1、Designation: D4373 14Standard Test Method for Rapid Determination ofCarbonate Content of Soils1This standard is issued under the fixed designation D4373; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、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 covers the determination of carbonatecontent of soils and soft rock which can be readily brokendown by mechanical eff
3、ort. It is a gasometric method that usesa simple portable apparatus. Results should be clearly stated asthe calcite equivalent in percent because different carbonatespecies cover a wide range of percent calcite equivalent asshown below for a number of carbonates:Species CationCalciteEquivalent, %Mag
4、nesite 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 yieldonly 86.4 % calcite equiva
5、lent. Calcite and aragonite reactionswill typically complete within about 10 minutes. This methoddoes not distinguish between the carbonate species and suchdetermination must be made using quantitative chemical analy-sis methods such as atomic absorption.1.2 UnitsThe values stated in SI units are to
6、 be regardedas the standard.1.3 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.3.1 The procedures used to specify how data are collected/recorded or calculated, in this standard are regarded as theindustry standard
7、. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the users objectives; and it is common practice toincrease or
8、 reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consider significant digits used in analyticalmethods for engineering design.1.4 This standard does not purport to address all of thesafety concerns, if any, associated
9、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. For specificprecaution statements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2C25 Test Metho
10、ds for Chemical Analysis of Limestone,Quicklime, and Hydrated LimeD653 Terminology Relating to Soil, Rock, and ContainedFluidsD3042 Test Method for Insoluble Residue in CarbonateAggregatesD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed
11、 in Engineering Design and ConstructionD4753 Guide for Evaluating, Selecting, and Specifying Bal-ances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD6026 Practice for Using Significant Digits in GeotechnicalDataE11 Specification for Woven Wire Test Sieve Cloth and Test
12、SievesE145 Specification for Gravity-Convection and Forced-Ventilation Ovens3. Terminology3.1 DefinitionsFor definitions of common technical termsused in this standard, refer to Terminology D653.4. Summary of Test Method4.1 The carbonate content (calcite equivalent) of soil isdetermined by treating
13、a 1-g dried soil specimen with hydro-chloric acid (HCl) in an enclosed reaction cylinder (reactor).1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.06 on Physical-ChemicalInteractions of Soil and Rock.Current editio
14、n approved May 1, 2014. Published June 2014. Originallyapproved in 1984. Last previous edition approved in 2007 as D4373 02 (2007).DOI: 10.1520/D4373-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSt
15、andards volume information, refer to the standards Document Summary page onthe ASTM website.*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 States1Carbon dioxide (CO2) gas is e
16、volved during the reactionbetween the acid and carbonate fraction of the specimen. 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 d
17、evice, that is pre-calibratedwith reagent grade calcium carbonate.5. Significance 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 anindex of approximate carbonate
18、content to assist with charac-terizing marine soils. Other test methods exist (such as MethodC25 and Test Method D3042) to evaluate calcium carbonateequivalency for purposes of characterizing use of calcareousmaterials as soil modifiers or agricultural lining materials.5.1.1 Calcium carbonates (CaCO
19、3) are known 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
20、 or contains cerrusite, witherite, and the like,which are carbonate species whose reactions with hydrochloricacid are either very slow or limited.5.2.2 Testing times may be extensive (longer than 1 hour)for some carbonate species (such as dolomite) if calciteequivalents within about 1 % are required
21、.5.2.3 The effects of 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. Agenci
22、es that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing/sampling/inspection, etc. Users of this standard arecautioned that compliance with Practice D3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice
23、 D3740provides a means of evaluating some of those factors.6. Apparatus6.1 Rapid Carbonate AnalyzerAschematic drawing of therapid 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 cy
24、linder. A clear plastic 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 or Soil Container, or Both, of clear plastic with abail han
25、dle to hold 20 mL of acid. Optionally, in addition to, orin place of the acid container, use a soil container of clearplastic to hold the soil specimen. Acid added to dry soil oftencauses considerable splashing and use of soil container reducessplashing before reactor is sealed.3Demars, K.R., Chaney
26、, 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 GaugeD4373 1426.1.4 Pressure Relief Valve, for safe release of CO2gaspressure.6.2 BalanceTh
27、e balance must meet the requirements ofSpecification D4753 and this section. A Class GP1 balancewith a minimum capacity of 100 g and a readability of 0.01 gis required to measure the soil mass.6.3 Drying Oven, thermostatically-controlled, preferably ofthe forced-draft type, meeting the requirements
28、of Specifica-tion E145 and capable of maintaining a uniform temperature of110 6 5C throughout the drying chamber.6.4 SieveNo. 40 (425 m) or finer sieve that conforms tothe requirements of Specification E11.6.5 Mortar and Rubber-Covered Pestle (Optional)Apparatus suitable for breaking up aggregations
29、 of air-driedsoil particles without breaking individual particles.6.6 Mechanical Agitation Device (Optional)A platform,wrist action or similar type shaker having a gyratory, orbital,reciprocating, or similar motion to assist in the reaction processby continuously agitating the soaking soil.6.7 Gradu
30、ated Cylinder, Flask, Pipet, or the LikeAglass or equivalent inert device with enough capacity to hold20 6 2 mL of hydrochloric acid and readable to the nearest 1mL.6.8 Miscellaneous ItemsItems such as a spatula, scoop, orhammer may be useful.7. Reagents7.1 Purity of ReagentsReagent grade chemicals
31、shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.47.2 Calcium Carbonate (CaCO3). Reagent grade (98-100 %) for ca
32、libration of reaction cylinder.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 distilledwater (pH = 7) in a 1-L volumetric flask. Dilute to the markwith commercial grade distilled water. Store
33、 in polyethylenebottle. Faster reaction times may achieved by increasing theconcentration to higher normal solutions (up to about 3 Nsolution). Hydrochloric acid is also commercially available ina1N solution.7.4 WaterDistilled or demineralized water is the onlypermissible test fluid.4Reagent Chemica
34、ls, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National F
35、ormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 2 Schematic Drawing of Rapid Carbonate AnalyzerD4373 1438. Hazards8.1 Use care in handling the hydrochloric acid so that noacid is spilled on either skin or clothing. If acid contacts theskin or eyes, immediately flush with larg
36、e quantities of water.Process concentrated hydrochloric acid beneath a laboratoryhood or in a well-ventilated area to reduce the inhalation offumes.8.2 The pressure relief valve of the carbonate analyzershould be opened following each test to dissipate gas pressureso that the cap can be safely remov
37、ed.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 hours.Pulverize the entire 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
38、than larger particleswhen treated with acid.10. Calibration10.1 Calibration is accomplished by using reagent gradeCaCO3to obtain the relationship between the mass of CaCO3and the pressure generated in the constant volume reactor. Eachcarbonate analyzer and pressure gage is individually calibrated.Pr
39、epare 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 carbonate for a test specimen of 1g.10.1.2 Set 2Two specimens at 0.4 6 0.01 g.10.1.3 Set 3Two specimens at 0.6 6 0.01 g.10.1.4 Set 4Two specimens at 0
40、.8 6 0.01 g.10.1.5 Set 5Two specimens at 1.0 6 0.01 g.10.2 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
41、toinitiate reaction between the acid and specimen. Mix thecontents by swirling or gentle shaking. If available, place thereactor on a mechanical agitation device for the duration of thetest.10.3 It is very rare that even calcite powder will completelyreact in less than 10 minutes. Therefore, it is e
42、ssential tomonitor the pressure to verify that the reaction is complete(pressure stabilized) 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 react
43、ortop cap. Dispose of the contents and rinse the reactor withdistilled water.10.5 Repeat 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
44、appropriate units forthe gauge used.10.6.2 Calibration data may be transferred to the 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 cal
45、citeequivalent from the pressure data.11. Procedure11.1 Select a 1 6 0.01-g specimen from the pulverized soil.Follow the procedures described in 10.2 10.4 to obtain adirect measurement of the calcite equivalent. If there is nopressure response, but a minor effervescent reaction isobserved, repeat th
46、e experiment with 2 6 0.01 g, 5 6 0.01 g,or 10 6 0.01 g of dry solids in the reactor and divide thiscarbonate reading by 2, 5, or 10, respectively to obtain the truecalcite equivalent.11.2 After a 10-minute reaction time, read the pressurevalue to obtain the carbonate content. If one wishes to evalu
47、atewhether other carbonate species are present, take additionalreadings as shown in 11.311.3 Continue reading pressure until the reaction is com-plete using the following criteria: (a) The change in calciteequivalent is less than 0.3 % over a 10-minute time period fortesting time up to 120 minutes;
48、or (b) The change in calciteequivalent is less than 0.3 % over a 30-minute time period fortesting time greater than 120 minutes.11.4 Take the pressure reading obtained above and deter-mine the corresponding percent calcite equivalent from thedata reduction method chosen in 10.6 to obtain the Carbona
49、teContent (percent calcite equivalent).12. Report: Test Data Sheet(s)/Form(s)12.1 The methodology used to specify how data are re-corded on the test data sheet(s)/form(s), as described below, iscovered in 1.3.12.2 Record as a minimum the following general informa-tion (data):12.2.1 Record the Carbonate Content (percent calciteequivalent) to the nearest 1 %.12.2.2 List sample source, project name and location (ifapplicable).12.2.3 Record the mass of the test specimen to the nearest0.01 grams.12.2.4 Record the technician/operator name or initials anddate o
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