1、Designation: D2950/D2950M 11Standard 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method describes a tes
3、t procedure for deter-mining the density of bituminous concrete by the attenuation 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
4、(Direct TransmissionMethod).1.2 The density, in mass per unit volume of the materialunder 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 sta
5、ndard. The values stated ineach system may not be exact equivalents; therefore, eachsystem 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, as
6、sociated 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 use. For specificwarning statements see Section 6 and Note 5.2. Referenced Documents2.1 ASTM Standards
7、:2C670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsD1188 Test Method for Bulk Specific Gravity and Densityof Compacted Bituminous Mixtures Using CoatedSamplesD1559 Test Method for Resistance of Plastic Flow ofBituminous Mixtures Using Marshall Appar
8、atus3D2041 Test Method for Theoretical Maximum SpecificGravity 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-terials3. Significance and Use3.1 The te
9、st method described is useful as a rapid, nonde-structive technique for determining the 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
10、 test method can be used to establish the properrolling effort and pattern to achieve 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 obta
11、ined by this test method arerelative. Correlation with other test methods such as D1188 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
12、new factor must be established at anytime a change is made in the paving mixture or in theconstruction process.4. Interferences4.1 The chemical composition of the material being testedmay significantly affect the measurement and adjustments maybe necessary. Certain elements with atomic numbers great
13、erthan 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 closestproximity to the nuclear source.4.2.1 When measuring the density of an overlay, it may benecessary to employ a correction fact
14、or if the underlying1This 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 Bituminous Mixtures.Current edition approved Dec. 1, 2011. Published December 2011. Originallyap
15、proved in 1971. Last previous edition approved in 2010 as D2950 10. DOI:10.1520/D2950_D2950M-11.2For 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 standards Docume
16、nt Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.material varies in thickness, mineral composition or de
17、gree ofconsolidation at different points within the project. (See AnnexA3.)4.2.2 The surface roughness 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
18、sample volume being tested is approximately0.0028 m30.0989 ft3 for the Backscatter Method and 0.0056m30.198 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
19、 1The volume of field compacted material represented by a testcan be effectively increased by repeating 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
20、 measured can be approximated by a 200mm 8 in. diameter cylinder located directly under the centerline 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 i
21、n. when using the Backscatter Method(Note 2).NOTE 2If the layer of bituminous concrete to be measured 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 Ann
22、ex A3. for the method used.)5. Apparatus5.1 Nuclear DeviceAn electronic counting instrument,capable 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 detec
23、tor suchas a Geiger-Mueller tube(s).5.2 Reference StandardAblock of dense material used forchecking 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
24、 the testsite to the required smoothness using fine sand or similarmaterial.5.4 Drive PinA steel 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 T
25、his equipment utilizes radioactive materials which maybe hazardous to the health of the users 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 safetypro
26、cedures, such as source leak tests, recording and evaluationof film badge data, etc. are a recommended 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 instr
27、ument in accordance with Annex A1.at least once each year. Adjust the calibrations as necessary inaccordance with Annex A2.8. Standardization and Reference Check8.1 Nuclear test devices are subject to long-term aging ofthe radioactive source, detectors, and electronic systems, whichmay change the re
28、lationship between 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 de
29、nsity range of 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 mass
30、es or other items 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
31、greater activity 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 m
32、easurement period 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.8.2.4 If the value obtained in 8.2.3 is within the followingstated limits, the apparatus is considered to be
33、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 check
34、. 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= av
35、erage of the past four values of Nstaken previously,andF = value of any prescale.NOTE 4The count per measurement periods shall be the total numberD2950/D2950M 112of gammas detected during the timed period. The displayed value must becorrected for any prescaling which is built into the instrument. Th
36、eprescale value (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 du
37、ring the days use,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
38、in accordance wtih 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 t
39、he base of the 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 ro
40、d to a depth of 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 Pl
41、ace the source 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 use
42、d takean additional 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)NOT
43、E 6Some instruments 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 A3.)NOTE
44、8Do not leave the gauge on a hot surface for an extendedperiod of time. Prolonged high temperatures may adversely affect theinstruments electronics. The gauge should be allowed to cool betweenmeasurements.10. Calculation of Results10.1 Using the calibration chart, calibration tables, or equa-tion, a
45、nd coefficients, or instrument direct readout feature, withappropriate calibration adjustments, determine the in-placedensity. 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 T
46、est Method D2726.10.2 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 apparat
47、us,11.1.2 Date 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 (bac
48、kscatter or direct trans-mission), depth, count rate, calculated density of each mea-surement 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 thatused six gauges from five manufactu
49、rers. Materials includedSuperpave 9.5, 12.5, 19.0, and 37.5 HMA used on a construc-tion project sponsored by the New York DOT. Density variedfrom 127.8 to 149.1 pounds per cubic foot with mean of 138.07and standard deviation 3.900. Each test with a single gauge wasconducted by the same operator, therefore, single-operatorprecision for this statement is also considered to be single-gauge precision if conducted by the same operator.12.1.2 Single Operator PrecisionThe single-operatorstandard deviation has been found to be 25.15 kgm31.57lb/ft3
