1、Designation: C842 05 (Reapproved 2010)1Standard Specification forApplication of Interior Gypsum Plaster1This standard is issued under the fixed designation C842; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTETypos were corrected editorially in Table 1 and 9.6.2.1 in October 2010.1. Scope1.1 This specification covers the minimum requirements
3、 forfull-thickness (in accordance with Table 1) interior gypsumplastering on gypsum, metal, masonry, or monolithic concretebases designed or prepared to receive gypsum plaster.1.1.1 Gypsum plaster applied to the interior side of exteriorwalls of masonry or concrete shall be isolated from the exterio
4、rwall.1.2 Gypsum plasters shall not be used in exterior locationsor interior “wet” areas.NOTE 1To secure desirable results, this specification should becoordinated with the provisions of Specification C841. General informa-tion concerning full thickness gypsum plastering is contained in AnnexA2, Ann
5、ex A3, and Annex A4.1.3 Details of construction for a specific assembly toachieve the required fire resistance shall be obtained fromreports of fire-resistance tests, engineering evaluations, orlistings from recognized fire testing laboratories.1.4 Details of construction to achieve required sound c
6、on-trol shall be obtained from reports of tests conducted atrecognized sound testing laboratories in accordance with theapplicable sound tests of Test Methods E90, C423,orE492.1.5 The values stated in inch-pound units are to be regardedas the standard. The SI (metric) values given in parentheses are
7、approximate and are provided for information purposes only.1.6 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.2. Referenced Documents2.
8、1 ASTM Standards:2C5 Specification for Quicklime for Structural PurposesC11 Terminology Relating to Gypsum and Related BuildingMaterials and SystemsC28/C28M Specification for Gypsum PlastersC35 Specification for Inorganic Aggregates for Use inGypsum PlasterC59/C59M Specification for Gypsum Casting P
9、laster andGypsum Molding PlasterC61/C61M Specification for Gypsum Keenes CementC206 Specification for Finishing Hydrated LimeC423 Test Method for Sound Absorption and Sound Ab-sorption Coefficients by the Reverberation Room MethodC631 Specification for Bonding Compounds for InteriorGypsum Plastering
10、C841 Specification for Installation of Interior Lathing andFurringC1489 Specification for Lime Putty for Structural PurposesE90 Test Method for Laboratory Measurement of AirborneSound Transmission Loss of Building Partitions and Ele-mentsE492 Test Method for Laboratory Measurement of ImpactSound Tra
11、nsmission Through Floor-Ceiling AssembliesUsing the Tapping Machine3. Terminology3.1 Definitions:3.1.1 Definitions shall be in accordance with TerminologyC11.3.2 Definitions of Terms Specific to This Standard:3.2.1 catfaces, nblemishes or rough depressions in thefinish coat.1This specification is un
12、der the jurisdiction of ASTM Committee C11 onGypsum and Related Building Materials and Systems and is the direct responsibilityof Subcommittee C11.03 on Specifications for theApplication of Gypsum and OtherProducts in Assemblies.Current edition approved Oct. 1, 2010. Published December 2010. Origina
13、llyapproved in 1976. Last previous edition approved in 2005 as C84205. DOI:10.1520/C0842-05R10e1.2For 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 Docum
14、ent Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2 coat, na thickness or layer of plaster applied over asurface in a single application.3.2.2.1 base coat, nthe sum of the scratch and browncoats
15、or the total coats in place prior to application of finishcoats.3.2.2.2 brown coat, nthe second coat of plaster applied inthree-coat work.3.2.2.3 finish coat, nthe last coat of plaster applied ineither two-coat or three-coat work.3.2.2.4 scratch coat, nthe first coat of plaster applied overa lath or
16、 other substrate.3.2.2.5 three-coat work, nplaster applied in three succes-sive coats, leaving time between coats for setting or drying, orboth, of the plaster.3.2.2.6 two-coat work, nscratch and brown coats appliedfrom the same mix with no time allowed for setting of thescratch coat before the brow
17、n coat is applied.3.2.3 gypsum ready mixed plaster, ncalcined gypsumplaster, mixed at the mill with a mineral aggregate, designed tofunction as a base coat to receive various finish coats.3.2.4 metal bases, nexpanded metal, welded or wovenwire, or punched sheet metal plaster bases.3.2.5 smooth-trowe
18、l finish, na finish resulting from steeltroweling.3.2.6 texture finish, na finish resulting from (1) trowelapplication followed by floating or texturing of the surface withany of a variety of tools using a minimum of water or (2)machine application which is or is not hand textured.4. Delivery of Mat
19、erials4.1 All manufactured materials shall be delivered in theoriginal packages, containers, or bundles bearing the brandname and manufacturer (or supplier) identification.5. Protection of Materials5.1 Plasters and other cementitious materials shall be keptdry until used; they shall be stored off th
20、e ground, under cover,and away from walls with condensation and other dampsurfaces. Metal products shall be protected, while stored,against rusting.6. Environmental Conditions6.1 TemperaturesWhere the ambient outdoor temperatureat the building site is less than 55 F (13 C), a temperature ofnot less
21、than 55 F (13 C) and not more than 80 F (27 C)shall be maintained continuously inside the building for aperiod of not less than one week prior to the application ofplaster (Note 2). Temporary heat shall be evenly distributed,using deflective or protective screens to prevent concentratedor uneven hea
22、t or cold on the plaster, and maintained until thepermanent HVAC system is activated.NOTE 2The requirement should minimize the possibility of plastercracking due to structural movements caused by thermal changes fromoutdoor temperature extremes during construction.6.2 VentilationSufficient ventilati
23、on shall be provided toremove excess water given off through the drying process. (SeeAppendix X2 for provisions for ventilating underside of roofsand glazed buildings with and without operable windows.)7. Materials7.1 Gypsum PlastersThe following plasters shall conformto Specification C28/C28M:7.1.1
24、 Ready mixed.7.1.2 Neat.7.1.3 Wood-fibered.7.1.4 Gauging for finish coat.7.2 Gypsum Casting and Molding PlastersSpecificationC5, C59/C59M.7.3 Gypsum Keenes CementSpecification C61/C61M.7.4 Lime:7.4.1 Finishing Hydrated LimeSpecification C206, TypeS.7.4.2 Quicklime for Structural PurposesSpecificatio
25、n C5.7.4.3 Lime Putty for Structural PurposesSpecificationC1489.7.5 Lime PuttyLime putty exceeding 8 weight % ofunhydrated magnesium oxide shall not be used for finish coatplaster.7.6 Aggregates:7.6.1 Aggregates for Base Coat PlasterSpecification C35.7.6.2 Aggregates for Finish Coat PlastersSpecific
26、ationC35, except that gradation shall be within the limits specifiedin Table 2.7.6.3 Sand for job mixed lime putty-gypsum gauged, sandfloat finish (see 9.6.6.1) shall be graded within the limitsspecified in Table 3.TABLE 1 Thickness of PlasterPlaster BaseThickness of Plaster Including FinishCoat, in
27、. (mm)Metal plaster base58 (16) minAll other types of plaster base12 (13) minUnit masonry58 (16) minMonolithic concrete surfaces:AVerticalBC 58 (16) minHorizontalC 18 (3) to58 (16)ABase coat plastering of the same proportions as specified for unit masonry isnot prohibited from being used over plain
28、or reinforced monolithic concrete,provided the surface is first covered with a metal plaster base or first coated witha bonding compound.BFinish coat plaster applied direct to a bonding compound over verticalmonolithic concrete shall be not more than316 in. (4.8 mm) in thickness. Wheremore than316 i
29、n. of finish coat is required to bring such vertical surface to a trueplane, a base coat of plaster shall first be applied to the bonding compound.CWhere horizontal or vertical monolithic concrete surfaces require more than38in. (9.5 mm) or58 in. (15.9 mm) of plaster, respectively, to produce requir
30、ed linesor surfaces, metal plaster base shall be attached to the concrete before applicationof plaster. Where concrete surface requires the application of more than 1 in. (25.4mm) of plaster to produce required lines or surfaces, lath shall be applied overfurring secured to the concrete.Typo correct
31、ed editorially October 2010.TABLE 2 Aggregate for Finish Coat Plasters, PercentageRetained on Each Sieve, CumulativeSieve SizePerlite, Natural and Manufactured SandVolume,% Weight, %max min max minNo. 20 (850 m) 0 . 0 .No. 30 (600 m) 10 . 0.5 .No. 100 (150 m) 100 40 100 40No. 200 (75 m) 100 70 100 7
32、0C842 05 (2010)127.7 WaterWater used in mixing and finishing plaster shallbe potable, and free of such amounts of mineral or organicsubstances that affect the set, the plaster, or any metal in thesystem.NOTE 3Water containing salt or alum, or water in which tools havebeen washed, accelerates the “se
33、t” and may cause efflorescence. Waterfrom stagnant pools and wells frequently contain organic or vegetablematter which may retard the “set,” cause staining, or interfere with thebond.7.8 Bonding CompoundsSpecification C631.8. Surface Preparation8.1 SubstratesSurfaces of substrates for the applicatio
34、n ofgypsum plaster shall be free of materials that will inhibit bondor adhesion, shall be straight, plumb, level, square, and true torequired plan angles and curves. See A2.5.8.1.1 All accessories shall be securely attached to thesubstrate and be installed to accommodate embedment offlanges.8.1.2 Gy
35、psum and Metal LathShall have been installed incompliance with Specification C841.8.2 Conditioning of SurfacesAll depressions in masonryand concrete surfaces deeper than18 in. (3.2 mm) shall bebrought flush to the surface with compatible materials prior toplaster application. Fins or protrusions ext
36、ending more than116in. (1.6 mm) from the surface shall be removed. Protrusionsless than116 in. (1.6 mm) shall be feathered out with compat-ible materials prior to plaster application.8.2.1 MasonryAll masonry surfaces shall be wetted im-mediately prior to the plaster application. No free water shallr
37、emain visible on the substrate surface.8.2.1.1 Where the surface is too smooth to provide mechani-cal key, the surface shall be roughened or bonding compoundshall be used. (See Annex A2.5 and A2.6.)8.2.1.2 Where bond cannot be obtained over the entiresurface by the methods specified in 8.2.1.1, self
38、-furring metallath shall be used in accordance with Specification C841.8.2.2 Monolithic concretebonding compounds shall beused prior to plastering all monolithic concrete surfaces. (SeeA2.6.)8.2.3 Grounds, beads, and screeds shall be installed prior tothe plastering as modified herein.8.3 Grouting:8
39、.3.1 Metal bases for solid partitions shall be grouted withgypsum plaster leaving14 in. (6.4 mm) below the top edge ofthe base, and be formed with a center groove so that the lathextends34 in. (19 mm) below the top edge of the base, orplaster grout shall be placed after installation of lath.8.3.2 Me
40、tal FramesHollow door and window framesshall be filled with gypsum plaster grout.9. Mix Design9.1 Mixing, GeneralAll plaster mixing shall be done bymechanical means unless hand mixing is specified.9.1.1 Retempered, partially set, frozen, caked or lumpymaterial shall not be used.9.1.2 Each batch shal
41、l be mixed separately and mixers shallbe free of all set and hardened materials prior to mixing eachbatch.9.1.3 All tools shall be kept clean.9.1.4 The setting time shall be not more than 4 h.9.2 Hand Mixingsee Annex A3.1.9.3 Mechanical MixingIn accordance with manufactur-ers printed directions. See
42、 Annex A3.2.9.4 Base Coat Proportions:9.4.1 Gypsum Neat PlasterProportions of sand, perlite, orvermiculite aggregate to 100 lb (45.4 kg) of gypsum neatplaster shall be not more than those specified in Table 4. (SeeA2.3 for equivalent measure for aggregates.)9.4.2 Gypsum Ready Mixed PlasterShall be u
43、sed with theaddition of water only.9.4.3 Gypsum Wood-Fibered PlasterProportion of damp,loose sand or perlite or vermiculite shall be not more than 1 ft3(0.028 m3) to 100 lb (45.4 kg) of gypsum wood-fibered plaster.9.5 Preparation of Lime Putty:9.5.1 Lime putty shall be prepared from Type S hydratedl
44、ime or pulverized quicklime, in accordance with the manufac-turers printed directions.9.5.2 Hydrated LimeType S lime shall only be used aftersoaking for the time period required in accordance with themanufacturers printed directions.9.6 Finish Coat Proportions:9.6.1 Finish coats shall be either read
45、y mixed or job mixedin accordance with Table 5 and Table 6.9.6.1.1 Where thickness of the finish coat is more than18in. (3.2 mm), the proportion of the gypsum gauging plastershall be increased to minimize shrinkage type cracks.9.6.2 Troweled Finishes of lime putty gauged with gypsumgauging plaster o
46、r ready mixed gypsum plaster shall beproportioned in accordance with Table 5.9.6.2.1 Where finish in 9.6.2 is to be applied over base coatscontaining perlite or vermiculite, the addition of not lessthan12 ft3(0.014 m3) or not more than 1 ft3(0.028 m3)offineaggregate meeting the sieve analysis of Tab
47、le 2 shall be addedto the mix.9.6.3 Troweled finishes of lime putty gauged with gypsumKeenes cement shall be specified as medium or hard and shallbe proportioned in accordance with Table 5.9.6.3.1 When finish in 9.6.3 is mechanically mixed, thewater shall be placed in the mixer first, then the lime,
48、 the fineaggregate (if used), and finally the gypsum Keenes cement.9.6.4 Troweled finishes of gypsum ready mixed plaster shallbe mixed in accordance with Table 5.9.6.5 Float finishes of lime putty gauged with gypsumgauging plaster shall be proportioned in accordance with Table5.TABLE 3 Sand for Job-
49、Mixed Lime Putty-Gypsum Gaged SandFloat Finish, Percent Retained on Each Sieve by Weight,CumulativeSieve Size max minNo. 16 (1.18 mm) 0 0No. 30 (600 m) 50 20No. 50 (300 m) 70 50No. 100 (150 m) 100 80C842 05 (2010)13TABLE 4 Base Coat ProportionsAPlaster BaseAggregatesBSand Perlite or VermiculiteCBy Volume, ft3(m3), Damp and Loose By Weight, lb (kg), Damp and Loose By Volume, ft3(m3)Over Gypsum LathTwo-coat work:Base coat 212 (0.071) 250 (113) 2 (0.06)Three-coat work:Scratch coat 2 (0.056) 200 (91)
