1、Designation: D2950/D2950M 14Standard Test Method forDensity of Bituminous Concrete in Place by NuclearMethods1This standard is issued under the fixed designation D2950/D2950M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a test procedure for deter-mining the density of bituminous concrete by the attenuatio
3、n ofgamma radiation, where the source and detector(s) remain onthe surface (Backscatter Method) or the source or detector isplaced at a known depth up to 300 mm 12 in. while thedetector or source remains on the surface (Direct TransmissionMethod).1.2 The density, in mass per unit volume of the mater
4、ialunder test, is determined by comparing the detected rate ofgamma emissions with previously established calibration data.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, e
5、achsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 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 es
6、tablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements see Section 6 and Note 5.2. Referenced Documents2.1 ASTM Standards:2C670 Practice for Preparing Precision and Bias Statementsfor Test Methods for C
7、onstruction MaterialsD1188 Test Method for Bulk Specific Gravity and Density ofCompacted Bituminous Mixtures Using Coated SamplesD1559 Test Method for Resistance to Plastic Flow of Bitu-minous Mixtures Using Marshall Apparatus (Withdrawn1998)3D2041 Test Method for Theoretical Maximum SpecificGravity
8、 and Density of Bituminous Paving MixturesD2726 Test Method for Bulk Specific Gravity and Densityof Non-Absorptive Compacted Bituminous MixturesD3665 Practice for Random Sampling of Construction Ma-terialsD6752 Test Method for Bulk Specific Gravity and Densityof Compacted Bituminous Mixtures Using A
9、utomaticVacuum Sealing MethodD7013 Guide for Nuclear Surface Moisture and DensityGauge Calibration Facility SetupD7759 Guide for Nuclear Surface Moisture and DensityGauge Calibration3. Significance and Use3.1 The test method described is useful as a rapid, nonde-structive technique for determining t
10、he in-place density ofcompacted bituminous mixtures.3.2 With proper calibration and confirmation testing, the testmethod is suitable for quality control and acceptance testing ofcompacted bituminous concrete.3.3 The test method can be used to establish the properrolling effort and pattern to achieve
11、 the required density.3.4 The non-destructive nature of the test allows repetitivemeasurements to be made at a single test location betweenroller passes and to monitor changes in density.3.5 The density results obtained by this test method arerelative. Correlation with other test methods such as D11
12、88 orD2726 are required to convert the results obtained using thismethod to actual density. It is recommended that at least sevencore densities and seven nuclear densities be used to establisha conversion factor. A new factor must be established at anytime a change is made in the paving mixture or i
13、n theconstruction process.1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.21 onSpecific Gravity and Density of Asphalt Mixtures.Current edition approved June 1, 2014. Published August 2014. Originallya
14、pproved in 1971. Last previous edition approved in 2011 as D2950/D2950M 11.DOI: 10.1520/D2950_D2950M-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standard
15、s Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Interferences4.1 The chemical composition of the materia
16、l being testedmay significantly affect the measurement and adjustments maybe necessary. Certain elements with atomic numbers greaterthan 20 may cause erroneously high test values.4.2 The test method exhibits spatial bias in that the instru-ment is most sensitive to the density of the material in clo
17、sestproximity to the nuclear source.4.2.1 When measuring the density of an overlay, it may benecessary to employ a correction factor if the underlyingmaterial varies in thickness, mineral composition or degree ofconsolidation at different points within the project. (See AnnexA1.)4.2.2 The surface ro
18、ughness of the material being testedmay cause lower than actual density determination.4.3 Oversize aggregate particles in the source-detector pathmay cause higher than actual density determination.4.4 The sample volume being tested is approximately0.0028 m30.0989 ft3 for the Backscatter Method and 0
19、.0056m30.198 ft3 for the Direct Transmission Method. The actualsample volume varies with the apparatus and the density of thematerial. In general, the higher the density the smaller thevolume (Note 1).NOTE 1The volume of field compacted material represented by a testcan be effectively increased by r
20、epeating the test at adjacent locations andaveraging the results.4.5 If samples of the measured material are to be taken forpurposes of correlation with other test methods such as D1188or D2726, the volume measured can be approximated by a 200mm 8 in. diameter cylinder located directly under the cen
21、terline of the radioactive source and detector(s). The height of thecylinder to be excavated will be the depth setting of the sourcerod when using the Direct Transmission Method or approxi-mately 75 mm 3 in. when using the Backscatter Method(Note 2).NOTE 2If the layer of bituminous concrete to be me
22、asured is less thanthe depth of measurement of the instrument, corrections must be made tothe measurements to obtain accurate results due to the influence of thedensity of the underlying material. (See Annex A1. for the method used.)5. Apparatus5.1 Nuclear DeviceAn electronic counting instrument,cap
23、able of being seated on the surface of the material undertest, and which contains:5.1.1 Gamma SourceA sealed high energy gamma sourcesuch as cesium or radium, and5.1.2 Gamma DetectorAny type of gamma detector suchas a Geiger-Mueller tube(s).5.2 Reference StandardA block of dense material used forche
24、cking instrument operation and to establish conditions for areproducible reference-count rate.5.3 Site Preparation DeviceAmetal plate, straightedge, orother suitable leveling tool which may be used to level the testsite to the required smoothness using fine sand or similarmaterial.5.4 Drive PinA ste
25、el rod of slightly larger diameter thanthe rod in the Direct Transmission Instrument, to prepare aperpendicular hole in the material under test for inserting therod. A drill may also be used.6. Hazards6.1 This equipment utilizes radioactive materials which maybe hazardous to the health of the users
26、unless proper precau-tions are taken. Users of this equipment must become familiarwith applicable safety procedures and government regulations.6.2 Effective user instructions together with routine safetyprocedures, such as source leak tests, recording and evaluationof film badge data, etc. are a rec
27、ommended part of theoperational guidelines for the use of this instrument.6.3 A regulatory agency radioactive materials license maybe required to possess this equipment.7. Calibration7.1 Calibrate the instrument in accordance to Guide D7759and Guide D7013.7.2 Calibration AdjustmentsThe calibration r
28、esponseshall be checked by the user prior to performing tests onmaterials that are distinctly different from the material typesused in establishing the calibration. The calibration responseshall also be checked on newly acquired or repaired apparatus.Take a sufficient number of measurements and comp
29、are themto other accepted methods (such as Test Method D2726 or TestMethod D6752) to establish a correlation.8. Standardization and Reference Check8.1 Nuclear test devices are subject to long-term aging ofthe radioactive source, detectors, and electronic systems, whichmay change the relationship bet
30、ween count rate and materialdensity. To offset this aging, the apparatus may be standardizedas the ratio of the measured count rate to a count rate made ona reference standard. The reference count rate should be of thesame order of magnitude as the measured count rate over theuseful density range of
31、 the apparatus.8.2 Standardization of equipment should be performed atthe start of each days work, and a permanent record of thisdata retained.8.2.1 Perform the standardization with the apparatus locatedat least 10 m 33 ft away from other sources of radioactivityand clear of large masses or other it
32、ems which may affect thereference count rate.NOTE 3The user is advised that the value given in section 8.2.1 isintended as a minimum distance for nuclear sources typical in surfacemoisture/density gauges. The user should consider requiring a greaterdistance if other nuclear sources of greater activi
33、ty are present.8.2.2 Turn on the apparatus prior to standardization andallow it to stabilize. Follow the manufacturers recommenda-tions in order to provide the most stable and consistent results.8.2.3 Using the reference standard, take at least four repeti-tive readings at the normal measurement per
34、iod and determinethe mean. If available on the apparatus, one measurementperiod of four or more times the normal period is acceptable.This constitutes one standardization check.D2950/D2950M 1428.2.4 If the value obtained in 8.2.3 is within the followingstated limits, the apparatus is considered to b
35、e in satisfactoryoperating condition and the value may be used to determine thecount ratios for the day of use. If the value is outside theselimits, allow additional time for the apparatus to stabilize,make sure the area is clear of sources of interference and thenconduct another standardization che
36、ck. If the second standard-ization check is within the limits, the apparatus may be used,but if it also fails the test, the apparatus shall be adjusted orrepaired as recommended by the manufacturer. The limits areas follows:?Ns2 No?#2.0 =No/F (1)where:Ns= value of current standardization count,No= a
37、verage of the past four values of Nstaken previously,andF = value of any prescale.NOTE 4The count per measurement periods shall be the total numberof gammas detected during the timed period. The displayed value must becorrected for any prescaling which is built into the instrument. Theprescale value
38、 (F) is a divisor which reduces the actual value for thepurpose of display. The manufacturer will supply this value if other than1.0.8.3 Use the value of Nsto determine the count ratios for thecurrent days use of the instrument. If for any reason themeasured density becomes suspect during the days u
39、se,perform another standardization check.9. Procedure9.1 In order to provide more stable and consistent results:(1) Turn the instrument on prior to use to allow it to stabilize,and (2) Leave the power on druing the days testing.9.2 Standardize the apparatus.9.3 Select a test location in accordance w
40、tih the projectspecifications, or, if not otherwise specified, in accordance withPractice D3665. If the instrument will be closer than 250 mm10 in. to any vertical mass that may influence the result,follow the instrument manufacturers correction procedure.9.4 Maximum contact between the base of the
41、instrumentand the surface of the material under test is critical. Themaximum void shall not exceed 6 mm 14 in. Use native finesor fine sand to fill the voids and level with the guide/scraperplate.9.5 For the Direct Transmission Method use the guide/scraper plate and drive the steel rod to a depth of
42、 at least 25 mm1 in. deeper than the desired measurement depth.NOTE 5Caution: Extreme care must be taken when driving the rodinto compacted bituminous concrete as it may cause a disturbance of thematerial which could cause errors in the measurement. Drilling may bemore suitable.9.6 Place the source
43、in the proper position. For the DirectTransmission Method measurements move the instrument sothat the rod is firmly against the side of the hole in the gammameasurement path.9.7 Take a count for the normal measurement period. If theBackscatter Method using the Air Gap Technique is used takean additi
44、onal measurement in the air-gap position as recom-mended by the manufacturer. (See Note 2)9.8 Determine the ratio of the reading to the standard countor the air-gap count. From this ratio and the calibration andadjustment data, determine the in-place density. (See Note 6and Note 7)NOTE 6Some instrum
45、ents have built-in provisions to compute theratio, bulk (or wet) density, and allow an adjustment bias.NOTE 7If the depth of the bituminous concrete layer under test is lessthan the depth of measurement of the instrument, the value obtained in 9.8must be adjusted. (See Annex A1.)NOTE 8Do not leave t
46、he gauge on a hot surface for an extended periodof time. Prolonged high temperatures may adversely affect the instru-ments electronics. The gauge should be allowed to cool betweenmeasurements.10. Calculation of Results10.1 Using the calibration chart, calibration tables, orequation, and coefficients
47、, or instrument direct readout feature,with appropriate calibration adjustments, determine the in-place density. This is the bulk (or wet) density.10.1.1 An adjustment bias can be calculated by comparingthe results from a number of instrument measurements to theresults obtained using Test Method D27
48、26.10.2 Compare the results obtained to samples compacted byTest Method D1559 or with the results of test methods such asD2041 to determine acceptability (percentage of compaction).11. Report11.1 Report the following information:11.1.1 Make, model, and serial number of the test apparatus,11.1.2 Date
49、 and source of calibration data,11.1.3 Date of test,11.1.4 Standard count for the day of the test,11.1.5 Test site description including project identificationnumber, location and mixture type(s),11.1.6 Thickness of layer tested and any adjustment bias,11.1.7 Method of measurement (backscatter or directtransmission), depth, count rate, calculated density of eachmeasurement and any adjustment data, and11.1.8 Percentage of compaction, if required.12. Precision and Bias412.1 Precision:12.1.1 Precision is based on a field experiment in 2008 that
