5.1 The rapid method is performed to quickly evaluate percent compaction and variation from optimum water content of soils used in construction without knowing the value of field water content at the time of the test.

5.1.1 Test results are usually determined within 1 to 2 h from the start of the test.

5.1.2 The value of percent compaction obtained using the rapid method will be the same as the percent compaction calculated using dry density values.

5.1.3 The value of the difference between field water content and optimum water content will be approximate, but will be within ±0.1 to 0.2 percentage point of the difference calculated once the field water content is known.

5.2 Test results may be used to determine if the compacted material meets density and water content control values that are specified as a percentage of a standard maximum density and optimum water content such as determined in Method A of Test Methods D698. A three-point compaction curve is used in place of the four- or five-point curve required in Test Methods D698.

5.3 This test method is based on the assumption that a three-point compaction curve is a parabola at the section of the curve close to optimum water content so that the peak point of the curve can be determined mathematically. This assumption results in the major difference between this test method and obtaining the maximum density and optimum water content from a full five-point compaction curve.

5.4 Once the field ovendry water content has been determined in accordance with Test Methods D2216, the values of dry density, dry unit weight, and optimum water content can be calculated (see Note 1).

5.5 This test method can also be used for foundation or borrow area material to compare in-place dry density and unit weight and water content to laboratory maximum dry density and unit weight and optimum water content.

5.6 This test method has the advantage that the maximum density value can be obtained on the same soil excavated during the in-place density test.

Note 1: Since there is no need to immediately determine the water contents of material from the in-place density test or the laboratory compaction points, use of rapid water content determinations such as microwave, direct heat, nuclear, etc., is not needed. However, if desired, the percent compaction and variation from optimum water content may be determined using dry density values based on rapid water content test methods. Using three compaction points and determining the maximum density mathematically would still apply. However, the rapid water content methods may give results that differ from the accepted oven-dried water content values and will lengthen the time of performing this test method.

Note 2: The quality of the results produced by this test method is dependent on the competence of the personnel performing it and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users of these test methods are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable testing depends on many factors; Practice D3740 provides a means of evaluating some of those factors.

1.1 This test method describes the procedure for rapidly determining the percent compaction and the variation from optimum water content of an in-place soil for use in controlling construction of compacted earth. These values are obtained by developing a three-point compaction curve at the same water content as the in-place soil without knowing the value of the water content. The soil used for the compaction curve is normally the same soil removed from the in-place density test. For the remainder of this designation, this test method will be referred to as the rapid method.

1.2 This test method is normally performed for soils containing more than 15 % fines (minus 75-µm (No. 200) sieve size).

1.3 When gravel-size particles are present in the soil being tested, this test method is limited to a comparison of the minus 4.75-mm (No. 4) sieve-size fraction of the in-place density material to a laboratory compaction test of minus 4.75-mm (No. 4) sieve-size material (Method A of Test Methods D698). Subject to the limitations of Practice D4718, this test method is also applicable to comparisons of other sieve-size fractions (for example, Method C of Test Methods D698) or other compactive efforts (for example, Test Methods D1557) if new water content adjustment values are determined (see 6.1 and Appendix X2).

1.4 Units—The values stated in SI units are to be regarded as standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this standard.

1.4.1 The use of balances or scales recording pounds of mass (lbm), or the recording of density in pounds of mass per cubic foot (lbm/ft³) should not be regarded as nonconformance with this test method.

1.4.2 The sieve designations are identified using the “standard” system in accordance with Specification E11, such as 25-mm and 75-μm, followed by the “alternative” system of 1-in. and No. 200, respectively, in parentheses.

1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 unless superseded by this standard.

1.5.1 For purposes of comparing, a measured or calculated value(s) with specified limits, the measured or calculated value(s) shall be rounded to the nearest decimal or significant digits in the specified limits.

1.5.2 The procedures used to specify how data are collected, recorded or calculated in this standard are regarded as the industry standard. In addition they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analytical methods for engineering design.

1.6 This standard does not purport to address all of the safety problems, 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. See Section 9.