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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