1、Designation: C 1383 04Standard Test Method forMeasuring the P-Wave Speed and the Thickness ofConcrete Plates Using the Impact-Echo Method1This standard is issued under the fixed designation C 1383; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, 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. Scope*1.1 This test method covers procedures for determining thethickness of concrete slabs, paveme
3、nts, bridge decks, walls, orother plate-like structure using the impact-echo method.1.2 The following two procedures are covered in this testmethod:1.2.1 Procedure A: P-Wave Speed MeasurementThis pro-cedure measures the time it takes for the P-wave generated bya short-duration, point impact to trave
4、l between two transduc-ers positioned a known distance apart along the surface of astructure. The P-wave speed is calculated by dividing thedistance between the two transducers by the travel time.1.2.2 Procedure B: Impact-Echo TestThis procedure mea-sures the frequency at which the P-wave generated
5、by ashort-duration, point impact is reflected between the parallel(opposite) surfaces of a plate. The thickness is calculated fromthis measured frequency and the P-wave speed obtained fromProcedure A.1.2.3 Unless specified otherwise, both Procedure A andProcedure B must be performed at each point wh
6、ere a thicknessdetermination is made.1.3 The values stated in SI units are to be regarded as thestandard.1.4 The text of this standard references notes and footnotesthat provide explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be consideredas requireme
7、nts of the standard.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 limitations prior to
8、 use.2. Referenced Documents2.1 ASTM Standards:2C 597 Test Method for Pulse Velocity Through ConcreteE 1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 acoustic impedancethe product of P-wave speedand density that is used in computations of characteristics ofstress
9、 wave reflection at boundaries.3.1.2 amplitude spectruma plot of relative amplitudeversus frequency that is obtained from the waveform using aFourier transform technique.3.1.3 Fourier transforma numerical technique used toconvert digital waveforms from the time domain to thefrequency domain.3.1.3.1
10、DiscussionThe peaks in the amplitude spectrumcorrespond to the dominant frequencies in the waveform.3.1.4 impact-echo methoda send-receive nondestructivetest method based on the use of a short-duration mechanicalimpact to generate transient stress waves and the use of abroadband receiving transducer
11、 placed adjacent to the impactpoint.3.1.4.1 DiscussionWaveforms are converted to the fre-quency domain and the resulting amplitude spectra are ana-lyzed to obtain the dominant frequencies in the structuresresponse to the impact. These frequencies are used to deter-mine the thickness of the structure
12、 or the presence of flaws.3.1.5 impact durationthe time that the impactor used togenerate stress waves is in contact with the test surface. Alsoreferred to as contact time.3.1.5.1 DiscussionThe impact duration is a critical aspectin the success of the two procedures covered by this method.Recommende
13、d impact durations are given. In practice, theimpact duration will depend on the type of impactor and thecondition of the concrete at the point of impact. Smooth, hard1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility
14、 of SubcommitteeC09.64 on Nondestructive and In-Place Testing.Current edition approved June 1, 2004. Published July 2004. Originally approvedin 1998. Last previous edition approved in 1998 as C 138398a.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Serv
15、ice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1942
16、8-2959, United States.surfaces will result in shorter impact durations than rough, softsurfaces. The user should verify that the impact durations arewithin the recommended ranges. An approximate measure ofthe impact duration can be obtained from the portion of thewaveform corresponding to the surfac
17、e wave arrival.3Fig. 1shows an example of the surface-wave portion of a waveformand the approximate contact time is indicated.3.1.6 P-wavethe dilatational (longitudinal or primary)stress wave that causes particle displacement parallel to thedirection of wave propagation. This wave produces normalstr
18、esses (tensile or compressive) as it propagates.3.1.7 P-wave speedthe speed with which the P-wavepropagates through a semi-infinite solid.3.1.7.1 DiscussionThe P-wave speed is the same as thecompressional pulse velocity measured according to TestMethod C 597.3.1.8 sampling frequencythe rate at which
19、 the points thatcomprise the waveform are recorded; the inverse of thesampling interval, expressed in Hz or samples/s (also referredto as sampling rate).3.1.9 sampling periodthe duration of the waveform,which equals the number of points in the waveform multipliedby the sampling interval.3.1.10 sampl
20、ing intervalthe time difference between anytwo adjacent points in the waveform.3.1.11 surface wavea stress wave in which the particlemotion is elliptical and the amplitude of particle motiondecreases rapidly with depth. Also known as Rayleigh wave (orR-wave).3.1.12 waveforma recorded signal from a t
21、ransducer thatis a plot of voltage versus time.3.1.13 Refer to Terminology E 1316 for additional defini-tions, related to nondestructive ultrasonic examination, that areapplicable to this test method.3.2 Definitions of Terms Specific to This Standard:3.2.1 apparent P-wave speed in a plate3,4a parame
22、ter thatis 0.96 of the P-wave speed:Cp, plate5 0.96 Cp(1)where:Cp, plate= the apparent P-wave speed in a plate, m/s, andCp= the P-wave speed in concrete that is obtainedfrom Procedure A, m/s.3.2.1.1 DiscussionThis parameter is used in thicknesscalculations in impact-echo measurements on plates. TheP
23、-wave speed in a material (concrete) is converted to theapparent P-wave speed in a plate that is used to calculate theplate thickness by the following equation:T 5Cp, plate2f(2)where:T = the thickness of the plate, m, andf = the frequency of the P-wave thickness mode of theplate obtained from the am
24、plitude spectrum, Hz.3.2.2 plateany prismatic structure where the lateral di-mensions are at least six times the thickness.3.2.2.1 DiscussionMinimum lateral dimensions are nec-essary to prevent plate modes3of vibration from interferingwith the identification of the thickness mode frequency in theamp
25、litude spectrum. The minimum lateral dimensions andacceptable sampling period are related, as explained in Note11.4. Significance and Use4.1 This test method may be used as a substitute for, or inconjunction with, coring to determine the thickness of slabs,pavements, decks, walls, or other plate str
26、uctures. There is acertain level of systematic error in the calculated thickness dueto the discrete nature of the digital records that are used. Theabsolute systematic error depends on the plate thickness, thesampling interval, and the sampling period.4.2 Because the wave speed can vary from point-t
27、o-point inthe structure due to differences in concrete age or batch-to-batch variability, the wave speed is measured (Procedure A) ateach point where a thickness determination (Procedure B) isrequired.4.3 The maximum and minimum thickness that can bemeasured is limited by the details of the testing
28、apparatus(transducer response characteristics and the specific impactor).The limits shall be specified by manufacturer of the apparatus,and the apparatus shall not be used beyond these limits. If testequipment is assembled by the user, thickness limitations shallbe established and documented.3Sansal
29、one, M. and Streett, W.B., Impact-Echo: Nondestructive Evaluation ofConcrete and Masonry, Bullbrier Press, Ithaca, NY and Jersey Shore, PA, 1997.4Sansalone, M., Lin, J. M., and Streett, W. B., “A Procedure for DeterminingP-wave Speed in Concrete for Use in Impact-Echo Testing Using P-wave SpeedMeasu
30、rement Technique,” ACI Journal, Vol. 94, No. 6, NovemberDecember 1997,pp. 531539.FIG. 1 Expanded View of Surface-Wave Portion of WaveformShowing the Width of the Surface Wave Signal as anApproximation of the Contact Time of the ImpactC13830424.4 This test method is not applicable to plate structures
31、with overlays, such as a concrete bridge deck with an asphaltor portland cement concrete overlay. The method is based onthe assumption that the concrete plate has the same P-wavespeed throughout its depth.4.5 Procedure A is performed on concrete that is air dry ashigh surface moisture content may af
32、fect the results.4.6 Procedure B is applicable to a concrete plate resting ona subgrade of soil, gravel, permeable asphalt concrete, or leanportland cement concrete provided there is sufficient differencein acoustic impedance3between the concrete and subgrade orthere are enough air voids at the inte
33、rface to produce measur-able reflections. If these conditions are not satisfied, thewaveform will be of low amplitude and the amplitude spectrumwill not include a dominant peak at the frequency correspond-ing to the thickness (Eq 2). If the interface between theconcrete and subgrade is rough, the am
34、plitude spectrum willhave a rounded peak instead of a sharp peak associated with aflat surface.4.7 The procedures described are not influenced by trafficnoise or low frequency structural vibrations set up by normalmovement of traffic across a structure.4.8 The procedures are not applicable in the pr
35、esence ofmechanical noise created by equipment impacting (jack ham-mers, sounding with a hammer, mechanical sweepers, and soforth) on the structure.4.9 Procedure A is not applicable in the presence of highamplitude electrical noise, such as may produced by a genera-tor or some other source, that is
36、transmitted to the data-acquisition system.PROCEDURE AP-WAVE SPEED MEASUREMENT5. Summary of Procedure5.1 An impact on the concrete surface is used to generatetransient stress waves. These waves propagate along thesurface of the concrete past two transducers, placed on a linethrough the impact point
37、and at a known distance apart.5.2 The time difference between the arrival of the P-wave(stress wave with highest speed) at each transducer is used todetermine the P-wave speed by dividing the time difference(travel time) by the known distance between the transducers.6. Apparatus56.1 ImpactorThe impa
38、ctor shall be spherical or spheri-cally tipped. It shall produce an impact duration of 30 6 10 swith sufficient energy to produce surface displacements due tothe P-wave that can be recorded by the two transducers (seeNote 1). The impactor shall be positioned to strike on thecenterline passing throug
39、h the two transducers at a distance of150 6 10 mm from the first transducer.NOTE 1Hardened steel balls ranging from 5 to 8 mm in diameter andattached to steel spring rods have been found to produce suitable impacts.6.2 TransducersTwo broadband transducers that respondto displacements normal to the s
40、urface. These transducers mustbe capable of detecting the small displacements that corre-spond to the arrival of the impact-generated P-wave travelingalong the surface. A small contact area between the piezoelec-tric element and the concrete surface is required to recordaccurately the arrival of the
41、 P-wave (see Note 2). Use a suitablematerial to couple the transducer to the concrete.NOTE 2A commercially available displacement transducer made froma conical piezoelectric element with a tip diameter of 1.5 mm and thelarger end attached to a brass backing block has been found suitable.6Alead sheet
42、 approximately 0.25 mm thick is a suitable coupling material forsuch a transducer.6.2.1 Acceptable transducers shall be previously docu-mented to produce accurate results for plate thicknesses similarto those being measured by this test method.6.3 Spacer DeviceA spacer device shall be provided tohol
43、d the transducers a fixed distance apart. It shall not interferewith the ability of the transducers to measure surface displace-ment. It shall be manufactured to minimize the possibility ofP-wave transmission through it so as to prevent interferencewith measurement of the P-wave travel time. The tra
44、nsducertips shall be placed about 300 mm apart. Measure and record tothe nearest 1 mm the actual distance between the centers of thetransducer tips.NOTE 3The accuracy of the measurement is affected if the distancebetween the tips of the two transducers is not known accurately. Thematerials and desig
45、n of the spacer device should be chosen to minimizethe change in separation of the transducers due to changes in temperature.6.4 Data-Acquisition SystemHardware and software foracquiring, recording, and processing the output of the twotransducers. This system can be a portable computer with atwo-cha
46、nnel data-acquisition card, or it can be a portabletwo-channel waveform analyzer.6.4.1 The sampling frequency for each channel shall be 500kHz or higher (sampling interval of 2 s or less). The systemshall be capable of triggering on the signal from one of therecording channels.6.4.2 The voltage rang
47、e and voltage resolution of the dataacquisition system shall be matched with the sensitivity of thetransducers so that the arrival of the P-wave is determinedaccurately.NOTE 4For example, a computer data acquisition card with a voltagerange of 62.5 V and 12-bit resolution has been found to be suitab
48、le for thetransducer described in Note 2.6.4.3 The display system shall include cursors, including acorresponding readout of time and voltage, that can be posi-tioned at the point in each waveform corresponding to theP-wave arrival.6.4.4 The data-acquisition system shall be operated by apower source
49、 that does not produce electrical noise detectableby the transducers and data acquisition system when the systemis set at the voltage sensitivity required to detect the arrivals ofthe P-wave.NOTE 5Battery-powered data acquisition systems have been foundsuitable.5Suitable apparatus is available commercially.6Proctor, T.M., Jr., “Some Details on the NBS Conical Transducer,” J. ofAcoustic Emission, Vol 1, No. 3, pp. 173178.C13830436.5 Cables and ConnectorsTo connect the transducers tothe data acquisition system. Connectors shall be high qualityand t
