1、Designation: D 4944 04Standard Test Method forField Determination of Water (Moisture) Content of Soil bythe Calcium Carbide Gas Pressure Tester1This standard is issued under the fixed designation D 4944; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method outlines procedures for determining thewater (moisture) content of
3、 soil by chemical reaction usingcalcium carbide as a reagent to react with the available waterin the soil producing a gas. A measurement is made of the gaspressure produced when a specified mass of wet or moist soilis placed in a testing device with an appropriate volume ofreagent and mixed.1.2 This
4、 test method is not intended as a replacement forTest Method D 2216; but as a supplement when rapid resultsare required, when testing is done in field locations, or wherean oven is not practical for use. Test Method D 2216 is to beused as the test method to compare for accuracy checks andcorrection.
5、1.3 This test method is applicable for most soils. Calciumcarbide, used as a reagent, reacts with water as it is mixed withthe soil by shaking and agitating with the aid of steel balls inthe apparatus. To produce accurate results, the reagent mustreact with all the water which is not chemically hydr
6、ated withsoil minerals or compounds in the soil. Some highly plasticclay soils or other soils not friable enough to break up may notproduce representative results because some of the water maybe trapped inside soil clods or clumps which cannot come incontact with the reagent. There may be some soils
7、 containingcertain compounds or chemicals that will react unpredictablywith the reagent and give erroneous results. Any such problemwill become evident as calibration or check tests with TestMethod D 2216 are made. Some soils containing compoundsor minerals that dehydrate with heat (such as gypsum)
8、whichare to have special temperature control with Test MethodD 2216 may not be affected (dehydrated) in this test method.1.4 This test method is limited to using calcium carbidemoisture test equipment made for 20 g, or larger, soil speci-mens and to testing soil which contains particles no larger th
9、anthe No. 4 Standard sieve size.1.5 This standard does not purport to address all of thesafety 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 limitati
10、ons prior to use. For specifichazards statements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil and RockD 3740 Practice for Minimum Requirements
11、for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionE 11 Specification for Wire-Cloth Sieves for Testing Pur-poses3. Terminology3.1 Definitions of terms used in this test method can befound in Terminology D 653.4. Summary of Test Method4
12、.1 A measured volume of calcium carbide, in excess of thatneeded to react with the water, is placed in the testing apparatusalong with two steel balls and a representative specimen of soilhaving all particles smaller than the No. 4 sieve size and havinga mass equal to that specified by the manufactu
13、rer of theinstrument or equipment. The apparatus is shaken vigorouslyin a rotating motion so the calcium carbide reagent can contactall the available water in the soil. Acetylene gas is producedproportionally to the amount of available water present. Theapparent water content is read from a pressure
14、 gage on theapparatus calibrated to read in percent water content for themass of soil specified.4.2 A calibration curve is developed for each instrument andeach soil type by plotting the pressure gage reading and thewater content determined from Test Method D 2216 usingrepresentative specimens of th
15、e soil. The calibration curve is1This test method is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.08 on Special andConstruction Control Tests.Current edition approved July 1, 2004. Published July 2004. Originally approvedin 1989. L
16、ast previous edition approved in 1998 as D 4944 98.2For 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 onthe ASTM website.1*A Summar
17、y of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.used to determine a corrected water content value for subse-quent tests on the same type of soil.5. Significance and Use5.1 The w
18、ater content of soil is used throughout geotechni-cal engineering practice, both in the laboratory and in the field.Results are sometimes needed within a short time period and inlocations where it is not practical to install an oven or totransport samples to an oven. This test method is used for the
19、seoccasions.5.2 The results of this test have been used for field controlof compacted embankments or other earth structures such as inthe determination of water content for control of soil moistureand dry density within a specified range.5.3 This test method requires specimens consisting of soilhavi
20、ng all particles smaller than the No. 4 sieve size.5.4 This test method may not be as accurate as otheraccepted methods such as Test Method D 2216. Inaccuraciesmay result because specimens are too small to properlyrepresent the total soil, from clumps of soil not breaking up toexpose all the availab
21、le water to the reagent and from otherinherent procedural, equipment or process inaccuracies. There-fore, other methods may be more appropriate when highlyaccurate results are required, or when the use of test results issensitive to minor variations in the values obtained.NOTE 1The quality of the re
22、sult produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of competentand objective testing/sampling/inspection. Users of thi
23、s standard arecautioned that compliance with Practice D 3740 does not in itself ensurereliable results. Reliable results depend on many factors; Practice D 3740provides a means of evaluating some of those factors.6. Apparatus6.1 Calcium Carbide Pressure Tester Set (including testingchamber with atta
24、ched pressure gage and a set of taredbalances), for water content testing of specimens having a massof at least 20 g, (10 g for the half measure required for wetterspecimens). Testers that use a smaller mass are available, butare considered too inaccurate for this standard. The testingchamber with p
25、ressure gage and the balances are calibrated asa set (see Section 8). A typical apparatus is shown in Fig. 1.6.2 Small Scoop, for measuring reagent.6.3 Two Steel Balls, (manufacturer supplied).6.4 Brush and Cloth, for cleaning and other incidentalitems.6.5 Sieve, No. 4 (4.75 mm), conforming to the r
26、equirementsof Specification E 11.6.6 Calcium Carbide Reagent, finely pulverized, of a gradethat will readily combine with the available sample moistureand is capable of producing acetylene gas in the amount of atleast 0.14 cubic meters/kg (2.25 cu ft/lb). It is best to purchasecalcium carbide in sma
27、ll containers with air tight replaceablelids, to store it in a dry place, to keep the lid on the containerat all times except when measuring out a portion for use in atest, and to use a complete container before opening a new one.Calcium carbide quality will deteriorate with time after itbecomes exp
28、osed to the atmosphere or any source of moisture.Periodic purchase of a new supply is recommended.6.7 Miscellaneous Clothing or Safety Equipment, such asgoggles to protect the operator (see 7.2).6.8 Equipment, as listed in Test Method D 2216, for per-forming comparison tests to make calibration curv
29、es.NOTE 2Calibration kits are available from manufacturers for testinggasket leakage and for calibrating the gage. Periodic checks for gasketleakage are recommended. The gasket should be changed when leakage issuspected. Gage calibration problems can usually be detected as theinstrument calibration
30、curves are made (see Section 8). When the gageneeds adjusting, any good quality calibrating gage can be used.7. Safety Hazards7.1 When combined with water, the calcium carbide reagentproduces a highly flammable or explosive acetylene gas.Testing should not be carried out in confined spaces or in the
31、vicinity of an open flame, embers or other source of heat thatcan cause combustion. Care should be exercised when releas-ing the gas from the apparatus to direct it away from the body.Lighted cigarettes, hot objects or open flames are extremelydangerous in the area of testing.7.2 As an added precaut
32、ion, the operator should use a dustmask, clothing with long sleeves, gloves and goggles to keepthe reagent from irritating the eyes, respiratory system, orhands and arms.7.3 Attempts to test excessively wet soils or improper use ofthe equipment, such as adding water to the testing chamber,could caus
33、e pressures to exceed the safe level for the apparatus.This may cause damage to the equipment and an unsafecondition for the operator.7.4 Care should be taken not to dispose or place a significantamount of the calcium carbide reagent where it may contactwater because it will produce an explosive gas
34、.8. Calibration8.1 The manufacturer-supplied equipment set, including thetesting chamber with attached gage and the balance scales, arecalibrated as a unit and paired together for the testing proce-dure.FIG. 1 Typical Calcium Carbide Gas Pressure Test Apparatus forWater Content of SoilD 4944 0428.2
35、Calibration curves must be developed for each equip-ment set using the general soil types to be tested and theexpected water content range of the soil. As new materials areintroduced, further calibration is needed to extend the curvedata for the specific instrument. If tests are made over a longperi
36、od of time on the same soil, a new calibration curve shouldbe made periodically, not exceeding 12 months. Before a newbatch of reagent is used for testing, two checkpoints shall becompared to the existing curve. If variation is exceeded bymore than 1.0 % of moisture, a new calibration curve shall be
37、established.8.3 Calibration curves are produced by selecting severalsamples representing the range of soil materials to be testedand having a relatively wide range of water content. Eachsample is carefully divided into two specimens by quarteringprocedures or use of a sample splitter. Taking care to
38、 not loseany moisture, one specimen is tested in accordance with theprocedure of this test method (see 10.1-10.6) without using acalibration curve, and the other specimen is tested in accor-dance with Test Method D 2216.8.4 The results of the oven dry water content determined byTest Method D 2216 fr
39、om all the selected samples are plottedversus the gage reading from the calcium carbide tester for thecorresponding test specimen pair. A best fit curve is plottedthrough the points to form a calibration curve for each soiltype. Comparisons should be relatively consistent. A widescatter in data indi
40、cates that either this test method or TestMethod D 2216 is not applicable to the soil or conditions. Fig.2 shows a typical calibration curve.8.5 A comparison of this test method with Test MethodD 2216 for a given soil can be made by using the calibrationcurve. Points that plot off the curve indicate
41、 deviations.Standard and maximum deviations can be determined ifdesired.9. Sampling9.1 For water content testing being done in conjunction withanother method (such as Test Method D 2216), the require-ments for sample and test specimen selection and handling inthe other standard shall govern.9.2 Equi
42、pment limitations require the use of specimenssmaller than is recommended to properly represent the totalsoil. Extra care must be exercised to select specimens that arerepresentative of the soil.9.3 Specimens are to contain only soil particles smaller thanthe No. 4 Standard sieve size.10. Procedure1
43、0.1 Remove the cap from the testing chamber of theapparatus and place the recommended amount of calciumcarbide reagent along with the two steel balls into the testingchamber. Most equipment built to test 20-g samples requiresFIG. 2 Typical Calibration CurveD 4944 043approximately 22 g of reagent (me
44、asured using the suppliedscoop, which is filled two times).10.2 Use the balance to obtain a specimen of soil that has amass recommended for the equipment and contains particlessmaller than the No. 4 sieve size. One-half specimen sizeshould be used when the water content is expected to exceedthe limi
45、ts of the gage on the gas pressure chamber or when itactually reaches or exceeds the gage limit in any test (see 10.6).10.3 Place the soil specimen in the testing chamber cap;then, with the apparatus in the horizontal position, insert thecap in the testing chamber and tighten the clamp to seal the c
46、apto the unit. Take care that no calcium carbide comes in contactwith the soil until a complete seal is achieved.NOTE 3The soil specimen may be placed in the chamber with thecalcium carbide in the cap if desired.10.4 Raise the apparatus to the vertical (upright) position sothat the contents of the c
47、ap fall into the testing chamber. Strikethe side of the apparatus with an open hand to assure that all thematerial falls out of the cap.10.5 Shake the apparatus vigorously with a rotating motionso that the steel balls roll around the inside circumference andimpact a grinding effect on the soil and r
48、eagent. This motionalso prevents the steel balls from striking the orifice that leadsto the pressure gage. Shake the apparatus for at least 1 min forsands, increasing the time for silts, and up to 3 min for clays.Some highly plastic clay soils may take more than 3 min.Periodically check the progress
49、 of the needle on the pressuregage dial. Allow time for the needle to stabilize as the heatfrom the chemical reaction is dissipated.10.6 When the pressure gage dial needle stops moving, readthe dial while holding the apparatus in the horizontal position.If the dial goes to the limit of the gage, 10.1-10.6 should berepeated using a new specimen having a mass half as large asthe recommended specimen. When a half size specimen isused, the final dial reading is multiplied by two for use with thecalibration curve.10.7 Record the final pressure gage dial reading and use theappropriate
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