ASTM C28/C28M-10(2020)
(Specification)Standard Specification for Gypsum Plasters
Standard Specification for Gypsum Plasters
ABSTRACT
This specification covers four gypsum plasters; gypsum mill-mixed plaster, gypsum neat plaster, gypsum wood fibered plaster, and gypsum gauging plaster. The plasters shall contain a volume of aggregate not more than requirements prescribed. Compressive strength test and Vicat test shall be performed to meet the requirements.
SCOPE
1.1 This specification covers gypsum mill-mixed plaster, gypsum neat plaster, gypsum wood-fibered plaster, and gypsum gauging plaster.
Note 1: Specification C842 contains application procedures for interior gypsum plaster.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. This units statement does not apply to the appendix.
1.3 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:C28/C28M −10 (Reapproved 2020)
Standard Specification for
Gypsum Plasters
This standard is issued under the fixed designation C28/C28M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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. Scope C11 Terminology Relating to Gypsum and Related Building
Materials and Systems
1.1 This specification covers gypsum mill-mixed plaster,
C22/C22M Specification for Gypsum
gypsum neat plaster, gypsum wood-fibered plaster, and gyp-
C35 Specification for Inorganic Aggregates for Use in Gyp-
sum gauging plaster.
sum Plaster
NOTE 1—Specification C842 contains application procedures for inte-
C471M Test Methods for ChemicalAnalysis of Gypsum and
rior gypsum plaster.
Gypsum Products (Metric)
1.2 The values stated in either SI units or inch-pound units
C472 Test Methods for Physical Testing of Gypsum, Gyp-
are to be regarded separately as standard. Within the text, the
sum Plasters, and Gypsum Concrete
SI units are shown in brackets. The values stated in each
C778 Specification for Standard Sand
system may not be exact equivalents; therefore, each system
C842 Specification forApplication of Interior Gypsum Plas-
shall be used independently of the other. Combining values
ter
from the two systems may result in non-conformance with the
E11 Specification for Woven Wire Test Sieve Cloth and Test
standard. This units statement does not apply to the appendix.
Sieves
1.3 The text of this standard references notes and footnotes
3. Terminology
which provide explanatory material. These notes and footnotes
3.1 Definitions:
(excluding those in tables and figures) shall not be considered
3.1.1 Definitions shall be in accordance with Terminology
as requirements of the standard.
C11.
1.4 This standard does not purport to address all of the
3.2 Definitions of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
3.2.1 gypsum gauging plaster for finish coat, n—a calcined
responsibility of the user of this standard to establish appro-
gypsum plaster designed to be mixed with lime putty for the
priate safety, health, and environmental practices and deter-
finish coat.
mine the applicability of regulatory limitations prior to use.
3.2.2 gypsum neat plaster, n—calcined gypsum mixed at the
1.5 This international standard was developed in accor-
mill with other ingredients to control working quality and
dance with internationally recognized principles on standard-
setting time.
ization established in the Decision on Principles for the
3.2.2.1 Discussion—Neat plaster is either fibered or unfi-
Development of International Standards, Guides and Recom-
bered. The addition of aggregate is required on the job.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. 3.2.3 gypsum mill-mixed plaster, n—calcined gypsum
plaster, mixed at the mill with a mineral aggregate, designed to
2. Referenced Documents
function as a base coat to receive various finish coats.
2 3.2.3.1 Discussion—Other materials are not prohibited from
2.1 ASTM Standards:
beingaddedtocontrolsettingtimeandotherdesirableworking
properties.
1 3.2.4 gypsum wood-fibered plaster, n—a calcined gypsum
This specification is under the jurisdiction of ASTM Committee C11 on
Gypsum and Related Building Materials and Systems and is the direct responsibility plaster in which wood fiber is used as an aggregate.
of Subcommittee C11.01 on Specifications and Test Methods for Gypsum Products.
Current edition approved June 1, 2020. Published June 2020. Originally 4. Materials
approved in 1920. Last previous edition approved in 2015 as C28/
4.1 Calcined Gypsum—Calcined gypsum shall be manufac-
C28M – 10 (2015). DOI: 10.1520/C0028_C0028M-10R20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or tured from gypsum meeting the requirements of Specification
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
C22/C22M.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 4.2 Vermiculite Aggregate—Specification C35.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C28/C28M−10 (2020)
TABLE 1 Composition and Physical Properties
B
Composition, Aggregate Per 100 lb
A Compressive Strength,
Setting Time
of Plaster, Not More Than Not Less Than
Product Aggregate Type
3 3
ft m hours psi MPa
mill-mixed plaster over lath base vermiculite 2 0.057 1 ⁄2 to 8 450 3.1
perlite 2 0.057 1 ⁄2 to 8 600 4.1
sand 2.5 0.071 1 ⁄2 to 8 700 4.8
mill-mixed plaster over masonry vermiculite 3 0.085 1 ⁄2 to 8 325 2.2
perlite 3 0.085 1 ⁄2 to 8 400 2.8
sand 3 0.085 1 ⁄2 to 8 400 2.8
C D
neat plaster none . . 2 to 16 750 5.2
wood fibered plaster none . . 1 ⁄2 to 8 1200 8.3
E
gauging plaster none . . 1200 8.3
A
Setting time shall be not less than the shorter time shown nor more than the longer time shown.
B
Compressive strengths are as tested at the setting times specified in Test Methods C472.
C
When mixed with three parts by weight of Ottawa sand.
D
When mixed with two parts by weight of Ottawa sand.
E
When not retarded, the setting time shall be not less than 20 nor more than 40 min and, when retarded, not less than 40 min.
4.3 Perlite Aggregate—Specification C35. selected at random. Samples shall be taken both from the outer
portion and the center of each package. The materials so
4.4 Sand Aggregate—Specification C35.
obtained shall be thoroughly mixed to provide a composite
4.5 Ottawa Sand—Specification C778 for 20–30 sand.
sample of not less than 7 lb [3.2 kg]. This composite sample
4.6 Wood Fiber—Non-staining wood fiber.
shall be placed immediately in a clean, dry, airtight container
for delivery to the laboratory.
5. Composition
5.1 When tested in accordance with Test Methods C471M,
8. Packaging and Package Marking
calcined gypsum shall contain no less than 66.0 weight %
8.1 Gypsum plasters shall be dry and free of lumps, and
CaSO · ⁄2 H O.
4 2
shall be shipped in packages.
5.2 Aggregate—Plastersshallcontainavolumeofaggregate
8.2 When shipped for resale, the following information
not more than that shown in Table 1.
shall be legibly marked on each package or on a tag of suitable
NOTE 2—An approximation of the aggregate content may be made by
size attached to the package:
using the test methods in the appendix. A more accurate method for
determining sand in plaster is described in Test Methods C471M. Test 8.2.1 Name of manufacturer or seller,
Methods C471M require that the original sand and plaster components be
8.2.2 Brand name, if any, and
available separately.
8.2.3 Net weight of the package.
6. Mechanical Properties
9. Inspection
6.1 Compressive Strength—When tested in accordance with
Test Methods C472 the compressive strength shall be as
9.1 Inspection of the gypsum plaster shall be agreed upon
specified in Table 1.
between the purchaser and the supplier as part of the purchase
6.2 Setting Time—When tested in accordance with Test
agreement.
MethodsC472usingtheVicatmethod,thesettingtimeshallbe
as specified in Table 1.
10. Rejection
NOTE 3—Setting Time—Attention is directed to conditions affecting job
10.1 Rejection of gypsum plaster that fails to conform to the
set of gypsum plasters that are usually beyond the control of the producer.
requirements of this specification shall be reported to the
Materials added at the site of application such as water and aggregates
producer or supplier promptly and in writing. The notice of
affect job sets. In addition, the various bases with different absorptive
values may affect job performance.The plaster may be retarded to provide rejection shall contain a statement documenting requirements
a setting time of not more than 4 h. Setting times more than 2 h may result
of this specification.
in lower compressive strengths.
6.3 Fineness of Gauging Plaster for Finish Coat—When
11. Certification
tested in accordance with Test Method C472 100 % shall pass
11.1 When specified in the purchase agreement, a
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