1、Designation: C 1699 09Standard 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 May 1, 2009. Publish
14、ed August 2009. Originallyapproved in 2008. Last previous edition approved in 2008 as C 169908.2For 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 Documen
15、t Summary page onthe ASTM website.3Withdrawn. The last approved version of this 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 exp
16、osed toan overpressure that can be adjusted, while the other side of theplate 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 lea
17、st 6 0.1 percent of the total specimen weight.5.4 Drying ovenA ventilated drying 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 e
18、nvironment or at low dryingtemperatures, it will be necessary to provide a supply 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
19、specimens.5.6 Kaolin paste and acetate fabricThis clay paste en-sures good hydraulic 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 manifold
20、Assembly of conduits and valvesregulating the air supplied to the extractors.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
21、five specimens shall be tested in eachpressure environment. The test procedure, 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.
22、7.3 For vacuum saturation (see Note 2), follow steps 7.3.1 to7.3.37.3.1 Place 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
23、 distilled water by pumping air out for 1 to 2hours.7.3.3 Use this water to 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 minimize
24、s the amount of drying that canoccur.7.4 For capillary saturation (see Note 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 kao
25、lin paste (see Note 4) by mixing 125g ofkaolin powder with 150g distilled water and apply it directlyonto the saturated plate.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
26、 and record specimen masses.7.9 Press each specimen firmly on the acetate cloth ensuringgood contact 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 1Typically, the following temper
27、atures are used for drying thetest specimens: (a) for materials which do not change either structure 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), forex
28、ample, some cellular plastics, use 70 6 2C (158 6 4F), (c) formaterials, in which elevated temperatures 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
29、aforementioned temperatures adverselyFIG. 1 Pressure Plate Test ApparatusC1699092affects the building 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 40C.NOT
30、E 2Vacuum saturation leads to the maximum possible equilib-rium moisture content in a material and is relevant to underwater andbelow-grade construction.NOTE 3Capillary saturation is relevant to above-grade construction.NOTE 4Kaolin from a previous test may be reused so long as there isno visible co
31、ntamination. The entire amount of damp kaolin should bescraped of the plate and weighed. Distilled water should be added to themixture to return the original weight of 275 g (125 g kaolin and 150 g ofwater) and the mixture should be well mixed.8. Procedure8.1 The room temperature shall remain consta
32、nt at 22 61C (736 2F) for the duration of the test. If the lid or thebody of the extractor cools down then condensation 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 e
33、xternal outflow tube to a flexible plastictube and place it into a burettes opening so it can be notedwhen moisture equilibrium is obtained.8.4 Open air-control valves to admit compressed air or gas.Adjust the pressure regulator (see Note 5) until the desiredpressure is reached in order to extract m
34、oisture from speci-mens. Record the pressure.8.5 Bring test specimens to equilibrium state of moisturecontent, first at 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 les
35、s than 0.05mL in 48 hours (see Note 6).8.6 Clamp off flexible plastic tube. Release the air pressurefrom the pressure plate 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
36、 a ceramic plate and repeat from step 8.3until all user-determined suction pressures are covered. De-pending on the pressure ranges, a combination of severaldifferent pressure plates/extractors will be required. Whenmoving from one extractor to another, a new saturated ceramicplate is used along wit
37、h fresh clay paste. Above 15 barpressure, the use of higher-pressure systems with cellulosemembranes instead of ceramic 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 moistur
38、e contents.NOTE 5 In order to avoid hysteresis effect it is important to managethe regulator so that the desired pressure is approached from a lowerpressure. That is, do not overpressure the chamber and then reduce thepressure to the desired level.NOTE 6Depending on the nature of the material, this
39、can take severaldays, weeks and even months.9. Calculation9.1 Calculate the moisture content, u (kgkg-1), for eachspecimen at each suction pressure (that is, gauge pressure) asfollows:u 5m 2 mo!mo(1)m = the mass of the specimen at equilibrium, andmo= that of the dry specimen.9.2 Calculate the averag
40、e 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 from Table 1. The equilibrium suctionpressure (Ph) can be converted to the RH (f) using:1nf5MrRTPh(2)M = the molar mass of waterR = the ideal gas c
41、onstantT = the thermodynamic temperature andr = the density of water10. Report10.1 The test report shall include the following:10.1.1 Reference to this ASTM 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 Produc
42、tion 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,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 D
43、ate 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 andmoisture content, temperature and10.1.4.2 Graph showing the RH vs. moisture content (U)plot.11. Precision and Bias11.1 The reproducibility and preci
44、sion of this test method isyet to be established.TABLE 1 Suction Pressure Set-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 98.90300000
45、0 30.0 97.81C169909312. Keywords12.1 moisture content; pressure plate apparatus; water vaporsorptionBIBLIOGRAPHY(1) Nordtest Method: NT BUILD 481, Building Materials: RetentionCurve and Pore Size Distribution.(2) Kumaran, M.K.; Mukhopadhyaya, P.; Normandin, N. 9Determina-tion of equilibrium moisture
46、 contents of building materials: somepractical difficulties,9 Journal of ASTM International, 3, (10), pp.1-9, (Also published in Symposium on Heat, Air and MoistureTransport Properties of Building Materials, ASTM, Toronto, On-tario, April 2006.) doi:10.1520/JAI100265, (NRCC-48382)URL:http:/irc.nrc-c
47、nrc.gc.ca/pubs/fulltext/nrcc48382/(3) Wilkes, K. E.; Atchley, J. A.; Childs, P. W.; Desjarlais. “Effects ofDrying Conditions, Phase Transformations, and Carbonation Reac-tions on Measurements of Sorption Isotherms of Building Materi-als,” Journal of ASTM International, 4, (8), September, pp. 1-10,(A
48、lso published in Symposium on Heat,Air and Moisture TransportProperties of Building Materials, ASTM, Toronto, Ontario, April2006) doi: 10.1520/JAI100459.(4) Wilkes, K. E.; Atchley, J. A.; and Childs, P. W., “Effect of DryingProtocols on Measurement of Sorption Isotherms of GypsumBuilding Materials,”
49、 Proceedings of the International Conferenceon Performance of Exterior Envelopes of Whole Buildings IX,2004.ASTM International takes no position respecting 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 standard is subject to revision at any time by the responsible technical committee and must
