ASTM D6925-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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: D6925 − 15 D6925 − 23
Standard Test Method for
Preparation and Determination of the Relative Density of
Asphalt Mix Specimens by Means of the Superpave
Gyratory Compactor
This standard is issued under the fixed designation D6925; 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 covers the compaction of an asphalt mix into cylindrical specimens using the Superpave Gyratory Compactor
(SGC). This standard also refers to the determination of the relative density of the compacted specimens at any point in the
compaction process. Compacted specimens are suitable for volumetric, physical property, and mechanical testing. Smaller
specimens may be cut from the compacted cylindrical specimen for specific test specimen geometry requirements. The compaction
procedures apply to Laboratory MixMixed Laboratory Compacted (LMLC) and Plant MixMixed Laboratory Compacted (PMLC)
asphalt mix.
1.2 The values stated in SI units are to be regarded as standard. The valuevalues given in degrees for the angle of gyration is a
mathematical conversiongyration, gyrations per minute, and hardness are mathematical conversions from the SI units and isare
provided for information regarding the commonly used unit of degree.units of degree, rotations per minute, and Rockwell hardness,
respectfully.
1.3 The text of this test method 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.
1.4 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
D8 Terminology Relating to Materials for Roads and Pavements
D979/D979M Practice for Sampling Asphalt Mixtures
D1188D1188/D1188M Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Coated
Samples
This test method is under the jurisdiction of ASTM Committee D04 on Road and Paving Materials and is the direct responsibility of Subcommittee D04.20 on Mechanical
Tests of Asphalt Mixtures.
Current edition approved Jan. 1, 2015Dec. 1, 2023. Published January 2015January 2024. Originally approved in 2003. Last previous edition approved in 20092015 as
D6925 – 09.D6925 – 15. DOI: 10.1520/D6925-15.10.1520/D6925-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6925 − 23
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
D3666 Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
D4402D4402/D4402M Test Method for Viscosity Determination of Asphalt at Elevated Temperatures Using a Rotational
Viscometer
D4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction
Materials Testing
D6752/D6752M Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Automatic Vacuum
Sealing Method
D6857/D6857M Test Method for Maximum Specific Gravity and Density of Asphalt Mixtures Using Automatic Vacuum Sealing
Method
D7115 Test Method for Measurement of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using Simulated
Loading
E10 Test Method for Brinell Hardness of Metallic Materials
E18 Test Methods for Rockwell Hardness of Metallic Materials
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
2.2 AASHTO Standards:
PP35R 18 Provisional Practice for Evaluation of Superpave Gyratory Compactors (SGCs)Standard Practice for Establishing and
Implementing a Quality Management System for Construction Materials Testing Laboratories
PP76R 99 Standard Practice for Troubleshooting Asphalt Specimen Volumetric Differences between Superpave Gyratory
Compactors (SGCs) Used in the Design and the Field Management of Superpave Mixtures
R30R 30 Standard Practice for Mixture Conditioning of Hot Mix Asphalt (HMA)
R35R 35 Standard Practice for Superpave Volumetric Design for Hot Mix Asphalt (HMA)
R47R 47 Standard Practice for Reducing Samples of Hot Mix Asphalt (HMA) to Testing Size
T312T 312 Standard Method of Test for Preparing and Determining the Density of Hot-Mix Asphalt (HMA) Specimens by
Means of the Superpave Gyratory Compactor
T 344 Standard Method of Test for Evaluation of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using
Simulated Loading
2.3 Other References:
ASME B46.1 Surface Texture (Surface Roughness, Waviness, and Lay)
Asphalt Institute MS-2 Mix Design Methods for Asphalt Concrete
3. Terminology
3.1 This test method uses terms as defined by Terminology D8.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 lab mix lab compacted (LMLC) asphalt mixture, n—asphalt mix samples that are prepared in the laboratory by weighing and
blending each constituent then compacting the blended mixture using a laboratory compaction apparatus.
3.2.1.1 Discussion—
LMLC typically occurs during the asphalt mixture design phase. Laboratory compaction devices such as the Superpave Gyratory
Compactor, Marshall Hammer or other laboratory compaction devices may be used.
3.2.2 plant mix laboratory compacted (PMLC) asphalt mixture, n—asphalt mixture samples that are manufactured in a production
plant, sampled prior to compaction, then immediately compacted using a laboratory compaction apparatus.
3.2.2.1 Discussion—
PMLC specimens are often used for quality control testing. The asphalt mixture is not permitted to cool substantially and it may
be necessary to place the mixture in a laboratory oven to equilibrate the mixture to the compaction temperature before molding.
Laboratory compaction devices such as the Superpave Gyratory Compactor, Marshall Hammer or other laboratory compaction
devices may be used.
3.2.3 reheated plant mix lab compacted (RPMLC) asphalt mixture, n—asphalt mixture samples that are manufactured in a
Available from American Association of State Highway and Transportation Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,
http://www.transportation.org.
Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
www.asme.org.
Available from Asphalt Institute, 2696 Research Park Dr., Lexington, KY 40511, http://www.asphaltinstitute.org.
D6925 − 23
production plant, sampled prior to compaction, allowed to cool to room temperature, then reheated in a laboratory oven and
compacted using a laboratory compaction apparatus.
3.2.3.1 Discussion—
RPMLC are often used for acceptance and verification testing. The reheating time should be as short as possible to obtain uniform
temperature to avoid artificially aging the specimens. Asphalt mixture conditioning, reheat temperature, and reheat time should be
defined in the applicable specification. Laboratory compaction devices such as the Superpave Gyratory Compactor, Marshall
Hammer, or other laboratory compaction devices may be used.
4. Significance and Use
4.1 This test method is used to prepare specimens for determining the volumetric and physical properties of compacted asphalt
mix.
4.2 This test method is useful for monitoring the density of test specimens during the compaction process. This test method is
suited for the laboratory design, field control of asphalt mix, forensics, imaging, and visualization of compacted asphalt mix.
NOTE 1—The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the
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. testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with
Specification D3666 alone does not completely assureensure 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. Apparatus
5.1 Superpave Gyratory Compactor—An electromechanical, electro-hydraulic, or electro-pneumatic A compactor comprised of
the following system components: ((1)1) reaction frame,frame and drive system, ((2)2) loading system, loading ram, and pressure
indicator, and ((3)3) recording system for height measurement and number of gyrations.
5.1.1 The reaction frame shall provide a structure against which the compaction pressure can be applied when compacting
specimens.
5.1.2 The compactor shall be designed to gyrate the mold at a constant angle of gyration during the compaction process. An
internal angle of gyration of 20.25 6 0.35 mrad (1.16 6 0.02°) as determined by Test Method D7115 shall be utilized.
NOTE 2—Research has shown external angle (measurement between the external mold wall and the frame of the compactor) to be different from the
internal angle (measurement between internal mold wall and top and bottom plate). The difference between these measurements varies for different types
of compactors. Some discrepancies in relative density have been resolved by use of the internal angle. If the external angle is chosen for operation the
recommendation is to use an external angle of 21.82 6 0.435 mrad (1.25 6 0.02°).
5.1.3 The gyration drive system shall be capable of gyrating the specimen at a rate of 30.0 6 0.5 revolutions per minute. The
system shall be capable of gyrating the specimen 250 gyrations.0.5 6 0.0083 Hz (30.0 6 0.5 gyrations per minute).
5.1.4 The loading system, ram, and force indicator shall be capable of providing and measuring a constant vertical force to provide
an applied pressure of 600 6 60 kPa during the first five gyrations,gyrations and 600 6 18 kPa during the remainder of the
compaction process. The applied pressure is defined as the applied force divided by the area of the nominal mold diameter (150
mm).
NOTE 3—The report on the ruggedness evaluation of AASHTO TP4 (T312)(T 312) indicated that the pressure tolerance of 618 kPa resulted in
significantly different values of bulk specific gravity of the compacted specimens (G ) in some cases. However, since the pressure is directly set at 600
mb
kPa, the tolerance of 618 kPa should apply only to the ability of the SGC to maintain vertical pressure during compaction. To minimize potential errors
caused by pressure, operators should take care during verification of calibration to assureensure that the specified pressure has been attained.
5.1.5 The axis of the loading ram shall be perpendicular to the platens of the compactor.
The Superpave Gyratory Compactor, McGennis, R; Kennedy, TW; Anderson, VL; Perdomo, D, Journal of the Association of Asphalt Paving Technologists Vol:
66McGennis, R., Kennedy, T. W., Anderson, V. L., Perdomo, D., “The Superpave Gyratory Compactor,” Journal of the Association of Asphalt Paving Technologists, Vol 66,
1997, pp. 277–311.
D6925 − 23
5.1.6 The height measurement and recording system shall be capable of continuously measuring and recording the height of the
specimen during the compaction process to the nearest 0.1 mm. The height shall be recorded once per gyration.
5.1.7 The system shall record test information,information such as specimen heights per gyration. This may be accomplished
through data acquisition or printing.
5.1.8 The system shall be capable of stopping at a specified number of gyrations or at a specified height through automatic control
or operator input.
5.2 Specimen Molds—Specimen molds shall have steel walls that are at least 7.5 mm thick and are hardened to Rockwell C48 or
better. New molds shall have an inside diameter of 149.90 mm to 150.00 mm and be at least 250 mm high. mm. The inside diameter
of molds in service shall be 149.90 to 150.20 mm. The inside finish of the molds shall be smooth (rms of 1.60 μm or smoother
when measured in accordance with ASME B46.1). The inside diameter of the molds shall be measured in accordance with Annex
A1.
5.3 Mold Plates and Ram Heads—All mold plates and ram heads in contact with the mixture shall be fabricated from steel with
a minimum Rockwell hardness of C48. hardness of 451 BHN according to Test Method E10 (Rockwell Hardness of C48 according
to Test Method E18). The mold plates and ram head surfaces in contact with the mixture shall be flat and shall have an outside
diameter of 149.50 to 149.75 mm. The outside diameter of the end plates shall be measured in accordance with Annex A1.
5.4 Thermometers—Calibrated liquid-in-glass thermometers of suitable range with subdivisions 0.2°F (0.1°C) or 0.5°F (0.2°C) of
0.1 °C or 0.2 °C conforming to the requirements of Specification E2251 shall be used (ASTM Thermometer Numbers S67F-03 or
S67C-03; S65F-03 or S65C- 03; S65C-03; S63F-03 or S63C-03; or equivalent). Alternatively, other thermometer may be used, for
example resistance thermometer (RTD, PRT, IPRT) of equal or better accuracy. Calibrate the temperature measurement system
(probe and readout) to ensure accurate measurements within 63°C.63 °C.
NOTE 4—Standardization practices specified in Specification D3666 are recommended for the thermometer used in this test method. Dial
thermometerthermometers may exhibit inaccuracies due to frequentlyfrequent use or mishandling. It is recommended that the standardization of dial
thermometers be conducted more frequently by a comparison to a reference thermometric device of equal or greater readability at a temperature within
the range of intended use.
5.5 Balance—The balance shall have a minimum capacity of 10 000 g with a sensitivity of 0.1 g. The balance shall conform to
Guide D4753 as a Class GP2 balance.
5.6 Oven—A forced draft forced-draft oven capable of maintaining the specimen at the required temperature. temperature for
heating aggregate, asphalt, and equipment. The oven shall have a range of 50°C50 °C to a minimum of 204°C,204 °C,
thermostatically controlled to 63°C. For laboratory produced mixtures, a second oven with a range of 50°C to a minimum of
204°C, thermostatically controlled to 63°C shall be available for heating aggregates, asphalt, and equipment.63 °C.
5.7 Miscellaneous—Miscellaneous equipment may include: flat bottom metal pans for heating aggregates; scoops for batching
aggregates; containers for heating asphalt binders; mixing spoons; trowels; spatulas; welderswelder’s gloves for handling hot
equipment; 150 mm paper disks; lubricants for moving parts; laboratory timers; and mechanical mixers.
6. Standardization
6.1 Items requiring periodic verificationstandardization of calibration include the vertical pressure, internal angle of gyration,
frequency of gyration, height measurement system, and oven temperature. VerificationCheck of the mold and platen dimensions
and smoothness of finish is also required. Verification of calibration, system standardization, and quality checks shall be performed
by the manufacturer, other agencies providing standardization services, or in-house personnel. Frequency of verification shall
follow Specification D3666 intervals.
6.2 CalibrateStandardize the internal angle of gyration, pressure (applied force (kN) divided by nominal mold area (m2)),(m )),
height measurement, and gyration speed annually and whenever there is reason to doubt the stability of the machine’s operation.
Check the mold bore diameter and end plate diameters annually.
D6925 − 23
6.3 Verification of calibrationstandardization shall be performed if the gyratory compactor is transported to a new location.
NOTE 5—Unknown SGC equipment should be evaluated using procedures such as AASHTO PP35Test Method D7115 to assess its ability to produce
compacted specimens at various compaction levels which are equivalent to existing SGC models which are known to have met the specifications. Such
assessments should utilize the calibration and operational parameters outlined in Section 5.
7. Preparation and Compaction of Lab MixMixed Lab Compacted (LMLC) Test Specimens
7.1 Preparation of Aggregates—Weigh and combine the appropriate aggregate fractions to the desired specimen weight. The
specimen weight will vary based on the ultimate disposition of the test specimens. If a target air void level is desired such as that
required for mechanical property tests, specimen weights shall be adjusted to create a given density in a known volume. If the
specimens are to be used for determination of volumetric properties, the weights shall be adjusted to result in a compacted
specimen having dimensions of 150 mm in diameter and 115 6 5 mm in height at the required number of gyrations.
NOTE 6—It may be necessary to produce a trial specimen to achieve this height requirement. Generally, 4500 to 4700 g of aggregate are required to achieve
this height for aggregates with combined bulk specific gravities of 2.55 to 2.70 respectively.
NOTE 7—Details of aggregate preparation may be found in any suitable mix design manual, such as the Asphalt Institute’s MS-2 or AASHTO R35.R 35.
7.2 Place the blended aggregate specimens and asphalt binder in an oven and bring to the required mixing temperature. Heat the
mixing container and all necessary mixing implements to the required temperature.
7.2.1 The laboratory mixing temperature range is typically defined as the range of temperatures where the unaged asphalt binder
has a viscosity of 170 6 20 mPa·s measured in accordance with Test Method D4402D4402/D4402M.
NOTE 8—Modified asphalt binders, especially those produced with polymer additives, generally do not adhere to the equiviscous ranges noted in 7.2.1
and 7.6.1. The user should refer to the asphalt binder manufacturer to establish appropriate mixing and compaction temperature ranges. In no case should
the mixing temperature exceed 175°C.175 °C.
7.3 Charge the heated mixing bowl with the dry, heated aggregate and mix the dry aggregates. Form a crater in the heated
aggregate blend and weigh the required amount of asphalt binder into the aggregate blend. Immediately initiate mixing.
7.4 Mix the asphalt binder and aggregate as quickly and thoroughly as possible to yield an asphalt mixture having a uniform
distribution of asphalt binder. Because of the large batch weights, a mechanical mixer is preferable for the mixing process.
7.5 After completing the mixing process, subject the loose mix to the appropriate conditioning in accordance with AASHTO R30
or other asphalt mix conditioning practice. Stir the mix every 60 6 5 min to maintain uniform conditioning.R 30.
NOTE 9—Different asphalt mix conditioning procedures may apply for volumetric design and mechanical property testing specimens.
7.6 Place a compaction mold assembly in an oven at the required compaction temperature 65°C for a minimum of 45 min prior
to the compaction of the first mixture specimen (during the time the mixture is in the conditioning process described in 7.5).
NOTE 10—Oven performance and temperature uniformity can significantly impact the time required for a mold to reach compaction temperature. Mold
temperature can be confirmed with an infrared thermometer.
7.6.1 The compaction temperature range is defined as the range of temperatures where the unaged asphalt binder has a viscosity
of 280 630 mPa·s measured in accordance with Test Method D4402. See also Note 8.
7.7 Verify the settings on the compactor. Unless noted otherwise, the SGC shall be initialized to provide specimen compaction
using the settings described in 5.1. The number of gyrations for specimens used for volumetric properties shall be determined by
AASHTO R35 or other governing specification. The final compacted specimen height may be used as the stop criteria for
mechanical test specimens compacted to a target air void.
7.8 At the end of the conditioning period, remove the loose mix sample and the compaction mold assembly from the oven. Place
a paper disk inside the mold to aid separation of the specimen from the base plate after compaction.
D6925 − 23
7.9 Quickly place the mixture into the mold using a transfer bowl or other suitable device. Take care to minimize segregation of
the mixture in the mold. After the mixture has been completely loaded into the mold place a paper disk on the mixture to avoid
material adhering to the ram head or top mold plate. If necessary, place the top mold plate on top of the paper disk.
7.10 Load the compaction mold into the SGC and initiate the compaction process. In most SGCs, this is an automatic process
consisting of pressing a key to start the compaction process. The compactor shall apply the specified pressure, induce the angle,
and begin compaction. Compaction shall proceed to the desired endpoint—either a required number of gyrations (for determination
of volumetric properties), or a specified height (for use in physical property testing).
NOTE 11—Some SGC models permit the mix to be placed into the mold after the mold is loaded into the machine.
7.11 At the end of the compaction process, remove the mold assembly from the SGC. After a suitable cooling period, extrude the
compacted specimen from the mold, and remove the paper disks.
NOTE 12—Some compactor configurations may permit extruding from the mold
...