STP623: Factors Affecting Spontaneous Dispersion of soil Materials as Evidenced by the Crumb Test

    Holmgren, GGS
    Soil scientist, National Soil Survey Laboratory, and civil engineer, Soil Mechanics Unit, Soil Conservation Service, Lincoln, Nebr.

    Flanagan, CP
    Soil scientist, National Soil Survey Laboratory, and civil engineer, Soil Mechanics Unit, Soil Conservation Service, Lincoln, Nebr.

    Pages: 22    Published: Jan 1977


    Abstract

    Sixty-three soils were examined for spontaneous dispersion by various modifications of the crumb test. This test is considered indicative of dispersive conditions if a colloidal cloud develops when a small soil specimen is immersed in a large volume of water. Soil specimens were examined by this test in the dry state and in a remolded, saturated condition (slightly above the liquid limit). These pieces were immersed in distilled water and in 1 milliequivalent/litre (0.001 N) sodium hydroxide. The results of these tests were compared with the pinhole test as a reference measure of dispersion.

    The use of saturated, remolded soil specimens resulted in a more conservative test for dispersion. More dispersive soils were identified properly, but more nondispersive soils were classified incorrectly as dispersive.

    The 63 soils were separated further into four classes, depending on the agreement or disagreement of the saturated crumb test with the pinhole test. Chemical, mineralogical, and engineering data were assembled to assist in the search for explanatory variables affecting the discrepancies.

    A second series of minicrumb tests was conducted using small remolded aggregates at various moisture contents and immersing them in an array of solutions of various pH and salinity. These arrays were photographed after 2 h to illustrate the effect of these variables on spontaneous dispersion.

    The data developed from these several studies were used to illustrate the effects of sodium, salinity, pH, mineralogy, and initial moisture content upon the spontaneous dispersion of soil materials.

    Keywords:

    clays, dispersions, salinity, pH, sodium, moisture content, laboratory tests, mineralogy, kaolinite, montmorillonite


    Paper ID: STP26990S

    Committee/Subcommittee: D18.02

    DOI: 10.1520/STP26990S


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