratio test. Record 100traces at the maximum data acquisition rate. Evaluate thesignal stability using the following equation:Amax2 AminAavg,0.01 1%! (2)where:Amax= the maximum amplitude of the metal plate reflec
34、tionfor all 100 traces,Amin= the minimum amplitude of the metal plate reflectionfor all 100 traces, andAavg= the average trace amplitude of all 100 traces.6.2.2.2 The signal stability test results for the GPR systemshould be less than or equal to 1 %.6.2.3 Linearity in the Time Axis and Time Window
35、Accu-racy:6.2.3.1 Variations in Time Calibration FactorUse thesame test configuration as described in the signal-to-noise ratiotest, except that the metal plate can be replaced by anyreflecting object. Collect a single waveform and measure thedistance from the antenna to the reflector. Perform this
36、test atthree different distances corresponding to approximately 15,30, and 50 % of the time window normally used with thesystem. The time delay between the echo from the aperture ofthe transmitting antenna and that from the reflecting object ismeasured as time t1(where subscript1represents position
37、1, andso forth). The difference between t2and t1and between t3andt2represents the travel time for a fixed distance in air. Thefactor Ci represents the speed between distance i and i+1. Theallowable variation in measured speed is shown as follows:C12 C2Mean of C1and C2,2%, (3)where:C1=Distance from P
38、osition 2 to Position 1T1C2=Distance from Position 3 to Position 2t26.2.3.2 The variation in time calibration factor should beless than 2 %.6.2.4 Long-Term Stability Test:6.2.4.1 Long-Term Amplitude VariationUse the same testconfiguration as described in the signal-to-noise ratio test.Switch on the
39、GPR and allow to operate for 2 h continuously.As a minimum, capture a single waveform every 1 min, 120total. Calculate the amplitude of a metal plate reflection andplot against time for each waveform. For the system to performadequately, the amplitude of reflection should remain constantafter a shor
40、t warm-up period. The stability criteria is asfollows:Amax2 A20A20,0.03 3%! (4)where:A20= the amplitude measured after 20 min, andAmax= the largest amplitude measured between 20 min and120 min.6.3 Pre-Operation Measurement:6.3.1 Free Space Signal (FSP)The equipment manufac-turer may require the GPR
41、antenna to be mounted in anoperational configuration, and 100 waveforms gathered in theabsence of the material to be inspected. Use the average of 100waveforms as a template for clutter removal.6.3.2 Flat Metal Plate (FMP)Position the GPR in anoperation configuration, and gather 100 waveforms whilei
42、lluminating a flat plate with dimensions recommended by themanufacturer. This is a measure of the emitted energy to beused in subsequent measurements, and as a template fordecorrelation or background removal, or both.6.4 GPR Data Acquisition:6.4.1 Air-Launched Antenna Systems:6.4.1.1 Make GPR inspec
43、tion passes in a longitudinal direc-tion parallel to the centerline of the bridge deck with theantenna mounted to maintain a manufacturer-recommendeddistance from the bridge deck surface.6.4.1.2 Use a transverse distance (dt ) between GPR inspec-tion passes 1 m is suggested.6.4.1.3 Use a longitudina
44、l distance (dl) between GPR scans150 mm.6.4.1.4 Determine the starting location for passes, that is, atabutments, joints, or a predetermined location.6.4.1.5 Determine the optimum speed of operation forcontiguous longitudinal coverage based on GPR range sweeprate and the scan-spacing.D6087 08 (2015)
45、136.4.2 Ground-Coupled Antenna Systems:6.4.2.1 Make GPR inspection passes either parallel to thedirection of traffic, or perpendicular to the direction of traffic,depending on the direction of the top layer of reinforcing. Thepass direction should be chosen so that the antenna crossesover the top la
46、yer of reinforcing at an angle nearest to 90.6.4.2.2 Use a transverse distance (dt) between GPR inspec-tion passes 0.6 m.6.4.2.3 Use a longitudinal distance (dl) between GPR scansnecessary to obtain sufficient data 150 mm is suggested.6.4.2.4 Determine the starting location for passes, that is, atab
47、utments, joints, or a predetermined location.7. Data Processing7.1 There are two different accepted GPR data processingmethodologies. Both methods employ reflection amplitudes.The first method, the bottom deck reflection attenuationtechnique, calculates deterioration based on the relative reflec-tio
48、n amplitudes from the bridge deck bottom relative to thebridge deck surface. The second method, the top reinforcingreflection attenuation technique, utilizes the relative reflectionamplitudes from the top layer of reinforcing to assess deterio-ration.7.2 Deterioration Measurements at Top Reinforcing
49、 Steelusing the Bottom Deck Reflection Attenuation Technique:7.2.1 Measure and record the applied signal strength, Vt,atthe deck surface.7.2.2 Measure and record the maximum signal strength ofthe deck bottom echo, Vbs.7.2.3 If Vbsis 0.0264 Vtfor a longitudinal GPR inspectionpass, proceed to 7.2.5. (The number 0.0264 is a constantderived from research data.)7.2.4 If Vbsis 0.0264 Vtafter repeating the longitudinalGPR inspection pass, the data are not reliable for determiningremoval quantities of bridge deck concrete. Processing of thedata will require an al
