ASTM D2950/D2950M-22

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D2950/D2950M − 14 D2950/D2950M − 22
Standard Test Method for
Density of Bituminous ConcreteAsphalt Mixtures in Place
by Nuclear Methods
This standard is issued under the fixed designation D2950/D2950M; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method describes a test procedure for determining the density of bituminous concreteasphalt mixtures by the
attenuation of gamma radiation, where the source and detector(s) remain on the surface (Backscatter Method)(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).(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 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformancenonconformance with the standard.
1.4 All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D6026.
1.5 For limitations, see Section 5 on Interferences.
1.6 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered as requirements of the standard. It is the recommendation of
Committee D04 that the following note be added to the end of the Significance and Use section of all applicable standards.
Applicable standards are those in which measurement or calibration are made, sample are procured, or products are selected. The
subcommittee shall determine the appropriateness of adding the note throughout the consensus process.
1.7 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For specific warning statements, see Section 67 and Note 5.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This test method is under the jurisdiction of ASTM Committee D04 on Road and Paving Materials and is the direct responsibility of Subcommittee D04.21 on Specific
Gravity and Density of Asphalt Mixtures.
Current edition approved June 1, 2014Dec. 15, 2022. Published August 2014January 2023. Originally approved in 1971. Last previous edition approved in 20112014 as
D2950/D2950M – 11.D2950/D2950M – 14. DOI: 10.1520/D2950_D2950M-14.10.1520/D2950_D2950M-22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2950/D2950M − 22
2. Referenced Documents
2.1 ASTM Standards:
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
D8 Terminology Relating to Materials for Roads and Pavements
D1188D1188/D1188M Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Coated
Samples
D1559 Test Method for Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus (Withdrawn 1998)
D2041D2041/D2041M Test Method for Theoretical Maximum Specific Gravity and Density of Asphalt Mixtures
D2726D2726/D2726M Test Method for Bulk Specific Gravity and Density of Non-Absorptive Compacted Asphalt Mixtures
D3665 Practice for Random Sampling of Construction Materials
D3666 Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
D6026 Practice for Using Significant Digits and Data Records in Geotechnical Data
D6752D6752/D6752M Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Automatic
Vacuum Sealing Method
D6926 Practice for Preparation of Asphalt Mixture Specimens Using Marshall Apparatus
D7013D7013/D7013M Guide for Calibration Facility Setup for Nuclear Surface Gauges
D7759D7759/D7759M Guide for Nuclear Surface Moisture and Density Gauge Calibration
3. Terminology
3.1 Definitions—See Terminology D8 for general definitions.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 detector, n—a device to detect and measure radiation.
3.2.2 gamma (radiation) source, n—a sealed source of radioactive material that emits gamma radiation as it decays.
3.2.3 nuclear gauge, n—a device containing one or more radioactive sources used to measure certain properties of asphalt
mixtures.
3.2.4 test count, n—the measured output of a detector for a specific type of radiation for a given test.
4. Significance and Use
4.1 The test method described is useful as a rapid, nondestructive technique for determining the in-place density of compacted
bituminousasphalt mixtures.
4.2 With proper calibration and confirmation testing, the test method is suitable for quality control and acceptance testing of
compacted bituminous concrete.asphalt mixtures.
4.3 The test method can be used to establish the proper rolling effort and pattern to achieve the required density.
4.4 The non-destructivenondestructive nature of the test allows repetitive measurements to be made at a single test location
between roller passes and to monitor changes in density.
4.5 The density results obtained by this test method are relative. Correlation with other test methods such as D1188D1188/
D1188M, D2726/D2726M, or D2726D6752/D6752M areis required to convert the results obtained using this method to actual
density. It is recommended that at least seven core densities and seven nuclear densities be used to establish a conversion factor.
A new factor must be established at any time a change is made in the paving mixture or in the construction process.
NOTE 1—The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the
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volume information, refer to the standard’s Document Summary page on the ASTM website.
D2950/D2950M − 22
capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Specification D3666 are generally considered capable
of competent and objective testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with Specification D3666 alone does
not completely ensure reliable results. Reliable results depend on many factors; following the suggestions of Specification D3666 or some similar
acceptable guideline provides a means of evaluating and controlling some of those factors.
5. Interferences
5.1 The chemical composition of the material being tested may significantly affect the measurement, and adjustments may be
necessary. Certain elements with atomic numbers greater than 20 may cause erroneously high test values.
5.2 The test method exhibits spatial bias in that the instrument is most sensitive to the density of the material in closest proximity
to the nuclear source.
5.2.1 When measuring the density of an overlay, it may be necessary to employ a correction factor if the underlying material varies
in thickness, mineral composition, or degree of consolidation at different points within the project. (See Annex A1.)
5.2.2 The surface roughness of the material being tested may cause lower than actual density determination.
5.3 Oversize aggregate particles in the source-detector path may cause higher than actual density determination.
3 3
5.4 The sample volume being tested is approximately 0.0028 m [0.0989 ft ] for the Backscatter Method and 0.0056 mbackscatter
3 3
method and 0.0056 m [0.198 ft ] for the Direct Transmission Method.direct transmission method. The actual sample volume
varies with the apparatus and the density of the material. In general, the higher the density the smaller the volume (Note 1).
NOTE 2—The volume of field compacted field-compacted material represented by a test can be effectively increased by repeating the test at adjacent
locations and averaging the results.
5.5 If samples of the measured material are to be taken for purposes of correlation with other test methods such as
D1188D1188/D1188M or , D2726D2726/D2726M, or D6752/D6752M, the volume measured can be approximated by a 200 mm
[8 in.] diameter cylinder located directly under the center line of the radioactive source and detector(s). The height of the cylinder
to be excavated will be the depth setting of the source rod when using the Direct Transmission Methoddirect transmission method
or approximately 75 mm [3 in.] when using the Backscatter Methodbackscatter method (Note 23).
NOTE 3—If the layer of bituminous concrete an asphalt mixture to be measured is less than the depth of measurement of the instrument, corrections must
be made to the measurements to obtain accurate results due to the influence of the density of the underlying material. (See Annex A1. for the method
used.)
6. Apparatus
6.1 Nuclear Device—An electronic counting instrument, capable of being seated on the surface of the material under test, and
which contains:
6.1.1 Gamma Source—A sealed high energy high-energy gamma source such as cesium or radium, and
6.1.2 Gamma Detector—Any type of gamma detector such as a Geiger-Mueller tube(s).
6.2 Reference Standard—A block of dense material used for checking instrument operation and to establish conditions for a
reproducible reference-count rate.
6.3 Site Preparation Device—Scraper Plate—A metal plate, straightedge, or other suitable leveling tool which may be used to
level the test site to the required smoothness using fine sand or similar material.
6.4 Drive Pin—A steel rod of slightly larger diameter than the rod in the Direct Transmission Instrument,direct transmission
instrument, to prepare a perpendicular hole in the material under test for inserting the rod. A drill may also be used.
D2950/D2950M − 22
7. Hazards
7.1 This equipment utilizes radioactive materials which may be hazardous to the health of the users unless proper precautions are
taken. Users of this equipment must become familiar with applicable safety procedures and government regulations.
7.2 Effective user instructions together with routine safety procedures, such as source leak tests, recording and evaluation of film
badge data, etc. are a recommended part of the operational guidelines for the use of this instrument.
7.3 A regulatory agency radioactive materials license may be required to possess this equipment.
8. Calibration
8.1 Calibrate the instrument in accordance to GuideGuides D7759D7759/D7759M and Guide D7013D7013/D7013M.
8.2 Calibration Adjustments—The calibration response shall be checked by the user prior to performing tests on materials that are
distinctly different from the material types used in establishing the calibration. calibration curve. The calibration response shall also
be checked on newly acquired or repaired apparatus. Take a sufficient number of measurements and compare them to other
accepted methods (such as Test Method D2726D1188/D1188M, D2726/D2726M, or Test Method D6752D6752/D6752M) to
establish a correlation.
9. Standardization and Reference Check
9.1 Nuclear test devices are subject to long-term aging of the radioactive source, detectors, and electronic systems, which may
change the relationship between count rate and material density. To offset this aging, the apparatus may be standardized 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 same order of
magnitude as the measured count rate over the useful density range of the apparatus.
9.2 Standardization of equipment should be performed at the start of each day’s work, and a permanent record of this data retained.
9.2.1 Perform the standardization with the apparatus located at least 10 m [33 ft] away from other sources of radioactivity and
clear of large masses or other items which may affect the reference count rate.
NOTE 4—The user is advised that the value given in section 8.2.19.2.1 is intended as a minimum distance for nuclear sources typical in surface
moisture/density gauges. The user should consider requiring a greater distance if other nuclear sources of greater activity are present.
9.2.2 Turn on the apparatus prior to standardization and allow it to stabilize. Follow the manufacturer’s recommendations in order
to provide the most stable and consistent results.
9.2.3 Using the reference standard, take at least four repetitive readings at the normal measurement period and determine the
mean. If available on the apparatus, one measurement period of four or more times the normal period is acceptable. This constitutes
one standardization check.
9.2.4 If the value obtained in 8.2.39.2.3 is within the following stated limits, the apparatus is considered to be in satisfactory
operating condition and the value may be used to determine the count ratios for the day of use. If the value is outside these limits,
allow additional time for the apparatus to stabilize, make sure the area is clear of sources of interference, and then conduct another
standardization check. If the second standardization check is within the limits, the apparatus may be used, but if it also fails the
test, the apparatus shall be adjusted or repaired as recommended by the manufacturer. The limits are as follows:
N 2 N # 2.0 =N /F (1)
s o o
? ?
where:
N = value of current standardization count,
s
N = average of the past four values of N taken previously, and
o s
F = value of any prescale.
NOTE 5—The count per measurement periods shall be the total number of gammas detected during the timed period. The displayed value must be corrected
D2950/D2950M − 22
for any prescaling which is built into the instrument. The prescale value (F) is a divisor which reduces the actual value for the purpose of display. The
manufacturer will supply this value if other than 1.0.
9.3 Use the value of
...