1、Designation: D4643 17Standard Test Method forDetermination of Water Content of Soil and Rock byMicrowave 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 of revision, the ye
2、ar 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 test method outlines
3、 procedures for determining thewater content of soils by incrementally drying soil in amicrowave oven.1.2 This test method can be used as a substitute for TestMethod D2216 when more rapid results are desired to expediteother phases of testing and slightly less accurate results areacceptable.1.3 When
4、 questions of accuracy between this test methodand Test Method D2216 arise, Test Method D2216 shall be thereferee method.1.4 This test method is applicable for most soil types. Forsome soils, such as those containing significant amounts ofhalloysite, mica, montmorillonite, gypsum or other hydratedma
5、terials, highly organic soils, or soils in which the pore watercontains significant amounts of dissolved solids (such as salt inthe case of marine deposits), this test method may not yieldreliable water content values due to the potential for heatingabove 110C or lack of means to account for the pre
6、sence ofprecipitated solids that were previously dissolved.1.5 The values stated in SI units are to be regarded as thestandard. Performance of the test method utilizing anothersystem of units shall not be considered non-conformance. Thesieve designations are identified using the “standard” system in
7、accordance with Specification E11, such as 2.0-mm and19-mm, followed by the “alternative” system of No. 10 and34-in., respectively, in parentheses.1.6 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026, unless otherwise
8、superseded by this standard.1.6.1 The procedures used to specify how data are collected/recorded or calculated in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider
9、material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the users objectives; and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consi
10、der significant digits used in analysismethods for engineering design.1.6.2 Significant digits are especially important if the watercontent will be used to calculate other relationships such asmoist mass to dry mass or vice versa, wet unit weight to dryunit weight or vice versa, and total density to
11、 dry density orvice versa. For example, if four significant digits are requiredin any of the above calculations, then the water content has tobe recorded to the nearest 0.1 %, for water contents below100 %. This occurs since 1 plus the water content (not inpercent) will have four significant digits
12、regardless of what thevalue of the water content is (below 100 %); that is, 1 plus0.1/100 = 1.001, a value with four significant digits. While, ifthree significant digits are acceptable, then the water contentcan be recorded to the nearest 1 %.1.7 This standard does not purport to address all of the
13、safety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. See Section 7.2. Referenced Documents2.1 ASTM Standards:2D653 Terminol
14、ogy Relating to Soil, Rock, and ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture) Content of Soil and Rock by MassD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD42
15、20 Practices for Preserving and Transporting SoilSamples1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.08 on Special andConstruction Control Tests.Current edition approved Feb. 1, 2017. Published February 2017. Or
16、iginallyapproved in 1987. Last previous edition approved in 2008 as D4643 08.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page ont
17、he ASTM website. DOI: 10.1520/D4643-08.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recogn
18、ized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1D4753 Guide for Evaluating, Selecting, and Specifying Bal-ances a
19、nd Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD5079 Practices for Preserving and Transporting Rock CoreSamples (Withdrawn 2017)3D6026 Practice for Using Significant Digits in GeotechnicalDataE11 Specification for Woven Wire Test Sieve Cloth and TestSieves3. Terminology3.
20、1 Definitions:3.1.1 For definitions of common technical terms used in thisstandard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 microwave heatinga process by which heat is in-duced within a material due to the interaction between dipolarmolecules of the materia
21、l and an alternating, high frequencyelectric field. Microwaves are electromagnetic waves with 1mm to 1 m wavelengths.4. Summary of Test Method4.1 A moist soil specimen is placed in a suitable containerand its mass is determined. It is then placed in a microwaveoven, subjected to an interval of dryin
22、g, and removed from theoven and its new mass is determined. This procedure isrepeated until the mass becomes nearly constant.4.2 The difference between the mass of the moist specimenand the dried specimen is used as the mass of water originallycontained in the specimen. The water content is determin
23、ed bydividing the mass of water by the dry mass of soil, multipliedby 100. For a given soil and sample size, the time to achieve aconstant dry mass can be noted and used as a minimum dryingtime for subsequent tests using the same size specimen of thesame soil.5. Significance and Use5.1 The water con
24、tent of a soil is used throughout geotech-nical engineering practice both in the laboratory and in thefield. The use of Test Method D2216 for water contentdetermination can be time consuming and there are occasionswhen a more expedient method is desirable. The use of amicrowave oven is one such meth
25、od.5.2 The principal objection to the use of the microwaveoven for water-content determination has been the possibilityof overheating the soil, thereby yielding a water content higherthan would be determined by Test Method D2216. While noteliminating this possibility, the incremental drying procedur
26、edescribed in this test method will minimize its effects. Somemicrowave ovens have settings at less than full power, whichcan also be used to reduce overheating.5.3 The behavior of a soil, when subjected to microwaveenergy, is dependent on its mineralogical compositions, and asa result no one proced
27、ure is applicable for all types of soil.Therefore, the procedure recommended in this test method ismeant to serve as a guide when using the microwave oven.5.4 This test method is best suited for minus 4.75-mm (No.4) sieve sized material. Larger size particles can be tested;however, care must be take
28、n because of the increased chance ofparticle shattering.5.5 The use of this method may not be appropriate whenhighly accurate results are required, or the test using the data isextremely sensitive to moisture variations.5.6 Due to the localized high temperatures that the specimenis exposed to in mic
29、rowave heating, the physical characteristicsof the soil may be altered. Degregation of individual particlesmay occur, along with vaporization or chemical transition. It istherefore recommended that samples used in this test methodnot be used for other tests subsequent to drying.NOTE 1The quality of
30、the results produced by this test method isdependent on the competence of the personnel performing it and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing. Users of this test metho
31、d are cautioned thatcompliance with Practice D3740 does not in itself ensure reliable results.Reliable results depend on many factors; Practice D3740 provides a meansof evaluating some of those factors.6. Apparatus6.1 Microwave OvenAmicrowave oven, preferably with avented chamber, is suitable. The r
32、equired size and power ratingof the oven is dependent on its intended use. Ovens withvariable power controls and input power ratings of about 700W have been found to be adequate for this use. Variable powercontrols are important and reduce the potential for overheatingof the test specimen.NOTE 2Micr
33、owave ovens equipped with built-in scales and computercontrols have been developed for use in drying soils. Their use iscompatible with this test method.6.2 BalancesAll balances must meet the requirements ofSpecification D4753 and this section. A Class GP2 balance of0.1 g readability is generally re
34、quired. However, the balanceused may be controlled by the number of significant digitsneeded (see 1.6).6.3 Specimen ContainersSuitable, microwave safe con-tainers made of a nonmetallic nonabsorbent material, resistantto thermal shock, and not subject to changes in mass or shapewhen subjected to repe
35、ated heating, cooling, or cleaning.Porcelain evaporating dishes and standard borosilicate glassdishes perform satisfactorily. Other containers, such as papercups or plates, also have been used satisfactorily; however,they may require pre-drying prior to use.6.4 Container Handling ApparatusA glove or
36、 holder,suitable for removing hot containers from the oven.6.5 Desiccator (optional)A desiccator cabinet or jar ofsuitable size containing silica gel, anhydrous calciumphosphate, or equivalent. It is preferable to use a desiccant thatchanges color to indicate that it needs reconstitution.6.6 Heat Si
37、nkAmaterial or liquid placed in the microwaveto absorb energy after the moisture has been driven from the3The last approved version of this historical standard is referenced onwww.astm.org.D4643 172test specimen. The heat sink reduces the possibility of over-heating the specimen and damage to the ov
38、en. Glass beakersfilled with water and materials that have a boiling point abovewater, such as nonflammable oils, have been used successfully.Moistened bricks have also been used.6.7 Stirring ToolsSpatulas, putty knives, and glass rodsfor cutting, breaking up, and stirring the test specimen beforean
39、d during the test. Short lengths of glass rods have been founduseful for stirring and may be left in the specimen containerduring testing, reducing the possibility of specimen loss due toadhesion to the stirring tool.7. Hazards7.1 Handle hot containers with a container holder. Some soiltypes can ret
40、ain considerable heat, and serious burns couldresult from improper handling.7.2 Suitable eye protection is recommended due to thepossibility of particle shattering during the heating, mixing, ormass determinations.7.3 Safety precautions supplied by the manufacturer of themicrowave should be observed
41、. Particular attention should bepaid to keeping the door sealing gasket and door interlocksclean and in good working condition.NOTE 3The use of a microwave oven for the drying of soils may beconsidered abusive by the manufacturers and constitute voiding ofwarranties. Microwave drying of soils contai
42、ning metallic materials maycause arcing in the oven. Highly organic soils and soils containing oils andcoal may ignite and burn during microwave drying. Continued operationof the oven after the soil has reached constant weight may also causedamage or premature failure of the microwave oven.NOTE 4Whe
43、n first introduced, microwave ovens were reported toaffect heart pacemakers, primarily because of the operating frequencies ofthe two devices. Since that time, pacemakers have been redesigned, andthe microwave oven is not regarded as the health hazard it once was.However, it may be advisable to post
44、 warnings that a microwave is in use.7.4 Highly organic soils and soils containing oil or othercontaminates may ignite into flames during microwave drying.Means for smothering flames to prevent operator injury or ovendamage should be available during testing. Fumes given offfrom contaminated soils o
45、r wastes may be toxic, and the ovenshould be vented accordingly.7.5 Due to the possibility of steam explosions, or thermalstress shattering porous or brittle aggregates, a covering overthe sample container may be appropriate to prevent operatorinjury or oven damage. A cover of heavy paper toweling h
46、asbeen found satisfactory for this purpose. This also preventsscattering of the test sample in the oven during the dryingcycle.7.6 Do not use metallic containers in a microwave ovenbecause arcing and oven damage may result.7.7 Observe manufacturers operating instructions wheninstalling and using the
47、 oven.7.8 The placement of the test specimen directly on the glassliner tray provided with some ovens is strongly discouraged.The concentrated heating of the specimen may result in theglass tray shattering, possibly causing injury to the operator.8. Samples8.1 Soil samples shall be preserved and tra
48、nsported inaccordance with Practice D4220 Section 8, Groups B, C, or D.Rock samples shall be preserved and transported in accordancewith Practice D5079 Section 7.5.2, Special Care Rock. Keepthe samples that are stored prior to testing in noncorrodibleairtight containers at a temperature between appr
49、oximately 3and 30C and in an area that prevents direct contact withsunlight. Disturbed samples in jars or other containers shall bestored in such a way to minimize moisture condensation on theinsides of the containers.8.2 The water content determination should be performed assoon as practical after sampling, especially if potentiallycorrodible containers (such as steel thin-walled tubes, paintcans, and the like) or unsealed sample bags are used.9. Test Specimen9.1 For water contents being determined as part of anotherASTM test method, the specimen selectio
