ASTM D4318-05

    Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils


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    1. Scope

    1.1 These test methods cover the determination of the liquid limit, plastic limit, and the plasticity index of soils as defined in Section on Terminology.

    1.2 Two methods for preparing test specimens are provided as follows: Wet preparation method, as described in . Dry preparation method, as described in . The method to be used shall be specified by the requesting authority. If no method is specified, use the wet preparation method.

    1.2.1 The liquid and plastic limits of many soils that have been allowed to dry before testing may be considerably different from values obtained on non-dried samples. If the liquid and plastic limits of soils are used to correlate or estimate the engineering behavior of soils in their natural moist state, samples should not be permitted to dry before testing unless data on dried samples are specifically desired.

    1.3 Two methods for determining the liquid limit are provided as follows: Method A, Multipoint test as described in Sections . Method B, One-point test as described in Sections . The method to be used shall be specified by the requesting authority. If no method is specified, use Method A.

    1.3.1 The multipoint liquid limit method is generally more precise than the one-point method. It is recommended that the multipoint method be used in cases where test results may be subject to dispute, or where greater precision is required.

    1.3.2 Because the one-point method requires the operator to judge when the test specimen is approximately at its liquid limit, it is particularly not recommended for use by inexperienced operators.

    1.3.3 The correlation on which the calculations of the one-point method are based may not be valid for certain soils, such as organic soils or soils from a marine environment. It is strongly recommended that the liquid limit of these soils be determined by the multipoint method.

    1.4 The plastic limit test is performed on material prepared for the liquid limit test.

    1.5 The liquid limit and plastic limit of soils (along with the shrinkage limit) are often collectively referred to as the Atterberg limits. These limits distinguished the boundaries of the several consistency states of plastic soils.

    1.6 The composition and concentration of soluble salts in a soil affect the values of the liquid and plastic limits as well as the water content values of soils (see Method D 2216). Special consideration should therefore be given to soils from a marine environment or other sources where high soluble salt concentrations may be present. The degree to which the salts present in these soils are diluted or concentrated must be given careful consideration.

    1.7 The methods described herein are performed only on that portion of a soil that passes the 425-m (No. 40) sieve. Therefore, the relative contribution of this portion of the soil to the properties of the sample as a whole must be considered when using these tests to evaluate properties of a soil.

    1.8 The values stated in acceptable metric units are to be regarded as the standard, except as noted below. The values given in parentheses are for information only.

    1.8.1 The standard units for the resilience tester covered in are inch-pound, not metric. The metric values given are for information only.

    1.9 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.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    C702 Practice for Reducing Samples of Aggregate to Testing Size

    D75 Practice for Sampling Aggregates

    D420 Guide for Site Characterization for Engineering Design and Construction Purposes

    D653 Terminology Relating to Soil, Rock, and Contained Fluids

    D1241 Specification for Materials for Soil-Aggregate Subbase, Base, and Surface Courses

    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)

    D3282 Practice for Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes

    D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction

    D4542 Test Methods for Pore Water Extraction and Determination of the Soluble Salt Content of Soils by Refractometer

    D4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction Materials Testing

    D6026 Practice for Using Significant Digits in Geotechnical Data

    E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves

    E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods

    E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method


    ICS Code

    ICS Number Code 93.020 (Earth works. Excavations. Foundation construction. Underground works)

    UNSPSC Code

    UNSPSC Code 11111501(Soil)


    Referencing This Standard
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    DOI: 10.1520/D4318-05

    Citation Format

    ASTM D4318-05, Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils, ASTM International, West Conshohocken, PA, 2005, www.astm.org

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