1、Designation: D 6087 07Standard Test Method forEvaluating Asphalt-Covered Concrete Bridge Decks UsingGround Penetrating Radar1This standard is issued under the fixed designation D 6087; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers several radar evaluation proce-dures that can be used to evaluate the condition
3、 of concretebridge decks overlaid with asphaltic concrete wearing surfaces.Specifically, this test method predicts the presence or absenceof concrete or rebar deterioration at or above the level of thetop layer of reinforcing bar.1.2 Deterioration in concrete bridge decks is manifested bythe corrosi
4、on of embedded reinforcement or the decompositionof concrete, or both. The most serious form of deterioration isthat which is caused by corrosion of embedded reinforcement.Corrosion is initiated by deicing salts, used for snow and icecontrol in the winter months, penetrating the concrete. In aridcli
5、mates, the corrosion can be initiated by chloride ionscontained in the mix ingredients.1.2.1 As the reinforcing steel corrodes, 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 locali
6、zed or may extend over asubstantial area, especially if the concrete cover to the rein-forcement is small. It is not uncommon for more than onedelamination to occur on different planes between the concretesurface and the reinforcing steel. Delaminations are not visibleon the concrete surface. Howeve
7、r, if repairs are not made, thedelaminations progress to open spalls and, with continuedcorrosion, eventually affect the structural integrity of the deck.1.2.2 The portion of concrete contaminated with excessivechlorides is generally structurally deficient compared withnon-contaminated concrete. Add
8、itionally, the chloride-contaminated concrete provides a pathway for the chloride ionsto initiate corrosion of the reinforcing steel. It is therefore ofparticular interest in bridge deck condition investigations tolocate not only the areas of active reinforcement corrosion, butalso areas of chloride
9、-contaminated and otherwise deterioratedconcrete.1.3 This test method may not be suitable for evaluatingbridges with delaminations 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
10、a conductive aggregate has been used in the asphalt(that is, blast furnace slag). This is because metals are perfectreflectors of electromagnetic waves, since the wave imped-ances for metals are zero.1.4 The values stated in SI units are to be regarded as thestandard. The inch-pound units given in p
11、arentheses are forinformation only.1.5 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 determine the applica-bility of regulatory limit
12、ations prior to use. Specific precau-tionary statements are given in Section 5.1.6 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.2. Summary of Test Method2.1 The data col
13、lection equipment consists of a short-pulseground penetrating radar device, data acquisition device, re-cording device, and data processing and interpretation equip-ment. The user makes repeated passes with the data collectionequipment in a direction parallel or perpendicular to thecenterline across
14、 an asphalt-covered bridge deck at specifiedlocations. Bridge deck condition is quantified based on the dataobtained.3. Significance and Use3.1 This test method provides information on the conditionof concrete bridge decks overlaid with asphaltic concretewithout necessitating removal of the overlay,
15、 or other destruc-tive procedures.1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.32 onBridges and Structures.Current edition approved Oct. 1, 2007. Published October 2007. Originallyapproved in 1997.
16、Last previous edition approved in 2005 as D 6087 - 05.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 A systematic approach to bridge deck rehabilitationrequires considerable data on the condition of the decks. In thepast, data h
17、as been collected using the traditional methods ofvisual inspection supplemented by physical testing and coring.Such methods have proven to be tedious, expensive, and oflimited accuracy. Consequently, radar provides a mechanism torapidly survey bridges in an efficient, non-destructive manner.3.3 Inf
18、ormation on the condition 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.3.4 Ground penetrating radar is currently the only non-destructive method tha
19、t can evaluate bridge deck condition onbridge decks containing an asphalt overlay.4. Apparatus4.1 Radar SystemThere are two categories of radar sys-tems, depending on the type of antenna utilized for datacollection.4.1.1 Radar control units capable of driving air-launchedhorn antennas with center fr
20、equencies 1 GHz and greater. Thecontrol units must operate at a transmit rate sufficient to collect20 scans/m (6 scans/ft). The equipment may consist of anair-coupled, short-pulse monostatic or bistatic antenna(s) withsufficient center frequency to provide the accurate measure-ment ofa5cm(2in.) thic
21、k asphalt pavement.4.1.2 Radar control units capable of driving ground-coupledantennas with central frequencies greater than 1 GHz. Thecontrol units must operate at a transmit rate sufficient to collect80 scans/m (24 scans/ft).4.2 Data Acquisition SystemA data acquisition system,consisting of equipm
22、ent for gathering radar data at the mini-mum data rates specified in 4.1.1 and 4.1.2. The system shall becapable of accurately acquiring radar data with a minimum of60-dB dynamic range.4.3 Distance Measurement SystemA distance measure-ment system consisting of a fifth-wheel or appropriate distanceme
23、asurement instrument (DMI) with accuracy of 6100mm/km (66.5 in./mile) and a resolution of 25 mm (1 in.).4.4 Test VehicleA vehicle with all equipment necessary toperform the test and proper warning and safety devicesinstalled.NOTE 1Fig. 1 shows a functional block diagram for multiple radarsand suppor
24、t equipment.5. Hazards5.1 During operation of the radar system, observe themanufacturers safety directions at all times. When conductinginspections, ensure that appropriate traffic protection is utilizedin accordance with accepted standards.6. Procedure6.1 Conditions for Testing:6.1.1 If soil, aggre
25、gate, or other particulate debris is presenton the bridge deck surface, clean the bridge deck.6.1.2 Test the bridge deck in a surface dry condition.6.2 System Performance ComplianceConduct a test onthe radar equipment to ensure proper performance, at leastonce per year, or after periods of prolonged
26、 storage, or inaccordance with manufacturers recommendations. For air-launched antennas, this test shall consist of the following:6.2.1 Signal-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
27、above a square metal plate with awidth of 43 antenna aperture, minimum. Turn on the radar unitFIG. 1 Block Diagram of Radar and Support EquipmentD6087072and allow to operate for a 20-min warm-up period or the timerecommended by the manufacturer. After warming up the unit,record 100 waveforms. Then e
28、valuate 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 each of the 100 wave-forms and the average signal-to-noise value of the 100 wave-forms will be ta
29、ken 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 reflection, normallyused with the antenna (that is, 1.0 GHz/20 ns: 10 ns.). Thesignal level (Amp) is
30、 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 Signal Stability TestUse the same test configura-tion as described in the signal-to-noise ratio tes
31、t. Record 100traces at the maximum data acquisition rate. Evaluate thesignal stability using the following equation:Amax AminAavg, 0.01 1%! (2)where:Amax= the maximum amplitude of the metal plate reflec-tion for all 100 traces,Amin= the minimum amplitude of the metal plate reflec-tion for all 100 tr
32、aces, 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 Accu-racy:6.2.3.1 Variations in Time Calibration FactorUse thesame test configuration as descr
33、ibed 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 test atthree different distances corresponding to approximately 15,30, and 50 % of the time wi
34、ndow 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 1,and so forth). The difference between t2and t1and between t3and t2represents the travel time
35、 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:C1C2Mean of C1and C2, 2 %, (3)where:C1= Distance from Position 2 to Position 1T1C2= Distance from Position 3 to Position 2t26.2.3.2 The variation i
36、n 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 radar and allow to operate for 2 h continuously.As a minimum, capture a single waveform eve
37、ry 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 short warm-up period. The stability criteria is asfollows:AmaxA20A20, 0.03 3%! (4)where:A20=
38、the amplitude measured after 20 min, andAmax= the largest amplitude measured between 20 minand 120 min.6.3 Pre-Operation Measurement:6.3.1 Free Space Signal (FSP)The equipment manufac-turer may require the radar antenna to be mounted in anoperational configuration, and 100 waveforms gathered in thea
39、bsence 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 radar in anoperation configuration, and gather 100 waveforms whileilluminating a flat plate with dimensions recommended by themanufacturer. This is a mea
40、sure of the emitted energy to beused in subsequent measurements, and as a template fordecorrelation or background removal, or both.6.4 Radar Data Acquisition:6.4.1 Air-Launched Antenna Systems:6.4.1.1 Make radar inspection passes in a longitudinaldirection parallel to the centerline of the bridge de
41、ck with theantenna mounted to maintain a manufacturer-recommendeddistance from the bridge deck surface.6.4.1.2 Use a transverse distance (dt) between radar inspec-tion passes 1 m (3 ft).6.4.1.3 Use a longitudinal distance (dl) between radar scans150 mm (6 in).6.4.1.4 Determine the starting location
42、for passes, that is, atabutments, joints, or a predetermined location.6.4.1.5 Determine the speed of operation for contiguouslongitudinal coverage based on the radar range sweep rate andthe manufacturer-recommended scan-spacing.6.4.2 Ground-Coupled Antenna Systems:6.4.2.1 Make radar inspection passe
43、s 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 layer of reinforcing at an angle nearest to 907. Data Processing7.1 There
44、are two different radar data processing method-ologies. Both methods employ reflection amplitudes. The firstD6087073method, the attenuation technique, calculates deteriorationbased on the relative reflection amplitudes from the bridgedeck bottom relative to the bridge deck surface. The secondmethod,
45、 the top reinforcing reflection technique, utilizes therelative reflection amplitudes from the top layer of reinforcingto assess deterioration.7.2 Deterioration Measurements at Top Reinforcing SteelAttenuation Technique:7.2.1 Measure and record the applied signal strength, Vt,atthe deck surface.7.2.
46、2 Measure and record the maximum signal strength ofthe deck bottom echo, Vbs.7.2.3 If Vbsis$0.0264 Vtfor a longitudinal radar 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 longitudinalradar inspection pass, t
47、he data are not reliable for determiningremoval quantities of bridge deck concrete. Processing of thedata will require an alternative technique, such as the techniquedescribed in Ontario Ministry of Transportation (MTO) re-ports.27.2.5 Measure and record the amplitude of the deck bottomecho, Vb, for
48、 each waveform.7.2.6 Determine delaminations at the top reinforcing steelusing the attenuation technique as follows:7.2.7 Consider the concrete delaminated if:Vb#0.385 Vbs(5)where:Vb= bottom echo amplitude, each scan,Vbs= bottom echo maximum amplitude, all scans, and0.385 = a constant derived from r
49、esearch data.7.2.8 Calculate the percent delaminated at the top steel ineach radar inspection pass using the following formula:Xtn5 Wdt!/Wdt1 Wst!# 100 (6)where:Xtn= percent delaminated in a radar inspection pass, n,attop steel,n = radar inspection pass identification number,Wdt= concrete delaminated at top steel, m, andWst= sound concrete at top steel, m.7.2.9 Calculate the estimated quantity of deck delaminatedat top steel for each radar inspection pass using the followingformula:Qt5 Xtn!Ln!dt! (7)where:Qt= square metres of deck delaminated at top steel,
