ASTM D5298-16

Standard Test Method for Measurement of Soil Potential (Suction) Using Filter Paper

SIGNIFICANCE AND USE
5.1 Soil suction is a measure of the free energy of the pore-water in a soil. Soil suction in practical terms is a measure of the affinity of soil to retain water and can provide information on soil parameters that are influenced by the soil water; for example, volume change, deformation, and strength characteristics of the soil.  
5.2 Soil suction is related with soil water content through water retention characteristic curves (see Test Methods D6836). Soil water content may be determined using Test Method D2216.  
5.3 Measurements of soil suction may be used with other soil and environmental parameters to evaluate hydrologic processes (1) and to evaluate the potential for heave or shrinkage, shear strength, modulus, in situ stress and hydraulic conductivity of unsaturated soils.  
5.4 The filter paper method of evaluating suction is straightforward with a range from 10 to 100,000 kPa (0.1 to 1000 bars).
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 ensure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
SCOPE
1.1 This test method covers laboratory filter papers as passive sensors to evaluate the soil matric and total potential (suction), a measure of the free energy of the pore-water or tension stress exerted on the pore-water by the soil matrix (1, 2).2 The term potential or suction is descriptive of the energy status of soil water.  
1.2 This test method controls the variables for measurement of the water content of filter paper that is in direct contact with soil or in equilibrium with the partial pressure of water vapor in the air of an airtight container enclosing a soil specimen. The filter paper is enclosed with a soil specimen in the airtight container until moisture equilibrium is established; that is, the partial pressure of water vapor in the air is in equilibrium with the vapor pressure of pore-water in the soil specimen.  
1.3 This test method provides a procedure for calibrating different types of filter paper for use in evaluating soil matric and total potential.  
1.4 Units—The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are mathematical conversions, which are provided for information purposes only and are not considered standard.  
1.5 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Published
• Publication Date: 14-Nov-2016
• ICS: 13.080.05 - Examination of soils in general
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.04 - Hydrologic Properties and Hydraulic Barriers

Relations

• Replaces: ASTM D5298-10 - Standard Test Method for Measurement of Soil Potential (Suction) Using Filter Paper
• Effective Date: 15-Nov-2016
• Refers: ASTM D4753-24 - Standard Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction Materials Testing
• Effective Date: 01-Feb-2024
• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM E230/E230M-23a - Standard Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
• Effective Date: 01-Nov-2023
• Refers: ASTM C114-23 - Standard Test Methods for Chemical Analysis of Hydraulic Cement
• Effective Date: 01-Oct-2023
• Refers: ASTM E230/E230M-23 - Standard Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
• Effective Date: 01-May-2023
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM E832-81(2019) - Standard Specification for Laboratory Filter Papers
• Effective Date: 01-Jul-2019
• Refers: ASTM E2877-12(2019) - Standard Guide for Digital Contact Thermometers
• Effective Date: 01-May-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D6836-16 - Standard Test Methods for Determination of the Soil Water Characteristic Curve for Desorption Using Hanging Column, Pressure Extractor, Chilled Mirror Hygrometer, or Centrifuge
• Effective Date: 15-Nov-2016
• Refers: ASTM D4753-15 - Standard Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction Materials Testing
• Effective Date: 01-May-2015
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM C114-13 - Standard Test Methods for Chemical Analysis of Hydraulic Cement
• Effective Date: 01-Oct-2013
• Refers: ASTM E2877-12e1 - Standard Guide for Digital Contact Thermometers
• Effective Date: 01-Nov-2012

Overview

ASTM D5298-16 is the Standard Test Method for Measurement of Soil Potential (Suction) Using Filter Paper. Developed by ASTM International, this method provides a laboratory procedure widely used in geotechnical engineering and soil science for evaluating soil suction, also known as soil water potential. Soil suction is an indicator of the free energy of pore-water in soil, reflecting the soil's capacity to retain water. Understanding soil suction is critical for assessing properties influenced by soil moisture, such as volume change, deformation, strength, heave/shrinkage potential, and hydraulic conductivity.

The filter paper technique is valued for being both straightforward and cost-effective, with applicability over a broad suction range (10 to 100,000 kPa). It employs filter paper as a passive sensor to measure soil matric and total potentials by equilibrating with the soil’s water content or vapor phase.

Key Topics

1. Soil Suction and Water Retention

• Soil suction measures the tendency of soil to retain water, revealing information about mechanical and hydraulic properties.
• The relationship between soil water content and suction is characterized by water retention curves.

2. Filter Paper Method

• Laboratory filter paper (Type II, ash-free) serves as a sensor, attaining equilibrium with the soil sample either by contact or vapor exchange.
• Two main measurements:
  • Matric suction: Filter paper in direct contact with the soil.
  • Total suction: Filter paper isolated from the soil, equilibrating with vapor only.

3. Calibration and Measurement Process

• Filter paper must be calibrated using standard salt solutions.
• After drying and preparing the filter paper, it is placed in a sealed container with the soil sample for at least seven days to achieve equilibrium.
• Following equilibration, the water content of the filter paper is measured and related back to soil suction using a calibration curve.

4. Reporting and Quality Assurance

• Accuracy depends on proper equipment, technique, and competent personnel.
• Results should include identifying information, test data, equipment calibration method, temperature, and bulk density of the soil sample.

Applications

ASTM D5298-16 is integral to soil mechanics, geotechnical engineering, and environmental studies. Key applications include:

• Foundation and Slope Stability Evaluation:
  • Assessing expansion, shrinkage, or collapse potential of unsaturated soils.
  • Evaluating the risk of heave or settlement due to moisture changes.
• Shear Strength and Modulus Estimation:
  • Correlating soil suction with soil strength for construction and earthwork projects.
• Hydrologic and Environmental Assessments:
  • Studying water migration in soil covers, landfill liners, embankments, and agricultural soils.
  • Investigating soil-atmosphere interactions and predicting water retention behavior.
• Civil Engineering Design and Construction:
  • Informing design decisions where unsaturated soil conditions may impact stability or long-term performance.

Related Standards

For comprehensive soil moisture and suction analysis, the following standards are commonly referenced alongside ASTM D5298-16:

• ASTM D6836: Determination of the Soil Water Characteristic Curve for Desorption
• ASTM D2216: Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• ASTM D653: Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D3740: Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock
• ASTM D1125: Test Methods for Electrical Conductivity and Resistivity of Water
• ASTM D4542: Methods for Pore Water Extraction and Soluble Salt Content of Soils

Practical Value

By quantifying soil suction using the filter paper method, professionals gain vital data supporting geotechnical design, site investigation, environmental remediation, and agricultural productivity. The standard’s broad measurement range, relative simplicity, and compatibility with other soil tests make it a fundamental tool in soil science and geotechnical engineering. Incorporating ASTM D5298-16 ensures reliable, consistent assessment of unsaturated soils, strengthening safety and performance across construction, research, and environmental applications.

Standards Content (Sample)

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.
Designation: D5298 − 16
Standard Test Method for
Measurement of Soil Potential (Suction) Using Filter Paper
This standard is issued under the fixed designation D5298; 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 D653 Terminology Relating to Soil, Rock, and Contained
Fluids
1.1 This test method covers laboratory filter papers as
D1125 Test Methods for Electrical Conductivity and Resis-
passive sensors to evaluate the soil matric and total potential
tivity of Water
(suction), a measure of the free energy of the pore-water or
D2216 Test Methods for Laboratory Determination of Water
tension stress exerted on the pore-water by the soil matrix (1,
2 (Moisture) Content of Soil and Rock by Mass
2). The term potential or suction is descriptive of the energy
D3740 Practice for Minimum Requirements for Agencies
status of soil water.
Engaged in Testing and/or Inspection of Soil and Rock as
1.2 This test method controls the variables for measurement
Used in Engineering Design and Construction
of the water content of filter paper that is in direct contact with
D4542 Test Methods for Pore Water Extraction and Deter-
soil or in equilibrium with the partial pressure of water vapor
mination of the Soluble Salt Content of Soils by Refrac-
intheairofanairtightcontainerenclosingasoilspecimen.The
tometer
filter paper is enclosed with a soil specimen in the airtight
D4753 Guide for Evaluating, Selecting, and Specifying Bal-
container until moisture equilibrium is established; that is, the
ances and Standard Masses for Use in Soil, Rock, and
partial pressure of water vapor in the air is in equilibrium with
Construction Materials Testing
the vapor pressure of pore-water in the soil specimen.
D6836 Test Methods for Determination of the Soil Water
1.3 This test method provides a procedure for calibrating Characteristic Curve for Desorption Using Hanging
Column, Pressure Extractor, Chilled Mirror Hygrometer,
different types of filter paper for use in evaluating soil matric
and total potential. or Centrifuge
E230/E230M Specification and Temperature-Electromotive
1.4 Units—The values stated in SI units are to be regarded
Force (emf) Tables for Standardized Thermocouples
as standard. The inch-pound units given in parentheses are
E337 Test Method for Measuring Humidity with a Psy-
mathematical conversions, which are provided for information
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
purposes only and are not considered standard.
peratures)
1.5 This standard does not purport to address all of the
E832 Specification for Laboratory Filter Papers
safety concerns, if any, associated with its use. It is the
E1137/E1137M Specification for Industrial Platinum Resis-
responsibility of the user of this standard to establish appro-
tance Thermometers
priate safety and health practices and determine the applica-
E2251 Specification for Liquid-in-Glass ASTM Thermom-
bility of regulatory limitations prior to use.
eters with Low-Hazard Precision Liquids
E2877 Guide for Digital Contact Thermometers
2. Referenced Documents
2.1 ASTM Standards:
3. Terminology
C114 Test Methods for Chemical Analysis of Hydraulic
3.1 Definitions:
Cement
3.1.1 For common definitions of technical terms in this
standard, refer to Terminology D653.
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
3.2 Definitions of Terms Specific to This Standard:
Rock and is the direct responsibility of Subcommittee D18.04 on Hydrologic
3.2.1 atmosphere—a unit of pressure equal to 76 cm Mer-
Properties and Hydraulic Barriers.
Current edition approved Nov. 15, 2016. Published December 2016. Originally cury or 101 kPa at 0°C.
approved in 1992. Last previous edition approved in 2010 as D5298–10. DOI:
3.2.2 matric suction (potential), hm (kPa)—in
10.1520/D5298-16.
geohydrology/hydrogeology, matric suction is the difference
The boldface numbers in parentheses refer to a list of references at the end of
this standard.
between the pore gas pressure, u , and the pore water pressure,
g
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
u , in soil; that is,y=u –u , which yields a positive value
w g w
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
–2
in either pressure FL or pressure head, L.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.2.2.1 Discussion—In most cases the pore gas is air at
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5298 − 16
atmospheric pressure. Matric suction is also referred to as 5. Significance and Use
capillary suction, capillary pressure, and capillary potential.
5.1 Soil suction is a measure of the free energy of the
Water flows from a soil with low matric suction (a moist soil)
pore-waterinasoil.Soilsuctioninpracticaltermsisameasure
to soil with a high suction (a dry soil). The term matrix should
of the affinity of soil to retain water and can provide informa-
not replace matric because only matric refers to the two
tiononsoilparametersthatareinfluencedbythesoilwater;for
solid-liquid binding mechanism (adsorption and capillarity)
example, volume change, deformation, and strength character-
contributing to the negative pore-water pressure, u .
w
istics of the soil.
3.2.3 molality, moles/1000 g—number of moles of solute
5.2 Soil suction is related with soil water content through
per 1000 g of solvent.
water retention characteristic curves (see Test Methods
3.2.4 mole—molecular weight of a substance in grams. D6836). Soil water content may be determined using Test
Method D2216.
3.2.5 osmotic (solute) suction, hs (kPa)—the negative pres-
sure to which a pool of pure water must be subjected in order 5.3 Measurements of soil suction may be used with other
soil and environmental parameters to evaluate hydrologic
to be in equilibrium through a semipermeable membrane with
processes (1) and to evaluate the potential for heave or
a pool containing a solution identical in composition with the
shrinkage, shear strength, modulus, in situ stress and hydraulic
soil water; decrease in relative humidity due to the presence of
conductivity of unsaturated soils.
dissolved salts in pore-water.
5.4 The filter paper method of evaluating suction is straight-
3.2.6 pF—a unit of negative pressure expressed as the
forward with a range from 10 to 100,000 kPa (0.1 to 1000
logarithm to the base ten of the height in centimeters that a
bars).
column of water will rise by capillary action or negative gauge
NOTE 1—The quality of the result produced by this standard is
pressure (kPa) divided by the unit weight of water (kN/m )
dependent on the competence of the personnel performing it, and the
times 1000. pF ≈ 3 + logarithm to the base ten of the negative
suitability of the equipment and facilities used. Agencies that meet the
pressure in atmospheres. Refer to capillary head or capillary
criteria of Practice D3740 are generally considered capable of competent
rise in Terminology D653.
and objective testing/sampling/inspection/etc. Users of this standard are
cautioned that compliance with Practice D3740 does not in itself ensure
3.2.7 soil relative humidity, R —the ratio of the vapor
h
reliable results. Reliable results depend on many factors; Practice D3740
pressure of pore water in the soil to the vapor pressure of free
provides a means of evaluating some of those factors.
pure water. Relative humidity in the soil is defined as relative
6. Apparatus
humidity measured by Test Method E337.
6.1 Filter Paper—The paper used must be ash-free quanti-
3.2.8 total potential (kPa)—the sum of gravitational,
tative Type II filter paper, see Specification E832; for example,
pressure, osmotic and external gas potentials. Potential may be
Whatman No. 42, Fisherbrand 9-790A, Schleicher and
identified with suction when gravitational and external gas
Schuell No. 589 White Ribbon. Asuitable diameter is 5.5 cm
potentials are neglected.
(2.2 in.).
3.2.9 total soil suction, h (kPa)—the negative pressure,
NOTE 2—Filter papers may be treated by dipping each paper in a 2 %
relative to the external gas pressure on the soil water, to which
concentration of formaldehyde prior to use to prevent organism growth on
a pool of pure water must be subjected to be in equilibrium
or biological decomposition of the filter paper. Biological decomposition
with the soil water through a semipermeable membrane that is
may be significant when filter papers are subject to a moist, warm
permeable to water molecules only. Total soil suction (ex-
environment for more than 14 days. Appropriate precautions should be
pressed as a positive value) is the sum of osmotic (solute) and
taken when preparing formaldehyde solutions and treating filter paper.
matric suctions.
6.2 Specimen Container—120 to 240 mL (4 to 8 fluid-oz)
3.2.10 vapor pressure of free pure water (kPa)—the satura- capacity metal or glass (rust free) container and lid (for
example, coated with zinc chromate to retard rusting) to
tion vapor pressure of free pure water at a given dry-bulb
temperature. contain the specimen and filter papers. The inside of these
containers may also be coated with wax to retard rusting.
3.2.11 vapor pressure of pore water in soil (kPa)—the
6.3 Filter Paper Container—This container holds filter
partial pressure of water vapor that is in equilibrium with
paper following the equilibration of suction and removal from
pore-water in soil at a given dry-bulb temperature.
the specimen container.
6.3.1 Metal Container Alternate—Two nominal 70 mL (2
4. Summary of Test Method
fluid-oz) capacity metal moisture containers (aluminum or
4.1 Filter papers are placed in an airtight container with a
stainless)withlidstodrythefilterpaper.Thecontainersshould
specimen for seven days to allow sufficient time for the vapor
be numbered by imprinting with a metal stamp.The containers
pressure of pore-water in the specimen, vapor pressure of pore
should not be written on with any type of marker or labeled in
water in the filter paper, and partial vapor pressure of water in
the air inside the container to reach equilibrium. The mass of
The sole source of supply of the apparatus known to the committee at this time
the filter papers is subsequently determined and the suction of
is Thomas Scientific Supply, P.O. Box 99, Swedesboro, NJ 08085. If you are aware
the specimen is determined from a calibration relationship of
of alternative suppliers, please provide this information to ASTM International
thefilterpaperwatercontentwithsuctionapplicabletothetype
Headquarters.Your comments will receive careful consideration at a meeting of the
of filter paper and the test procedure of this test method. responsible technical committee, which you may attend.
D5298 − 16
any manner. Throw-away vinyl surgical non-powdered or
v = volume of 1000 moles of liquid water, 0.018 m , and
similar gloves should be used anytime the small containers
R = relative humidity, fraction.
h
designatedforfilterpapermeasurementsarehandledtoprevent
7.1.3 Standard critical tables may be used to evaluate the
body oils from influencing any mass measurements made prior
relative humidity of water in equilibrium with the salt solution
to handling.
as illustrated in Table 1. Refer to Test Method E337 for further
6.3.2 Plastic Bag Alternate—Plastic bag large enough to
information on relative humidity.
accommodate the filter paper disks (approximately 50 mm in
7.2 Typical calibration curves for filter papers (for example,
dimension) capable of an airtight seal.
4 4
Whatman No. 42, Schleicher and Schuell No. 589), see Fig.
3 3
6.4 Insulated Chest—Aboxofapproximately0.03m (1ft )
1,consistsoftwoparts.Theuppersegmentrepresentsmoisture
capacity insulated with foamed polystyrene or other material
retained as films adsorbed to particle surfaces, while the lower
capable of maintaining temperature within 61°C when exter-
segment represents moisture retained by capillary or surface
nal temperatures vary 63°C.
tension forces between particles. The filter paper water content
6.5 Balance—A balance or scale having a minimum capac-
break point is w = 45.3 percent for Whatman No. 42 (3, 4)
f
ity of 20 g and meeting the requirements of 4.2.1.1 of
and w = 54 % for Schleicher and Schuell No. 589 (2, 4).
f
Specification C114 for a balance of 0.0001 g readability. In
7.3 The calibration curves in Fig. 1 are applicable to total
addition, balances for performance of Test Method D2216,
suction. Variability in results is less than 2 % of the suction
meeting requirements of Specification D4753.
above 100 kPa. Soil disturbance has minimal influence on
6.6 Drying Oven—Thermostatically-controlled, preferably
suction above 20 kPa. At moisture contents with suctions less
of the forced-draft type, and capable of maintaining a uniform
than 20 kPa, sample disturbance increases variability of mea-
temperature of 110 6 5°C throughout the drying chamber and
surement (2, 4). The right vertical axis of Fig. 1 provides the
meeting requirements of Test Method D2216.
suction in units pF and atmospheres pressure; for example,
h = 2 log atmospheres is a suction of 100 atmospheres, while
6.7 Metal Block—A metal block >500 g mass with a flat
pF = 5 or 100,000 cm water.
surface to hasten cooling of the metal containers with filter
paper.
NOTE 5—Filter paper may be calibrated by using the pressure
membrane, see Test Methods D6836 for the range 100 to 1500 kPa (1 to
6.8 Thermometer—Aninstrumenttodeterminethetempera-
15 atm), and the ceramic plate, see Test Methods D6836 for the range 10
ture of the tested soil to an accuracy of 61°C in accordance
to 100 kPa (0.1 to 1 atm).
with E230/E230M, E1137/E1137M, E2251,or E2877.
8. Procedure
6.9 Miscellaneous Equipment—Tweezers, trimming knife,
flexibleplasticelectricaltape,O-rings,screenwire,brassdiscs,
8.1 Filter Paper Preparation—Dry filter papers selected for
etc. Tweezers should be at least 110 mm (4.5 in.) in length.
testing at least 16 h or overnight in the drying oven. Place filter
papers in a desiccant jar over desiccant after drying for storage
6.10 Desiccator—A desiccator jar of suitable size contain-
until use.
ing silica gel or anhydrous calcium sulfate.
8.2 Measurement of Suction—Total suction will be mea-
NOTE 3—Anhydrous calcium sulfate is sold under the trade name
sured if filter papers are not in contact with the soil specimen;
Drierite.
NOTE4—Itispreferabletouseadesiccantthatchangescolortoindicate
moisture transfer will be limited to vapor transfer through the
when it needs reconstitution.
air inside the specimen container. Matric suction will be
measured if the filter paper is in physical contact with the soil.
7. Calibration
Physical contact between the soil and filter
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: D5298 − 10 D5298 − 16
Standard Test Method for
Measurement of Soil Potential (Suction) Using Filter Paper
This standard is issued under the fixed designation D5298; 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 laboratory filter papers as passive sensors to evaluate the soil matric (matrix) and total potential
(suction), a measure of the free energy of the pore-water or tension stress exerted on the pore-water by the soil matrix (1, 2). The
term potential or suction is descriptive of the energy status of soil water.
1.2 This test method controls the variables for measurement of the water content of filter paper that is in direct contact with soil
or in equilibrium with the partial pressure of water vapor in the air of an airtight container enclosing a soil specimen. The filter
paper is enclosed with a soil specimen in the airtight container until moisture equilibrium is established; that is, the partial pressure
of water vapor in the air is in equilibrium with the vapor pressure of pore-water in the soil specimen.
1.3 This test method provides a procedure for calibrating different types of filter paper for use in evaluating soil matric and total
potential.
1.4 Units—The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are
approximate.mathematical conversions, which are provided for information purposes only and are not considered standard.
1.5 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
C114 Test Methods for Chemical Analysis of Hydraulic Cement
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D1125 Test Methods for Electrical Conductivity and Resistivity of Water
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4542 Test Methods for Pore Water Extraction and Determination of the Soluble Salt Content of Soils by Refractometer
D4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction
Materials Testing
D6836 Test Methods for Determination of the Soil Water Characteristic Curve for Desorption Using Hanging Column, Pressure
Extractor, Chilled Mirror Hygrometer, or Centrifuge
E1E230/E230M Specification for ASTM Liquid-in-Glass Thermometersand Temperature-Electromotive Force (emf) Tables for
Standardized Thermocouples
E337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
E832 Specification for Laboratory Filter Papers
E1137/E1137M Specification for Industrial Platinum Resistance Thermometers
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
E2877 Guide for Digital Contact Thermometers
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.04 on Hydrologic Properties
and Hydraulic Barriers.
Current edition approved July 1, 2010Nov. 15, 2016. Published August 2010December 2016. Originally approved in 1992. Discontinued December 2002 and reinstated
as D5298–03. Last previous edition approved in 20032010 as D5298–03.–10. DOI: 10.1520/D5298-10.10.1520/D5298-16.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5298 − 16
3. Terminology
3.1 Definitions:
3.1.1 For common definitions of technical terms in this standard, refer to Terminology D653.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 atmosphere—a unit of pressure equal to 76 cm Mercury or 101 kPa at 0 °C.0°C.
3.2.2 matric (matrix) suction,suction (potential), hm (kPa)—the negative pressure (expressed as a positive value), relative to
ambient atmospheric pressure on the soil water, to which a solution identical in composition with the soil water must be subjected
in order to be in equilibrium through a porous permeable wall with the soil water; pressure equivalent to that measured by Test
Methods in geohydrology/hydrogeology, matric D6836. Matric suction is a function of the relative humidity due to the difference
in air the difference between the pore gas pressure, u , and water pressure acrossthe pore water pressure, u the water surface; the
g w
relative humidity or, in soil; that is, y = u water vapor– u pressure decreases as the radius of curvature of the, which yields a
g w
–2
positive value in either pressure FL water surface decreases. The term “matric” is grammatically correct, while matrix is
commonly used in the civil engineering literature.or pressure head, L.
3.2.2.1 Discussion—
In most cases the pore gas is air at atmospheric pressure. Matric suction is also referred to as capillary suction, capillary pressure,
and capillary potential. Water flows from a soil with low matric suction (a moist soil) to soil with a high suction (a dry soil). The
term matrix should not replace matric because only matric refers to the two solid-liquid binding mechanism (adsorption and
capillarity) contributing to the negative pore-water pressure, u .
w
3.2.3 molality, moles/1000 g—number of moles of solute per 1000 g of solvent.
3.2.4 mole—molecular weight of a substance in grams.
3.2.5 osmotic (solute) suction, hs (kPa)—the negative pressure to which a pool of pure water must be subjected in order to be
in equilibrium through a semipermeable membrane with a pool containing a solution identical in composition with the soil water;
decrease in relative humidity due to the presence of dissolved salts in pore-water.
3.2.6 pF—a unit of negative pressure expressed as the logarithm to the base ten of the height in centimeters that a column of
water will rise by capillary action or negative gauge pressure (kPa) divided by the unit weight of water (kN/m ) times 1000. pF
≈ 3 + logarithm to the base ten of the negative pressure in atmospheres. Refer to capillary head or capillary rise in Terminology
D653.
3.2.7 soil relative humidity, R —the ratio of the vapor pressure of pore water in the soil to the vapor pressure of free pure water.
h
Relative humidity in the soil is defined as relative humidity measured by Test Method E337.
3.2.8 total potential (kPa)—the sum of gravitational, pressure, osmotic and external gas potentials. Potential may be identified
with suction when gravitational and external gas potentials are neglected.
3.2.9 total soil suction, h (kPa)—the negative pressure, relative to the external gas pressure on the soil water, to which a pool
of pure water must be subjected to be in equilibrium with the soil water through a semipermeable membrane that is permeable to
water molecules only. Total soil suction (expressed as a positive value) is the sum of osmotic (solute) and matric (matrix) suctions.
3.2.10 vapor pressure of free pure water (kPa)—the saturation vapor pressure of free pure water at a given dry-bulb temperature.
3.2.11 vapor pressure of pore water in soil (kPa)—the partial pressure of water vapor that is in equilibrium with pore-water in
soil at a given dry-bulb temperature.
4. Summary of Test Method
4.1 Filter papers are placed in an airtight container with a specimen for seven days to allow sufficient time for the vapor pressure
of pore-water in the specimen, vapor pressure of pore water in the filter paper, and partial vapor pressure of water in the air inside
the container to reach equilibrium. The mass of the filter papers is subsequently determined and the suction of the specimen is
determined from a calibration relationship of the filter paper water content with suction applicable to the type of filter paper and
the test procedure of this test method.
5. Significance and Use
5.1 Soil suction is a measure of the free energy of the pore-water in a soil. Soil suction in practical terms is a measure of the
affinity of soil to retain water and can provide information on soil parameters that are influenced by the soil water; for example,
volume change, deformation, and strength characteristics of the soil.
5.2 Soil suction is related with soil water content through water retention characteristic curves (see Test Methods D6836). Soil
water content may be found fromdetermined using Test Method D2216.
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5.3 Measurements of soil suction may be used with other soil and environmental parameters to evaluate hydrologic processes
(1) and to evaluate the potential for heave or shrinkage, shear strength, modulus, in situ stress and hydraulic conductivity of
unsaturated soils.
5.4 The filter paper method of evaluating suction is simple and economical straightforward with a range from 10 to
100 000100,000 kPa (0.1 to 1000 bars).
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 assureensure reliable results.
Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
6. Apparatus
6.1 Filter Paper—The paper used must be ash-free quantitative Type II filter paper, see Specification E832; for example,
4 4
Whatman No. 42, Fisherbrand 9-790A, Schleicher and Schuell No. 589 White Ribbon. A suitable diameter is 5.5 cm (2.2 in.).
NOTE 2—Filter papers may be treated by dipping each paper in a 2 % concentration of formaldehyde prior to use to prevent organism growth on or
biological decomposition of the filter paper. Biological decomposition may be significant when filter papers are subject to a moist, warm environment
for more than 14 days. Appropriate precautions should be taken when preparing formaldehyde solutions and treating filter paper.
6.2 Specimen Container—120 to 240 mL (4 to 8 oz)fluid-oz) capacity metal or glass (rust free) container and lid (for example,
coated with zinc chromate to retard rusting) to contain the specimen and filter papers. The inside of these containers may also be
coated with wax to retard rusting.
6.3 Filter Paper Container—This container holds filter paper following the equilibration of suction and removal from the
specimen container.
6.3.1 Metal Container Alternate—Two nominal 70 mL (2 oz)fluid-oz) capacity metal moisture containers (aluminum or
stainless) with lids to dry the filter paper. The containers should be numbered by imprinting with a metal stamp. The containers
should not be written on with any type of marker or labelledlabeled in any manner. Throw-away vinyl surgical non-powdered or
similar gloves should be used anytime the small containers designated for filter paper measurements are handled to prevent body
oils from influencing any mass measurements made prior to handling.
6.3.2 Plastic Bag Alternate—Plastic bag large enough to accommodate the filter paper disks (approximately 50 mm in
dimension) capable of an airtight seal.
3 3
6.4 Insulated Chest—A box of approximately 0.03 m (1 ft ) capacity insulated with foamed polystyrene or other material
capable of maintaining temperature within 6 1 °C 61°C when external temperatures vary 6 3 °C.63°C.
6.5 Balance—A balance or scale having a minimum capacity of 20 g and meeting the requirements of 4.2.1.1 of Specification
C114 for a balance of 0.0001 g readability. In addition, balances for performance of Test Method D2216, meeting requirements
of Specification D4753.
6.6 Drying Oven—Thermostatically-controlled, preferably of the forced-draft type, and capable of maintaining a uniform
temperature of 110 6 5 °C 5°C throughout the drying chamber and meeting requirements of Test Method D2216.
6.7 Metal Block—A metal block > 500 >500 g mass with a flat surface to hasten cooling of the metal containers with filter paper.
6.8 Thermometer—An instrument to determine the temperature of the tested soil to an accuracy of 6 1 °C 61°C in accordance
with E1E230/E230M, E1137/E1137M, E2251or , or E2251E2877.
6.9 Miscellaneous Equipment—Miscellaneous EquipmentTweezers, —Tweezers, trimming knife, flexible plastic electrical tape,
O-rings, screen wire, brass discs, etc. Tweezers should be at least 110 mm (4.5 in.) in length.
6.10 Desiccator—A desiccator jar of suitable size containing silica gel or anhydrous calcium sulfate.
NOTE 3—Anhydrous calcium sulfate is sold under the trade name Drierite.
NOTE 4—It is preferable to use a desiccant that changes color to indicate when it needs reconstitution.
7. Calibration
7.1 Obtain a calibration curve applicable to a specific filter paper by following the procedure in Section 8, except for replacing
the soil specimen with salt solutions such as reagent grade potassium chloride or sodium chloride of known molality in distilled
water.
7.1.1 Suspend the filter paper above at least 50 ccmL of a salt solution in the specimen container, see 6.2, by placing it on an
improvised platform made of inert material such as plastic tubing or stainless steel screen.
7.1.2 Calculate the suction of the filter paper from the relative humidity of the air above the solution by:
The sole source of supply of the apparatus known to the committee at this time is Thomas Scientific Supply, P.O. Box 99, Swedesboro, NJ 08085. If you are aware of
alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible
technical committee, which you may attend.
D5298 − 16
RT
h 5 ·lnR (1)
h
v
where:
h = suction, kPa,
R = ideal gas constant, 8.31432 Joules/mole·K,
T = absolute temperature, degrees kelvin (K),
v = volume of 1000 moles of liquid water, 0.018 m , and
R = relative humidity, fraction.
h
7.1.3 Standard critical tables may be used to evaluate the relative humidity of water in equilibrium with the salt solution as
illustrated in Table 1. Refer to Test Method E337 for further information on relative humidity.
4 4
7.2 Typical calibration curves for filter papers (for example, Whatman No. 42, Schleicher and Schuell No. 589), see Fig. 1,
consists of two parts. The upper segment represents moisture retained as films adsorbed to particle surfaces, while the lower
segment represents moisture retained by capillary or surface tension forces between particles. The filter paper water content break
4 4
point is w = 45.3 percent for Whatman No. 42 (3, 4) and w = 54 % for Schleicher and Schuell No. 589 (2, 4).
f f
7.3 The calibration curves in Fig. 1 are applicable to total suction. Variability in results is less than 2 % of the suction above
100 kPa. Soil disturbance has minimal influence on suction above 20 kPa. At moisture contents with suctions less than 20 kPa,
sample disturbance increases variability of measurement (2, 4).
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