ASTM D6572-00
(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
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 (1). 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 (2).
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 D4647 and D4221, 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 (3).
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.7 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:D6572–00
Standard Test Methods for
Determining Dispersive Characteristics of Clayey Soils by
the Crumb Test
This standard is issued under the fixed designation D 6572; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 653 Terminology Relating to Soil, Rock, and Contained
Fluids
1.1 These test methods provide a qualitative indication of
D 1193 Specification for Reagent Water
the natural dispersive characteristics of clayey soils.
D 2216 TestMethodforLaboratoryDeterminationofWater
1.2 These test methods are not applicable for soils with less
(Moisture) Content of Soil and Rock
than 12 % fraction finer than 0.005 mm and with a plasticity
D 3740 Practice for Minimum Requirements for Agencies
index less than or equal to 8.
Engaged in the Testing and/or Inspection of Soil and Rock
1.3 The crumb test method has some limitations in its
as Used in Engineering Design and Construction
usefulness as an indicator of dispersive clay. A dispersive soil
D 4221 Test Method for Dispersive Characteristics of Clay
maysometimesgiveanondispersivereactioninthecrumbtest.
Soil by Double Hydrometer
Soils containing kaolinite with known field dispersion prob-
D 4647 Test Method for Identification and Classification of
lems have shown nondispersive reactions in the crumb test
Dispersive Clay Soils by the Pinhole Test
(1) . However, if the crumb test indicates dispersion, the soil is
E 1 Specification for ASTM Thermometers
probably dispersive.
E 11 Specification for Wire-Cloth Sieves for Testing Pur-
1.4 Oven-driedsoilshouldnotbeusedtopreparecrumbtest
poses
specimens, as irreversible changes could occur to the soil
pore-water physicochemical properties responsible for disper-
3. Terminology
sion (2).
3.1 Definitions:
1.5 Thecrumbtestmethod,whileagoodquickindicationof
3.1.1 dispersive clays—soils that disperse (deflocculate)
dispersive clay, should usually be run in conjunction with a
easily and rapidly without significant mechanical assistance in
pinhole test and a double hydrometer test, Test Methods
water of low-salt concentration.
D 4647 and D 4221, respectively.
3.1.1.1 Discussion—Such soils usually have a high propor-
NOTE 1—In some cases, the results of the pinhole, crumb, and
tion of their adsorptive capacity saturated with sodium cations
double-hydrometer test methods may disagree. Crumb test methods are a
althoughadsorbedlithiumandmagnesiummayalsoplayarole
better indicator of dispersive clays than of nondispersive clays (3).
(4). Such soils also generally have a high shrink-swell poten-
1.6 The values stated in SI units are to be regarded as the
tial, have low resistance to erosion, and have low permeability
standard. The values given in parentheses are for information
in an intact state.
only.
3.2 Fordefinitionsofothertermsusedinthesetestmethods,
1.7 This standard does not purport to address all of the
refer to Terminology D 653.
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4.1 A cube of remolded soil approximately 15 mm ( ⁄8 in.)
bility of regulatory limitations prior to use.
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
2. Referenced Documents
on the bottom of a white porcelain dish containing 250 mL of
2.1 ASTM Standards:
distilled water.
4.2 Temperature of the water is recorded and visual deter-
minations of dispersion grade are made and recorded at 2 min,
These test methods are under the jurisdiction ofASTM Committee D18 on Soil
and Rock and are the direct responsibility of Subcommittee D18.06on Physical-
Chemical Interactions of Soil and Rock. Annual Book of ASTM Standards, Vol 04.08.
Current edition approved June 10, 2000. Published August 2000. Annual Book of ASTM Standards, Vol 11.01.
2 5
The boldface numbers in parentheses refer to the list of references at the end of Annual Book of ASTM Standards, Vol 14.03.
this standard. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6572
1 h, and 6 h. Determination of grade is based on the formation, during the test program and will depend on the degree of
extent, and turbidity of a dense “cloud” or halo of colloidal- agreement of individual test results.
sized particles extending from the soil crumb. 6.6 These test methods are not applicable to soils with less
4.3 Determinations consist of: Grade 1 (Nondispersive), than 12 % fraction finer than 0.005 mm and with a plasticity
Grade 2 (Intermediate), Grade 3 (Dispersive), and Grade 4 index less than or equal to 8.
(Highly Dispersive).
7. Apparatus
5. Significance and Use
7.1 Specimen Container—Dish, porcelain, evaporating,
5.1 The crumb test method provides a simple, quick method 300-mL capacity.
for field or laboratory identification of a dispersive clay soil.
NOTE 3—Plastic bowls or cups can also be used but they should be
The internal erosion failures of a number of homogeneous
white or clear to help in distinguishing the colloidal cloud. The container
earth dams, erosion along channel or canal banks, and rainfall
should be at least 85 mm (3 in.) across the bottom if flat-bottomed.
erosion of earthen structures have been attributed to colloidal
7.2 Thermometer—0 to 50°C range, 0.1°C divisions, con-
erosion along cracks or other flow channels formed in masses
forming to the requirements of Specification E 1.
of dispersive clay (5).
7.3 Sieve, 4.75-mm (No. 4) and 2-mm (No. 10) sieve, in
5.2 The crumb test method, as originally developed by
accordance with Specification E 11.
Emerson (6), was called the aggregate coherence test and had
seven different categories of soil-water reactions. Sherard (5)
8. Reagents and Materials
latersimplifiedthetestbycombiningsomesoil-waterreactions
8.1 Purity of Water—Type IV of Specification D 1193 with
so that only four categories, or grades, of soil dispersion are
a pH between 5.5 and 7.0 shall be used for conducting the test
observed during the test.The crumb test is a relatively accurate
method and preparing remolded specimens. Distilled water is
positive indicator of the presence of dispersive properties in a
preferred.
soil. The crumb test, however, is not a completely reliable
negative indicator that soils are not dispersive. The crumb test,
9. Sampling, Test Specimens, and Test Units
canseldomberelieduponasasoletestmethodfordetermining
the presence of dispersive clays. The double-hydrometer test
9.1 Sampling—Obtain a representative soil sample of
(Test Method D 4221) and pinhole test (Test Method D 4647)
–4.75-mm (No. 4) soil. Depending on the percentage of coarse
are test methods that provide valuable additional insight into
sand in the material, approximately 25 to 75 g of material is
the probable dispersive behavior of clay soils.
needed to perform a crumb test method and approximately 400
to 500 g of material is needed to perform the crumb, pinhole,
NOTE 2—The quality of the result produced by these test methods is
and double-hydrometer tests.
dependent on the competence of the personnel performing it, and the
suitability of the equipment and facilities used. Agencies that meet the
NOTE 4—Do not use oven-dried material for the crumb test method
criteria of Practice D 3740 are generally considered capable of competent
because irreversible changes may occur to the soil pore-water physico-
and objective testing. Users of these test methods are cautioned that
chemical properties responsible for dispersion. Soil at natural moisture or
compliance with Practice D 3740 does not in itself ensure reliable testing.
at specified compaction moisture is preferred.
Reliable testing depends on several factors; Practice D 3740 provides a
means of evaluating some of those factors.
9.2 Test Specimens:
9.2.1 Test specimens may be from natural, irregularly
6. Interferences
shaped soil crumbs (Test MethodA) or may be remolded from
6.1 Oven-dried soil shall not be used in performing the material passing a 2-mm (No. 10) sieve (Test Method B).
crumb test as irreversible changes could occur to the soil
Material for the crumb test method should be selected as soon
pore-water physicochemical properties responsible for disper- as possible after obtaining the soil sample.
sion (2).
9.2.2 Test Method A—Natural Soil Crumbs:
6.2 Using other than Type IV water in accordance with 9.2.2.1 A natural, irregularly shaped soil crumb is selected
Specification D 1193, can interfere with dispersion of the that has been preserved at natural moisture or only allowed to
colloidal clay particles. air-dry. This soil crumb should be approximately the same
6.3 Carefullyplacethecubeorcrumbdirectlyonthebottom volume as a cube 15 mm ( ⁄8 in.) on each side (about the size
of the dish when submerging the crumb. Dropping the crumb of a single die of a pair of dice). Smaller soil crumbs down to
from the water surface can cause excessive slaking and may a volume equivalent to a cube 7 mm ( ⁄4 in.) on each side may
result in erroneous interpretation of the dispersion grade. be used if larger ones are unavailable.
6.4 Jarring or moving the soil specimen or porcelain dish 9.2.2.2 Use of natural soil crumbs may result in a specimen
once the test method has begun can cause excessive turbidity that is not representative of the total sample. Therefore, it is
and may result in erroneous interpretation of the dispersion recommendedthatseveralcrumbspecimensbetestedtoensure
grade. the total sample is represented. The number chosen is depen-
6.5 The use of
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