1、Designation: D4944 11D4944 18Standard Test Method forField Determination of Water (Moisture) Content of Soil bythe Calcium Carbide Gas Pressure Tester1This standard is issued under the fixed designation D4944; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the case 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.1. Scope*1.1 This test method outlines procedures for determining the water (moisture) cont
3、ent of soil by chemical reaction using calciumcarbide as a reagent to react with the available water in the soil producing a gas. A measurement is made of the gas pressureproduced when a specified mass of wet or moist soil is placed in a testing device with an appropriate volume of reagent and mixed
4、.1.2 This test method is not intended as a replacement for Test Method D2216; but as a supplement when rapid results arerequired, when testing is done in field locations, or where an oven is not practical for use. Test Method D2216 is to be used asthe test method to compare for accuracy checks and c
5、orrection.1.3 This test method is applicable for most soils. Calcium carbide, used as a reagent, reacts with water as it is mixed with thesoil by shaking and agitating with the aid of steel balls in the apparatus. To produce accurate results, the reagent must react withall the water which is not che
6、mically hydrated with soil minerals or compounds in the soil. Some highly plastic clay soils or othersoils not friable enough to break up may not produce representative results because some of the water may be trapped inside soilclods or clumps which cannot come in contact with the reagent. There ma
7、y be some soils containing certain compounds orchemicals that will react unpredictably with the reagent and give erroneous results. Any such problem will become evident ascalibration or check tests with Test Method D2216 are made. Some soils containing compounds or minerals that dehydrate withheat (
8、such as gypsum) which are to have special temperature control with Test Method D2216 may not be affected (dehydrated)in this test method.1.4 This test method is limited to using calcium carbide moisture test equipment made for 20 g, or larger, soil specimens andto testing soil which contains particl
9、es no larger than the No. 4 4.75 mm (No. 4) Standard sieve size.1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this Theinch-pound units given in parentheses are mathematical conversions, which are provided for information purposes only
10、 and arenot considered standard.1.5.1 Cited sieve sizes are the standard sieve sizes given in Table 1 of Specification E11.1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in PracticeD6026 unless superseded by this standard.1.6.1
11、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 variation, purpose for obt
12、aining the data, special purpose studies, or any considerations for the users objectives;it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It isbeyond the scope of this standard to consider significant digits used in analyti
13、cal methods for engineering design.1.7 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 safety, health, and healthenvironmental practices and determine theapplic
14、ability of regulatory limitations prior to use. For specific hazards statements, see Section 7.1.8 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Stand
15、ards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.1 This test method is under the jurisdiction ofASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.08 on Special and ConstructionControl Tests.Curre
16、nt edition approved Nov. 1, 2011Feb. 15, 2018. Published December 2011February 2018. Originally approved in 1989. Last previous edition approved in 20042011as D4944 04.11. DOI: 10.1520/D4944-11.10.1520/D4944-18.This document is not an ASTM standard and is intended only to provide the user of an ASTM
17、 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 editions as appropriate. In all cases only the current versionof the standard as published b
18、y 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 19428-2959. United States12. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to
19、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/or Inspection of Soil and Rock as Used inEngineering Design and ConstructionD4753 Guide for
20、Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and ConstructionMaterials TestingD6026 Practice for Using Significant Digits in Geotechnical DataE11 Specification for Woven Wire Test Sieve Cloth and Test SievesE177 Practice for Use of the Terms Precision and
21、 Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 DefinitionsDefinitions:3.1.1 Definitions of terms used in this test method can be found in Terminology D653.4. Summary of Test Method4.1 A measured volume of c
22、alcium carbide, in excess of that needed to react with the water, is placed in the testing apparatusalong with two steel balls and a representative specimen of soil having all particles smaller than the No. 4 4.75 mm (No. 4) sievesize and having a mass equal to that specified by the manufacturer of
23、the instrument or equipment. The apparatus is shakenvigorously in a rotating motion so the calcium carbide reagent can contact all the available water in the soil. Acetylene gas isproduced proportionally to the amount of available water present. The apparent water content is read from a pressure gau
24、ge onthe apparatus calibrated to read in percent water content for the mass of soil specified.4.2 Acalibration curve is developed for each instrument and each soil type by plotting the pressure gauge reading and the watercontent determined from Test Method D2216 using representative specimens of the
25、 soil. The calibration curve is used to determinea corrected water content value for subsequent tests on the same type of soil.5. Significance and Use5.1 The water content of soil is used throughout geotechnical engineering practice, both in the laboratory and in the field.Results are sometimes need
26、ed within a short time period and in locations where it is not practical to install an oven or to transportsamples to an oven. This test method is used for these occasions.5.2 The results of this test have been used for field control of compacted embankments or other earth structures such as in thed
27、etermination of water content for control of soil moisture and dry density within a specified range.5.3 This test method requires specimens consisting of soil having all particles smaller than the No. 4 4.75 mm (No. 4) sievesize.5.4 This test method may not be as accurate as other accepted methods s
28、uch as Test Method D2216. Inaccuracies may resultbecause specimens are too small to properly represent the total soil, from clumps of soil not breaking up to expose all the availablewater to the reagent and from other inherent procedural, equipment or process inaccuracies. Therefore, other methods m
29、ay be moreappropriate when highly accurate results are required, or when the use of test results is sensitive to minor variations in the valuesobtained.NOTE 1The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of thee
30、quipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objectivetesting/sampling/inspection. Users of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliableresults
31、 depend on many factors; Practice D3740 provides a means of evaluating some of those factors.6. Apparatus6.1 Calcium Carbide Pressure Tester Set Including:6.1.1 Testing chamber with attached pressure gauge.NOTE 2The testing chamber with pressure gauge and the balances are calibrated as a set (see Se
32、ction 8).6.1.2 A set of tared manual balances or portable electronic balance meeting the requirements of a GP2 of Specification D4753.NOTE 2Testers that use a smaller mass are available, but are considered too inaccurate for this standard. The testing chamber with pressure gaugeand the balances are
33、calibrated as a set (see Section 8). A typical apparatus is shown in Fig. 1.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. ForAnnual Book ofASTM Standardsvolume information, refer to the standards Document Summary page on the
34、ASTM website.D4944 1826.1.3 Carrying case.6.1.4 Typical apparatus configurations are shown in Fig. 1. The typical pressure chamber is constructed of a die-cast aluminumthat is approximately 20 cm (8 in.) deep and 15 cm (6 in.) in diameter at its widest dimension. It has a removable cap on one endand
35、 an integrated pressure gauge on the other end.NOTE 3Testers that use a smaller mass are available, but cannot be used with this standard given the inaccuracies outlined in 5.4.6.2 Small Scoop, for measuring reagent.6.3 Two Steel Balls, (manufacturer supplied). The two solid steel balls are included
36、 and matched to the specific gauge. They areapproximately 30 mm (1.2 in.) in diameter and weigh approximately 130 grams (4.6 oz).6.4 Brush and Cloth, for cleaning and other incidental items.6.5 Sieve, No. 4 (4.75 mm),4.75 mm (No. 4), conforming to the requirements of Specification E11.6.6 Calcium Ca
37、rbide Reagent, finely pulverized, of a grade that will readily combine with the available sample moisture andis capable of producing acetylene gas in the amount of at least 0.14 cubic meters/kg (2.25 cu ft/lb). It is bestrecommended topurchase calcium carbide in manufactured expressly for use in moi
38、sture testing equipment and in small containers with air tightreplaceable lids, to store it in a dry place, to keep the lid on the container at all times except when measuring out a portion foruse in a test, and to use a complete container before opening a new one. Calcium carbide quality will deter
39、iorate with time afterit becomes exposed to the atmosphere or anya source of moisture. Periodic purchase of a new supply is recommended.6.7 Miscellaneous Clothing or Safety Equipment, such as goggles to protect the operator (see 7.2).6.8 Equipment, as listed in Test Method D2216, for performing comp
40、arison tests to make calibration curves.NOTE 3Calibration kits are available from manufacturers for testing gasket leakage and for calibrating the gauge. Periodic checks for gasket leakageare recommended. The gasket should be changed when leakage is suspected. Gauge calibration problems can usually
41、be detected as the instrumentcalibration curves are made (see Section 8). When the gauge needs adjusting, any good quality calibrating gauge can be used.7. Safety Hazards7.1 When combined with water, the calcium carbide reagent produces a highly flammable or explosive acetylene gas. Testingshould no
42、t be carried out in confined spaces or in the vicinity of an open flame, embers or other source of heat that can causecombustion. Care should be exercised when releasing the gas from the apparatus to direct it away from the body. Lighted cigarettes,hot objects or open flames are extremely dangerous
43、in the area of testing.7.2 As an added precaution, the operator should use a dust mask, clothing with long sleeves, gloves and goggles to keep thereagent from irritating the eyes, respiratory system, or hands and arms.7.3 Attempts to test excessively wet soils or improper use of the equipment, such
44、as adding water to the testing chamber, couldcause pressures to exceed the safe level for the apparatus. This may cause damage to the equipment and an unsafe condition forthe operator.7.4 Care should be taken not to dispose or place a significant amount of the calcium carbide reagent where it may co
45、ntact waterbecause it will produce an explosive gas.FIG. 1 Typical Calcium Carbide Gas Pressure Test Apparatus for Water Content of SoilFIG. FIG. 1a (left) Apparatus Set with Manual Tared Balance FIG. FIG. 1b(right) Apparatus Set with Portable Electronic BalanceD4944 1837.5 Calcium carbide is classi
46、fied as a hazardous material and the user should conform to appropriate regulations regarding theuse, storage, handling and transportation of calcium carbide.8. Calibration8.1 The manufacturer-supplied equipment set, including the testing chamber with attached gauge and the balance scales, arecalibr
47、ated as a unit and paired together for the testing procedure.8.2 Calibration curves must be developed for each equipment set using the general soil types to be tested and the expected watercontent range of the soil. As new materials are introduced, further calibration is needed to extend the curve d
48、ata for the specificinstrument. If tests are made over a long period of time on the same soil, a new calibration curve should be made periodically, notexceeding 12 months. Before a new batch of reagent is used for testing, two checkpoints at least 3 dial readings apart shall becompared to the existi
49、ng curve. If variation is exceeded by more than 1.0 % of moisture, a new calibration curve shall beestablished.8.3 Calibration curves are produced by selecting several samples representing the range of soil materials to be tested and havinga relatively wide range of water content. Each sample is carefully divided into two specimens by quartering procedures or use ofa sample splitter. Taking care to not lose any moisture, one specimen is tested in accordance with the procedure of this test method(see 10.1 10.6) without using a calibration curve, and the other specimen is
