ASTM D 6572 : 2012

1.1Two test methods are provided to give a qualitative indication of the natural dispersive characteristics of clayey soils. Method A is for natural soil clumps and method B for remolded soil.

1.2These test methods are not applicable for soils with less than 12 % finer than 0.005 mm and with a plasticity index less than or equal to 8.

1.3The crumb test method has some limitations in its usefulness as an indicator of dispersive clay. A dispersive soil may sometimes give a non-dispersive reaction in the crumb test. Soils containing 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.

1.4Oven-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).

1.5The 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.

1.6All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.

1.7The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.8This 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.