ASTM_C_28_-_C_28M_-_10_2015.pdf

Designation:C28/C28M10(Reapproved 2015)Standard Specification forGypsum Plasters1This standard is issued under the fixed designation C28/C28M;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This specification covers gypsum mill-mixed plaster,gypsum neat plaster,gypsum wood-fibered plaster,and gyp-sum gauging plaster.NOTE1Specification C842 contains application procedures for inte-rior gypsum plaster.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.Within the text,theSI units are shown in brackets.The values stated in eachsystem may not be exact equivalents;therefore,each systemshall be used independently of the other.Combining valuesfrom the two systems may result in non-conformance with thestandard.This paragraph does not apply to the appendix.1.3 The text of this standard references notes and footnoteswhich provide explanatory material.These notes and footnotes(excluding those in tables and figures)shall not be consideredas requirements of the standard.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 prior to use.2.Referenced Documents2.1 ASTM Standards:2C11 Terminology Relating to Gypsum and Related BuildingMaterials and SystemsC22/C22M Specification for GypsumC35 Specification for Inorganic Aggregates for Use in Gyp-sum PlasterC471M Test Methods for ChemicalAnalysis of Gypsum andGypsum Products(Metric)C472 Test Methods for Physical Testing of Gypsum,Gyp-sum Plasters and Gypsum ConcreteC778 Specification for SandC842 Specification for Application of Interior Gypsum Plas-terE11 Specification for Woven Wire Test Sieve Cloth and TestSieves3.Terminology3.1 DefinitionsDefinitions shall be in accordance withTerminology C11.3.2 Definitions of Terms Specific to This Standard:3.2.1 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 at themill with other ingredients to control working quality andsetting time.3.2.2.1 DiscussionNeat plaster is either fibered or unfi-bered.The addition of aggregate is required on the job.3.2.3 gypsum mill-mixed plaster,ncalcined gypsumplaster,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 added 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/C22M.4.2 Vermiculite Aggregate,Specification C35.4.3 Perlite Aggregate,Specification C35.4.4 Sand Aggregate,Specification C35.4.5 Ottawa Sand,Specification C778 for 2030 sand.4.6 Wood Fiber,non staining wood fiber.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 Gypsum Products.Current edition approved Oct.1,2010.Published October 2015.Originallyapproved in 1920.Last previous edition approved in 2010 as C28/C28M 10.DOI:10.1520/C0028_C0028M-10R15.2For 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 5.Composition5.1 When tested in accordance with Test Methods C471M,calcined gypsum shall contain no less than 66.0 weight%CaSO412H2O.5.2 Aggregateplasters shall contain a volume of aggregatenot more than that shown in Table 1.NOTE2An approximation of the 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 C471M.TestMethods C471M requires that the original sand and plaster components beavailable separately.6.Mechanical Properties6.1 Compressive StrengthWhen tested in accordance withTest Methods C472 the compressive strength shall be asspecified in Table 1.6.2 Setting TimeWhen tested in accordance with TestMethods C472 using the Vicat method,the setting time shall beas specified in Table 1.NOTE3Setting TimeAttention is directe