ASTM D2746/D2746M-18(2023)

Standard Test Method for Staining Tendency of Asphalt (Stain Index)

SIGNIFICANCE AND USE
4.1 This test method measures the tendency for oil components to separate spontaneously from asphalt. The separation of oil components can cause staining in asphalt roofing products and adjacent materials in storage and use.  
4.2 The stain index is related to the thermal stability of the asphalt. Higher stain index values indicate lower stability and greater tendency for staining.  
4.3 Use this procedure to determine the staining tendency of asphalt and to compare the results against a material for which the staining tendency is known.
SCOPE
1.1 This test method covers the determination of the staining tendency of asphalt and the assignment of a stain index proportional to the extent of staining observed.  
1.2 This test method is applicable to asphalts having ring-and-ball softening points of 85 °C [185 °F] or greater.  
Note 1: This test method may be modified for use with other bituminous materials with softening points less than 85 °C [185 °F] by using a different temperature than specified in Section 7 by agreement of the interested parties. The report of results from such a test may cite this method but must clearly state the temperature employed in the exception and acknowledge that the interpretation of results in Section 9 and the precision and bias stated in Section 10 may not apply.  
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 nonconformance with the standard.  
1.4 This standard does not purport to address 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: 30-Apr-2023
• ICS: 75.140 - Waxes, bituminous materials and other petroleum products
• ICS: 91.100.50 - Binders. Sealing materials
• Technical Committee: D08 - Roofing and Waterproofing
• Drafting Committee: D08.02 - Steep Roofing Products and Assemblies

Relations

• Refers: ASTM D140/D140M-16(2023) - Standard Practice for Sampling Asphalt Materials
• Effective Date: 01-Dec-2023
• Refers: ASTM E230/E230M-23a - Standard Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
• Effective Date: 01-Nov-2023
• Refers: ASTM E230/E230M-23 - Standard Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
• Effective Date: 01-May-2023
• Refers: ASTM D36/D36M-14(2020) - Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)
• Effective Date: 01-May-2020
• Refers: ASTM D140/D140M-16 - Standard Practice for Sampling Asphalt Materials
• Effective Date: 01-Jun-2016
• Refers: ASTM D140/D140M-15 - Standard Practice for Sampling Bituminous Materials
• Effective Date: 01-Jun-2015
• Refers: ASTM D36/D36M-14 - Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)
• Effective Date: 01-Jul-2014
• Refers: ASTM D140/D140M-14 - Standard Practice for Sampling Bituminous Materials
• Effective Date: 01-Jun-2014
• Refers: ASTM D36/D36M-12 - Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)
• Effective Date: 01-May-2012
• Refers: ASTM E230/E230M-11 - Standard Specification and Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
• Effective Date: 15-May-2011
• Refers: ASTM E230/E230M-11e1 - Standard Specification and Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
• Effective Date: 15-May-2011
• Refers: ASTM E2251-11 - Standard Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
• Effective Date: 01-May-2011
• Refers: ASTM E2251-10 - Standard Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
• Effective Date: 01-Nov-2010
• Refers: ASTM D36/D36M-09 - Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)
• Effective Date: 15-Dec-2009
• Refers: ASTM D140/D140M-09 - Standard Practice for Sampling Bituminous Materials
• Effective Date: 01-Jun-2009

Overview

ASTM D2746/D2746M-18(2023): Standard Test Method for Staining Tendency of Asphalt (Stain Index) provides a reliable, standardized approach to assess the propensity of asphalt materials to cause staining. Developed by ASTM International, this standard is instrumental in the roofing and waterproofing industry for evaluating and comparing different asphalts based on their tendency to release oil components-an effect directly related to product longevity and material compatibility.

This method measures the tendency of oil components to separate from asphalt, which can result in visible staining on roofing products and adjacent materials during storage or use. The stain index produced from this test is a useful indicator of the asphalt’s thermal stability, where a higher stain index denotes lower stability and greater staining potential.

Key Topics

• Test Scope: Applies to asphalts with ring-and-ball softening points of 85°C [185°F] or greater. The method may be adapted for other bituminous materials by agreement, provided any modifications are clearly reported.
• Measurement Technique:
  • A disc of asphalt is cast within a brass ring and placed on filter paper.
  • The assembly is heated in an oven at 80°C [175°F] for 120 hours.
  • After cooling, the diameter of the stained area on the filter paper is measured.
  • The stain index is calculated by subtracting the initial disc diameter from the stained circle diameter.
• Interpretation:
  • Lower stain index values (0-10) indicate low staining tendency.
  • Values from 10-20 are considered moderate.
  • Values greater than 20 indicate high staining propensity.
• Precision: The method provides guidelines for expected variability within and between laboratories, helping ensure accurate, repeatable results.

Applications

The ASTM D2746/D2746M test method is highly relevant in the following scenarios:

• Quality Control for Asphalt Roofing: Manufacturers utilize this standard to ensure that asphalt used in roofing shingles and waterproofing membranes does not cause undesirable staining that could affect product appearance or performance.
• Material Specification and Comparison: Enables selection of asphalts with proven low staining tendencies, enhancing product reliability and minimizing customer complaints.
• Product Development: Research and development teams use the stain index to innovate new asphalt formulations with optimized stability and minimal oil separation.
• Compliance and Certification: Helps fulfill regulatory and industry requirements for documented quality and consistency in asphalt products.

The practical value of this standard lies in supporting best practices in asphalt selection and application across the roofing industry, helping stakeholders maintain material integrity during transportation, storage, and installation.

Related Standards

In practice, ASTM D2746/D2746M is often used alongside other key ASTM standards to ensure comprehensive assessment and quality control:

• ASTM D36/D36M: Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)
• ASTM D140/D140M: Practice for Sampling Asphalt Materials
• ASTM E2251: Specification for Liquid-in-Glass ASTM Thermometers
• ASTM E1137/E1137M: Specification for Industrial Platinum Resistance Thermometers
• ASTM E230/E230M: Specification for Temperature-Electromotive Force Tables for Thermocouples

Using these referenced standards together enhances the reliability of asphalt testing, helping industry professionals meet international requirements for quality and performance.

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Keywords: ASTM D2746, stain index, asphalt staining, roofing materials, asphalt test method, oil separation, thermal stability, roofing products, bituminous materials, asphalt quality control.

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: D2746/D2746M − 18 (Reapproved 2023)
Standard Test Method for
Staining Tendency of Asphalt (Stain Index)
This standard is issued under the fixed designation D2746/D2746M; 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 D36/D36M Test Method for Softening Point of Bitumen
(Ring-and-Ball Apparatus)
1.1 This test method covers the determination of the stain-
D140/D140M Practice for Sampling Asphalt Materials
ing tendency of asphalt and the assignment of a stain index
E230/E230M Specification for Temperature-Electromotive
proportional to the extent of staining observed.
Force (emf) Tables for Standardized Thermocouples
1.2 This test method is applicable to asphalts having ring-
E1137/E1137M Specification for Industrial Platinum Resis-
and-ball softening points of 85 °C [185 °F] or greater.
tance Thermometers
E2251 Specification for Liquid-in-Glass ASTM Thermom-
NOTE 1—This test method may be modified for use with other
bituminous materials with softening points less than 85 °C [185 °F] by
eters with Low-Hazard Precision Liquids
using a different temperature than specified in Section 7 by agreement of
the interested parties. The report of results from such a test may cite this
3. Summary of Test Method
method but must clearly state the temperature employed in the exception
and acknowledge that the interpretation of results in Section 9 and the
3.1 A horizontal disc of asphalt, cast in a brass retaining
precision and bias stated in Section 10 may not apply.
ring, is placed on a sheet of filter paper supported on a flat plate
1.3 The values stated in either SI units or inch-pound units
and heated at 80 °C [175 °F] for 120 h. The diameter of the
are to be regarded separately as standard. The values stated in
resulting stained circle on the paper is compared to the inside
each system may not be exact equivalents; therefore, each
diameter of the brass ring to determine the staining character-
system shall be used independently of the other. Combining
istic of the asphalt. The stain index is the difference between
values from the two systems may result in nonconformance
the diameter of the stained circle and the initial disc diameter
with the standard.
measured to the nearest 0.5 mm [ ⁄64 in.].
1.4 This standard does not purport to address the safety
4. Significance and Use
concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety,
4.1 This test method measures the tendency for oil compo-
health, and environmental practices and determine the appli-
nents to separate spontaneously from asphalt. The separation of
cability of regulatory limitations prior to use.
oil components can cause staining in asphalt roofing products
1.5 This international standard was developed in accor-
and adjacent materials in storage and use.
dance with internationally recognized principles on standard-
4.2 The stain index is related to the thermal stability of the
ization established in the Decision on Principles for the
asphalt. Higher stain index values indicate lower stability and
Development of International Standards, Guides and Recom-
greater tendency for staining.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
4.3 Use this procedure to determine the staining tendency of
asphalt and to compare the results against a material for which
2. Referenced Documents
the staining tendency is known.
2.1 ASTM Standards:
5. Apparatus
5.1 Rings—Square shouldered brass retaining rings con-
forming to the dimensions required for use in the ring-and-ball
This test method is under the jurisdiction of ASTM Committee D08 on Roofing
and Waterproofing and is the direct responsibility of Subcommittee D08.02 on
softening point apparatus (see Fig. 1(a) of Test Method
Steep Roofing Products and Assemblies.
D36/D36M).
Current edition approved May 1, 2023. Published May 2023. Originally
5.1.1 The inside diameter of the ring to be placed in contact
approved in 1991. Last previous edition approved in 2018 as D2746/D2746M – 18.
DOI: 10.1520/D2746_D2746M-18R23. with the filter paper during the test is 16 mm [ ⁄64 in.].
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
NOTE 2—This test method depends on accurate measurement of
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on diameter and precise alignment of the face and rim of the ring on a flat
the ASTM website. surface. Therefore, deformed rings must not be used.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2746/D2746M − 18 (2023)
5.2 Pouring Plate—A flat, smooth, brass plate approxi- 7.2.1 The known material (Note 3) must be placed on the
mately 50 by 75 mm [2 by 3 in.]. same piece of filter paper and support plate as the sample(s)
being tested.
5.3 Paper—Filter paper of the standard double acid-washed
analytical grade. NOTE 3—The “known” material for the purpose of this test is a material
whose staining tendency is known to the investigator and which is used to
5.3.1 The filter paper must be of sufficient area to accom-
compare with the material being tested (see also Note 6).
modate the number of samples and the known material
7.2.2 Identify each asphalt sample and known material by
arranged as described in 7.3.
appropriately marking the filter paper in pencil near each ring.
5.4 Support Plate—A flat, clean, smooth metal plate ap-
7.3 Place the entire assembly on the support plate in the
proximately 1.5 mm [ ⁄16 in.] thick and area at least sufficient to
oven, preheated to 80 6 1 °C [175 6 2 °F], and allow to
support the size of filter paper being used.
remain at that temperature for 120 6 1 h.
5.5 Oven—A constant temperature oven capable of main-
7.4 Remove the assembly on the support plate from the
taining the test temperature of 80 °C [175 °F] within 61 °C
oven and allow to cool to room temperature (about 24 °C
[62 °F].
[75 °F]).
5.6 Thermometric Device—The thermometric device used
7.5 Remove the ring and the asphalt disc from the filter
shall be at least: (1) of equal accuracy to that of the S12C
...