ASTM D7981-20

Standard Practice for Compaction of Prismatic Asphalt Specimens by Means of the Shear Box Compactor

SIGNIFICANCE AND USE
5.1 Asphalt prisms compacted with the shear box compactor can be used to obtain specimens for further testing, including bulk specific gravity following Test Methods D6752/D6752M and D2726/D2726M; dynamic modulus following AASHTO T 342; dynamic modulus, flow number, and flow time following AASHTO T 378; and fatigue performance characteristics following AASHTO T 321.  
5.2 Specimens to perform other standard tests could also be obtained, as long as their volume is contained within the volume of a prism having maximum width, length, and height (W × L × H) of 150 mm, 450 mm, and 185 mm, respectively. The maximum prism height depends on the mix type, the target air voids, and the equipment limitations.
Note 1: The aggregate orientation in the samples produced by this method may be different from samples produced by other laboratory compaction methods. This should be considered when comparing mechanical test results from different compaction methods.
Note 2: 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. 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.
SCOPE
1.1 This practice covers the fabrication of prismatic specimens of asphalt mixture using the shear box compactor (SBC). Compacted specimens are suitable for volumetric and physical property testing. This standard practice should not be used for acceptance or rejection of a material or for purchasing purposes.  
1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard with exception of degrees (°) where angle is specified.  
1.3 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.  
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, 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.

General Information

• Status: Published
• Publication Date: 14-Mar-2020
• ICS: 93.080.20 - Road construction materials
• Technical Committee: D04 - Road and Paving Materials
• Drafting Committee: D04.20 - Mechanical Tests of Asphalt Mixtures

Relations

• Replaces: ASTM D7981-15 - Standard Practice for Compaction of Prismatic Asphalt Specimens by Means of the Shear Box Compactor
• Effective Date: 15-Mar-2020
• Refers: ASTM D6857/D6857M-23 - Standard Test Method for Maximum Specific Gravity and Density of Asphalt Mixtures Using Automatic Vacuum Sealing Method
• Effective Date: 01-Nov-2023
• Refers: ASTM D6752/D6752M-23 - Standard Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Automatic Vacuum Sealing Method
• Effective Date: 01-Nov-2023
• Refers: ASTM E644-11(2019) - Standard Test Methods for Testing Industrial Resistance Thermometers
• Effective Date: 01-Nov-2019
• Refers: ASTM D2041/D2041M-19 - Standard Test Method for Theoretical Maximum Specific Gravity and Density of Asphalt Mixtures
• Effective Date: 01-Jun-2019
• Refers: ASTM D6857/D6857M-18 - Standard Test Method for Maximum Specific Gravity and Density of Asphalt Mixtures Using Automatic Vacuum Sealing Method
• Effective Date: 15-Aug-2018
• Refers: ASTM D6752/D6752M-18 - Standard Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Automatic Vacuum Sealing Method
• Effective Date: 15-Aug-2018
• Refers: ASTM D2726/D2726M-17 - Standard Test Method for Bulk Specific Gravity and Density of Non-Absorptive Compacted Asphalt Mixtures
• Effective Date: 01-Jun-2017
• Refers: ASTM D6857/D6857M-17 - Standard Test Method for Maximum Specific Gravity and Density of Asphalt Mixtures Using Automatic Vacuum Sealing Method
• Effective Date: 01-Jun-2017
• Refers: ASTM D6752/D6752M-17 - Standard Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Automatic Vacuum Sealing Method
• Effective Date: 01-Jun-2017
• Refers: ASTM D3666-16 - Standard Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
• Effective Date: 01-Oct-2016
• Refers: ASTM D3666-13 - Standard Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
• Effective Date: 01-Dec-2013
• Refers: ASTM D2726/D2726M-13 - Standard Test Method for Bulk Specific Gravity and Density of Non-Absorptive Compacted Bituminous Mixtures
• Effective Date: 01-Jul-2013
• Refers: ASTM D3666-11 - Standard Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
• Effective Date: 01-Dec-2011
• Refers: ASTM D6857/D6857M-11 - Standard Test Method for Maximum Specific Gravity and Density of Bituminous Paving Mixtures Using Automatic Vacuum Sealing Method
• Effective Date: 01-Jun-2011

Overview

ASTM D7981-20, "Standard Practice for Compaction of Prismatic Asphalt Specimens by Means of the Shear Box Compactor," provides procedures for fabricating asphalt mixture specimens using a shear box compactor (SBC). This standard supports consistent production of prismatic test specimens for laboratory evaluations of asphalt mixtures' physical and mechanical properties. Adhering to this practice enables agencies and labs to generate reliable specimens for various standardized performance and volumetric tests, supporting quality control, research, and product development in the field of asphalt pavement.

Key Topics

• Compaction Methodology: Details the use of a shear box compactor to prepare prismatic asphalt specimens with controlled application of static vertical and variable cyclic horizontal loads.
• Specimen Dimensions: Specifies that resulting specimens should not exceed 150 mm x 450 mm x 185 mm (width x length x height), depending on mix and compactor capability.
• Equipment and Calibration: Outlines requirements for loading systems, temperature control, molds, and periodic calibration of vertical force, shear angle, and measurement systems.
• Testing Suitability: Prismatic specimens created by this method are suitable for further tests, including:
  • Bulk specific gravity (ASTM D6752/D2726)
  • Dynamic modulus (AASHTO T 342, AASHTO T 378)
  • Flow number and flow time (AASHTO T 378)
  • Fatigue performance (AASHTO T 321)
• Quality Assurance: Emphasizes personnel competency, equipment maintenance, and adherence to agency standards, such as those in ASTM D3666.

Applications

ASTM D7981-20 is widely applicable in areas including:

• Pavement Materials Research: Producing laboratory compacted specimens that simulate field conditions for performance studies.
• Laboratory Testing: Fabricating prisms for routine or advanced evaluation of asphalt mixture density, air voids, modulus, and fatigue life.
• Quality Control: Providing consistent compaction to obtain reproducible specimens for verifying production or construction quality.
• Product Development: Allowing material developers to assess the impact of new binder or aggregate combinations under controlled compaction methods.
• Comparison Studies: Recognizing that aggregate orientation may differ from other compaction techniques, labs can use SBC specimens to develop comparative data for mechanical performance.

Important Considerations:

• This practice is not for determining material acceptance or for procurement decisions.
• Accurate results depend on operator skill and properly calibrated, maintained equipment.
• Adherence to recognized safety and environmental practices is essential due to the handling of hot asphalt materials.

Related Standards

ASTM D7981-20 incorporates or references several widely-used standards in the asphalt industry, facilitating integration across laboratory activities:

• ASTM D6752/D6752M: Bulk Specific Gravity of Compacted Asphalt Mixtures Using Automatic Vacuum Sealing Method
• ASTM D2726/D2726M: Bulk Specific Gravity and Density of Non-Absorptive Compacted Asphalt Mixtures
• ASTM D2041/D2041M & D6857/D6857M: Theoretical Maximum Specific Gravity and Density
• ASTM D3666: Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
• AASHTO T 342: Dynamic Modulus of Hot-Mix Asphalt Concrete Mixtures
• AASHTO T 378: Determination of Dynamic Modulus and Flow Number for Hot Mix Asphalt Mixtures
• AASHTO T 321: Fatigue Life of Compacted Hot Mix Asphalt Mixtures Subjected to Repeated Flexural Bending

Keywords: compaction, prismatic asphalt specimens, shear box compactor, asphalt mixture performance, laboratory testing, dynamic modulus, fatigue performance, air voids, bulk specific gravity, ASTM D7981-20, paving materials.

Standards Content (Sample)

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.
Designation: D7981 − 20
Standard Practice for
Compaction of Prismatic Asphalt Specimens by Means of
the Shear Box Compactor
This standard is issued under the fixed designation D7981; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D3666Specification for Minimum Requirements for Agen-
cies Testing and Inspecting Road and Paving Materials
1.1 This practice covers the fabrication of prismatic speci-
D6752/D6752MTest Method for Bulk Specific Gravity and
mensofasphaltmixtureusingtheshearboxcompactor(SBC).
Density of CompactedAsphalt Mixtures UsingAutomatic
Compacted specimens are suitable for volumetric and physical
Vacuum Sealing Method
property testing. This standard practice should not be used for
D6857/D6857MTest Method for Maximum Specific Grav-
acceptance or rejection of a material or for purchasing pur-
ity and Density of Asphalt Mixtures Using Automatic
poses.
Vacuum Sealing Method
1.2 Units—The values stated in SI units are to be regarded
E644Test Methods for Testing Industrial Resistance Ther-
asstandard.Nootherunitsofmeasurementareincludedinthis
mometers
standardwithexceptionofdegrees(°)whereangleisspecified.
2.2 AASHTO Standards:
1.3 The text of this standard references notes and footnotes AASHTO T 378Standard Method of Test for Determining
whichprovideexplanatorymaterial.Thesenotesandfootnotes
the Dynamic Modulus and Flow Number for Asphalt
(excluding those in tables and figures) shall not be considered Mixtures Using the Asphalt Mixture Performance Tester
as requirements of the standard.
(AMPT)
AASHTO T 321Standard Method of Test for Determining
1.4 This standard does not purport to address all of the
the Fatigue Life of Compacted Asphalt Mixtures Sub-
safety concerns, if any, associated with its use. It is the
jected to Repeated Flexural Bending
responsibility of the user of this standard to establish appro-
AASHTO T 342Standard Method of Test for Determining
priate safety, health, and environmental practices and deter-
DynamicModulusofHot-MixAsphaltConcreteMixtures
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
3.1 Definitions:
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 3.1.1 load cycle—the angular movement of the shearing
platensinthecompactorgoingfromtheverticalpositiontothe
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. positionofmaximumshearangleatoneside,thengoingtothe
maximum shear angle at the other side and back to the vertical
2. Referenced Documents
position (90 6 0.25° with reference to the horizontal plane).
2.1 ASTM Standards:
3.1.2 shear angle—the external angle measured between a
D2041/D2041MTest Method for Theoretical Maximum
vertical plane (angle of 90° with respect to a horizontal plane)
Specific Gravity and Density of Asphalt Mixtures
and the plane formed by a shearing plate in the compactor
D2726/D2726MTest Method for Bulk Specific Gravity and
when it has reached its maximum travel. Set at 4°.
Density of Non-Absorptive Compacted Asphalt Mixtures
4. Summary of Practice
1 4.1 A sample of loose asphalt mixture is compacted in a
This practice is under the jurisdiction ofASTM Committee D04 on Road and
Paving Materials and is the direct responsibility of Subcommittee D04.20 on fully automatic apparatus by the combination of a static
Mechanical Tests of Asphalt Mixtures.
vertical force and a horizontal cyclic shear force applied to
Current edition approved March 15, 2020. Published March 2020. Originally
twin vertical parallel platens up to a fixed maximum shear
approved in 2015. Last previous edition approved in 2015 as D7981–15. DOI:
10.1520/D7981-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from American Association of State Highway and Transportation
Standards volume information, refer to the standard’s Document Summary page on Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,
the ASTM website. http://www.transportation.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7981 − 20
the required load can be electro-pneumatic, electro-mechanic, or hydrau-
angle,toproduceaprismaticspecimenofcompactedasphaltto
lic.
a target uncorrected density (that is, based on the geometric
volume of the specimen).
6.1.2 Shear force of at least 50 kN, with the capability to
perform horizontal cyclic loading at a rate of three to four
5. Significance and Use cycles every minute.
6.1.3 Shear angle fixed at 4° (60.25°).
5.1 Asphaltprismscompactedwiththeshearboxcompactor
6.1.4 The compactor must be capable of producing com-
can be used to obtain specimens for further testing, including
pactedprismaticspecimens450mm(61.0mm)long,150mm
bulk specific gravity following Test Methods D6752/D6752M
(61.0 mm) wide, and with a height ranging from 120 mm to
andD2726/D2726M;dynamicmodulusfollowingAASHTOT
200 mm (61.0 mm).
342; dynamic modulus, flow number, and flow time following
AASHTO T 378; and fatigue performance characteristics 6.1.5 Thecontrollermustbeabletoautomaticallyterminate
following AASHTO T 321.
acompactionrunaftermeetingoneoftwoterminationcriteria:
sample height or number of loading cycles. The sample height
5.2 Specimens to perform other standard tests could also be
and vertical load shall be recorded.
obtained, as long as their volume is contained within the
6.1.6 The reaction frame shall be rigid and capable of
volume of a prism having maximum width, length, and height
sustaining the maximum forces generated during the compac-
(W × L × H) of 150 mm, 450 mm, and 185 mm, respectively.
tion process with system compliance of less than 0.1 mm per
Themaximumprismheightdependsonthemixtype,thetarget
1kN.Itshallalsobeabletosustainshearreactionforcesbeing
air voids, and the equipment limitations.
applied to the mold side plates and pivots.
NOTE 1—The aggregate orientation in the samples produced by this
method may be different from samples produced by other laboratory
6.1.7 The loading system (Fig. 1) shall consist of a con-
compaction methods. This should be considered when comparing me-
trolled dual-axis loading system (vertical and horizontal). A
chanical test results from different compaction methods.
constant vertical force shall be applied to achieve a vertical
NOTE 2—The quality of the results produced by this standard are
stress as per specified above. The horizontal force shall be
dependent on the competence of the personnel performing the procedure
and the capability, calibration, and maintenance of the equipment used. perpendicular to the vertical load axis, and applied through a
Agencies that meet the criteria of Specification D3666 are generally
system that ensures the rotational parallel movement of the
considered capable of competent and objective testing, sampling,
walls of the mold during the compaction process. The pivot
inspection, etc. Users of this standard are cautioned that compliance with
points shall be concentrically located at both ends of the mold
Specification D3666 alone does not completely ensure reliable results.
wallssuchthat 62mmofparallelismcanbeachieved;seeFig.
Reliable results depend on many factors. Following the suggestions of
Specification D3666 or some similar acceptable guideline provides a 1.
means of evaluating and controlling some of those factors.
6.1.8 The horizontal loading system shall be capable of
inducing a preset constant maximum degree of rotation (maxi-
6. Apparatus
mum shear angle) during a compaction of 4° (60.25°).
6.1 Shear Box Compactor—A compactor capable of fabri-
6.1.9 Theverticalactuatororthereactionelementshallslide
cating asphalt prisms comprised of the following system
freely and parallel to the horizontal loading axis (Fig. 2). The
components: (1) reaction frame; (2) fully integrated loading
verticalforceappliedshallbemeasuredduringthecompaction
system,includingloadingrams,controller,anddataacquisition
process with suitable transducers.
to record vertical force applied, height measurements, and
6.1.10 The shear box compactor system shall also include a
number of cycles; and (3) top and bottom compaction platens
specimen extraction unit.
and wearing plates. The compactor shall have an integrated
6.2 Mold Plates, Wear Plates Used on Top and Bottom of
heating system capable of preheating the SBC mold to the
the Specimen, and Ram Heads—Allmoldplatesandramheads
designated compaction temperature; if it does not, an alternate
shall be fabricated from steel with a minimum Rockwell
means of heating the mold is required.
hardness of C48. The mold plates and vertical ram heads shall
NOTE 3—Consider pouring and compacting a hot sample into the mold
be flat (<0.1 mm over 500 mm).
to allow all machine components to heat up, prior to fabricating samples
for actual testing.
6.3 Loading Chute—A purpose-built, heat-resistant chute
NOTE 4—Porous asphalt mixtures have significantly higher air voids
approximately445mmlong,140mmwide,and295mmhigh,
compared to dense-graded mixtures, so the cooling rate of the porous
with horizontal slots near the bottom of the chute approxi-
asphaltmixturewillbefasterthanstandardasphaltmixture.Itisnotgood
mately 75 mm apart and 75 mm tall, and with quick-release
practice to overheat porous asphalt mixtures, as it can result in binder
holding gates at the base to ensure the mix is transferred
drain-down issues in the mix.The use of the SBC heater is recommended
to preheat the mold to the required compaction temperature prior to mix
uniformly from the heating trays to the compaction mold
loading.
assembled within the shear box compactor.
6.4 Thermometers—A platinum resistance thermometer
The compactor must comply with the following specifica-
(PRT),thermocouple,ordial-typethermometerwitharangeof
tions:
at least 10 to 232°C. Calibrate the thermometer system (probe
6.1.1 Vertical stress adjustable by the user up to 1.0 MPa.
and readout) in accordance with Test Me
...

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: D7981 − 15 D7981 − 20
Standard Practice for
Compaction of Prismatic Asphalt Specimens by Means of
the Shear Box Compactor
This standard is issued under the fixed designation D7981; 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 practice covers the fabrication of prismatic specimens of asphalt mixture using the Shear Box Compactorshear box
compactor (SBC). Compacted specimens are suitable for volumetric and physical property testing. This standard practice should
not be used for acceptance or rejection of a material or for purchasing purposes.
1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard with exception of degrees (°) where angle is specified.
1.3 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.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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.
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:
D1188 Test Method for Bulk Specific Gravity and Density of Compacted Bituminous Mixtures Using Coated Samples
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
D6752D6752/D6752M Test Method for Bulk Specific Gravity and Density of Compacted Asphalt Mixtures Using Automatic
Vacuum Sealing Method
D6857D6857/D6857M Test Method for Maximum Specific Gravity and Density of Asphalt Mixtures Using Automatic Vacuum
Sealing Method
D6925 Test Method for Preparation and Determination of the Relative Density of Asphalt Mix Specimens by Means of the
Superpave Gyratory Compactor
E644 Test Methods for Testing Industrial Resistance Thermometers
2.2 AASHTO Standards:
AASHTO TP79T 378 Standard Method of Test for Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt
(HMA)Mixtures Using the Asphalt Mixture Performance Tester (AMPT)
This practice 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 Aug. 1, 2015March 15, 2020. Published September 2015March 2020. Originally approved in 2015. Last previous edition approved in 2015 as
D7981 – 15. DOI: 10.1520/D7981-15.10.1520/D7981-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7981 − 20
AASHTO T321T 321 Standard Method of Test for Determining the Fatigue Life of Compacted Hot Mix Asphalt
(HMA)Mixtures Subjected to Repeated Flexural Bending
AASHTO T342T 342 Standard Method of Test for Determining Dynamic Modulus of Hot Mix Hot-Mix Asphalt Concrete
Mixtures
3. Terminology
3.1 Definitions:
3.1.1 load cycle—the angular movement of the shearing platens in the compactor going from the vertical position to the position
of maximum shear angle at one side, then going to the maximum shear angle at the other side and back to the vertical position
(90 6 0.25° with reference to the horizontal plane).
3.1.2 shear angle—the external angle measured between a vertical plane (angle of 90° with respect to a horizontal plane) and
the plane formed by a shearing plate in the compactor when it has reached its maximum travel. Set at 4°.
4. Summary of Practice
4.1 A sample of loose asphalt mixture is compacted in a fully automatic apparatus by the combination of a static vertical force
and a horizontal cyclic shear force applied to twin vertical parallel platens up to a fixed maximum shear angle, to produce a
prismatic specimen of compacted asphalt to a target uncorrected density (that is, based on the geometric volume of the specimen).
5. Significance and Use
5.1 Asphalt prisms compacted with the Shear Box Compactorshear box compactor can be used to obtain specimens for further
testing, including bulk specific gravity following Test Methods D6752D6752/D6752M and D2726D2726/D2726M, Dynamic;
dynamic modulus following AASHTO T342, T 342; dynamic modulus, flow number, and flow time following AASHTO TP79,
T 378; and fatigue performance characteristics following AASHTO T321.T 321.
5.2 Specimens to perform other standard tests could also be obtained, as long as their volume is contained within the volume
of a prism having maximum width, length, and height (W×L×H) (W × L × H) of 150 mm, 450 mm, and 185 mm, respectively.
The maximum prism height depends on the mix type, the target air voids, and the equipment limitations.
NOTE 1—The aggregate orientation in the samples produced by this method maybe may be different from samples produced by other laboratory
compaction methods. This should be considered when comparing mechanical test results from different compaction methods.
NOTE 2—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 chr(59). factors. Following the
suggestions of Specification D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.
6. Apparatus
6.1 Shear Box Compactor—A compactor capable of fabricating asphalt prisms comprised of the following system components:
(1) reaction frame,frame; (2) fully integrated loading system, including loading rams, controller, and data acquisition to record
vertical force applied, height measurements, and number of cycles,cycles; and (3) top and bottom compaction platens and wearing
plates. The compactor must comply with the following specifications:shall have an integrated heating system capable of preheating
the SBC mold to the designated compaction temperature; if it does not, an alternate means of heating the mold is required.
NOTE 3—Consider pouring and compacting a hot sample into the mold to allow all machine components to heat up, prior to fabricating samples for
actual testing.
NOTE 4—Porous asphalt mixtures have significantly higher air voids compared to dense-graded mixtures, so the cooling rate of the porous asphalt
mixture will be faster than standard asphalt mixture. It is not good practice to overheat porous asphalt mixtures, as it can result in binder drain-down issues
in the mix. The use of the SBC heater is recommended to preheat the mold to the required compaction temperature prior to mix loading.
The compactor must comply with the following specifications:
6.1.1 Vertical Stressstress adjustable by the user up to 1.0 MPa.
NOTE 5—The maximum vertical force required considering the specimen dimensions should be 67.5 kN (measured and controlled to an accuracy of
6 5% 65 % of applied load),load). The loading system used to achieve the required load can be electro-pneumatic, electro-mechanic, or hydraulic.
6.1.2 Shear Forceforce of at least 50 kN, with the capability to perform horizontal cyclic loading at a rate of 3three to 4four
cycles every minute.
6.1.3 Shear Angleangle fixed at 4° (6 0.25°).(60.25°).
6.1.4 The compactor must be capable of producing compacted prismatic specimens 450 mm (6 1.0 (61.0 mm) long, 150 mm
(6 1.0 (61.0 mm) wide, and with a height ranging from 120 mm to 185200 mm (6 1.0 (61.0 mm).
6.1.5 The controller must be capableable to automatically terminate a compaction run after meeting one of two termination
criteria: sample height or,or number of loading cycles. The sample height and vertical load shall be recorded.
D7981 − 20
6.1.6 The reaction frame shall be rigid and capable of sustaining the maximum forces generated during the compaction process
with system compliance of less than 0.1 mm per 1 kN. 1 kN. It shall also be able to sustain shear reaction forces being applied
to the mold side plates and pivots.
6.1.7 The loading system (Fig. 1) shall consist of a controlled dual axis dual-axis loading system (vertical and horizontal). A
constant vertical force shall be applied to achieve a vertical stress as per specified above . above. The horizontal force shall be
perpendicular to the vertical load axis, and applied through a system that ensures the rotational parallel movement of the walls of
the mold during the compaction process. The pivot points shall be concentrically located at both endends of the mold walls such
that 62 mm of parallelism can be achievedachieved; see Fig. 1.
6.1.8 The horizontal loading system shall be capable of inducing a preset constant maximum degree of rotation (maximum shear
angle) during a compaction of 4° (6 0.25°).(60.25°).
6.1.9 The vertical actuator or the reaction element shall slide freely and parallel to the horizontal loading axis (Fig. 2.). The
vertical force applied shall be measured during the compaction process with suitable transducers.
6.1.10 The shear box compactor system shall also include a specimen extraction unit.
6.2 Mold Plates, Wear Plates usedUsed on topTop and bottomBottom of the specimenSpecimen, and Ram Heads—All mold
plates and ram heads shall be fabricated from steel with a minimum Rockwell hardness of C48. The mold plates and vertical ram
heads shall be flat (< 0.1 (<0.1 mm over 500 mm).
6.3 Loading Chute—A purpose built heat resistant purpose-built, heat-resistant chute approximately 445 mm long, 140 mm
wide,
...