ASTM C1794-2015 Standard Test Methods for Determination of the Water Absorption Coefficient by Partial Immersion《采用局部浸湿法测定吸水系数的标准试验方法》.pdf

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1、Designation: C1794 15Standard Test Methods forDetermination of the Water Absorption Coefficient by PartialImmersion1This standard is issued under the fixed designation C1794; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year

2、 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 defines a procedure to determine thewater absorption coefficient of a material by partial submer-

3、sion. The scope is to evaluate the rate of absorption of waterdue to capillary forces for building materials in contact withnormal or driving rain above grade. The procedure is typicallysuitable mainly for masonry material, plaster, or a coating incombination with a substrate; but it can also be use

4、d forinsulation materials. This test method is designed to be usedonly on homogeneous materials and does not apply to materialsthat are composites or non-homogeneous (for example, FacedRigid Closed-cell Insulation). It is not within the scope of thisstandard to determine liquid uptake phenomena in b

5、elow-gradeapplications. The water absorption coefficient is mainly used asan input datum for numerical simulation of the combined heatand moisture transport in building envelopes for design andforensic investigation purposes.1.2 The values stated in either SI units or inch-pound unitsare to be regar

6、ded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard. However, derived results can be convertedfrom one system to t

7、he other using appropriate conversionfactors (see Table 1).1.3 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-bi

8、lity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C168 Terminology Relating to Thermal Insulation2.2 Other Standards:3ISO 9346 Hygrothermal performance of buildings and build-ing materialsPhysical quantities for mass transferVocabularyISO 15148 Determination of w

9、ater absorption coefficient bypartial immersion3. Terminology3.1 Definitions of TermsFor definitions associated withthermal insulation issues refer to Terminology C168. Fordefinitions associated with water absorption refer to the termsand definitions given in ISO 9346.3.2 Definitions of Terms Specif

10、ic to This Standard:3.2.1 homogeneous material, nmaterials, which proper-ties are uniform on a macroscopic scale.3.2.2 water absorption coeffcient, nmass of water ab-sorbed by a test specimen per face area and per square root oftime (see Eq 2).3.3 Symbols and Unitsthe Symbols and Units shown inTable

11、 2 are used.4. Summary of Test Method and Use4.1 Water absorption by partial submersion will be calcu-lated by measuring the change in weight of the specimen in asituation when the bottom surface is in contact with liquidwater within a time range of at least 24 h. Liquid water that isonly adsorbed o

12、n the surface shall not be taken into accountand shall be removed before weighing, for example., byblotting with a sponge.4.2 The purpose is of this test is to derive reliable data onthe capillary water uptake of building materials in appropriateunits using a simple apparatus. These data can also be

13、 used asmaterial properties for hygrothermal simulation of the buildingenvelope for design and forensic purposes.5. Significance and Use5.1 The purpose of these tests is to obtain, by means ofsimple apparatus, reliable and easy to determine values of1This test method is under the jurisdiction ofASTM

14、 Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.33 on InsulationFinishes and Moisture.Current edition approved March 1, 2015. Published April 2015. DOI: 10.1520/C1794-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cust

15、omer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM Internat

16、ional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1liquid water transport for capillary active materials expressedin suitable units. These values are for use as part of the materialproperties in hygrothermal analysis tools for building envelopedesign and foren

17、sic studies. As the topic of liquid transportphenomena in porous materials is very complex, Appendix X1in ISO 15148 shows some more detailed background informa-tion.6. Apparatus6.1 The apparatus must contain the following:6.1.1 A scale to measure the weight of the specimen with anaccuracy within 60.

18、1 % of the specimens mass.6.1.2 A water tank with a regulation system to keep thewater level constant within 63mm(618 in.) and equipment tokeep the position of the specimen at least 5 mm (14 in.) abovethe bottom of the tank without harming the specimen.6.1.3 Equipment to measure the time with accura

19、cy of atleast 1 second.7. Test Specimen7.1 ShapeThe shape shall represent typical material di-mensions and must have a constant area to ensure one-dimensional moisture flow. The surfaces shall be as flat aspossible.7.2 AreaThe area which is in contact with the water mustbe at least 50 cm2(8 in.2). H

20、owever, in the case of materialsincluding macroscopic particles such as aggregates, the side ofa square specimen or the smallest diameter of the face shall beat least ten times the largest particle size. Influences of irregularsurface structures shall be neglected if those irregular surfacestructure

21、s are part of the materials design.NOTE 1Larger specimens, preferably with a face area of at least 100cm2(16 in.2), are advised as they will lead to greater accuracy.7.3 ThicknessWhere possible, use a specimen thicknesswhich represents the full product thickness. When specimensare cut from products

22、they shall be representative of thematerial to be assessed and thick enough to enable handlingwithout damage. In the case of materials including macro-scopic particles such as aggregates, it is preferable that thethickness be at least ten times the largest particle size, but shallbe no less than fiv

23、e times, the largest particle size.7.4 NumberAt least three specimens shall be tested. If thewater contact area of the individual specimens is less than 100cm2(16 in.2), at least six specimens shall be tested representinga total area of at least 300 cm2(47 in2).7.5 PreparationTest specimens shall be

24、 representative ofthe whole material and shall be cut so that they do not includeproduct edges. In the case of materials known to be non-isotropic, sets of test specimens shall be prepared in allorientations of the potential use of the material. The testspecimens shall be prepared by methods that do

25、 not change theoriginal structure of the product; any skins, facings or coatingsshall be retained. In the case of products such as coatings, thinrendering or plasterwork that are normally adhered to asubstrate in use, specimens shall be made up from the productand a normal substrate combined. The to

26、tal thickness then isthe sum of the coating and the substrate. The sides of a solidspecimen shall be sealed with a water and vapor tight sealantthat does not react chemically with it or significantly penetratethe pores of the product as shown in Fig. 1. It is especiallyimportant that the sides of sp

27、ecimens with surface coatings aresealed to prevent bypassing of the coating. If sealing is notpossible in the case of very low density fibrous or loose fillmaterials place them in a tightly fitting tube supported on awire mesh placed over the mouth of the tube. The open area ofthe mesh shall be as l

28、arge as possible while completelysupporting the sample during the whole course of the test. Inthis case, to minimize the edge effects, the face area of thespecimen shall be at least 100 cm2(16 in2). The surface incontact with the water shall be plane, allowing for the normalsurface roughness of the

29、material.7.6 ConditioningThe test specimens shall be stored underthe test conditions (see 8.1) until the mass of each specimenhas stabilized to within 0.1 % of its total mass, when measuredover 24 h. In case the stability of 0.1 % of mass cannot bereached, additionally the relative humidity shall be

30、 controlled,for example, by using a climatic-controlled room or chamber,to be within 50 % 6 5 % and furthermore the specimen mustbe exposed to these conditions until the end of the measure-ment except of the short time of the weighing process.8. Procedure8.1 The procedure must be conducted within th

31、e conditionsstated in Table 3.TABLE 1 Metric Units and Conversion FactorsAMultiply byTo Obtain (for thesame test condition)Aream210.8 ft2ft29.29 10-2m2Masskg 2.20 lblb 0.454 kgMass per Areakg/m20.205 lb/ft2lb/ft24.88 kg/m2Water Absorption Coefficientkg/(m2=s) 0.205 lb/(ft2=s)lb/(ft2=s) 4.88 kg/(m2=s

32、)kg/(m2=h) 0.205 lb/(ft2=h)lb/(ft2=h) 4.88 kg/(m2=h)AThe IP unit system includes several meanings of the pound unit lb. In thisstandard the unit lb refers to pound mass only.TABLE 2 Symbols and UnitsASymbol Quantity SI unit IP unitA Face Area m2ft2AwWater Absorption Coefficient kg/(m2=s) lb/(ft2=s)A

33、wtWater Absorption Coefficient, relatedto a specific time, t, in secondskg/(m2=s) lb/(ft2=s)mtmass gain per face area after time t kg/m2lb/ft2MiInitial mass of specimen kg lbmtMass of specimen after time t kg lbmiStarting mass kg lbt Time s or h hWwWater Absorption Coefficient kg/(m2=h) lb/(ft2=h)Ww

34、tWater Absorption Coefficient, relatedto a specific time, t, in hourskg/(m2=h) lb/(ft2=h)AThe IP unit system includes several meanings of the pound unit lb. In thisstandard the unit lb refers to pound mass only.C1794 1528.2 Weigh each specimen at steady state with an accuracy of6 0.1 % of mass to de

35、termine the initial mass miafterconditioning.8.3 Fill the tank with water to the specified level stated instep 8.4. Wait until the temperature of the water has reached thespecimen temperature.8.4 Put the specimen into the tank and ensure a distancebetween the specimen and the tank bottom of at least

36、 5 mm (14in.) by using distance pins as shown in Fig. 1. The pins shallnot affect the liquid uptake at the specimen surface. It must beensured that no air pockets are trapped between the surface andthe water. If necessary, place a weight on the top of thespecimen. The water level shall be kept at a

37、constant 5 6 2.5mm (0.2 6 0.1 in.) above the highest point of the absorbingsurface of the specimen.8.5 If a weight is used to fix the specimens position, it mustbe ensured that the specimen is not mechanically influenced bythe weight.8.6 To avoid anisotropic effects half the specimens of ahomogeneou

38、s material cut from the same sample must beplaced with one major face downwards. The other half withthis must face upwards. Specimens of non-homogeneousmaterials shall be placed with the face which is normallyexposed to driving rain or other expected water sourcesdownwards. This is especially import

39、ant in the case of rendersand coatings which are tested on their substrate.8.7 Start the time measurement precisely when the speci-men first contacts the liquid water.8.8 After approximately 5 min, remove the specimen fromthe water and remove surface-adhered water drops using amoist sponge that has

40、been squeezed out beforehand. Weighthe specimen with an accuracy of 60.1 % of the mass, mi,attime t. Put the specimen back into the water. Repeat themeasurement at least two more times within 24 h to derive a 1h, 2 h, 4 h, 8 h series of measurements for miat time t. Be sureto take a measurement at 4

41、 h.NOTE 2The measurement shall be accomplished as quickly aspossible and the specimen returned to the water immediately afterwards.A time of less than a minute expected to be appropriate.8.9 The method of evaluation depends on the shape of thecurve stated in Section 9, and the shape of the curve dep

42、endsalmost entirely on how drying is handled. Conduct the calcu-lations and plots of the curve immediately after the weighing todetermine the end of the weighing process.NOTE 3Some materials can cause some nonlinear effects especially atthe beginning.8.10 If liquid water is visible on the top surfac

43、e of thespecimen, the measurement shall be terminated.8.11 If the liquid uptake is less than 0.001 kg/m2(0.0002lb/ft2) of the absorbing surface, the measurement can beterminated and the material can be specified as resistant againstliquid water uptake.8.12 After termination of the measurement the sp

44、ecimenshall be investigated for cracking of the sealant which wasapplied to the specimen in 7.5.9. Calculation and Expression of Results9.1 Calculate the area A in m2(ft2) perpendicular to thedirection of flow of the water. In the case of a low-density fiberor loose fill material, the area of the tu

45、be shall be used.9.2 Calculate the difference between the area-related massat each weighing according to the equation:mt5mt2 miA(1)and plot these against the square root of the time t.FIG. 1 Example of a Suitable Testing ApparatusTABLE 3 Test ConditionsTemperatureAllowed range of test conditions 18

46、to 23 C (64 to 73 F)Allowed variation during test 2 C ( 4 F)C1794 1539.3 The graph resulting from step 8.2 will be one of twodifferent types (type A or B) shown in Figs. 2 and 3. It must bedistinguished whether liquid water was seen on the top surfaceof the specimen after the test was terminated.9.4

47、 Type A GraphAs shown in Fig. 2 left, type A graphsshow a linear relationship until the end of the test; a regressioncurve can be used through the points of mtagainst t. Extendthe regression curve to the vertical axes to determine m0. Thewater absorption coefficient Awand Wwwill then be calculatedfr

48、om:Aw5mtf2 m0=tf(2)where:mtf= value of m on the regression curve at time tf,inkg/m2(lb/ft2), andtf= duration of the test (typically 1 day) in seconds.orWw5mtf2 m0=tf(3)where:tf= the duration of the test (typically 1 day) in hours.9.4.1 If the graph shows a slope with a sudden decrease ofthe slope, a

49、s can be seen at right in Fig. 2, the water front insidethe specimen has most likely reached the top surface. In thiscase, the points after the sudden decrease of the slope shall beignored.9.5 Type B GraphAs shown in Fig. 3, type B graphs showa nonlinear relationship between mtand t. In this case, themeasured value of mtat4h(2 h) shall be used for mtfandAwor Wwshall be calculated according to:Aw,45mtf2 m0=14400s(4)Ww,45mtf2 m02=h(5)9.5.1 If liquid water has reached the top surface of thespecimen before t