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Significance and Use
5.1 Dispersive clays are those which normally deflocculate when exposed to water of low-salt concentration, the opposite of aggregated clays that would remain flocculated in the same soil-water system (. Generally, dispersive clays are highly erosive, possibly subject to high shrink-swell potential, may have lower shear strength, and have lower permeability rates than aggregated clays. , , )
5.2 When the percent dispersion equals 100, it indicates a completely dispersive clay-size fraction. When the percent dispersion equals 0, it indicates completely nondispersive clay-size fraction.
5.3 Available data ( indicates that the test method has about 85 % reliance in predicting dispersive performance (85 % of dispersive clays show more than 35 % dispersion). )
5.4 Since this test method may not identify all dispersive clays, design decisions based solely on this test method may not be conservative. It is often run in conjunction with the crumb test ( ) (, the pinhole test ( , ) ), or the analysis of the pore water extract ( ) (, or combination thereof, to identify possible dispersive clay behavior. , )
Note 1: The quality of the result produced by this standard is dependent on the competence of the personal performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice does not in itself assure reliable results. Reliable results depends on many factors; Practice provides a means of evaluating some of those factors.
1.1 This test method provides an indication of the natural dispersive characteristics of clay soils by comparing the amount of particles finer than 2-μm as determined by this method compared to the amount of particles finer than 2-μm as determined by Test Method (. ) In order to do this comparison, two similar specimens must be obtained from the sample.
1.2 This test method follows the procedure given in Test Method with the exception that the soil slurry is not mechanically dispersed and no dispersing agent is added.
1.3 This test method is applicable only to soils where the position of the plasticity index versus liquid limit plots (Test Methods ) falls on or above the “A” line (Practice ) and more than 12 % of the soil fraction is finer than 2-μm as determined in accordance with Test Method (. )
1.4 Since this test method may not identify all dispersive clay soils, other tests such as, pinhole dispersion (Test Methods ), crumb (Test Methods ) ( and the analysis of pore water extraction (Test Methods ) ) () may be performed individually or used together to help verify dispersion.
1.5 Units—The values stated in SI units are to be regarded as the standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method.
1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice .
1.6.1 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 analysis methods for engineering design.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.8 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 (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D653 Terminology Relating to Soil, Rock, and Contained Fluids
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)
D2488 Practice for Description and Identification of Soils (Visual-Manual Procedures)
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
D4220/D4220M Practices for Preserving and Transporting Soil Samples
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
D6572 Test Methods for Determining Dispersive Characteristics of Clayey Soils by the Crumb Test
D6913 Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis
D7928 Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis
ICS Number Code 91.100.15 (Mineral materials and products)
UNSPSC Code 11111800(Clays)
|Link to Active (This link will always route to the current Active version of the standard.)|
ASTM D4221-18, Standard Test Method for Dispersive Characteristics of Clay Soil by Double Hydrometer, ASTM International, West Conshohocken, PA, 2018, www.astm.orgBack to Top