ASTM_C_1498_-_04a_2016.pdf

Designation:C149804a(Reapproved 2016)Standard Test Method forHygroscopic Sorption Isotherms of Building Materials1This standard is issued under the fixed designation C1498;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method specifies a laboratory procedure for thedetermination of hygroscopic sorption isotherms of any con-struction materials.The method was originally developed forthe ASTM Thermal Insulation committee.1.2 For material characterization,the primary emphasis ison the adsorption isotherm(that is,sorption isotherm thatdescribes the wetting process of the material from the oven-drycondition).1.3 Determination of desorption isotherm,(that is,sorptionisotherm that describes the drying process of a material fromthe state of absolute saturation with water)is performed wheninformation on drying characteristics of construction materialsis required.Typically both adsorption and desorption isothermsare required for the purpose of hygrothermal models.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated 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.2.Referenced Documents2.1 ASTM Standards:2E104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous SolutionsE337 Test Method for Measuring Humidity with a Psy-chrometer(the Measurement of Wet-and Dry-Bulb Tem-peratures)3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 adsorption isothermthe sorption isotherm measuredexclusively during the hygroscopic adsorption process startedfrom the oven-dry condition.3.1.2 desorption isothermthe sorption isotherm measuredexclusively during the hygroscopic desorption process startedfrom the condition of full water saturation of the material.3.1.3 hygroscopic adsorptionfixation of water moleculesfrom ambient air on surfaces of a material until equilibrium isestablished.3.1.4 hygroscopic desorptionrelease of adsorbed watermolecules from surfaces of a material into the ambient air untilequilibrium is established.3.1.5 hysteresisa physical phenomenon which makes thedesorption isotherm different from the adsorption isotherm dueto the difference in the energy level of pore water.3.1.6 moisture content,by massmass of water retained inthe specimen divided by the dry mass of the specimen.3.1.7 moisture content,by volumevolume of water re-tained in the specimen divided by the volume of the dryspecimen.3.1.8 sorption isothermrelationship between the relativehumidity(RH)(see Test Method E337)and the equilibriummoisture content of the material,at a specified temperature.4.Significance and Use4.1 The purpose of these tests is to obtain,for a specifiedtemperature,by means of a specified laboratory procedure,thevalues of the equilibrium moisture content at various levels ofRH.These values are used either as means to characterize thematerial or as material characteristics needed as input toappropriate computer models that can simulate wetting ordrying potential of individual building materials or materialassemblies under specified environmental conditions.4.2 A specified value of the equilibrium moisture contentcan also be used for material characterization.If this type ofmaterial characterization is called for in a material specification(for example,mineral or cellulose fiber insulation),the equi-librium at 95 6 3%RH shall be used.1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.33 on InsulationFinishes and Moisture.Current edition approved Aug.15,2016.Published August 2016.Originallyapproved in 2001.Last previous edition approved in 2010 as C1498 04a(2010)1.DOI:10.1520/C1498-04AR16.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.3 For ease and repeatability of measurements,the mea-surements for characterization are performed on adsorptionisotherms.Though desorption is the reverse of adsorption,most porous materials reach different equilibrium levels duringthese two processes.Usually,the equilibrium moisture contenton the desorption isotherm is higher than that on the adsorptionisotherm for the same level of RH.5.Apparatus5.1 Weighing CupsWeighing cups,made from