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1.1 This test method allows for determination of expansion potential of soils when inundated with distilled water.2 This test method measures a qualitative index property of the soil rather than a design parameter to be used for calculation of the actual amount of expansion. The expansion index, EI, provides an indication of swelling potential of a soil.

1.2 This test method provides a simple, yet sensitive, method for evaluation of expansion potential of soils for practical engineering applications using an index parameter.

1.3 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this standard.

1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026, unless superseded by this test method.

1.5 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.

1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 The expansion index, EI, value is used by engineers and other professionals as an indicator of the soil’s swelling potential. It may also be used to determine the suitability of a soil to satisfy requirements set by specifying agencies.

5.2 The EI test is not used to duplicate any particular field conditions such as soil density, water content, loading, in-place soil structure, or soil water chemistry. However, consistent test conditions are used in preparation of compacted specimens such that direct correlation of data can be made.

5.3 Based on experience with expansive soils, the recommended qualitative classification of potential expansion in a soil based on EI is provided in Table 1.

5.4 The measurement of the magnitude of one-dimensional wetting-induced swell or collapse (hydrocompression) under different vertical (axial) pressures, as well as the magnitude of swell pressure and the magnitude of free swell, and also the determination of data for stress-induced compression following wetting-induced swell or collapse are covered by Test Methods D4546. The ability to test intact specimens for measuring one-dimensional wetting-induced swell or collapse is also covered in Methods D4546.