1、Designation: C 1699 08Standard Test Method forMoisture Retention Curves of Porous Building MaterialsUsing Pressure Plates1This standard is issued under the fixed designation C 1699; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he 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 the water retention curve (or moi
3、sture storagecapacity) of porous building materials at very high relativehumidity (RH) levels ( 95 to 100% RH) corresponding to thecapillary moisture region of the sorption isotherm. This isachieved by using the pressure plate test apparatus. Thistechnique was originally developed to study soil mois
4、turecontent and eventually had been adapted to building construc-tion materials.1.2 At higher RH levels ( 95 to 100% RH) of the sorptionisotherm (see Test Method C 1498), use of climatic chamber isnot an option. This technique uses overpressure to extractwater out of the pore structure of porous mat
5、erials untilequilibrium between the moisture content in the specimens andthe corresponding overpressure is achieved. Using the pressureplate extractors, equilibrium can only be reached by desorp-tion.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are i
6、ncluded in thisstandard.1.4 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 prio
7、r to use.2. Referenced Documents2.1 ASTM Standards:2C 1498 Test Method for Hygroscopic Sorption Isotherms ofBuilding MaterialsD 2325 Test Method for Capillary-Moisture Relationshipsfor Coarse- and Medium-Textured Soils by Porous-PlateApparatus3D 3152 Test Method for Capillary-Moisture Relationshipsf
8、or Fine-Textured Soils by Pressure-MembraneApparatus3E 337 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 desorption isothermthe sorption isotherm measuredexclusively d
9、uring the hygroscopic desorption process startedfrom the condition of full water saturation of the material.3.1.2 sorption isothermrelationship between the relativehumidity (see Test Method E 337) and the equilibrium mois-ture content of the material, at a specified temperature.3.1.3 pressure-plate
10、facilityHeavy steel vessel capable ofholding different pressure levels.3.1.4 moisture content, by massmass of water retained inthe specimen divided by the dry mass of the specimen.4. Significance and Use4.1 The purpose of this test is to obtain, by means of aspecified laboratory procedure, the value
11、s of the equilibriummoisture content at higher RH levels ( 95 to 100%). Thesevalues are used either as means to characterize the material oras material characteristics needed as input to appropriatecomputer models that can simulate wetting or drying potentialof individual building materials or mater
12、ial assemblies underspecified environmental conditions.5. Apparatus5.1 Pressure vesselHeavy-duty steel vessels of approxi-mately 305 mm in diameter and about 75 mm or 250 mm highwith heavy top lid tightly-held against O-ring gasket byclamping bolts (see Fig. 1).5.2 Porous ceramic platesThis is the p
13、late upon which thespecimens sit and is composed of microscopic pores allowing1This 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 Oct. 15, 2008. Publi
14、shed November 2008.2For 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.3Withdrawn. The last approved version of t
15、his historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.only water to flow through it. The plate assembly is exposed toan overpressure that can be adjusted, while the other side of theplat
16、e is always at atmospheric pressure resulting in a pressuredifference over the plate and the specimens.5.3 BalanceAn analytical balance capable of weighingwithin 1 mg shall be used. The accuracy of the balance shall beat least 6 0.1 percent of the total specimen weight.5.4 Drying ovenA ventilated dr
17、ying oven, capable ofmaintaining the required drying temperature within 62K fortemperatures less than 75C and 64K for temperatures above75C , and a relative humidity of less than 10%, shall be used.In warm-humid laboratory environment or at low dryingtemperatures, it will be necessary to provide a s
18、upply of driedair to achieve the less than 10 % relative humidity specificationin the drying oven.5.5 Desiccator equipped with outflow knobUsed as avacuum chamber to remove air (that is, evacuate) from thewater and evacuate specimens.5.6 Kaolin paste and acetate fabricThis clay paste en-sures good h
19、ydraulic contact between plate/specimen. Theacetate fabric prevents contamination of the specimens by theclay.5.7 Pressure sourceCompressed air or nitrogen in cylin-ders, or high-pressure air compressor.5.8 Pressure manifoldAssembly of conduits and valvesregulating the air supplied to the extractors
20、.6. Test Specimens6.1 A test specimen shall be cut to approximately 15 cm2and have a thickness as minimal as possible ( 5mm,depending on the structure of the material) to reduce the timeto reach equilibrium.6.2 A minimum of five specimens shall be tested in eachpressure environment. The test procedu
21、re, as specified below,and the precision of weighing shall be applied to eachspecimen.7. Preparations of Test Specimens7.1 Dry specimens in oven to constant weight (see Note 1).7.2 Measure and record dry specimen dimensions.7.3 For vacuum saturation (see Note 2), follow steps 7.3.1 to7.3.37.3.1 Plac
22、e them in a vacuum chamber (that is, desiccatorequipped with outflow knob and connected to vacuum pump)and evacuate for 24 hours. This ensures that no air remains inthe pores when specimens are being saturated.7.3.2 Evacuate distilled water by pumping air out for 1 to 2hours.7.3.3 Use this water to
23、saturate the specimens undervacuum. The assembly remains under vacuum for at least 3days or until no air bubbles are observed. Keep the specimensfully submerged in the vacuum chamber until ready formeasurement. This minimizes the amount of drying that canoccur.7.4 For capillary saturation (see Note
24、3), specimens shall beimmersed completely in distilled water (kept at room tempera-ture) until a constant weight is attained.7.5 Soak the porous ceramic plate(s) in distilled water for aminimum of 8 hours.7.6 Prepare the kaolin paste by mixing 125g of kaolinpowder with 150g water and apply it direct
25、ly onto the saturatedplate.7.7 Cover the paste with a layer of acetate cloth to preventthe kaolin from sticking to the specimens.7.8 Remove excess water off specimen surfaces by pattingon a damp sponge and record specimen masses.7.9 Press each specimen firmly on the acetate cloth ensuringgood contac
26、t and also removal of any air bubbles underneath.7.10 Close the pressure plate extractor lid after ensuringgood connection of the outflow tube to the ceramic plate.NOTE 1ypically, the following temperatures are used for drying thetest specimens: (a) for materials which do not change either structure
27、 ordimensions at 105C, (221F), for example, some mineral materials, use105 6 4C (221 6 8F), (b) for materials, in which structural ordimensional changes occur between 70C (158F) and 105C (221F), forexample, some cellular plastics, use 70 6 2C (158 6 4F), (c) formaterials, in which elevated temperatu
28、res bring about chemical orphysical changes, for example, crystalline water in gypsum or blowingagent solubility in some cellular plastics, use 40 6 2C (104 6 4F), and(d) when drying at the specified aforementioned temperatures adverselyFIG. 1 Pressure Plate Test ApparatusC1699082affects the buildin
29、g material, dry specimen to moisture free weight (that isdry weight, see 7.1) in a desiccator at room temperature or inside anairtight chamber flushed with dry air having a dew point less than ape 40C.NOTE 2Vacuum saturation leads to the maximum possible equilib-rium moisture content in a material a
30、nd is relevant to underwater andbelow-grade construction.NOTE 3Capillary saturation is relevant to above-grade construction.8. Procedure8.1 The room temperature shall remain constant at 22 61C (736 2F) for the duration of the test. If the lid or thebody of the extractor cools down then condensation
31、will occurinside the pressure vessel and it will give erroneous results.8.2 Check the initial pressure transducer voltage readingand make adjustment, if necessary.8.3 Connect the external outflow tube to a flexible plastictube and place it into a burettes opening so it can be notedwhen moisture equi
32、librium is obtained.8.4 Open air-control valves to admit compressed air or gas.Adjust the pressure regulator (see Note 4) until the desiredpressure is reached in order to extract moisture from speci-mens. Record the pressure.8.5 Bring test specimens to equilibrium state of moisturecontent, first at
33、one of the lower suction pressure, given inTable 1, and consecutively at other user-determined pressurelevels. Equilibrium is achieved when the water outflow (in theburette) is less than 0.05mL in 48 hours (see Note 5).8.6 Clamp off flexible plastic tube. Release the air pressurefrom the pressure pl
34、ate extractor, open the lid and removespecimens to immediately determine their masses gravimetri-cally.8.7 Rewet Kaolin paste with excess of distilled water. Placespecimens back on a ceramic plate and repeat from step 8.3until all user-determined suction pressures are covered. De-pending on the pres
35、sure ranges, a combination of severaldifferent pressure plates/extractors will be required. Whenmoving from one extractor to another, a new saturated ceramicplate is used along with fresh clay paste. Above 15 barpressure, the use of higher-pressure systems with cellulosemembranes instead of ceramic
36、plates is necessary.8.8 After all pressure plate measurements are completed,place specimens in oven and dry to constant weight. This finaldry mass (m0) is used to calculate moisture contents.NOTE 4 It is important to manage the regulator so that the desiredpressure is approached from a lower pressur
37、e. That is, do not overpressurethe chamber and then reduce the pressure to the desired level.NOTE 5Depending on the nature of the material, this can take severaldays, weeks and even months.9. Calculation9.1 Calculate the moisture content, u (kgkg-1), for eachspecimen at each suction pressure (that i
38、s, gauge pressure) asfollows:u 5m02 m0!m0(1)m = the mass of the specimen at equilibrium, andm0 = that of the dry specimen.9.2 Calculate the average moisture content, U (kgkg-1), ofspecimens at each suction pressure levels.9.3 The relative humidity (RH) can be calculated eitherfrom Eq 2 or obtained f
39、rom Table 1. The equilibrium suctionpressure (Ph) can be converted to the RH (f) using:1nf5MrRTPh(2)M = the molar mass of waterR = he ideal gas constantT = the thermodynamic temperature andr = the density of water10. Report10.1 The test report shall include the following:10.1.1 Reference to this AST
40、M Standard.10.1.2 Product identification:10.1.2.1 Name, manufacturer or supplier,10.1.2.2 Type, as in manufacturers specification,10.1.2.3 Production code number, if any,10.1.2.4 Packaging,10.1.2.5 The form in which it arrived at the laboratory,10.1.2.6 Nominal physical characteristics; for example,
41、bulk density, thickness, etc.,10.1.3 Test procedure with:10.1.3.1 Factors if any, which have had the potential toinfluence the results,10.1.3.2 Date of test, and10.1.3.3 Drying temperature, relative humidity and dryingprocedure10.1.4 Results:10.1.4.1 Table of measured pressures, equivalent RH andmoi
42、sture content, temperature and10.1.4.2 Graph showing the RH vs. moisture content (U)plot.11. Precision and Bias11.1 The reproducibility and precision of this test method isyet to be established.12. Keywords12.1 moisture content; pressure plate apparatus; water vaporsorptionTABLE 1 Suction Pressure S
43、et-Points and CorrespondingRelative HumiditySuction PressurePAEquivalent PressurebarRH%50000 0.50 99.9675000 0.75 99.94100000 1.0 99.93350000 3.5 99.74500000 5.0 99.63750000 7.5 99.451000000 10.0 99.271500000 15.0 98.903000000 30.0 97.81C1699083BIBLIOGRAPHY(1) Nordtest Method: NT BUILD 481, Building
44、 Materials: RetentionCurve and Pore Size Distribution.(2) Kumaran, M.K.; Mukhopadhyaya, P.; Normandin, N. 9Determina-tion of equilibrium moisture contents of building materials: somepractical difficulties,9 Journal of ASTM International, 3, (10),November, (Toronto, Ontario, April 01, 2006), pp. 1-9,
45、 November01, 2006 (Also published in Symposium on Heat, Air and MoistureTransport Properties of Building Materials, ASTM, Toronto, On-tario, April 2006, pp. 1-18.) doi:10.1520/JAI100265, (NRCC-48382)URL: http:/irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc48382/ASTM International takes no position respecting
46、 the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standar
47、d is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International
48、 Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.Thi
49、s standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).C1699084
