ASTM D6931-17

Standard Test Method for Indirect Tensile (IDT) Strength of Asphalt Mixtures

SIGNIFICANCE AND USE
4.1 The values of IDT strength may be used to evaluate the relative quality of asphalt mixtures in conjunction with laboratory mix design testing and for estimating the potential for rutting or cracking. The results can also be used to determine the potential for field pavement moisture damage when results are obtained on both moisture-conditioned and unconditioned specimens.
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. 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 test method covers procedures for preparing and testing laboratory-fabricated or field-recovered cores of asphalt mixtures to determine the indirect tensile (IDT) strength.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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.  
1.4 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: 30-Jun-2017
• ICS: 93.080.20 - Road construction materials
• Technical Committee: D04 - Road and Paving Materials
• Drafting Committee: D04.26 - Fundamental/Mechanistic Tests

Relations

• Replaces: ASTM D6931-12 - Standard Test Method for Indirect Tensile (IDT) Strength of Bituminous Mixtures
• Effective Date: 01-Jul-2017
• Refers: ASTM D6925-23 - Standard Test Method for Preparation and Determination of the Relative Density of Asphalt Mix Specimens by Means of the Superpave Gyratory Compactor
• Effective Date: 01-Dec-2023
• Refers: ASTM D6926-20 - Standard Practice for Preparation of Asphalt Mixture Specimens Using Marshall Apparatus
• Effective Date: 01-Jan-2020
• Refers: ASTM D3549/D3549M-17 - Standard Test Method for Thickness or Height of Compacted Asphalt Mixture Specimens
• Effective Date: 01-Oct-2017
• Refers: ASTM D1074-17 - Standard Test Method for Compressive Strength of Asphalt Mixtures
• Effective Date: 01-Apr-2017
• Refers: ASTM D6926-16 - Standard Practice for Preparation of Asphalt Mixture Specimens Using Marshall Apparatus
• Effective Date: 15-Dec-2016
• 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 D6925-15 - Standard Test Method for Preparation and Determination of the Relative Density of Asphalt Mix Specimens by Means of the Superpave Gyratory Compactor
• Effective Date: 01-Jan-2015
• 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 E1-13 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-May-2013
• Refers: ASTM D3549/D3549M-11 - Standard Test Method for Thickness or Height of Compacted Bituminous Paving Mixture Specimens
• Effective Date: 01-Dec-2011
• 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 D3387-11 - Standard Test Method for Compaction and Shear Properties of Bituminous Mixtures by Means of the U.S. Corps of Engineers Gyratory Testing Machine (GTM) (Withdrawn 2020)
• Effective Date: 01-Aug-2011
• Refers: ASTM D6926-10 - Standard Practice for Preparation of Bituminous Specimens Using Marshall Apparatus
• Effective Date: 15-Jun-2010
• Refers: ASTM D3666-09a - Standard Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
• Effective Date: 01-Dec-2009

Overview

ASTM D6931-17: Standard Test Method for Indirect Tensile (IDT) Strength of Asphalt Mixtures is an established ASTM standard that outlines procedures for determining the indirect tensile strength of asphalt mixtures. The method applies to both laboratory-fabricated specimens and field-recovered cores, allowing evaluation of asphalt mixture quality, assessment of rutting or cracking potential, and analysis of susceptibility to moisture damage. This standard is widely used in pavement engineering, supporting both research and practical applications in road and pavement material testing.

Key Topics

• Indirect Tensile (IDT) Strength: The IDT test evaluates the strength of cylindrical asphalt specimens loaded across their vertical diametral plane. The procedure measures the peak load at failure and uses it to calculate tensile strength, expressed in kilopascals (kPa).
• Specimen Types: Tests may be conducted on laboratory-molded asphalt samples or on core specimens extracted from field pavements.
• Test Conditions: The standard specifies detailed requirements regarding specimen preparation, conditioning, temperature control, loading rate, and measurement accuracy.
• Moisture Conditioning: By testing both moisture-conditioned and unconditioned specimens, the method helps assess the potential for pavement moisture damage.
• Quality and Equipment: The reliability of test results depends on the competence of personnel, proper calibration, and maintenance of testing equipment.

Applications

The robust procedures described in ASTM D6931-17 provide essential data for various pavement engineering tasks:

• Asphalt Mix Design Evaluation: Helps laboratories and engineers determine and compare the quality of different asphalt mixtures during the design phase.
• Field Performance Analysis: Used to assess in-service pavements for durability, rutting resistance, and cracking tendency based on actual field cores.
• Moisture Susceptibility Testing: When combined with moisture conditioning procedures, the IDT test can indicate the likelihood of moisture-related damage, such as stripping or premature pavement failure.
• Quality Control and Research: Supports quality control practices and research by providing repeatable, comparable tensile strength measurements.

While valuable for comparative analysis and design validation, ASTM D6931-17 is not recommended for material acceptance or rejection in procurement due to ongoing evaluation of its reproducibility across laboratories.

Related Standards

Several ASTM and AASHTO standards are often referenced and used alongside ASTM D6931-17 to manage bituminous mixture preparation, specimen conditioning, and additional mechanical property assessment:

• ASTM D1074 - Test Method for Compressive Strength of Asphalt Mixtures
• ASTM D1561/D1561M - Practice for Preparation of Bituminous Mixture Test Specimens by Means of California Kneading Compactor
• ASTM D3387 - Test Method for Compaction and Shear Properties of Bituminous Mixtures by Means of the U.S. Corps of Engineers Gyratory Testing Machine
• ASTM D3549/D3549M - Test Method for Thickness or Height of Compacted Bituminous Paving Mixture Specimens
• ASTM D3666 - Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
• ASTM D4867/D4867M - Test Method for Effect of Moisture on Asphalt Concrete Paving Mixtures
• ASTM D5581 - Test Method for Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus
• ASTM D6925 - Test Method for Preparation and Determination of the Relative Density of Asphalt Mix Specimens by Means of the Superpave Gyratory Compactor
• ASTM D6926 - Practice for Preparation of Asphalt Mixture Specimens Using Marshall Apparatus
• ASTM D6927 - Test Method for Marshall Stability and Flow of Asphalt Mixtures
• AASHTO T245 and T312 - Methods for Resistance to Plastic Flow and Density Determination of Hot Mix Asphalt

Conclusion

ASTM D6931-17 is a critical tool for assessing the quality, performance characteristics, and moisture susceptibility of asphalt mixtures using standardized indirect tensile strength testing procedures. Its adoption supports improved pavement design, performance prediction, and research in the field of asphalt technology, aligning with internationally recognized best practices for road and infrastructure quality.

Keywords: ASTM D6931-17, indirect tensile strength, IDT, asphalt mixture, bituminous mixture, pavement testing, moisture susceptibility, rutting, cracking, asphalt quality, laboratory mix design.

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: D6931 − 17
Standard Test Method for
Indirect Tensile (IDT) Strength of Asphalt Mixtures
This standard is issued under the fixed designation D6931; 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 D3549/D3549M Test Method for Thickness or Height of
Compacted Bituminous Paving Mixture Specimens
1.1 This test method covers procedures for preparing and
D3666 Specification for Minimum Requirements for Agen-
testing laboratory-fabricated or field-recovered cores of asphalt
cies Testing and Inspecting Road and Paving Materials
mixtures to determine the indirect tensile (IDT) strength.
D4013 Practice for Preparation of Test Specimens of Bitu-
1.2 The values stated in SI units are to be regarded as
minous Mixtures by Means of Gyratory Shear Compactor
standard. No other units of measurement are included in this 3
(Withdrawn 2013)
standard.
D4867/D4867M Test Method for Effect of Moisture on
1.3 This standard does not purport to address all of the
Asphalt Concrete Paving Mixtures
safety concerns, if any, associated with its use. It is the D5581 Test Method for Resistance to Plastic Flow of Bitu-
responsibility of the user of this standard to establish appro-
minous Mixtures Using Marshall Apparatus (6 inch-
priate safety and health practices and determine the applica- Diameter Specimen)
bility of regulatory limitations prior to use.
D6925 Test Method for Preparation and Determination of
1.4 This international standard was developed in accor- the Relative Density ofAsphalt Mix Specimens by Means
dance with internationally recognized principles on standard-
of the Superpave Gyratory Compactor
ization established in the Decision on Principles for the D6926 Practice for Preparation of Asphalt Mixture Speci-
Development of International Standards, Guides and Recom-
mens Using Marshall Apparatus
mendations issued by the World Trade Organization Technical D6927 Test Method for Marshall Stability and Flow of
Barriers to Trade (TBT) Committee.
Asphalt Mixtures
E1 Specification for ASTM Liquid-in-Glass Thermometers
2. Referenced Documents
2.2 AASHTO Standards:
2.1 ASTM Standards:
AASHTO T 245 Standard Method for Resistance to Plastic
D1074 Test Method for Compressive Strength of Asphalt
Flow of Bituminous Mixtures Using Marshall Apparatus
Mixtures
AASHTO T 312 Standard Method for Preparing and Deter-
D1561/D1561M Practice for Preparation of Bituminous
mining the Density of Hot Mix Asphalt (HMA) Speci-
MixtureTest Specimens by Means of California Kneading
mens by Means of the Superpave Gyratory Compactor
Compactor
D3387 Test Method for Compaction and Shear Properties of 3. Summary of Test Method
Bituminous Mixtures by Means of the U.S. Corps of
3.1 The IDT strength of asphalt mixtures is determined by
Engineers Gyratory Testing Machine (GTM)
loading a cylindrical specimen across its vertical diametral
D3496 Practice for Preparation of Bituminous Mixture
plane at a specified rate of deformation and test temperature.
Specimens for Dynamic Modulus Testing (Withdrawn
The peak load at failure is recorded and used to calculate the
2010)
IDT strength of the specimen.
4. Significance and Use
This test method is under the jurisdiction of ASTM Committee D04 on Road
and Paving Materials and is the direct responsibility of Subcommittee D04.26 on
4.1 The values of IDT strength may be used to evaluate the
Fundamental/Mechanistic Tests.
relative quality of asphalt mixtures in conjunction with labo-
Current edition approved July 1, 2017. Published July 2017. Originally approved
ratory mix design testing and for estimating the potential for
in 2007. Last previous edition approved in 2012 as D6931 – 12. DOI: 10.1520/
D6931-17.
rutting or cracking. The results can also be used to determine
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
The last approved version of this historical standard is referenced on Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,
www.astm.org. http://www.transportation.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6931 − 17
the potential for field pavement moisture damage when results with a nominal diameter of 150 mm. A minimum of three
are obtained on both moisture-conditioned and unconditioned replicates shall be prepared for each mixture.
specimens.
6.2 Core Specimens—Cores should have smooth surfaces
and parallel faces, conforming to the height and diameter
NOTE 1—The quality of the results produced by this standard are
dependent on the competence of the personnel performing the procedure
requirements specified for laboratory-molded specimens, ex-
and the capability, calibration, and maintenance of the equipment used.
cept that a minimum height of 38 mm is permitted for
Agencies that meet the criteria of Specification D3666 are generally
specimens with a nominal diameter of 100 mm.Aminimum of
considered capable of competent and objective testing, sampling,
three replicates from an in-service pavement shall be prepared
inspection, etc. Users of this standard are cautioned that compliance with
for testing.
Specification D3666 alone does not completely ensure reliable results.
Reliable results depend on many factors; following the suggestions of
NOTE 3—Specimens with a nominal diameter of 100 mm are suitable
Specification D3666 or some similar acceptable guideline provides a for mixtures with a nominal maximum particle size of 19 mm or less.
means of evaluating and controlling some of those factors.
Specimens with a nominal diameter of 150 mm are suitable for mixtures
with a nominal maximum particle size of 37.5 mm or less.
5. Apparatus
7. Procedure
5.1 Loading Device—Loading jack and ring dynamometer
or a mechanical or servo-hydraulic testing machine with an
7.1 Determine the specimen height in accordance with Test
electronic load cell, in accordance with Test Method D6927,
Method D3549/D3549M, to the nearest 1 mm.
capable of applying a compressive load at a controlled defor-
7.2 For core specimens, measure the diameter at the mid
mation rate while measuring the load and deformation.
height along axes that are 90° apart, and record the average to
5.2 Loading Strips—Steel loading strips with a concave
the nearest 1 mm.
surfacehavingaradiusofcurvatureequaltothenominalradius
7.3 Bring the specimen to test temperature 61 °C by any of
of the test specimen. For specimens with nominal diameter of
the following three alternative procedures. The recommended
100 mm, the loading strips shall be 12.70 6 0.3 mm wide. For
test temperature is 25 °C.
specimens with nominal diameter of 150 mm, the loading
NOTE4—Basedonpreviousexperience,astandardtemperaturethathas
strips shall be 19.05 6 0.3 mm wide.The length of the loading
been used for most IDT strength testing is 25 °C. Other test temperatures
strips shall exceed the thickness of the specimen. The outer
may be used at the discretion of the user.
edges of the loading strips shall be beveled slightly to remove
7.3.1 Procedure A—Place the specimen in an air bath for a
sharp edges.
minimum of 4 h.
5.2.1 Theloadingstripsshallbepartofatestfixture,similar
7.3.2 Procedure B—Place the specim
...

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: D6931 − 12 D6931 − 17
Standard Test Method for
Indirect Tensile (IDT) Strength of BituminousAsphalt
Mixtures
This standard is issued under the fixed designation D6931; 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 procedures for preparing and testing laboratory-fabricated or field-recovered cores of bitumi-
nousasphalt mixtures to determine the Indirect Tensileindirect tensile (IDT) Strength.strength.
1.2 The within-laboratory repeatability standard deviation, for the recommended rate of loading (50 mm/min) and test
temperature (25ºC), has been determined to be 80 kPa for 101.6 mm diameter specimens, based on 28 labs using either 2 or 4 test
replicates with 11 different mix samples. Additional data is provided in Table for the user’s information. The between-laboratory
reproducibility of this test method is being determined and will be available on or before August 2012. Therefore, this test method
should not be used for acceptance or rejection of materials for purchasing purposes.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
1.4 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:
D1074 Test Method for Compressive Strength of Asphalt Mixtures
D1561D1561/D1561M Practice for Preparation of Bituminous Mixture Test Specimens by Means of California Kneading
Compactor
D3387 Test Method for Compaction and Shear Properties of Bituminous Mixtures by Means of the U.S. Corps of Engineers
Gyratory Testing Machine (GTM)
D3496 Practice for Preparation of Bituminous Mixture Specimens for Dynamic Modulus Testing (Withdrawn 2010)
D3549D3549/D3549M Test Method for Thickness or Height of Compacted Bituminous Paving Mixture Specimens
D3666 Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
D4013 Practice for Preparation of Test Specimens of Bituminous Mixtures by Means of Gyratory Shear Compactor (Withdrawn
2013)
D4867/D4867M Test Method for Effect of Moisture on Asphalt Concrete Paving Mixtures
D5581 Test Method for Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus (6 inch-Diameter
Specimen)
D6925 Test Method for Preparation and Determination of the Relative Density of Asphalt Mix Specimens by Means of the
Superpave Gyratory Compactor
D6926 Practice for Preparation of Asphalt Mixture Specimens Using Marshall Apparatus
D6927 Test Method for Marshall Stability and Flow of Asphalt Mixtures
This test method is under the jurisdiction of ASTM Committee D04 on Road and Paving Materials and is the direct responsibility of Subcommittee D04.26 on
Fundamental/Mechanistic Tests.
Current edition approved Feb. 1, 2012July 1, 2017. Published February 2012July 2017. Previous version published in 2007 Originally approved in 2007. Last previous
edition approved in 2012 as D6931– – 12. DOI: 10.1520/D6931-12.10.1520/D6931-17.
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.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6931 − 17
TABLE 1 Single-Laboratory Repeatability and Reproducibility
Standard Standard
Number Specimen Loading Test Average d2s d2s
Deviation Deviation
Source of Data of Diameter Rate Temperature Strength (2.83×SE) (2.83×SE)
Strength Strength
Replicates (mm) (mm/min) (°C) (kPa) (kPa) (% mean)
(kPa) (% mean)
Anderson and
3 150 12.5 -10 2870 200 566 7.0 19.8
A
McGennis
Anderson and
3 150 12.5 –10 2870 200 566 7.0 19.8
A
McGennis
N CHRP
3 150 12.5 -10 - - - 9 22–32
B
Report 530
N CHRP
3 150 12.5 –10 - - - 9 22 – 32
B
Report 530
(4 aggregate
types; 2 150 12.5 -10 - - - 11
4 binders)
(4 aggregate
types; 2 150 12.5 –10 - - - 11
4 binders)
(nom max size:
9.5 mm to 25
mm)
Solaimanian
and
4 100 50 25 - 103 292 – –
C
Kennedy
—dry
Solaimanian
and 4 100 50 25 - 103 292 - -
C
Kennedy – dry
moisture-
50 25 - 83 234 – –
conditioned
moisture-
50 25 - 83 234 - -
conditioned
(9 labs; 3
aggregate
types; 2
binders)
Test Method
D4867/D4867M
2 100 50 25 - 55 159 – –
(dry or condi-
tioned)
Test Method
D4867/D4867M
2 100 50 25 - 55 159 - -
(dry or condi-
tioned)
(19 labs;
5 mixtures)
Suggested
Single 50 25 80
Lab Precision
A
R. M. Anderson and R. B. McGennis, “Ruggedness Evaluation of AASHTO TP7 and TP9,” Phase I, FHWA HIPT (Task J), Federal Highway Administration, November
1998.
B
W. Christensen and R. F. Bonaquist, “Evaluation of Indirect Tensile Test (IDT) Procedures for Low-Temperature Performance of Hot Mix Asphalt,” NCHRP Report 530.
C
Solaimanian and T. W. Kennedy, “Precision of the Moisture Susceptibility Test Method TEX-531-C,” Project Summary Report 4909-S, November 2000.
E1 Specification for ASTM Liquid-in-Glass Thermometers
2.2 AASHTO Standards:
AASHTO T245T 245 Standard Method for Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus
AASHTO T312T 312 Standard Method for Preparing and Determining the Density of Hot Mix Asphalt (HMA) Specimens by
Means of the Superpave Gyratory Compactor
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.
D6931 − 17
3. Summary of Test Method
3.1 The IDT strength of bituminousasphalt mixtures is conducteddetermined by loading a cylindrical specimen across its
vertical diametral plane at a specified rate of deformation and test temperature. The peak load at failure is recorded and used to
calculate the IDT strength of the specimen.
4. Significance and Use
4.1 The values of IDT strength may be used to evaluate the relative quality of bituminousasphalt mixtures in conjunction with
laboratory mix design testing and for estimating the potential for rutting or cracking. The results can also be used to determine the
potential for field pavement moisture damage when results are obtained on both moisture-conditioned and unconditioned
specimens.
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. 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. Apparatus
5.1 Loading Device—Loading jack and ring dynamometer or a mechanical or servo-hydraulic testing machine with an
electronic load cell, in accordance with Test Method D6927, capable of applying a compressive load at a controlled deformation
rate while measuring the load and deformation.
5.2 Loading Strips—Steel loading strips with a concave surface having a radius of curvature equal to the nominal radius of the
test specimen. For specimens with nominal diameter of 101.6100 mm, the loading strips shall be 12.70 6 0.3 mm wide. For
specimens with nominal diameter of 150 mm, the loading strips shall be 19.05 6 0.3 mm wide. The length of the loading strips
shall exceed the thickness of the specimen. The outer edges of the loading st
...