1、Designation: D 4373 02 (Reapproved 2007)Standard Test Method for Rapid Determination ofCarbonate Content of Soils1This standard is issued under the fixed designation D 4373; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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. Scope1.1 This test method covers the determination of carbonatecontent of soils and soft rock which can be readily brokendo
3、wn by mechanical effort. It is a gasometric method thatutilizes a simple portable apparatus. Results should be clearlystated as the calcite equivalent in percent because differentcarbonate species cover a wide range of percent calciteequivalent as shown below for a number of carbonates:Species Catio
4、nCalciteEquivalent, %Magnesite Mg 117.0Dolomite Ca, Mg 108.6Calcite Ca 100.0Aragonite Ca 100.0Rhodocrosite Mn 87.1Siderite Fe 86.4Smithsonite Zn 79.8Witherite Ba 50.7Cerrusite Pb 37.5For example, a 100 % dolomite would be expected to yield108.6 % calcite equivalent while 100 % siderite would yieldon
5、ly 86.4 % calcite equivalent. Calcite and aragonite reactionswill typically complete within about 10 min. This method doesnot distinguish between the carbonate species and such deter-mination must be made using quantitative chemical analysismethods such as atomic absorption.1.2 The values stated in
6、SI units are to be regarded as thestandard.1.3 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 6026.1.4 The method used to specify how data are collected,calculated, or recorded in this standard is not directly related to
7、the accuracy to which the data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.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
8、this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificprecaution statements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2C25 Test Methods for Chemical Analysis of Limestone,Quicklime, and
9、Hydrated LimeD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Sta
10、ndard Masses for Use in Soil, Rock, andConstruction Materials TestingD 6026 Practice for Using Significant Digits in Geotechni-cal DataE 145 Specification for Gravity-Convection and Forced-Ventilation Ovens3. Terminology3.1 For definitions of terms used in this standard seeTerminology D 653.4. Summa
11、ry of Test Method4.1 The carbonate content (calcite equivalent) of soil isdetermined by treating a 1-g dried soil specimen with hydro-chloric acid (HCl) in an enclosed reaction cylinder (reactor).Carbon dioxide (CO2) gas is evolved during the reactionbetween the acid and carbonate fraction of the sp
12、ecimen. Theresulting pressure generated in the closed reactor is propor-tional (see Fig. 1) to the calcite equivalent of the specimen.This pressure is measured with a suitable pressure gauge, orequivalent pressure-measuring device, that is pre-calibratedwith reagent grade calcium carbonate.5. Signif
13、icance and Use5.1 This test method is used to determine the presence andquantity of carbonate in a soil specimen in terms of the calciteequivalent. The method is generally intended for use as an1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct respons
14、ibility of Subcommittee D18.06 on Physical-ChemicalInteractions of Soil and Rock.Current edition approved Sept. 1, 2007. Published October 2007. Originallyapproved in 1984. Last previous edition approved in 2002 as D 4373 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon
15、tact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.index of approximate
16、carbonate content to assist with charac-terizing marine soils. Other test methods exist (such as MethodC25) to evaluate calcium carbonate equivalency for purposesof characterizing use of calcareous materials as soil modifiersor agricultural lining materials.5.1.1 Calcium carbonates (CaCO3) are known
17、 cementingagents, are water soluble at pH 7, and are soft on the Mohsscale compared to other soil minerals.5.2 This test method has limitations as follows:5.2.1 If low carbonate contents (calcite equivalents) aremeasured, the user does not know whether the soil is low incarbonate content or contains
18、 cerrusite, witherite, etc., whichare carbonate species whose reactions with hydrochloric acidare either very slow or limited.5.2.2 Testing times may be extensive (longer than 1 h) forsome carbonate species (such as dolomite) if calcite equiva-lents within about 1 % are required.5.2.3 The effects of
19、 specimen grain size, duration of testing,pH and specimen mass are discussed in the literature.3NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecrite
20、ria of Practice D 3740 are generally considered capable of competentand objective testing/sampling/inspection, etc. Users of this standard arecautioned that compliance with Practice D 3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D 3740provides a m
21、eans of evaluating some of those factors.6. Apparatus6.1 Rapid Carbonate AnalyzerA schematic drawing ofthe rapid carbonate analyzer is shown in Fig. 2. The basiccomponents of this apparatus include:6.1.1 Reaction Cylinder (Reactor), with threaded cap andO-ring seal to enclose the cylinder. A clear p
22、lastic cylinderallows viewing of effervescent reaction.6.1.2 Pressure Gauge (Bourdon Tube-type or ElectronicPressure Transducer), 70 kPa (10 psi), with an accuracy of0.25 %, and a readability of 0.5 kPa (0.1 psi).6.1.3 Acid Container, of clear plastic with a bail handle tohold 20 mL of acid. Optiona
23、lly, in lieu of the acid container,use a soil container of clear plastic to hold1gofsoil, withapproximate dimensions of 25 mm diameter by 6 mm highwith a nominal 4 mm notch down the side of the soil container.Acid added to dry soil often causes considerable splashing anduse of soil container reduces
24、 splashing before reactor is sealed.6.1.4 Pressure Relief Valve, for safe release of CO2gaspressure.6.2 BalanceThe balance must meet the requirements ofSpecification D 4753 and this section. A Class GP1 balancewith a minimum capacity of 100 g and a readability of 0.01 gis required to measure the soi
25、l mass.6.3 Drying Oven, thermostatically-controlled, preferably ofthe forced-draft type, meeting the requirements of Specifica-tion E 145 and capable of maintaining a uniform temperatureof 110 6 5C throughout the drying chamber.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in
26、 all tests. Unless otherwise indicated, it is intended that3Demars, K.R., Chaney, R.C., Richter, J.A., “The Rapid Carbonate Analyzer,”Geotechnical Testing Journal, ASTM, Vol. 6, No. 1, March 1981, pp. 3034.FIG. 1 Typical Calibration Curve for 0.374L Test Cell and 70 kPa (10 psi) Pressure GageD 4373
27、02 (2007)2all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use wit
28、hout lessening theaccuracy of the determination.7.2 Calcium Carbonate (CaCO3).7.3 Hydrochloric Acid (HCl), (in about 1 N solution)Prepare 1 L of about 1 N solution by placing 80 mL ofconcentrated, reagent grade HCl in about 800 mL of commer-cial grade distilled water in a 1L volumetric flask Dilute
29、to themark with commercial grade distilled water. Store in polyeth-ylene bottle. Faster reaction times may achieved by increasingthe concentration to higher normal solutions (up to about 3 Nsolution). Hydrochloric acid is also commercially available ina1N solution.8. Safety Precautions8.1 Use care i
30、n handling the hydrochloric acid so that noacid is spilled on either skin or clothing. If acid contacts theskin or eyes, immediately flush with large quantities of water.Process concentrated hydrochloric acid beneath a laboratoryhood or in a well-ventilated area to reduce the inhalation offumes.8.2
31、The pressure relief valve of the carbonate analyzershould be opened following each test to dissipate gas pressureso that the cap can be safely removed.9. Test Specimens9.1 Select 5 to 10-g specimens from a core or surface grabsample. Oven dry at 110 6 5C for a period of 12 to 24 h.Pulverize the enti
32、re sample with a mortar and pestle (orhammer) until all of the particles pass a No. 40 (0.425-mm) orfiner sieve. Smaller particles react faster than larger particleswhen treated with acid.10. Calibration10.1 Calibration is accomplished by using reagent gradeCaCO3to obtain the relationship between th
33、e mass of CaCO3and the pressure generated in the constant volume reactor. Eachcarbonate analyzer and pressure gage is individually calibrated.Prepare five sets of duplicate specimens with the followingmasses of CaCO3:10.1.1 Set 1Two specimens at 0.2 6 0.01 g, that is,analogous to 20 % calcium carbon
34、ate for a test specimen of 1g.10.1.2 Set 2Two specimens at 0.4 6 0.01 g.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryCh
35、emicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D 4373 02 (2007)310.1.3 Set 3Two specimens at 0.6 6 0.01 g.10.1.4 Set 4Two specimens at 0.8 6 0.01 g.10.1.5 Set 5Two specimens at 1.0 6 0.01 g.10
36、.2 Place the specimen into the reactor (using soil con-tainer if available). Add 20 6 2 mL of acid solution into thereactor (using acid container if available). Seal the reactor withtop cap and close the pressure relief valve. Tilt the reactor toinitiate reaction between the acid and specimen. Mix t
37、hecontents by swirling. If available, place the reactor on amechanical shaker for the duration of the test.10.3 It is very rare that even calcite powder will completelyreact in less than 10 minutes. Therefore, it is essential tomonitor the pressure to verify that the reaction is complete(pressure st
38、abilized) and to confirm that the reactor is properlysealed (pressure does not decrease). Record the pressurereading to the nearest 0.5 kPa (0.1 psi) or better.10.4 Open the pressure release valve and remove the reactortop cap. Dispose of the contents and rinse the reactor withdistilled water.10.5 R
39、epeat 10.2 through 10.4 for remaining calibrationspecimens.10.6 Data reduction may use any one or all of the following:10.6.1 Make a graph of percent calcite equivalent (usingmass of calcite added) versus pressure in appropriate units forthe gauge used.10.6.2 Calibration data may be transferred to t
40、he face of thepressure gauge for direct reading of percent calcite equivalentas shown in Fig. 1.10.6.3 Use a least squares regression fit of the calibrationdata to arrive at an equation for calculating the percent calciteequivalent from the pressure data.11. Procedure11.1 Select a 1 6 0.01-g specime
41、n from the pulverized soil.Follow the procedures described in 10.2-10.4 to obtain a directmeasurement of the calcite equivalent. If there is no pressureresponse, but a minor effervescent reaction is observed, repeatthe experiment with 2, 5, or 10 g of dry solids in the reactor anddivide this carbona
42、te reading by 2, 5, or 10, respectively toobtain the true calcite equivalent.11.2 After a 10 min reaction time, read the pressure value toobtain the carbonate content. If one wishes to evaluate whetherother carbonate species are present, take additional readings asshown in 11.311.3 Continue reading
43、pressure until the reaction is com-plete using the following criteria: (a) The change in calciteequivalent is less than 0.3 % over a ten-min time period fortesting time up to 120 min; and (b) The change in calciteequivalent is less than 0.3 % over a 30-min time period fortesting time greater than 12
44、0 min.12. Report12.1 Report all results to the nearest 1 %.12.2 List sample source, project name and location (ifapplicable).13. Precision and Bias13.1 PrecisionDue to the nature of the soil and rockmaterials tested by this method it is either not feasible or toocostly at this time to produce multip
45、le specimens that haveuniform physical properties.Any variation observed in the datais just as likely to be due to specimen variation as to operatoror laboratory testing variation. Subcommittee D18.13 wel-comes proposals that would allow for development of a validprecision statement.13.2 BiasThere i
46、s no accepted reference value for this testmethod, therefore, bias cannot be determined.13.3 Some information on performance statistics of this testis provided in the literature.514. Keywords14.1 calcareous soils; calcite equivalent; carbonate content;Karbanat Bombe; marine soilsASTM International t
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