ASTM C1498-04a(2023)
(Test Method)Standard Test Method for Hygroscopic Sorption Isotherms of Building Materials
Standard Test Method for Hygroscopic Sorption Isotherms of Building Materials
SIGNIFICANCE AND USE
4.1 The purpose of these tests is to obtain, for a specified temperature, by means of a specified laboratory procedure, the values of the equilibrium moisture content at various levels of RH. These values are used either as means to characterize the material or as material characteristics needed as input to appropriate computer models that can simulate wetting or drying potential of individual building materials or material assemblies under specified environmental conditions.
4.2 A specified value of the equilibrium moisture content can also be used for material characterization. If this type of material characterization is called for in a material specification (for example, mineral or cellulose fiber insulation), the equilibrium at 95 ± 3 %RH shall be used.
4.3 For ease and repeatability of measurements, the measurements for characterization are performed on adsorption isotherms. Though desorption is the reverse of adsorption, most porous materials reach different equilibrium levels during these two processes. Usually, the equilibrium moisture content on the desorption isotherm is higher than that on the adsorption isotherm for the same level of RH.
SCOPE
1.1 This test method specifies a laboratory procedure for the determination of hygroscopic sorption isotherms of any construction materials. The method was originally developed for the ASTM Thermal Insulation committee.
1.2 For material characterization, the primary emphasis is on the adsorption isotherm (that is, sorption isotherm that describes the wetting process of the material from the oven-dry condition).
1.3 Determination of desorption isotherm, (that is, sorption isotherm that describes the drying process of a material from the state of absolute saturation with water) is performed when information on drying characteristics of construction materials is required. Typically both adsorption and desorption isotherms are required for the purpose of hygrothermal models.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 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.
General Information
Relations
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: C1498 − 04a (Reapproved 2023)
Standard Test Method for
Hygroscopic Sorption Isotherms of Building Materials
This standard is issued under the fixed designation C1498; 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 E104 Practice for Maintaining Constant Relative Humidity
by Means of Aqueous Solutions
1.1 This test method specifies a laboratory procedure for the
E337 Test Method for Measuring Humidity with a Psy-
determination of hygroscopic sorption isotherms of any con-
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
struction materials. The method was originally developed for
peratures)
the ASTM Thermal Insulation committee.
1.2 For material characterization, the primary emphasis is
3. Terminology
on the adsorption isotherm (that is, sorption isotherm that
3.1 Definitions of Terms Specific to This Standard:
describes the wetting process of the material from the oven-dry
3.1.1 adsorption isotherm—the sorption isotherm measured
condition).
exclusively during the hygroscopic adsorption process started
1.3 Determination of desorption isotherm, (that is, sorption
from the oven-dry condition.
isotherm that describes the drying process of a material from
3.1.2 desorption isotherm—the sorption isotherm measured
the state of absolute saturation with water) is performed when
exclusively during the hygroscopic desorption process started
information on drying characteristics of construction materials
from the condition of full water saturation of the material.
is required. Typically both adsorption and desorption isotherms
are required for the purpose of hygrothermal models.
3.1.3 hygroscopic adsorption—fixation of water molecules
from ambient air on surfaces of a material until equilibrium is
1.4 The values stated in SI units are to be regarded as
established.
standard. No other units of measurement are included in this
standard.
3.1.4 hygroscopic desorption—release of adsorbed water
molecules from surfaces of a material into the ambient air until
1.5 This standard does not purport to address all of the
equilibrium is established.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.1.5 hysteresis—a physical phenomenon which makes the
priate safety, health, and environmental practices and deter-
desorption isotherm different from the adsorption isotherm due
mine the applicability of regulatory limitations prior to use.
to the difference in the energy level of pore water.
1.6 This international standard was developed in accor-
3.1.6 moisture content, by mass—mass of water retained in
dance with internationally recognized principles on standard-
the specimen divided by the dry mass of the specimen.
ization established in the Decision on Principles for the
3.1.7 moisture content, by volume—volume of water re-
Development of International Standards, Guides and Recom-
tained in the specimen divided by the volume of the dry
mendations issued by the World Trade Organization Technical
specimen.
Barriers to Trade (TBT) Committee.
3.1.8 sorption isotherm—relationship between the relative
2. Referenced Documents
humidity (RH) (see Test Method E337) and the equilibrium
moisture content of the material, at a specified temperature.
2.1 ASTM Standards:
4. Significance and Use
This test method is under the jurisdiction of ASTM Committee C16 on Thermal
4.1 The purpose of these tests is to obtain, for a specified
Insulation and is the direct responsibility of Subcommittee C16.33 on Insulation
temperature, by means of a specified laboratory procedure, the
Finishes and Moisture.
values of the equilibrium moisture content at various levels of
Current edition approved March 15, 2023. Published April 2023. Originally
RH. These values are used either as means to characterize the
approved in 2001. Last previous edition approved in 2016 as C1498 – 04a (2016).
DOI: 10.1520/C1498-04AR23.
material or as material characteristics needed as input to
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
appropriate computer models that can simulate wetting or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
drying potential of individual building materials or material
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. assemblies under specified environmental conditions.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1498 − 04a (2023)
4.2 A specified value of the equilibrium moisture content capable of maintaining the test conditions within 63 % for the
can also be used for material characterization. If this type of full range of RH. Temperature shall be maintained within
material characterization is called for in a material specification 60.5K.
(for example, mineral or cellulose fiber insulation), the equi-
5.5 Desiccator, with (a) calcium chloride as desiccant for
librium at 95 6 3 %RH shall be used.
drying, or (b) with saturated salt solution to generate specific
4.3 For ease and repeatability of measurements, the mea- relative humidity level.
surements for characterization are performed on adsorption
6. Test Specimens
isotherms. Though desorption is the reverse of adsorption,
most porous materials reach different equilibrium levels during
6.1 A test specimen shall have a mass of at least 10 g. The
these two processes. Usually, the equilibrium moisture content
test specimen may be cut into several smaller pieces, but not
on the desorption isotherm is higher than that on the adsorption
powdered, to reduce the time to reach equilibrium with the
isotherm for the same level of RH.
environment.
6.2 A minimum of three specimens shall be tested in each
5. Apparatus
environment. The test procedure as specified below, and the
5.1 Weighing Cups—Weighing cups, made from non-
precision of weighing in particular, shall be applied to each
absorbing material , for example, glass, shall be provided with
specimen.
tight-fitting lids and the volume shall not be less than 15 cm .
5.2 Balance—An analytical balance capable of weighing the 7. Procedure
cups within 1 mg shall be used. The accuracy of the balance
7.1 Unless otherwise specified, the temperature of 23°C
shall be at least 6 0.1 percent of the total specimen weight.
shall be used for the test.
5.3 Drying Oven—A ventilated drying oven, capable of
7.2 Determine the dry weight of each specimen by placing
maintaining the required drying temperature within 62K for
it in the drying oven (see 5.3) at the required temperature for a
temperatures less than 75°C and 64K for temperatures above
minimum of 24 h (see Note 1). Cool the specimen to room
75°C, and a relative humidity of less than 10 %, shall be used.
temperature (> 20–25°C) either in a desiccator with calcium
In warm-humid laboratory environment or at low drying
chloride as desiccant or in a weighing cup with tight-fitting lids
temperatures, it will be necessary to provide a supply of dried
and reweigh. Repeat the whole process, until three successive
air to achieve the less than 10 % relative humidity specification
daily weighings agree to within 0.1 % of the specimen weight
in the drying oven.
obtained in the latest weighing. Record the average of these
5.4 Environment Chamber—The specimens shall be ex- three weights as the dry weight of the specimen.
posed to controlled environmental conditions. The precise
7.3 Determination of Adsorption Isotherms—Prior to testing
condition for the test environment shall be maintained in one of
water adsorption, each test specimen is to be dried to a constant
the following two ways, (a) with desiccators placed in a room
mass. Note 1 provides recommendations on selection of the
with controlled temperature , or (b) with a climatic chamber.
appropriate temperature. Determination of adsorption iso-
5.4.1 The test conditions can be generated within the
therms can be performed with either the procedure described in
desiccators that contain saturated salt solutions , (see also
5.4.1 or with that described in 5.4.2 and the steps as described
Practice E104). Since the partial pressure of the vapor above
below.
the solution is strongly dependent on the temperature stability,
7.3.1 Place the weighing cup with the dried specimen in the
temperature oscillation in the desiccator should be as small as
test environment having the lowest RH, typically about
possible. The range 60.1K is recommended. The maximum
30 %RH. The test environment is achieved either in the
variation permitted by this standard shall not exceed 60.5K.
desiccator that contains a salt solution and placed in the
Normally, the desiccators are placed inside a chamber or a
constant temperature room (5.4.1) or in the climatic chamber
room with controlled temperature. In this case, it is recom-
(5.4.2). Place the lid beside the weighing cup. Periodically
mended that the chamber or room is capable of maintaining the
weigh the weighing cup with the specimen until it is in
test conditions within 61K.
equilibrium with the environment. At each weighing, before
5.4.2 If the climatic chamber is used f
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