1、Designation: D4643 08D4643 17Standard Test Method forDetermination of Water (Moisture) Content of Soil and Rockby Microwave Oven Heating1This standard is issued under the fixed designation D4643; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 This t
3、est method outlines procedures for determining the water (moisture) content of soils by incrementally drying soil ina microwave oven.1.2 This test method can be used as a substitute for Test Method D2216 when more rapid results are desired to expedite otherphases of testing and slightly less accurat
4、e results are acceptable.1.3 When questions of accuracy between this test method and Test Method D2216 arise, Test Method D2216 shall be the refereemethod.1.4 This test method is applicable for most soil types. For some soils, such as those containing significant amounts of halloysite,mica, montmori
5、llonite, gypsum or other hydrated materials, highly organic soils, or soils in which the pore water containssignificant amounts of dissolved solids (such as salt in the case of marine deposits), this test method may not yield reliable watercontent values.values due to the potential for heating above
6、 110C or lack of means to account for the presence of precipitatedsolids that were previously dissolved.1.5 The values stated in SI units are to be regarded as the standard. No other units Performance of the test method utilizinganother system of units shall not be considered non-conformance. The si
7、eve designations are identified using the “standard” systemin accordance with Specification E11of measurement are included, such as 2.0-mm and 19-mm, followed by the “alternative”system of No. 10 and 34in this test method. -in., respectively, in parentheses.1.6 Refer to All observed and calculated v
8、alues shall conform to the guidelines for significant digits and rounding establishedin Practice D6026 for guidance concerning the use of significant figures. This is especially important if the water content will beused to calculate other relationships such as moist mass to dry mass or vice versa,
9、wet unit weight to dry unit weight or vice versa,and total density to dry density or vice versa. For example, if four significant digits are required in any of the above calculations,then the water content has to be recorded to the nearest 0.1 %. This occurs since 1 plus the water content (not in pe
10、rcent) will havefour significant digits regardless of what the value of the water content is; that is, 1 plus 0.1/100 = 1.001, a value with foursignificant digits. While, if three significant digits are acceptable, then the water content can be recorded to the nearest 1 %., unlessotherwise supersede
11、d by this standard.1.6.1 The procedures used to specify how data are collected/recorded or calculated in this standard are regarded as the industrystandard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do notconsider material v
12、ariation, purpose for obtaining the data, special purpose studies, or any considerations for the users objectives;and 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 signi
13、ficant digits used in analysis methods for engineering design.1.6.2 Significant digits are especially important if the water content will be used to calculate other relationships such as moistmass to dry mass or vice versa, wet unit weight to dry unit weight or vice versa, and total density to dry d
14、ensity or vice versa.For example, if four significant digits are required in any of the above calculations, then the water content has to be recorded tothe nearest 0.1 %, for water contents below 100 %. This occurs since 1 plus the water content (not in percent) will have foursignificant digits rega
15、rdless of what the value of the water content is (below 100 %); that is, 1 plus 0.1/100 = 1.001, a value withfour significant digits. While, if three significant digits are acceptable, then the water content can be recorded to the nearest 1 %.1 This test method is under the jurisdiction ofASTM Commi
16、ttee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.08 on Special and ConstructionControl Tests.Current edition approved Jan. 1, 2008Feb. 1, 2017. Published February 2008February 2017. Originally approved in 1987. Last previous edition approved in 20002008as D4643 00.D4643
17、 08.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior
18、 editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428
19、-2959. United States11.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to
20、use. See Section 7.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and Contained FluidsD2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by MassD3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/o
21、r Inspection of Soil and Rock as Used inEngineering Design and ConstructionD4220 Practices for Preserving and Transporting Soil SamplesD4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and ConstructionMaterials TestingD5079 Practices for Preser
22、ving and Transporting Rock Core Samples (Withdrawn 2017)3D6026 Practice for Using Significant Digits in Geotechnical DataE11 Specification for Woven Wire Test Sieve Cloth and Test Sieves3. Terminology3.1 Definitions:3.1.1 All definitions are in accordance with For definitions of common technical ter
23、ms used in this standard, refer toTerminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 microwave heatinga process by which heat is induced within a material due to the interaction between dipolar moleculesof the material and an alternating, high frequency electric field. Microwa
24、ves are electromagnetic waves with 1 mm to 1 mwavelengths.3.2.2 water (moisture) contentthe ratio, expressed as a percentage, of the mass of “pore” or “free” water in a given mass ofsoil to the mass of the solid particles.4. Summary of Test Method4.1 A moist soil specimen is placed in a suitable con
25、tainer and its mass is determined. It is then placed in a microwave oven,subjected to an interval of drying, and removed from the oven and its new mass is determined. This procedure is repeated untilthe mass becomes nearly constant.4.2 The difference between the mass of the moist specimen and the dr
26、ied specimen is used as the mass of water originallycontained in the specimen. The water content is determined by dividing the mass of water by the dry mass of soil, multiplied by100. For a given soil and sample size, the time to achieve a constant dry mass can be noted and used as a minimum drying
27、timefor subsequent tests using the same size specimen of the same soil.5. Significance and Use5.1 The water content of a soil is used throughout geotechnical engineering practice both in the laboratory and in the field. Theuse of Test Method D2216 for water content determination can be time consumin
28、g and there are occasions when a more expedientmethod is desirable. The use of a microwave oven is one such method.5.2 The principal objection to the use of the microwave oven for water-content determination has been the possibility ofoverheating the soil, thereby yielding a water content higher tha
29、n would be determined by Test Method D2216. While noteliminating this possibility, the incremental drying procedure described in this test method will minimize its effects. Somemicrowave ovens have settings at less than full power, which can also be used to reduce overheating.5.3 The behavior of a s
30、oil, when subjected to microwave energy, is dependent on its mineralogical compositions, and as a resultno one procedure is applicable for all types of soil. Therefore, the procedure recommended in this test method is meant to serveas a guide when using the microwave oven.5.4 This test method is bes
31、t suited for minus No. 4 4.75-mm (No. 4) sieve sized material. Larger size particles can be tested;however, care must be taken because of the increased chance of particle shattering.5.5 The use of this method may not be appropriate when highly accurate results are required, or the test using the dat
32、a isextremely sensitive to moisture variations.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website. DOI: 10.1520/
33、D4643-08.3 The last approved version of this historical standard is referenced on www.astm.org.D4643 1725.6 Due to the localized high temperatures that the specimen is exposed to in microwave heating, the physical characteristicsof the soil may be altered. Degregation of individual particles may occ
34、ur, along with vaporization or chemical transition. It istherefore recommended that samples used in this test method not be used for other tests subsequent to drying.NOTE 1The quality of the results produced by this test method is dependent on the competence of the personnel performing it and the su
35、itability ofthe equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing.Users of this test method are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable result
36、s depend on manyfactors; Practice D3740 provides a means of evaluating some of those factors.6. Apparatus6.1 Microwave OvenA microwave oven, preferably with a vented chamber, is suitable. The required size and power rating ofthe oven is dependent on its intended use. Ovens with variable power contro
37、ls and input power ratings of about 700 W have beenfound to be adequate for this use. Variable power controls are important and reduce the potential for overheating of the testspecimen.NOTE 2Microwave ovens equipped with built-in scales and computer controls have been developed for use in drying soi
38、ls. Their use is compatiblewith this test method.6.2 Balances, Balanceshaving a capacity of 2000 g or greater and meeting All balances must meet the requirements ofSpecification D4753 for a and this section. A Class GP2 balance of 0.1 g readability.readability is generally required. However,the bala
39、nce used may be controlled by the number of significant digits needed (see 1.6).6.3 Specimen ContainersSuitable Suitable, microwave safe containers made of a nonmetallic nonabsorbent material, resistantto thermal shock, and not subject to changes in mass or shape when subjected to repeated heating,
40、cooling, or cleaning. Porcelainevaporating dishes and standard borosilicate glass dishes perform satisfactorily. Other containers, such as paper cups or plates, alsohave been used satisfactorily; however, they may require pre-drying prior to use.6.4 Container Handling ApparatusA glove or holder, sui
41、table for removing hot containers from the oven.6.5 DesiccatorDesiccator (optional)A desiccator cabinet or jar of suitable size containing silica gel, anhydrous calciumphosphate, or equivalent. It is preferable to use a desiccant that changes color to indicate that it needs reconstitution.6.6 Heat S
42、inkA material or liquid placed in the microwave to absorb energy after the moisture has been driven from the testspecimen. The heat sink reduces the possibility of overheating the specimen and damage to the oven. Glass beakers filled withwater and materials that have a boiling point above water, suc
43、h as nonflammable oils, have been used successfully. Moistenedbricks have also been used.6.7 Stirring ToolsSpatulas, putty knives, and glass rods for cutting cutting, breaking up, and stirring the test specimen beforeand during the test. Short lengths of glass rods have been found useful for stirrin
44、g and may be left in the specimen container duringtesting, reducing the possibility of specimen loss due to adhesion to the stirring tool.7. Hazards7.1 Handle hot containers with a container holder. Some soil types can retain considerable heat, and serious burns could resultfrom improper handling.7.
45、2 Suitable eye protection is recommended due to the possibility of particle shattering during the heating, mixing, or massdeterminations.7.3 Safety precautions supplied by the manufacturer of the microwave should be observed. Particular attention should be paidto keeping the door sealing gasket and
46、door interlocks clean and in good working condition.NOTE 3The use of a microwave oven for the drying of soils may be considered abusive by the manufacturers and constitute voiding of warranties.Microwave drying of soils containing metallic materials may cause arcing in the oven. Highly organic soils
47、 and soils containing oils and coal may igniteand burn during microwave drying. Continued operation of the oven after the soil has reached constant weight may also cause damage or premature failureof the microwave oven.NOTE 4When first introduced, microwave ovens were reported to affect heart pacema
48、kers, primarily because of the operating frequencies of the twodevices. Since that time, pacemakers have been redesigned, and the microwave oven is not regarded as the health hazard it once was. However, it maybe advisable to post warnings that a microwave is in use.7.4 Highly organic soils and soil
49、s containing oil or other contaminates may ignite into flames during microwave drying. Meansfor smothering flames to prevent operator injury or oven damage should be available during testing. Fumes given off fromcontaminated soils or wastes may be toxic, and the oven should be vented accordingly.7.5 Due to the possibility of steam explosions, or thermal stress shattering porous or brittle aggregates, a covering over thesample container may be appropriate to prevent operator injury or oven damage. A cover of heavy paper toweling has been foundsatisfactory for thi
