1、Designation: C 842 05Standard Specification forApplication of Interior Gypsum Plaster1This standard is issued under the fixed designation C 842; 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
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This specification covers the minimum requirements forfull-thickness (in accordance with Table 1) interior gypsumplastering on gypsum, metal,
3、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 exteriorwall.1.2 Gypsum plasters shall not be used in exterior locationsor interior “wet” areas.NOT
4、E 1To secure desirable results, this specification should becoordinated with the provisions of Specification C 841. General informa-tion concerning full thickness gypsum plastering is contained in AnnexA2, Annex A3, and Annex A4.1.3 Details of construction for a specific assembly toachieve the requi
5、red 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 con-trol shall be obtained from reports of tests conducted atrecognized sound testing labora
6、tories in accordance with theapplicable sound tests of Test Methods E 90, C 423, or E 492.1.5 The values stated in inch-pound units are to be regardedas the standard. The SI (metric) values given in parentheses areapproximate and are provided for information purposes only.1.6 The text of this standa
7、rd 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 Documents2.1 ASTM Standards:2C5 Specification for Quicklime for Structural PurposesC11 Terminolog
8、y Relating to Gypsum and Related Build-ing Materials and SystemsC28 Specification for Gypsum PlastersC35 Specification for Inorganic Aggregates for Use inGypsum PlasterC 59/C 59M Specification for Gypsum Casting and Mold-ing PlasterC 61/C 61M Specification for Gypsum Keenes CementC 206 Specification
9、 for Finishing Hydrated LimeC 423 Test Method for Sound Absorption and Sound Ab-sorption Coefficients by the Reverberation Room MethodC 631 Specification for Bonding Compounds for InteriorGypsum PlasteringC 841 Specification for Installation of Interior Lathing andFurringC 1489 Specification for Lim
10、e Putty for Structural PurposesE90 Test Method for Laboratory Measurement ofAirborne-Sound Transmission Loss of Building Partitionsand ElementsE 492 Test Method for Laboratory Measurement of ImpactSound Transmission Through Floor-Ceiling AssembliesUsing the Tapping Machine3. Terminology3.1 Definitio
11、ns: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.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
12、of the scratch and browncoats 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
13、 plaster applied overa lath or other substrate.1This specification is under 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
14、.Current edition approved May 1, 2005. Published May 2005. Originallyapproved in 1976. Last previous edition approved in 1999 as C 842 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
15、information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2.5 three-coat work, nplaster applied
16、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 brown coat is applied.3.2.3 gypsum ready mixed plaster, ncalcin
17、ed 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-trowel finish, na finish resulting from steeltroweling.3.2.6 tex
18、ture 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 Materials4.1 All manufactured materials shall be delivered in
19、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 the ground, under cover,and away from walls with condensation
20、 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 than 55 F (13 C) and not more than 80 F (27 C)shall be main
21、tained 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 heat or cold on the plaster, and maintained until thepermanent
22、 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 ventilation shall be provided toremove excess water given off throug
23、h 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 C28:7.1.1 Ready mixed.7.1.2 Neat.7.1.3 Wood-fibered.7.1.4 Gauging for fin
24、ish coat.7.2 Gypsum Casting and Molding PlastersSpecificationC 59/C 59M.7.3 Gypsum Keenes CementSpecification C 61/C 61M.7.4 Lime:7.4.1 Finishing Hydrated LimeSpecification C 206, TypeS.7.4.2 Quicklime for Structural PurposesSpecificationC5.7.4.3 Lime Putty for Structural PurposesSpecificationC 1489
25、.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 PlasterSpecificationC35.7.6.2 Aggregates for Finish Coat PlastersSpecificationC35, except that gradation shall be within the limits speci
26、fiedin 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 3.7.7 WaterWater used in mixing and finishing plaster shallbe potable, and free of such amounts of mineral or organicsubstances that affect the set, th
27、e plaster, or any metal in thesystem.NOTE 3Water containing salt or alum, or water in which tools havebeen washed, accelerates the “set” and may cause efflorescence. Waterfrom stagnant pools and wells frequently contain organic or vegetablematter which may retard the “set,” cause staining, or interf
28、ere with thebond.TABLE 1 Thickness of PlasterPlaster BaseThickness of Plaster Including FinishCoat, in. (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 (10)ABase coat plaster
29、ing of the same proportions as specified for unit masonry isnot prohibited from being used over plain 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 ove
30、r verticalmonolithic concrete shall be not more than316 in. (4.8 mm) in thickness. Wheremore than316 in. 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 s
31、urfaces require more than38in. (9.5 mm) or58 in. (15.9 mm) of plaster, respectively, to produce required 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 prod
32、uce required lines or surfaces, lath shall be applied overfurring secured to the concrete.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 .
33、 0.5 .No. 100 (150 m) 100 40 100 40No. 200 (75 m) 100 70 100 70C8420527.8 Bonding CompoundsSpecification C 631.8. Surface Preparation8.1 SubstratesSurfaces of substrates for the application ofgypsum plaster shall be free of materials that will inhibit bondor adhesion, shall be straight, plumb, level
34、, 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 Gypsum and Metal LathShall have been installed incompliance with Specification C 841.8.2 Conditioning of SurfacesA
35、ll 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 extending more than116in. (1.6 mm) from the surface shall be removed. Protrusionsless than116 in. (1.6 mm) shall b
36、e 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 shallremain visible on the substrate surface.8.2.1.1 Where the surface is too smooth to provide mechani-cal key, the
37、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-furring metallath shall be used in accordance with Specification C 841.8.2.2 Monolithic concretebonding compou
38、nds 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:8.3.1 Metal bases for solid partitions shall be grouted withgypsum plaster leaving14 in. (6.4 mm) below the top
39、 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 Metal FramesHollow door and window framesshall be filled with gypsum plaster grout.9. Mix Design9.1 Mixing, Gene
40、ralAll 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 shall be mixed separately and mixers shallbe free of all set and hardened materials prior to mixing eachbatch.9.1.
41、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 Annex A3.2.9.4 Base Coat Proportions:9.4.1 Gypsum Neat PlasterProportions of sand, perlite, orvermiculite agg
42、regate 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 used with theaddition of water only.9.4.3 Gypsum Wood-Fibered PlasterProportion of damp,loose sand or perlite o
43、r 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 hydratedlime or pulverized quicklime, in accordance with the manufac-turers printed directions.9.5.2 Hydrated LimeType
44、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 ready mixed or job mixedin accordance with Table 5 and Table 6.9.6.1.1 Where thickness of the finish coat is more
45、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 or ready mixed gypsum plaster shall beproportioned in accordance with Table 5.9.6.2.1 Where finish in 9.6.2 is
46、to be applied over base coatscontaining perlite or vermiculite, the addition of not lessthan12 ft3(0.14 m3) or not more than 1 ft3(0.028 m3)offineaggregate meeting the sieve analysis of Table 2 shall be addedto the mix.9.6.3 Troweled finishes of lime putty gauged with gypsumKeenes cement shall be sp
47、ecified 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, the fineaggregate (if used), and finally the gypsum Keenes cement.9.6.4 Troweled finishes of gypsum ready mixe
48、d 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 Table5.9.6.5.1 When finish in 9.6.6 is to be mixed with sand, thesand shall be graded within the limits shown for basecoats inSpecification
49、 C35except that all of the sand shall pass a No.8 (2.36 mm) sieve.9.6.6 Float finishes of lime putty gauged with gypsumKeenes cement shall be proportioned in accordance with Table5.9.6.6.1 When the finish in 9.6.6 is to be mechanically mixedwet, follow procedures in 9.6.3.1. For mixing dry, add limeTABLE 3 Sand for Job-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
