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ASTM D6572-2021 pdf free download

ASTM D6572-2021 pdf free download.Standard Test Methods for Determining Dispersive Characteristics of Clayey Soils by the Crumb Test
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 de- scribed in 10.1. 1.1.2 Method B- Procedure for Remolded Soil Crumbs described in 10.2 1.2 The crumb tesl, 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. L.3 The crumb lest 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 contain- ing 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 of above the“A” line (Practice D2487) and more than 12 % of the soil fraction is finer than 2-um as determined in accordance with Test Mecthod 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 disper- sion C2) NOTE 1-In some cases, the results of the pinhole, crumb, and double-hydromcter test methods may disagree. The crumb test is a better indicator of dispersive soils than of no-dispersive soils (3). 1.6 Units–The values stated in SI units are to be regarded as standard. No other units of mcasurement are included in this standard. 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 ane regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained, The proce- dures used do not consider material variation, purpose for obtaining the data, special purpose studics, or any consider- ations for the user ‘s objectives; and it is common practice to increase or reduce significant digits of teported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digis used in analytical methods for engineering design. 1.8 This standard does not purport to address all of the safety concems, i any; associated with its use. I1 is the responsibility of the user of this slandand 1o establish appro- priate safery, health, and environmental practices and deler mine the applicability of regulatory limiations prior to use. 1.9 This internctional slandard was developed i accor- dance with internationally recognized principles on slandard. ization established in the Decision on Principles for the Development of Intemational Standands, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Comminee.
5. Significance and Use
5.1 The crumb test provides a simple, quick method for field or laboralory identification of a dispersive clayey soil. The intermal erosion failures of a number of homogeneous earth dams, crosion along channel or canal banks, and rainfall erosion of earthen structures have been attributed to colloidal erosion along cracks or other Alow channcls formed in masses of dispersive clay 5) 5.2 The crumb test, as originally developed by Emerson (6, was called the aggregale coherence test and had seven different calegories 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 tesL. 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 indicalor 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.

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