ASTM D6572-06
(Test Method)Standard Test Methods for Determining Dispersive Characteristics of Clayey Soils by the Crumb Test
Standard Test Methods for Determining Dispersive Characteristics of Clayey Soils by the Crumb Test
SIGNIFICANCE AND USE
The crumb test method provides a simple, quick method for field or laboratory identification of a dispersive clay 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).
The crumb test method, 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 D 4221) and pinhole test (Test Method D 4647) 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 these test methods 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 D 3740 are generally considered capable of competent and objective testing. Users of these test methods are cautioned that compliance with Practice D 3740 does not in itself ensure reliable testing. Reliable testing depends on several factors; Practice D 3740 provides a means of evaluating some of those factors.
SCOPE
1.1 These test methods provide a qualitative indication of the natural dispersive characteristics of clayey soils.
1.2 These test methods are not applicable for soils with less than 12 % fraction finer than 0.005 mm and with a plasticity index less than or equal to 8.
1.3 The crumb test method has some limitations in its usefulness as an indicator of dispersive clay. A dispersive soil may sometimes give a nondispersive reaction in the crumb test. Soils containing kaolinite with known field dispersion problems have shown nondispersive reactions in the crumb test (). However, if the crumb test indicates dispersion, the soil is probably dispersive.
1.4 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 ().
1.5 The crumb test method, while a good quick indication of dispersive clay, should usually be run in conjunction with a pinhole test and a double hydrometer test, Test Methods D 4647 and D 4221, respectively.Note 1
In some cases, the results of the pinhole, crumb, and double-hydrometer test methods may disagree. Crumb test methods are a better indicator of dispersive clays than of nondispersive clays ().
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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.
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Designation: D6572 − 06
StandardTest Methods for
Determining Dispersive Characteristics of Clayey Soils by
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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 2. Referenced Documents
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1.1 These test methods provide a qualitative indication of
2.1 ASTM Standards:
the natural dispersive characteristics of clayey soils.
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
1.2 These test methods are not applicable for soils with less
D1193 Specification for Reagent Water
than 12 % fraction finer than 0.005 mm and with a plasticity
D2216 Test Methods for Laboratory Determination of Water
index less than or equal to 8.
(Moisture) Content of Soil and Rock by Mass
1.3 The crumb test method has some limitations in its
D3740 Practice for Minimum Requirements for Agencies
usefulness as an indicator of dispersive clay. A dispersive soil
Engaged in Testing and/or Inspection of Soil and Rock as
maysometimesgiveanondispersivereactioninthecrumbtest.
Used in Engineering Design and Construction
Soils containing kaolinite with known field dispersion prob-
D4221 Test Method for Dispersive Characteristics of Clay
lems have shown nondispersive reactions in the crumb test
Soil by Double Hydrometer
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(1) . However, if the crumb test indicates dispersion, the soil is
D4318 Test Methods for Liquid Limit, Plastic Limit, and
probably dispersive.
Plasticity Index of Soils
1.4 Oven-driedsoilshouldnotbeusedtopreparecrumbtest
D4647 Test Method for Identification and Classification of
specimens, as irreversible changes could occur to the soil
Dispersive Clay Soils by the Pinhole Test
pore-water physicochemical properties responsible for disper-
D6026 Practice for Using Significant Digits in Geotechnical
sion (2).
Data
E1 Specification for ASTM Liquid-in-Glass Thermometers
1.5 Thecrumbtestmethod,whileagoodquickindicationof
E11 Specification for Woven Wire Test Sieve Cloth and Test
dispersive clay, should usually be run in conjunction with a
Sieves
pinholetestandadoublehydrometertest,TestMethodsD4647
and D4221, respectively.
3. Terminology
NOTE 1—In some cases, the results of the pinhole, crumb, and
3.1 Definitions:
double-hydrometer test methods may disagree. Crumb test methods are a
better indicator of dispersive clays than of nondispersive clays (3).
3.1.1 dispersive clays—soils that disperse (deflocculate)
easily and rapidly without significant mechanical assistance in
1.6 The values stated in SI units are to be regarded as the
water of low-salt concentration.
standard. The values given in parentheses are for information
only.
3.1.1.1 Discussion—Such soils usually have a high propor-
tion of their adsorptive capacity saturated with sodium cations
1.7 This standard does not purport to address all of the
althoughadsorbedlithiumandmagnesiummayalsoplayarole
safety concerns, if any, associated with its use. It is the
(4). Such soils also generally have a high shrink-swell
responsibility of the user of this standard to establish appro-
potential, have low resistance to erosion, and have low
priate safety and health practices and determine the applica-
permeability in an intact state.
bility of regulatory limitations prior to use.
3.2 Fordefinitionsofothertermsusedinthesetestmethods,
refer to Terminology D653.
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These test methods are under the jurisdiction ofASTM Committee D18 on Soil
and Rock and are the direct responsibility of Subcommittee D18.06 on Physical-
Chemical Interactions of Soil and Rock
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Current edition approved Nov. 1, 2006. Published December 2006. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D6572-06. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6572 − 06
4. Summary of Test Method from the water surface can cause excessive slaking and may
result in erroneous interpretation of the dispersion grade.
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4.1 A cube of remolded soil approximately 15 mm ( ⁄8 in.)
on each side (about the size of a single die in a pair of dice) or 6.4 Jarring or moving the soil specimen or porcelain dish
once the test method has begun can cause excessive turbidity
a natural soil crumb of approximately similar volume is placed
on t
...
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