ASTM D4373-21

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Designation: D4373 − 14 D4373 − 21
Standard Test Method for Rapid Determination of
Carbonate Content of Soils
This standard is issued under the fixed designation D4373; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers the determination of carbonate content of soils and soft rock which can be readily broken down by
mechanical effort. It is a gasometric method that uses a simple portable apparatus. Results should be clearly stated as the calcite
equivalent in percent because different carbonate species cover a wide range of percent calcite equivalent as shown below for a
number of carbonates:
Calcite
Species Cation
Equivalent, %
Magnesite Mg 117.0
Dolomite Ca, Mg 108.6
Calcite Ca 100.0
Aragonite Ca 100.0
Rhodocrosite Mn 87.1
Siderite Fe 86.4
Smithsonite Zn 79.8
Witherite Ba 50.7
Cerrusite Pb 37.5
For example, a 100 % dolomite would be expected to yield 108.6 % calcite equivalent while 100 % siderite would yield only
86.4 % calcite equivalent. Calcite and aragonite reactions will typically complete within about 10 minutes. This method does not
distinguish between the carbonate species and such determination must be made using quantitative chemical analysis methods such
as atomic absorption.
1.2 Units—The values stated in SI units are to be regarded as the standard.standard. The values given in parentheses are provided
for information only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as
nonconformance with this standard
1.3 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.3.1 The procedures used to specify how data are collected/recorded or calculated, in this standard are regarded as the industry
standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not
consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives;
and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations.
It is beyond the scope of this standard to consider significant digits used in analytical methods for engineering design.
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.06 on Physical-Chemical
Interactions of Soil and Rock.
Current edition approved May 1, 2014June 15, 2021. Published June 2014June 2021. Originally approved in 1984. Last previous edition approved in 20072014 as
D4373 – 02 (2007).D4373 – 14. DOI: 10.1520/D4373-14.10.1520/D4373-21.
*A Summary 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
D4373 − 21
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.For specific precaution statements, see Section 8.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C25 Test Methods for Chemical Analysis of Limestone, Quicklime, and Hydrated Lime
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D3042 Test Method for Insoluble Residue in Carbonate Aggregates
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction
Materials Testing
D6026 Practice for Using Significant Digits in Geotechnical Data
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E145 Specification for Gravity-Convection and Forced-Ventilation Ovens
3. Terminology
3.1 Definitions—For definitions of common technical terms used in this standard, refer to Terminology D653.
4. Summary of Test Method
4.1 The carbonate content (calcite equivalent) of soil is determined by treating a 1-g dried soil specimen with hydrochloric acid
(HCl) in an enclosed A representative sample is oven dried and then pulverized to pass a 0.425 mm (No. 40) or finer sieve. A 1
g specimen is obtained from the representative sample and placed inside the reaction cylinder (reactor). Carbon dioxide
(COHydrochloric acid ) gas is evolved during the reaction between the acid and carbonate fraction of the specimen. is added to
the reactor using a container and the reactor sealed. The reactor is tilted and then shaken to allow the acid to react with the
specimen. After the pressure reading has stabilized, the pressure reading is taken. The resulting pressure generated in the closed
reactor is proportional (see Fig. 1) to the calcite equivalent of the specimen. This pressure is measured with a suitable pressure
gauge, or equivalent pressure-measuring device, that is pre-calibrated with reagent grade calcium carbonate.
5. Significance and Use
5.1 This test method is used to determine the presence and quantity of carbonate in a soil or soft rock specimen in terms of the
calcite equivalent. The method is generally intended for use as an index of approximate carbonate content to assist with
characterizing marine soils. soils, but can be used for other soils and soft rock. Other test methods exist (such as Method C25 and
Test Method D3042) to evaluate calcium carbonate equivalency for purposes of characterizing use of calcareous materials as soil
modifiers or agricultural lining materials.
5.1.1 Calcium carbonates (CaCO ) are known cementing agents, are water soluble at pH < 7, and are soft on the Mohs’ scale
compared to other soil minerals.
5.2 This test method has limitations as follows:
5.2.1 If low carbonate contents (calcite equivalents) are measured, the user does not know whether the soil is low in carbonate
content or contains cerrusite, witherite, and the like, which are carbonate species whose reactions with hydrochloric acid 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 calcite equivalents
within about 1 % are required.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D4373 − 21
FIG. 12 Typical Calibration Curve for 0.374L (12.6 oz) Test Cell and 70 kPa (10 psi) Pressure Gauge
5.2.3 The effects of specimen grain size, duration of testing, pH and specimen mass are discussed in the literature.
NOTE 1—The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective
testing/sampling/inspection, etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results.
Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
6. Apparatus
6.1 Rapid Carbonate Analyzer—A schematic drawing of the rapid carbonate analyzer is shown in Fig. 21. The analyzer must be
calibrated prior to initial use, after repair, and once every 12 months (Section 10). The basic components of this apparatus include:
6.1.1 Reaction Cylinder (Reactor), (Reactor)—with A clear plastic cylinder which allows viewing the effervescent reaction, with
a threaded cap and O-ring seal to enclose the cylinder. A clear plastic cylinder allows viewing of effervescent reaction.
6.1.2 Pressure Gauge (Bourdon Tube-type or Electronic Pressure Transducer), Gauge—A Bourdon Tube-type or Electronic
Pressure Transducer with a capacity of 70 kPa (10 psi), with an accuracy of 0.25 %,1.5 %, and a readability of 0.5 kPa (0.1 psi).
6.1.3 Acid or Soil Container, or Both, Container—ofA clear plastic container with a bail handle to hold 20 mL of acid. Optionally,
in addition to, or in place of the acid container, use a soil container of clear plastic to hold the soil soil/soft rock specimen. Acid
added to dry soil often causes considerable splashing and use of soil container reduces splashing before reactor is sealed.
6.1.4 Pressure Relief Valve, Valve—Used for safe release of CO gas pressure.
6.2 Balance—The balance must meet shall conform to the requirements of SpecificationGuide D4753 and this section. . A Class
GP1 balance with a minimum capacity of 100 g and a readability of 0.01 g is requiredneeded to measure the soil soil/soft rock
mass.
Demars, K.R., Chaney, R.C., Richter, J.A., “The Rapid Carbonate Analyzer,” Geotechnical Testing Journal, ASTM, Vol. 6, No. 1, March 1981, pp. 30–34.
D4373 − 21
FIG. 21 Schematic Drawing of Rapid Carbonate Analyzer
6.3 Drying Oven, Oven—thermostatically-controlled, preferably of the forced-draft type, meeting the requirements of Specifica-
tion Vented, thermostatically controlled oven E145 and capable of maintaining a uniform temperature of 110 6 5°C 110 6 5°C
(230 6 9°F) throughout the drying chamber.chamber (preferably of the forced-draft type).
6.4 Sieve—No. 40 (425 μm)425 μm (No. 40) or finer sieve that conforms to the requirements of Specification E11.
6.5 Mortar and Rubber-Covered Pestle (Optional)—Apparatus suitable for breaking up aggregations o
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