ASTM D6572-21

Standard Test Methods for Determining Dispersive Characteristics of Clayey Soils by the Crumb Test

SIGNIFICANCE AND USE
5.1 The crumb test provides a simple, quick method for field or laboratory identification of a dispersive clayey soil. The internal erosion failures of a number of homogeneous earth dams, erosion along channel or canal banks, and rainfall erosion of earthen structures have been attributed to colloidal erosion along cracks or other flow channels formed in masses of dispersive clay (5).  
5.2 The crumb test, as originally developed by Emerson (6), was called the aggregate coherence test and had seven different categories of soil-water reactions. Sherard (5) later simplified the test by combining some soil-water reactions so that only four categories, or grades, of soil dispersion are observed during the test. The crumb test is a relatively accurate positive indicator of the presence of dispersive properties in a soil. The crumb test, however, is not a completely reliable negative indicator that soils are not dispersive. The crumb test can seldom be relied upon as a sole test method for determining the presence of dispersive clays. The double-hydrometer test (Test Method D4221) and pinhole test (Test Method D4647/D4647M) are test methods that provide valuable additional insight into the probable dispersive behavior of clay soils.
Note 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depends on several factors; Practice D3740 provides a means of evaluating some of those factors.
SCOPE
1.1 Two test methods are provided to give a qualitative indication of the natural dispersive characteristics of clayey soils: Method A and Method B.  
1.1.1 Method A—Procedure for Natural Soil Crumbs described in 10.1.  
1.1.2 Method B—Procedure for Remolded Soil Crumbs described in 10.2.  
1.2 The crumb test, while a good, quick indication of dispersive soil, should usually be run in conjunction with a pinhole test and a double hydrometer test, Test Methods D4647/D4647M and D4221, respectively. Since this test method may not identify all dispersive clay soils, other tests such as, pinhole dispersion (Test Methods D4647/D4647M), double hydrometer (Test Method D4221) and the analysis of pore water extraction (Test Methods D4542) may be performed individually or used together to help verify dispersion.  
1.3 The crumb test has some limitations in its usefulness as an indicator of dispersive soil. A dispersive soil may sometimes give a non-dispersive reaction in the crumb test. Soils containing kaolinite with known field dispersion problems, have shown non-dispersive reactions in the crumb test (1).2 However, if the crumb test indicates dispersion, the soil is probably dispersive.  
1.4 These test methods are applicable only to soils where the position of the plasticity index versus liquid limit plots (Test Methods D4318) falls on or above the “A” line (Practice D2487) and more than 12 % of the soil fraction is finer than 2-μm as determined in accordance with Test Method D7928.  
1.5 Oven-dried soil should not be used to prepare crumb test specimens, as irreversible changes could occur to the soil pore-water physicochemical properties responsible for dispersion (2).
Note 1: In some cases, the results of the pinhole, crumb, and double-hydrometer test methods may disagree. The crumb test is a better indicator of dispersive soils than of non-dispersive soils (3).  
1.6 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding establish...

General Information

• Status: Published
• Publication Date: 30-Apr-2021
• ICS: 13.080.20 - Physical properties of soils
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.06 - Physical-Chemical Interactions of Soil and Rock

Relations

• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D4647/D4647M-13(2020) - Standard Test Methods for Identification and Classification of Dispersive Clay Soils by the Pinhole Test
• Effective Date: 01-Feb-2020
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D4221-18 - Standard Test Method for Dispersive Characteristics of Clay Soil by Double Hydrometer
• Effective Date: 01-Jan-2018
• Refers: ASTM D2487-17e1 - Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
• Effective Date: 15-Dec-2017
• Refers: ASTM D2487-17 - Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
• Effective Date: 15-Dec-2017
• Refers: ASTM D4221-17 - Standard Test Method for Dispersive Characteristics of Clay Soil by Double Hydrometer
• Effective Date: 01-Jul-2017
• Refers: ASTM D4318-17e1 - Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
• Effective Date: 01-Jun-2017
• Refers: ASTM D4318-17 - Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
• Effective Date: 01-Jun-2017
• Refers: ASTM D7928-16e1 - Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis
• Effective Date: 01-May-2016
• Refers: ASTM D7928-16 - Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis
• Effective Date: 01-May-2016
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM E11-13 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-Oct-2013
• Refers: ASTM E1-13 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-May-2013

Overview

ASTM D6572-21: Standard Test Methods for Determining Dispersive Characteristics of Clayey Soils by the Crumb Test provides procedures to quickly assess the potential for colloidal erosion in clayey soils. Dispersive clay soils, when exposed to water, can break down and erode, posing risks such as internal erosion in earth dams, erosion along channels and canals, and surface erosion of earthen structures. The crumb test is a widely used field and laboratory method for identifying dispersive clays, helping to prevent failures in geotechnical and civil engineering projects.

Key Topics

• Dispersive Soils: Soils that easily deflocculate in water, often due to a high sodium content, leading to increased susceptibility to internal and surface erosion.
• Crumb Test Methods: Two qualitative methods:
  • Method A: Uses natural soil crumbs.
  • Method B: Utilizes remolded soil crumbs.
• Dispersion Grading: Soils are visually classified as:
  • Grade 1: Non-dispersive
  • Grade 2: Intermediate
  • Grade 3: Dispersive
  • Grade 4: Highly dispersive
• Field and Laboratory Use: The crumb test offers a simple, rapid assessment suitable for both field and laboratory conditions.
• Complementary Tests: Since the crumb test is not a definitive indicator for all soils, results are best interpreted alongside:
  • Double hydrometer test (ASTM D4221)
  • Pinhole test (ASTM D4647/D4647M)
  • Pore water extraction (ASTM D4542)
• Applicability: The standard applies to clayey soils with a plasticity index and liquid limit plotting above the “A” line (Unified Soil Classification, ASTM D2487) and more than 12% of the soil fraction finer than 2 μm (ASTM D7928).

Applications

ASTM D6572-21 is a vital tool for:

• Geotechnical Engineers and Soil Scientists: Quickly assessing the erosion potential of clay soils in situ or from samples.
• Dam and Levee Construction: Preventing internal erosion by identifying dispersive soils during site investigation and material selection.
• Channel, Canal, and Embankment Projects: Evaluating and minimizing the risk of bank failure or surface erosion by detecting dispersive clays.
• Slope Stability Assessment: Informing design criteria where dispersive clays can undermine slope integrity.
• Quality Control and Assurance: Providing guidance for soil acceptance and material suitability on construction projects involving clay soils.

The test methods promote early detection of problem soils, enabling timely mitigation strategies, such as soil amendment or avoidance, thus contributing to increased safety and durability of earthen structures.

Related Standards

For comprehensive evaluation of dispersive clayey soils, ASTM D6572-21 should be used in conjunction with the following standards:

• ASTM D4221: Test method for dispersive characteristics of clay soil by double hydrometer.
• ASTM D4647/D4647M: Test methods for identification and classification of dispersive clay soils by the pinhole test.
• ASTM D4318: Test methods for liquid limit, plastic limit, and plasticity index of soils.
• ASTM D2487: Practice for classification of soils for engineering purposes (Unified Soil Classification System).
• ASTM D4542: Test methods for pore water extraction and determination of the soluble salt content of soils.
• ASTM D7928: Test method for particle-size distribution (gradation) of fine-grained soils using hydrometer analysis.

By integrating the crumb test with these associated standards, professionals gain a robust understanding of soil behavior, leading to safer and more effective geotechnical designs.

Keywords: ASTM D6572-21, crumb test, dispersive clay, clayey soils, erosion, soil testing, civil engineering, geotechnical analysis, dispersibility, standard test methods

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: D6572 − 21
Standard Test Methods for
Determining Dispersive Characteristics of Clayey Soils by
the Crumb Test
This standard is issued under the fixed designation D6572; 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.
NOTE 1—In some cases, the results of the pinhole, crumb, and
1. Scope*
double-hydrometer test methods may disagree. The crumb test is a better
1.1 Two test methods are provided to give a qualitative
indicator of dispersive soils than of non-dispersive soils (3).
indication of the natural dispersive characteristics of clayey
1.6 Units—The values stated in SI units are to be regarded
soils: Method A and Method B.
as standard. No other units of measurement are included in this
1.1.1 Method A—Procedure for Natural Soil Crumbs de-
standard.
scribed in 10.1.
1.7 All observed and calculated values shall conform to the
1.1.2 Method B—Procedure for Remolded Soil Crumbs
guidelines for significant digits and rounding established in
described in 10.2.
Practice D6026.
1.2 The crumb test, while a good, quick indication of
1.7.1 Theproceduresusedtospecifyhowdataarecollected/
dispersive soil, should usually be run in conjunction with a
recorded or calculated in this standard are regarded as the
pinhole test and a double hydrometer test, Test Methods
industry standard. In addition, they are representative of the
D4647/D4647M and D4221, respectively. Since this test
significant digits that generally should be retained. The proce-
method may not identify all dispersive clay soils, other tests
dures used do not consider material variation, purpose for
such as, pinhole dispersion (Test Methods D4647/D4647M),
obtaining the data, special purpose studies, or any consider-
double hydrometer (Test Method D4221) and the analysis of
ations for the user’s objectives; and it is common practice to
porewaterextraction(TestMethodsD4542)maybeperformed
increase or reduce significant digits of reported data to be
individually or used together to help verify dispersion.
commensuratewiththeseconsiderations.Itisbeyondthescope
1.3 The crumb test has some limitations in its usefulness as
of this standard to consider significant digits used in analytical
anindicatorofdispersivesoil.Adispersivesoilmaysometimes
methods for engineering design.
give a non-dispersive reaction in the crumb test. Soils contain-
1.8 This standard does not purport to address all of the
ing kaolinite with known field dispersion problems, have
safety concerns, if any, associated with its use. It is the
shown non-dispersive reactions in the crumb test (1).
responsibility of the user of this standard to establish appro-
However, if the crumb test indicates dispersion, the soil is
priate safety, health, and environmental practices and deter-
probably dispersive.
mine the applicability of regulatory limitations prior to use.
1.4 These test methods are applicable only to soils where
1.9 This international standard was developed in accor-
the position of the plasticity index versus liquid limit plots dance with internationally recognized principles on standard-
(Test Methods D4318) falls on or above the “A” line (Practice
ization established in the Decision on Principles for the
D2487) and more than 12 % of the soil fraction is finer than Development of International Standards, Guides and Recom-
2-µm as determined in accordance with Test Method D7928.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.5 Oven-driedsoilshouldnotbeusedtopreparecrumbtest
specimens, as irreversible changes could occur to the soil
2. Referenced Documents
pore-water physicochemical properties responsible for disper-
2.1 ASTM Standards:
sion (2).
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
These test methods are under the jurisdiction ofASTM Committee D18 on Soil
D1193 Specification for Reagent Water
and Rock and are the direct responsibility of Subcommittee D18.06 on Physical-
Chemical Interactions of Soil and Rock
Current edition approved May 1, 2021. Published May 2021. Originally
approved in 2000. Last previous edition approved in 2020 as D6572 – 20. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D6572-21. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
The boldface numbers in parentheses refer to the list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6572 − 21
D2216 Test Methods for Laboratory Determination of Water 5. Significance and Use
(Moisture) Content of Soil and Rock by Mass
5.1 Thecrumbtestprovidesasimple,quickmethodforfield
D2487 Practice for Classification of Soils for Engineering
or laboratory identification of a dispersive clayey soil. The
Purposes (Unified Soil Classification System)
internal erosion failures of a number of homogeneous earth
D3740 Practice for Minimum Requirements for Agencies
dams, erosion along channel or canal banks, and rainfall
Engaged in Testing and/or Inspection of Soil and Rock as
erosion of earthen structures have been attributed to colloidal
Used in Engineering Design and Construction
erosion along cracks or other flow channels formed in masses
D4221 Test Method for Dispersive Characteristics of Clay
of dispersive clay (5).
Soil by Double Hydrometer
5.2 The crumb test, as originally developed by Emerson (6),
D4318 Test Methods for Liquid Limit, Plastic Limit, and
was called the aggregate coherence test and had seven different
Plasticity Index of Soils
categories of soil-water reactions. Sherard (5) later simplified
D4542 Test Methods for Pore Water Extraction and Deter-
the test by combining some soil-water reactions so that only
mination of the Soluble Salt Content of Soils by Refrac-
four categories, or grades, of soil dispersion are observed
tometer
during the test. The crumb test is a relatively accurate positive
D4647/D4647M Test Methods for Identification and Classi-
indicator of the presence of dispersive properties in a soil. The
fication of Dispersive Clay Soils by the Pinhole Test
crumb test, however, is not a completely reliable negative
D6026 Practice for Using Significant Digits in Geotechnical
indicator that soils are not dispersive. The crumb test can
Data
seldomberelieduponasasoletestmethodfordeterminingthe
D7928 Test Method for Particle-Size Distribution (Grada-
presence of dispersive clays. The double-hydrometer test (Test
tion) of Fine-Grained Soils Using the Sedimentation
Method D4221) and pinhole test (Test Method D4647/
(Hydrometer) Analysis
D4647M) are test methods that provide valuable additional
E1 Specification for ASTM Liquid-in-Glass Thermometers
insight into the probable dispersive behavior of clay soils.
E11 Specification for Woven Wire Test Sieve Cloth and Test
Sieves
NOTE 2—The quality of the result produced by this standard is
dependent on the competence of the personnel performing it, and the
E2251 Specification for Liquid-in-Glass ASTM Thermom-
suitability of the equipment and facilities used. Agencies that meet the
eters with Low-Hazard Precision Liquids
criteria of Practice D3740 are generally considered capable of competent
and objective testing/sampling/inspection/etc. Users of this standard are
3. Terminology
cautioned that compliance with Practice D3740 does not in itself assure
reliable results. Reliable results depends on several factors; Practice
3.1 Definitions:
D3740 provides a means of evaluating some of those factors.
3.1.1 For definitions of common technical terms in this
6. Interferences
standard, refer to Terminology D653.
6.1 Oven-dried soil shall not be used in performing the
3.2 Definitions of Terms Specific to This Standard:
crumb test as irreversible changes could occur to the soil
3.2.1 dispersive clays, n—soils that deflocculate easily and
rapidly without significant mechanical assistance, in water of pore-water physicochemical properties responsible for disper-
sion (2).
low-salt concentration.
3.2.1.1 Discussion—Such soils usually have a high propor-
6.2 The use of water other than Type IV in accordance with
tion of their adsorptive capacity saturated with sodium cations
Specification D1193, can interfere with dispersion of the
althoughadsorbedlithiumandmagnesiummayalsoplayarole
colloidal clay particles.
(4). Such soils also generally have a high shrink-swell
6.3 The cube or crumb shall be carefully placed directly on
potential, have low resistance to erosion, and have low
the bottom of the dish when submerging the crumb. Dropping
permeability in an intact state.
the crumb from the water surface can cause excessive slaking
and may result in erroneous interpretation of the dispersion
4. Summary of Test Method
grade.
4.1 Acube of remolded soil with approximately 15 65mm
6.4 Jarring or moving the soil specimen or container once
on each side (about the size of a single die in a pair of dice) or
the test method has begun can cause excessive turbidity and
a natural soil crumb of approximately similar volume is placed
may result in erroneous interpretation of the dispersion grade.
on the bottom of a 300-mL container containing 250 mL of
6.5 The use of a single, natural, irregular-shaped soil crumb
Type IV or distilled water.
may result in a specimen that is not representative of the total
4.2 The temperature of the water is recorded and visual
sample. Therefore, several crumb test specimens should be
determinations of the dispersion grade are made and recorded
selected to make sure that representative test results are
at2min 615s,1h 68min,and6h 645min.Determination
obtained. The total number of test specimens should be
of grade is based on the formation, extent, and turbidity of a
determined during the test program and will depend on the
dense “cloud” or halo of colloidal-sized particles extending
degree of agreement of individual test results.
from the soil crumb.
7. Apparatus
4.3 Determinations consist of: Grade 1 (Non-Dispersive),
Grade 2 (Intermediate), Grade 3 (Dispersive), and Grade 4 7.1 Specimen Container—A white or clear, non-porous,
(Highly Dispersive). glass or equivalent inert container with a minimum capacity of
D6572 − 21
300 mLand having a flat bottom of at least 85-mm across.The sure the total sample is represented. The number chosen is
container shall be large enough to allow for the specimen to be dependent on the homogeneity of the total sample.
fully immersed when placed in the container.
10.2 Test Method B—Remolded Soil Crumbs:
7.2 Thermometer—0 to 50°C range, 0.1°C divisions, con-
10.2.1 Process the representative sample over a 2.0 mm
forming to the requirements of Specification E1. Temperature
(No. 10) sieve and retain the soil passing the 2.0 mm (No. 10)
measuring devices, such as RTDs, thermistors, or liquid-in-
sieve.
glass thermometers (for example, Specification E2251) con-
10.2.2 Prepare a test specimen from the soil passing the 2.0
forming to Specification E1 and the temperature range and
mm (No. 10) sieve by lightly compressing the moist soil into a
accuracy, may be used.
cube approximately 15 6 5 mm on each side. Use the thumbs
and index finger to gently form the cube. Record the test
7.3 Sieve(s)—4.75 mm (No. 4) and 2.0 mm (No. 10) sieve,
specimen identification information and begin the test as soon
in accordance with Specification E11.
as practicable after obtaining the test specimen(s).
7.4 Timing Device—A clock, stopwatch, digital timer, or
10.3 If the crumb test is performed in conjunction with the
alike readable to 1 second or better.
pinhole test (Test Method D4647/D4647M), the cube can be
7.5 Camera (optional)—A device capable of taking photo-
prepared from soil cured to the water content desired for
graphs.
compacting the pinhole specimen. Alternatively, air-dried soil
or soil at the natural water content can be passed through a 2.0
8. Reagents
mm (No. 10) sieve and
...

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: D6572 − 20 D6572 − 21
Standard Test Methods for
Determining Dispersive Characteristics of Clayey Soils by
the Crumb Test
This standard is issued under the fixed designation D6572; 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 Two test methods are provided to give a qualitative indication of the natural dispersive characteristics of clayey soils: Method
A and Method B.
1.1.1 Method A—Procedure for Natural Soil Crumbs described in 10.1.
1.1.2 Method B—Procedure for Remolded Soil Crumbs described in 10.2.
1.2 The crumb test, while a good, quick indication of dispersive soil, should usually be run in conjunction with a pinhole test and
a double hydrometer test, Test Methods D4647/D4647M and D4221, respectively. Since this test method may not identify all
dispersive clay soils, other tests such as, pinhole dispersion (Test Methods D4647/D4647M), double hydrometer (Test Method
D4221) and the analysis of pore water extraction (Test Methods D4542) may be performed individually or used together to help
verify dispersion.
1.3 The crumb test has some limitations in its usefulness as an indicator of dispersive soil. A dispersive soil may sometimes give
a non-dispersive reaction in the crumb test. Soils containing kaolinite with known field dispersion problems, have shown
non-dispersive reactions in the crumb test (1). However, if the crumb test indicates dispersion, the soil is probably dispersive.
1.4 These test methods are applicable only to soils where the position of the plasticity index versus liquid limit plots (Test Methods
D4318) falls on or above the “A” line (Practice D2487) and more than 12 % of the soil fraction is finer than 2-μm as determined
in accordance with Test Method D7928.
1.5 Oven-dried soil should not be used to prepare crumb test specimens, as irreversible changes could occur to the soil pore-water
physicochemical properties responsible for dispersion (2).
NOTE 1—In some cases, the results of the pinhole, crumb, and double-hydrometer test methods may disagree. The crumb test is a better indicator of
dispersive soils than of non-dispersive soils (3).
1.6 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
These test methods are under the jurisdiction of ASTM Committee D18 on Soil and Rock and are the direct responsibility of Subcommittee D18.06 on Physical-Chemical
Interactions of Soil and Rock
Current edition approved March 1, 2020May 1, 2021. Published March 2020May 2021. Originally approved in 2000. Last previous edition approved in 20132020 as
ɛ2
D6572 – 13D6572 – 20. . DOI: 10.1520/D6572-20.10.1520/D6572-21.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6572 − 21
1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.7.1 The procedures used to specify how data are collected/recorded or calculated in this standard are regarded as the industry
standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not
consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives;
and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations.
It is beyond the scope of this standard to consider significant digits used in analytical methods for engineering design.
1.8 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.
1.9 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:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D1193 Specification for Reagent Water
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
D2487 Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4221 Test Method for Dispersive Characteristics of Clay Soil by Double Hydrometer
D4318 Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
D4542 Test Methods for Pore Water Extraction and Determination of the Soluble Salt Content of Soils by Refractometer
D4647/D4647M Test Methods for Identification and Classification of Dispersive Clay Soils by the Pinhole Test
D6026 Practice for Using Significant Digits in Geotechnical Data
D7928 Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer)
Analysis
E1 Specification for ASTM Liquid-in-Glass Thermometers
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
3. Terminology
3.1 Definitions:
3.1.1 For definitions of common technical terms in this standard, refer to Terminology D653.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 dispersive clays, n—soils that deflocculate easily and rapidly without significant mechanical assistance, in water of low-salt
concentration.
3.2.1.1 Discussion—
Such soils usually have a high proportion of their adsorptive capacity saturated with sodium cations although adsorbed lithium and
magnesium may also play a role (4). Such soils also generally have a high shrink-swell potential, have low resistance to erosion,
and have low permeability in an intact state.
4. Summary of Test Method
4.1 A cube of remolded soil with approximately 15 6 5 mm on each side (about the size of a single die in a pair of dice) or a
natural soil crumb of approximately similar volume is placed on the bottom of a 300-mL container containing 250 mL of Type
IV or distilled water.
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.
D6572 − 21
4.2 The temperature of the water is recorded and visual determinations of the dispersion grade are made and recorded at 2 min
6 15 s, 1 h 6 8 min, and 6 h 6 45 min. Determination of grade is based on the formation, extent, and turbidity of a dense “cloud”
or halo of colloidal-sized particles extending from the soil crumb.
4.3 Determinations consist of: Grade 1 (Non-Dispersive), Grade 2 (Intermediate), Grade 3 (Dispersive), and Grade 4 (Highly
Dispersive).
5. Significance and Use
5.1 The crumb test provides a simple, quick method for field or laboratory identification of a dispersive clayey soil. The internal
erosion failures of a number of homogeneous earth dams, erosion along channel or canal banks, and rainfall erosion of earthen
structures have been attributed to colloidal erosion along cracks or other flow channels formed in masses of dispersive clay (5).
5.2 The crumb test, as originally developed by Emerson (6), was called the aggregate coherence test and had seven different
categories of soil-water reactions. Sherard (5) later simplified the test by combining some soil-water reactions so that only four
categories, or grades, of soil dispersion are observed during the test. The crumb test is a relatively accurate positive indicator of
the presence of dispersive properties in a soil. The crumb test, however, is not a completely reliable negative indicator that soils
are not dispersive. The crumb test can seldom be relied upon as a sole test method for determining the presence of dispersive clays.
The double-hydrometer test (Test Method D4221) and pinhole test (Test Method D4647/D4647M) are test methods that provide
valuable additional insight into the probable dispersive behavior of clay soils.
NOTE 2—The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective
testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable
results depends on several factors; Practice D3740 provides a means of evaluating some of those factors.
6. Interferences
6.1 Oven-dried soil shall not be used in performing the crumb test as irreversible changes could occur to the soil pore-water
physicochemical properties responsible for dispersion (2).
6.2 The use of water other than Type IV in accordance with Specification D1193, can interfere with dispersion of the colloidal
clay particles.
6.3 The cube or crumb shall be carefully placed directly on the bottom of the dish when submerging the crumb. Dropping the
crumb from the water surface can cause excessive slaking and may result in erroneous interpretation of the dispersion grade.
6.4 Jarring or moving the soil specimen or container once the test method has begun can cause excessive turbidity and may result
in erroneous interpretation of the dispersion grade.
6.5 The use of a single, natural, irregular-shaped soil crumb may result in a specimen that is not representative of the total sample.
Therefore, several crumb test specimens should be selected to make sure that representative test results are obtained. The total
number of test specimens should be determined during the test program and will depend on the degree of agreement of individual
test results.
7. Apparatus
7.1 Specimen Container—A white or clear, non-porous, glass or equivalent inert container with a minimum capacity of 300 mL
and having a flat bottom of at least 85-mm across. The container shall be large enough to allow for the specimen to be fully
immersed when placed in the container.
7.2 Thermometer—0 to 50°C range, 0.1°C divisions, conforming to the requirements of Specification E1. Temperature measuring
devices, such as RTDs, thermistors, or liquid-in-glass thermometers (for example, Specification E2251) conforming to
Specification E1 and the temperature range and accuracy, may be used.
D6572 − 21
7.3 Sieve(s)—4.75 mm (No. 4) and 2.0 mm (No. 10) sieve, in accordance with Specification E11.
7.4 Timing Device—A clock, stopwatch, digital timer, or alike readable to 1 second or better.
7.5 Camera (optional)—A device capable of taking photographs.
8. Reagents
8.1 Purity of Water—Type IV water in accordance with Specification D1193 or distilled water with a pH between 5.5 and 7.0
shouldshall be used for conducting the test methods and preparing remolded specimens. Distilled Type IV water is preferred.
9. Sampling
9.1 Obtain a representative, homogenous soil sample passing the 4.75 mm (No. 4) sieve. Depending on the percentage of coarse
sand in the soil, approximately 25 to 75 g of soil is needed to perform a crumb test. If using Method A, more soil may be needed
in order to make sure representative test results are obtained. Soil for the crumb test should be selected as soon as possible after
obtaining the representative sample.
NOTE 3—Approximately 400 to 500 g of soil is needed to perform the crumb, pinhole, and double hydrometer tests.
9.1.1 Determine the water content of the representative sample prior to specimen(s) selection in accordance with Test Method
D2216 and record to the nearest 0.1 %. Record t
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