Astm 422

Designation: D 422 – 63 (Reapproved 1998)

Standard Test Method for

Particle-Size Analysis of Soils1
This standard is issued under the fixed designation D 422; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e)indicates an editorial change since the last revision or reapproval.

1. Scope 1.1 This test method covers the quantitative determination of the distribution of particle sizes in soils. The distribution of particle sizes larger than 75 µm (retained on the No. 200 sieve) is determined by sieving, while the distribution of particle sizes smaller than 75 µm is determined by a sedimentation process,using a hydrometer to secure the necessary data (Note 1 and Note 2).
NOTE 1—Separation may be made on the No. 4 (4.75-mm), No. 40 (425-µm), or No. 200 (75-µm) sieve instead of the No. 10. For whatever sieve used, the size shall be indicated in the report. NOTE 2—Two types of dispersion devices are provided: (1) a highspeed mechanical stirrer, and (2) air dispersion. Extensive investigationsindicate that air-dispersion devices produce a more positive dispersion of plastic soils below the 20-µm size and appreciably less degradation on all sizes when used with sandy soils. Because of the definite advantages favoring air dispersion, its use is recommended. The results from the two types of devices differ in magnitude, depending upon soil type, leading to marked differences in particle sizedistribution, especially for sizes finer than 20 µm.

stirring device in which a suitably mounted electric motor turns a vertical shaft at a speed of not less than 10 000 rpm without load. The shaft shall be equipped with a replaceable stirring paddle made of metal, plastic, or hard rubber, as shown in Fig. 1. The shaft shall be of such length that the stirring paddle will operate not less than3⁄4 in. (19.0 mm) nor more than 11⁄2 in. (38.1 mm) above the bottom of the dispersion cup. A special dispersion cup conforming to either of the designs shown in Fig. 2 shall be provided to hold the sample while it is being dispersed. 3.2.2 Apparatus B shall consist of an air-jet dispersion cup5 (Note 3) conforming to the general details shown in Fig. 3 (Note 4 and Note 5).
NOTE 3—The amount of airrequired by an air-jet dispersion cup is of the order of 2 ft3/min; some small air compressors are not capable of supplying sufficient air to operate a cup. NOTE 4—Another air-type dispersion device, known as a dispersion tube, developed by Chu and Davidson at Iowa State College, has been shown to give results equivalent to those secured by the air-jet dispersion cups. When it is used, soaking ofthe sample can be done in the sedimentation cylinder, thus eliminating the need for transferring the slurry. When the air-dispersion tube is used, it shall be so indicated in the report. NOTE 5—Water may condense in air lines when not in use. This water must be removed, either by using a water trap on the air line, or by blowing the water out of the line before using any of the air for dispersionpurposes.

2. Referenced Documents 2.1 ASTM Standards: D 421 Practice for Dry Preparation of Soil Samples for Particle-Size Analysis and Determination of Soil Constants2 E 11 Specification for Wire-Cloth Sieves for Testing Purposes3 E 100 Specification for ASTM Hydrometers4 3. Apparatus 3.1 Balances—A balance sensitive to 0.01 g for weighing the material passing a No. 10 (2.00-mm) sieve, and abalance sensitive to 0.1 % of the mass of the sample to be weighed for weighing the material retained on a No. 10 sieve. 3.2 Stirring Apparatus—Either apparatus A or B may be used. 3.2.1 Apparatus A shall consist of a mechanically operated
1 This test method is under the jurisdiction of ASTM Committee D-18 on Soil and Rock and is the direct responsibility of Subcommittee D18.03 on Texture,...