1、Designation: C 28/C 28M 00 (Reapproved 2005)Standard Specification forGypsum Plasters1This standard is issued under the fixed designation C 28/C 28M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last revision. A numb
2、er in parentheses indicates the year of last reapproval.A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This specification covers four gypsum plasters; gypsummil
3、l-mixed plaster, gypsum neat plaster, gypsum wood fiberedplaster and gypsum gauging plaster.NOTE 1Specification C 842 contains application procedures for inte-rior gypsum plaster.1.2 The values stated in either inch-pound or SI (metric)units are to be regarded separately as the standard. Within thet
4、ext, the SI units are shown in brackets. The values stated ineach system shall be used independently of the other. Valuesfrom the two systems shall not be combined. This paragraphdoes not apply to the appendix.1.3 The text of this standard references notes and footnoteswhich provide explanatory mate
5、rial. These notes and footnotes(excluding those in tables and figures) shall not be consideredas requirements of the standard.1.4 The following safety hazards caveat pertains only to thetest methods described in the appendix to this specification.This standard does not purport to address all of the
6、safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C11 Terminology Relating to Gypsu
7、m and Related Build-ing Materials and SystemsC22 Specification for GypsumC35 Specification for Inorganic Aggregates for Use inGypsum PlasterC 471M Test Methods for Chemical Analysis of Gypsumand Gypsum ProductsC 472 Test Methods for Physical Testing of Gypsum, Gyp-sum Plasters, and Gypsum ConcreteC
8、778 Specification for Standard SandC 842 Specification for Application of Interior GypsumPlasterE11 Specification for Wire-Cloth and Sieves for TestingPurposes3. Terminology3.1 DefinitionsDefinitions shall be in accordance withTerminology C11.3.2 Definitions of Terms Specific to This Standard:3.2.1
9、gypsum gauging plaster for finish coat, na calcinedgypsum plaster designed to be mixed with lime putty for thefinish coat.3.2.2 gypsum neat plaster, ncalcined gypsum mixed atthe mill with other ingredients to control working quality andsetting time.3.2.2.1 DiscussionNeat plaster is either fibered or
10、 unfi-bered. The addition of aggregate is required on the job.3.2.3 gypsum mill-mixed plaster, ncalcined gypsum plas-ter, mixed at the mill with a mineral aggregate, designed tofunction as a base coat to receive various finish coats.3.2.3.1 DiscussionOther materials are not prohibited frombeing adde
11、d to control setting time and other desirable workingproperties.3.2.4 gypsum wood-fibered plaster, nA calcined gypsumplaster in which wood fiber is used as an aggregate.4. Materials4.1 Calcined GypsumCalcined gypsum shall be manufac-tured from gypsum meeting the requirements of SpecificationC22.4.2
12、Vermiculite Aggregate, Specification C35.4.3 Perlite Aggregate, Specification C35.1This specification is under the jurisdiction of ASTM Committee C11 onGypsum and Related Building Materials and Systems and is the direct responsibilityof Subcommittee C11.01 on Specifications and Test Methods for Gyps
13、um Products.Current edition approved Oct. 1, 2005. Published October 2005. Originallyapproved in 1920. Last previous edition approved in 2000 as C 28/C 28M 001.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
14、 ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.4 Sand Aggregate, Specification C35.4.5 Ottawa Sand, Specification C 778 for 2030 sa
15、nd.4.6 Wood Fiber, non staining wood fiber.5. Composition5.1 When tested in accordance with Test Methods C 471M,calcined gypsum shall contain no less than 66.0 weight %CaSO412 H2O.5.2 Aggregateplasters shall contain a volume of aggregatenot more than that shown in Table 1.NOTE 2An approximation of t
16、he aggregate content may be made byusing the test methods in the appendix. A more accurate method fordetermining sand in plaster is described in Test Methods C 471M. TestMethods C 471M requires that the original sand and plaster componentsbe available separately.6. Mechanical Properties6.1 Compressi
17、ve StrengthWhen tested in accordance withTest Methods C 472 the compressive strength shall be asspecified in Table 1.6.2 Setting TimeWhen tested in accordance with TestMethods C 472 using the Vicat method, the setting time shallbe as specified in Table 1.NOTE 3Setting TimeAttention is directed to co
18、nditions affecting jobset of gypsum plasters that are usually beyond the control of the producer.Materials added at the site of application such as water and aggregatesaffect job sets. In addition, the various bases with different absorptivevalues may affect job performance. The plaster may be retar
19、ded to providea setting time of not more than 4 h. Setting times more than 2 h may resultin lower compressive strengths.6.3 Fineness of Gauging Plaster for Finish CoatWhentested in accordance with Test Method C 472 all shall pass aNo. 14 1.4 mm sieve and not less than 60 % shall pass a No.100 150 m
20、sieve.37. Sampling7.1 At least 1 % of the packages, but not less than 5packages, shall be sampled. Packages to be sampled shall beselected at random. Samples shall be taken both from the outerportion and the center of each package. The materials soobtained shall be thoroughly mixed to provide a comp
21、ositesample of not less than 7 lb 3.2 kg. This composite sampleshall be placed immediately in a clean, dry, airtight containerfor delivery to the laboratory.8. Packaging and Package Marking8.1 Gypsum plasters shall be dry and free of lumps, andshall be shipped in packages.8.2 When shipped for resale
22、, the following informationshall be legibly marked on each package or on a tag of suitablesize attached to the package:8.2.1 Name of manufacturer or seller,8.2.2 Brand, and8.2.3 Net weight of the package.9. Inspection9.1 Inspection of the gypsum plaster shall be agreed uponbetween the purchaser and
23、the supplier as part of the purchaseagreement.10. Rejection10.1 Rejection of gypsum plaster that fails to conform to therequirements of this specification shall be reported to theproducer or supplier promptly and in writing. The notice ofrejection shall contain a statement documenting requirementsof
24、 this specification.11. Certification11.1 When specified in the purchase agreement, a manufac-turers or suppliers report shall be furnished at the time ofshipment certifying that the product is in compliance with thisspecification.12. Keywords12.1 aggregate; gauging plaster; gypsum plaster; mill-mix
25、edplaster; neat plaster; plaster; wood fibered plaster3Detailed requirements for these sieves are given in Specification E11.TABLE 1 Composition and Physical PropertiesProduct Aggregate TypeComposition, Aggregate per 100 lbof Plaster, not more thanSetting TimeACompressive StrengthBnot less thanft3m3
26、hours psi MPaMill-Mixed Plaster over Lath Base Vermiculite 2 0.057 112 to 8 450 3.1Perlite 2 0.057 112 to 8 600 4.1Sand 2.5 0.071 112 to 8 700 4.8Mill-Mixed Plaster over Masonry Vermiculite 3 0.085 112 to 8 325 2.2Perlite 3 0.085 112 to 8 400 2.8Sand 3 0.085 112 to 8 400 2.8Neat Plaster none . . 2 t
27、o 16C750D5.2Wood Fibered Plaster none . . 112 to 8 1200 8.3Gauging Plaster none . .E1200 8.3ASetting time shall be not less than the shorter time shown nor more than the longer time shown.BCompressive strengths are as tested at the setting times specified in Test Methods C 472.CWhen mixed with 3 par
28、ts by weight of Ottawa sand.DWhen mixed with 2 parts by weight of Ottawa sand.EWhen not retarded, the setting time shall be not less than 20 nor more than 40 minutes and, when retarded, not less than 40 minutes.C 28/C 28M 00 (2005)2APPENDIX(Nonmandatory Information)X1. DETERMINATION OF AGGREGATE CON
29、TENT OF MILL-MIXED PLASTERINTRODUCTIONThe determination of the aggregate content of mill-mixed plaster is normally not precise. Mostgypsum plasters contain natural impurities that cannot be separated from the aggregate by eithermechanical or chemical means. A better estimate can be made by obtaining
30、 the approximate purity ofthe gypsum plaster used in the product from the manufacturer.An accurate method for determining sand in set plaster is contained in Test Methods C 471M.Separate specimens of the sand and gypsum plaster used in the mill-mixed plaster are required for TestMethods C 471M.X1.1
31、ScopeX1.1.1 This appendix covers mechanical and chemical testmethods for separating the aggregate from gypsum plaster.X1.2 Mechanical SeparationX1.2.1 Significance and Use:X1.2.1.1 This test method is used to estimate the weight orvolume of aggregate contained in mill-mixed gypsum plastersby mechani
32、cal separation.X1.2.2 Interferences:X1.2.2.1 It is assumed by this test method that the aggregatemeets Specification C35and that only a minor portion of theaggregate passes through a 100-mesh (150 m) sieve. To theextent that a greater portion passes the 100 mesh sieve, theresults will show lower val
33、ues for volume of the aggregate, andhigher values for the weight of the gypsum plaster, thanactually in the sample.X1.2.3 Apparatus:X1.2.3.1 SieveSpecification E11, 100 mesh (150 m).X1.2.3.2 Balancewith a capacity of not less than 100 gand a precision of at least 0.1 g.X1.2.4 Procedure:X1.2.4.1 Weig
34、h 100 g of the sample to 60.1 g.X1.2.4.2 Sieve the 100 g specimen through the 100 mesh(150 m) sieve. Examine the material on the sieve to be suresmall lumps or agglomerates of plaster are not retained. Theretained portion is assumed to be aggregate. If the weight ratioof the aggregate and plaster is
35、 to be determined, weigh eachportion to the nearest 0.1 g. If the volume ratio of aggregate tothe weight of plaster is to be determined, measure the volumeof aggregate retained on the sieve to the nearest mL and weighthe material passing through the sieve to the nearest 0.1 g.X1.2.5 Calculation and
36、Report:X1.2.5.1 Weight Ratio Calculate and report the weightratio as pounds of aggregate/100 lb (45 kg) of plaster per EqX1.1.WR5wawp3 100 (X1.1)where:WR= weight ratio, lbs of aggregate/100 lbs (45 kg) ofplaster,wa= weight of aggregate, g, and,wp= weight of plaster, g.X1.2.5.2 Volume Ratio Calculate
37、 and report the volumeratio as cubic feet of aggregate/100 lbs (45 kg) of plaster per EqX1.2.VR5vawp3 1.60 (X1.2)where:VR= Volume ratio, cubic feet of aggregate per 100 lbs ofplaster,va= volume of aggregate, mL, andwp= weight of plaster, g.X1.2.6 Precision and Bias:X1.2.6.1 It is not practical to sp
38、ecify the precision or thebias of this test method because of the unknown variabilities inthe particle sizes of the aggregates.X1.3 Chemical SeparationX1.3.1 Significance and Use:X1.3.1.1 This test method is used to estimate the weight orvolume of aggregate contained in mill-mixed gypsum plastersby
39、chemical separation.X1.3.2 Interferences:X1.3.2.1 It is assumed in this test method that all of thematerial insoluble in ammonium acetate is aggregate and thesoluble material is plaster. In many cases there is a significantamount of insoluble material in the plaster. To the extent thatthis is true i
40、t will produce erroneous calculated amounts ofaggregate and plaster. If possible, obtain the approximatepurity of the plaster from the manufacturer. This informationwill greatly increase the accuracy of the results.C 28/C 28M 00 (2005)3X1.3.2.2 In the volume calculation it is assumed that thevolume
41、of the insoluble material in the plaster is insignificantcompared to the volume of the aggregate. This is usually thecase.X1.3.3 Apparatus:X1.3.3.1 Analytical Balancewith a precision of 0.001 g.X1.3.3.2 Drying Oven capable of maintaining a tempera-ture of 100 to 110C.X1.3.4 Reagents:X1.3.4.1 Ammoniu
42、m Acetate Solution (250 g/L)dissolve250 g of ammonium acetate (NH4C2H3O2) in water and diluteto1L.X1.3.4.2 Ammonium Hydroxide (1+59)Mix one volumeof concentrated (NH4OH) (sp gr 0.90) with 59 volumes ofwater.X1.3.5 Procedure:X1.3.5.1 Accurately weigh 40 6 0.05 g of the sample intoa 1-L beaker. Add 60
43、0 to 700 mL of (NH4C2H3O2) solutionthat is slightly alkaline to litmus paper. If acidic, add a few mLof (NH4OH) (1+59) to the stock (NH4C2H3O2) solution torender it slightly alkaline prior to the addition of the testsample.X1.3.5.2 Warm the suspension to a temperature of 70 6 5Cand stir continuously
44、 for 20 to 30 min. Filter the warmsuspension through a small Buchner funnel or Gooch cruciblein which filter paper has previously been formed, the funneland mat having been dried at 110C to a constant weight within0.01 g. Refilter the first 100 mL of the filtrate. Wash theaggregate remaining in the
45、beaker onto the filter with anadditional 100 mL of warm (NH4C2H3O2) solution. Wash thebeaker and residue with 200 to 300 mL of water, dry the funneland aggregate at 100C to constant weight.X1.3.6 Calculation and Report:X1.3.6.1 Weight Ratio Calculate and report the weightratio as pounds of aggregate
46、/100 lbs (45 kg) of plaster per EqX1.3.WR5w12w12 w2pw12 w2p3 100 (X1.3)where:WR= weight ratio, lbs of aggregate/100 lbs (45 kg) ofplaster,w1= Weight of original specimen, g,w2= weight of insoluble residue retained on filter, g, andp = Purity of gypsum plaster expressed as a decimal (thatis, 85 % pur
47、ity = 0.85). If purity is unknown use 0.9(90 %) as an estimate.X1.3.6.2 Volume Ratio Calculate the volume ratio ascubic feet of aggregate/100 lbs (45 kg) of plaster per Eq X1.4.VR5v1w12 w2p3 1.6 (X1.4)where:VR= volume ratio, cubic feet of aggregate/100 lbs (45 kg)of plaster,v1= volume of insoluble r
48、esidue retained on filter, mL,w1= weight of original specimen, g,w2= weight of insoluble residue retained on filter, g, andp = purity of gypsum plaster expressed as a decimal (thatis, 85 % purity = 0.85). If purity is unknown use 0.9(90 %) as an estimate.X1.3.7 Precision and Bias:X1.3.7.1 It is not
49、practical to specify the precision or thebias of this test method because of the unknown variabilities inthe purity of the plaster.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
