ASTM C1498-04a(2010)e1
(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
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.
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.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: C1498 − 04a(Reapproved 2010)
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.
ε NOTE—The units statement was editorially added and the units were editorially corrected in January 2011.
1. Scope 3. Terminology
1.1 This test method specifies a laboratory procedure for the 3.1 Definitions of Terms Specific to This Standard:
determination of hygroscopic sorption isotherms of any con- 3.1.1 adsorption isotherm—the sorption isotherm measured
struction materials. The method was originally developed for exclusively during the hygroscopic adsorption process started
the ASTM Thermal Insulation committee. from the oven-dry condition.
3.1.2 desorption isotherm—the sorption isotherm measured
1.2 For material characterization, the primary emphasis is
exclusively during the hygroscopic desorption process started
on the adsorption isotherm (that is, sorption isotherm that
from the condition of full water saturation of the material.
describes the wetting process of the material from the oven-dry
condition).
3.1.3 hygroscopic adsorption—fixation of water molecules
from ambient air on surfaces of a material until equilibrium is
1.3 Determination of desorption isotherm, (that is, sorption
established.
isotherm that describes the drying process of a material from
the state of absolute saturation with water) is performed when
3.1.4 hygroscopic desorption—release of adsorbed water
information on drying characteristics of construction materials
molecules from surfaces of a material into the ambient air until
isrequired.Typicallybothadsorptionanddesorptionisotherms
equilibrium is established.
are required for the purpose of hygrothermal models.
3.1.5 hysteresis—a physical phenomenon which makes the
1.4 The values stated in SI units are to be regarded as desorption isotherm different from the adsorption isotherm due
standard. No other units of measurement are included in this to the difference in the energy level of pore water.
standard.
3.1.6 moisture content, by mass—mass of water retained in
1.5 This standard does not purport to address all of the the specimen divided by the dry mass of the specimen.
safety concerns, if any, associated with its use. It is the
3.1.7 moisture content, by volume—volume of water re-
responsibility of the user of this standard to establish appro-
tained in the specimen divided by the volume of the dry
priate safety and health practices and determine the applica-
specimen.
bility of regulatory limitations prior to use.
3.1.8 sorption isotherm—relationship between the relative
humidity (RH) (see Test Method E337) and the equilibrium
2. Referenced Documents
moisture content of the material, at a specified temperature.
2.1 ASTM Standards:
E104 Practice for Maintaining Constant Relative Humidity
4. Significance and Use
by Means of Aqueous Solutions
4.1 The purpose of these tests is to obtain, for a specified
E337 Test Method for Measuring Humidity with a Psy-
temperature, by means of a specified laboratory procedure, the
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
values of the equilibrium moisture content at various levels of
peratures)
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
ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal
drying potential of individual building materials or material
Insulation and is the direct responsibility of Subcommittee C16.33 on Insulation
Finishes and Moisture.
assemblies under specified environmental conditions.
Current edition approved Nov. 1, 2010. Published January 2011. Originally
4.2 A specified value of the equilibrium moisture content
approved in 2001. Last previous edition approved in 2004 as C1498–04a. DOI:
10.1520/C1498-04AR10E01.
can also be used for material characterization. If this type of
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
materialcharacterizationiscalledforinamaterialspecification
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
(for example, mineral or cellulose fiber insulation), the equi-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. librium at 95 6 3 %RH shall be used.
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C1498 − 04a (2010)
4.3 For ease and repeatability of measurements, the mea- 6. Test Specimens
surements for characterization are performed on adsorption
6.1 A test specimen shall have a mass of at least 10 g. The
isotherms. Though desorption is the reverse of adsorption,
test specimen may be cut into several smaller pieces, but not
most porous materials reach different equilibrium levels during
powdered, to reduce the time to reach equilibrium with the
these two processes. Usually, the equilibrium moisture content
environment.
onthedesorptionisothermishigherthanthatontheadsorption
isotherm for the same level of RH. 6.2 A minimum of three specimens shall be tested in each
environment. The test procedure as specified below, and the
5. Apparatus
precision of weighing in particular, shall be applied to each
specimen.
5.1 Weighing Cups—Weighing cups, made from non-
absorbing material , for example, glass, shall be provided with
7. Procedure
tight-fitting lids and the volume shall not be less than 15 cm .
5.2 Balance—Ananalyticalbalancecapableofweighingthe 7.1 Unless otherwise specified, the temperature of 23°C
cups within 1 mg shall be used. The accuracy of the balance shall be used for the test.
shall be at least 6 0.1 percent of the total specimen weight.
7.2 Determine the dry weight of each specimen by placing
5.3 Drying Oven—A ventilated drying oven, capable of
it in the drying oven (see 5.3) at the required temperature for a
maintaining the required drying temperature within 62K for
minimum of 24 h (see Note 1). Cool the specimen to room
temperatures less than 75°C and 64K for temperatures above
temperature (> 20–25°C) either in a desiccator with calcium
75°C, and a relative humidity of less than 10 %, shall be used.
chlorideasdesiccantorinaweighingcupwithtight-fittinglids
In warm-humid laboratory environment or at low drying
and reweigh. Repeat the whole process, until three successive
temperatures, it will be necessary to provide a supply of dried
daily weighings agree to within 0.1 % of the specimen weight
airtoachievethelessthan10 %relativehumidityspecification
obtained in the latest weighing. Record the average of these
in the drying oven.
three weights as the dry weight of the specimen.
5.4 Environment Chamber—The specimens shall be ex-
7.3 Determination of Adsorption Isotherms—Priortotesting
posed to controlled environmental conditions. The precise
wateradsorption,eachtestspecimenistobedriedtoaconstant
conditionforthetestenvironmentshallbemaintainedinoneof
mass. Note 1 provides recommendations on selection of the
the following two ways, (a) with desiccators placed in a room
appropriate temperature. Determination of adsorption iso-
with controlled temperature , or (b) with a climatic chamber.
thermscanbeperformedwitheithertheproceduredescribedin
5.4.1 The test conditions can be generated within the
5.4.1 or with that described in 5.4.2 and the steps as described
desiccators that contain saturated salt solutions , (see also
below.
Practice E104). Since the partial pressure of the vapor above
7.3.1 Place the weighing cup with the dried specimen in the
the solution is strongly dependent on the temperature stability,
test environment having the lowest RH, typically about
temperature oscillation in the desiccator should be as small as
30 %RH. The test environment is achieved either in the
possible. The range 60.1K is recommended. The maximum
desiccator that contains a salt solution and placed in the
variation permitted by this standard shall not exceed 60.5K.
constant temperature room (5.4.1) or in the climatic chamber
Normally, the desiccators are placed inside a chamber or a
(5.4.2). Place the lid beside the weighing cup. Periodically
room with controlled temperature. In this case, it is recom-
weigh the weighing cup with the specimen until it is in
mendedthatthechamberorroomiscapableofmaintainingthe
equilibrium with the environment. At each weighing, before
test conditions within 61K.
the cup with the specimen is removed from the environment to
5.4.2 If the climatic chamber is used for the determination
the balance, put the lid on the cup. After weighing, return the
of the hygroscopic sorption isotherms, the chamber shall be
cup with the specimen to the test environment, with the lid
capable of maintaining the test conditions within 63 % for the
beside it. Constant mass is reached if in five successive
full range of RH. Temperature shall be maintained within
weighings, w
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