ASTM D2950-91(1997)
(Test Method)Standard Test Method for Density of Bituminous Concrete in Place by Nuclear Methods
Standard Test Method for Density of Bituminous Concrete in Place by Nuclear Methods
SCOPE
1.1 This test method describes a test procedure for determining the density of bituminous concrete by the attenuation of gamma radiation, where the source and detector(s) remain on the surface (Backscatter Method) or the source or detector is placed at a known depth up to 300 mm (12 in.) while the detector or source remains on the surface (Direct Transmission Method).
1.2 The density, in mass per unit volume of the material under test, is determined by comparing the detected rate of gamma emissions with previously established calibration data.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific warning statements see Section 6 and Note 4.
1.4 The values stated in SI units are to be regarded as the standard. The inch-pound equivalents may be approximate.
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Designation:D2950–91 (Reapproved 1997)
Standard Test Method for
Density of Bituminous Concrete in Place by Nuclear
Methods
This standard is issued under the fixed designation D 2950; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) 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. Scope 3. Significance and Use
1.1 This test method describes a test procedure for deter- 3.1 The test method described is useful as a rapid, nonde-
miningthedensityofbituminousconcretebytheattenuationof structive technique for determining the in-place density of
gamma radiation, where the source and detector(s) remain on compacted bituminous mixtures.
the surface (Backscatter Method) or the source or detector is 3.2 Withpropercalibrationandconfirmationtesting,thetest
placed at a known depth up to 300 mm (12 in.) while the method is suitable for quality control and acceptance testing of
detector or source remains on the surface (Direct Transmission compacted bituminous concrete.
Method). 3.3 The test method can be used to establish the proper
1.2 The density, in mass per unit volume of the material rolling effort and pattern to achieve the required density.
under test, is determined by comparing the detected rate of 3.4 The non-destructive nature of the test allows repetitive
gamma emissions with previously established calibration data. measurements to be made at a single test location between
1.3 This standard does not purport to address all of the roller passes and to monitor changes in density.
safety concerns, if any, associated with its use. It is the 3.5 The density results obtained by this test method are
responsibility of the user of this standard to establish appro- relative. Correlation with other test methods such as D 1188 or
priate safety and health practices and determine the applica- D 2726 are required to convert the results obtained using this
bility of regulatory limitations prior to use. For specific method to actual density. It is recommended that at least seven
warning statements see Section 6 and Note 4. core densities and seven nuclear densities be used to establish
1.4 The values stated in SI units are to be regarded as the a conversion factor. A new factor must be established at any
standard. The inch-pound equivalents may be approximate. time a change is made in the paving mixture or in the
construction process.
2. Referenced Documents
4. Interferences
2.1 ASTM Standards:
D 1188 Test Method for Bulk Specific Gravity and Density 4.1 The chemical composition of the material being tested
of Compacted Bituminous Mixtures Using Paraffin-Coated may significantly affect the measurement and adjustments may
Specimens be necessary. Certain elements with atomic numbers greater
D 1559 Test Method for Resistance to Plastic Flow of than 20 may cause erroneously high test values.
Bituminous Mixtures Using Marshall Apparatus 4.2 The test method exhibits spatial bias in that the instru-
D 2041 Test Method for Theoretical Maximum Specific ment is most sensitive to the density of the material in closest
Gravity of Bituminous Paving Mixtures proximity to the nuclear source.
D 2726 Test Method for Bulk Specific Gravity and Density 4.2.1 When measuring the density of an overlay, it may be
of Non-Absorptive Compacted Bituminous Mixtures necessary to employ a correction factor if the underlying
D 3665 Practice for Random Sampling of Construction material varies in thickness, mineral composition or degree of
Materials consolidation at different points within the project. (SeeAnnex
A3.)
4.2.2 The surface roughness of the material being tested
This test method is under the jurisdiction of ASTM Committee D-4 on Road
may cause lower than actual density determination.
and Paving Materials and is the direct responsibility of Subcommittee D04.21 on
4.3 Oversize aggregate particles in the source-detector path
Specific Gravity and Density of Bituminous Mixtures.
may cause higher than actual density determination.
Current edition approved Jan. 25, 1991. Published March 1991. Originally
published as D 2950 – 71T. Last previous edition D 2950 – 82.
Annual Book of ASTM Standards, Vol 04.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D2950
4.4 The sample volume being tested is approximately 8. Standardization and Reference Check
3 3
0.0028 m (0.0989 ft ) for the Backscatter Method and 0.0056
8.1 Nuclear test devices are subject to long-term aging of
3 3
m (0.198 ft ) for the Direct Transmission Method. The actual
theradioactivesource,detectors,andelectronicsystems,which
sample volume varies with the apparatus and the density of the
may change the relationship between count rate and material
material. In general, the higher the density the smaller the
density.To offset this aging, the apparatus may be standardized
volume (Note 1).
as the ratio of the measured count rate to a count rate made on
a reference standard. The reference count rate should be of the
NOTE 1—The volume of field compacted material represented by a test
can be effectively increased by repeating the test at adjacent locations and same order of magnitude as the measured count rate over the
averaging the results.
useful density range of the apparatus.
8.2 Standardization of equipment should be performed at
4.5 If samples of the measured material are to be taken for
the start of each day’s work, and a permanent record of this
purposes of correlation with other test methods such as D 1188
data retained.
orD 2726,thevolumemeasuredcanbeapproximatedbya200
8.2.1 Perform the standardization with the apparatus located
mm (8 in.) diameter cylinder located directly under the center
atleast8m(25ft)awayfromothersourcesofradioactivityand
line of the radioactive source and detector(s). The height of the
clear of large masses or other items which may affect the
cylinder to be excavated will be the depth setting of the source
reference count rate.
rod when using the Direct Transmission Method or approxi-
8.2.2 Turn on the apparatus prior to standardization and
mately 75 mm (3 in.) when using the Backscatter Method
allow it to stabilize. Follow the manufacturer’s recommenda-
(Note 2).
tions in order to provide the most stable and consistent results.
NOTE 2—If the layer of bituminous concrete to be measured is less than
8.2.3 Using the reference standard, take at least four repeti-
the depth of measurement of the instrument, corrections must be made to
tive readings at the normal measurement period and determine
the measurements to obtain accurate results due to the influence of the
the mean. If available on the apparatus, one measurement
density of the underlying material. (See Annex A3. for the method used.)
period of four or more times the normal period is acceptable.
5. Apparatus
This constitutes one standardization check.
5.1 Nuclear Device— An electronic counting instrument,
8.2.4 If the value obtained in 8.2.3 is within the following
capable of being seated on the surface of the material under stated limits, the apparatus is considered to be in satisfactory
test, and which contains:
operatingconditionandthevaluemaybeusedtodetermine the
5.1.1 GammaSource—Asealed high energy gamma source
count ratios for the day of use. If the value is outside these
such as cesium or radium, and
limits, allow additional time for the apparatus to stabilize,
5.1.2 Gamma Detector—Any type of gamma detector such
make sure the area is clear of sources of interference and then
as a Geiger-Mueller tube(s).
conduct another standardization check. If the second standard-
5.2 ReferenceStandard—Ablock of dense material used for
ization check is within the limits, the apparatus may be used,
checking instrument operation and to establish conditions for a
but if it also fails the test, the apparatus shall be adjusted or
reproducible reference-count rate.
repaired as recommended by the manufacturer. The limits are
5.3 SitePreparationDevice—Ametalplate,straightedge,or
as follows:
other suitable leveling tool which may be used to level the test
?N 2 N ?# 2.0 N /F (1)
=
s o o
site to the required smoothness using fine sand or similar
material.
where:
5.4 Drive Pin—A steel rod of slightly larger diameter than N 5 value of current standardization count,
s
the rod in the Direct Transmission Instrument, to prepare a N 5 averageofthepastfourvaluesofN takenpreviously,
o s
and
perpendicular hole in the material under test for inserting the
F 5 value of any prescale.
rod. A drill may also be used.
NOTE 3—The count per measurement periods shall be the total number
6. Hazards
of gammas detected during the timed period. The displayed value must be
6.1 Thisequipmentutilizesradioactivematerialswhichmay
corrected for any prescaling which is built into the instrument. The
be hazardous to the health of the users unless proper precau-
prescale value (F) is a divisor which reduces the actual value for the
tions are taken. Users of this equipment must become familiar
purpose of display. The manufacturer will supply this value if other than
with applicable safety procedures and government regulations. 1.0.
6.2 Effective user instructions together with routine safety
8.3 Use the value of N to determine the count ratios for the
s
procedures, such as source leak tests, recording and evaluation
current day’s use of the instrument. If for any reason the
of film badge data, etc. are a recommended part of the
measured density becomes suspect during the day’s use,
operational guidelines for the use of this instrument.
perform another standardization check.
6.3 A regulatory agency radioactive materials license may
be required to possess this equipment.
9. Procedure
7. Calibration
9.1 In order to provide more stable and consistent results:
7.1 Calibrate the instrument in accordance with Annex A1. (1) Turn the instrument on prior to use to allow it to stabilize,
and (2) Leave the power on druing the day’s testing.
at least once each year. Adjust the calibrations as necessary in
accordance with Annex A2. 9.2 Standardize the apparatus.
D2950
9.3 Select a test location in accordance wtih the project 11. Report
specifications,or,ifnototherwisespecified,inaccordancewith
11.1 Report the following information:
Practice D 3665. If the instrument will be closer than 250 mm
11.1.1 Make,model,andserialnumberofthetestapparatus,
(10 in.) to any vertical mass that may influence the result,
11.1.2 Date and source of calibration data,
follow the instrument manufacturer’s correction procedure.
11.1.3 Date of test,
9.4 Maximum contact between the base of the instrument
11.1.4 Standard count for the day of the test,
and the surface of th
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