ASTM C631-95a(2000)
(Specification)Standard Specification for Bonding Compounds for Interior Gypsum Plastering
Standard Specification for Bonding Compounds for Interior Gypsum Plastering
SCOPE
1.1 This specification covers minimum requirements for bonding compounds for adhering interior gypsum plaster to structurally sound surfaces.
1.2 This specification also covers test methods for determining performance requirements and physical properties.
1.3 The values stated in inch-pound units are to be regarded as the standard. The SI equivalents of inch-pound units are approximate.
1.4 The following safety hazards caveat pertains only to the test methods described in this specification: 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C 631 – 95a (Reapproved 2000)
Standard Specification for
Bonding Compounds for Interior Gypsum Plastering
This standard is issued under the fixed designation C 631; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope * compound shall be tinted to show, by visual inspection, where
it has been applied. The tinting material shall not show through
1.1 This specification covers minimum requirements for
the material being bonded. The surfaces to which bonding
bonding compounds for adhering interior gypsum plaster to
compounds are applied shall be relatively smooth, clean, and
structurally sound surfaces.
dry. Surface coatings shall be removed if their nature indicates
1.2 This specification also covers test methods for determin-
an unsatisfactory condition. Surfaces shall be prepared in
ing performance requirements and physical properties.
accordance with the manufacturer’s directions.
1.3 The values stated in inch-pound units are to be regarded
4.2 Consistency—The bonding compound shall be of a
as the standard. The SI equivalents of inch-pound units are
homogeneous nature with no settling of the solids. The
approximate.
compound shall be free of foreign matter, and when applied in
1.4 The following safety hazards caveat pertains only to the
accordance with the manufacturer’s directions, shall cover
test methods described in this specification: This standard does
evenly.
not purport to address all of the safety concerns, if any,
4.3 Film Characteristics—A dry film of the bonding com-
associated with its use. It is the responsibility of the user of this
pound shall be uniform and smooth and shall remain flexible.
standard to establish appropriate safety and health practices
The film shall not be noticeably affected by mild acid or alkali.
and determine the applicability of regulatory limitations prior
to use.
5. Performance Requirements
2. Referenced Documents 5.1 Bonding Capability—A dry film of bonding compound
shall be capable of bonding gypsum plaster immediately after
2.1 ASTM Standards:
drying and 10 days after drying when tested as specified in
C 11 Terminology Relating to Gypsum and Related Build-
Section 12.
ing Materials and Systems
2 5.2 Degradation—Bonding compound that separates shall
C 28 Specification for Gypsum Plasters
be able to be re-mixed to a uniform consistency when tested as
C 472 Test Methods for Physical Testing of Gypsum, Gyp-
2 specified in Section 10.
sum Plasters, and Gypsum Concrete
5.3 High Temperature Stability—The bond strength shall be
C 511 Specification for Moist Cabinets, Moist Rooms and
not less than 20 psi (138 kPa) when tested as specified in
Water Storage Tanks Used in the Testing of Hydraulic
Section 9.
Cements and Concretes
5.4 Freeze-Thaw Stability—The bond strength shall be not
3. Terminology
less than 20 psi (138 kPa) when tested as specified in Section
11.
3.1 Definitions—For definitions relating to gypsum and
5.5 Bond Strength—Bond strength of a fresh sample or a 30
related building materials and systems, see Terminology C 11.
day old sample shall be not less than 20 psi (138 kPa) when
4. Physical Properties
tested as specified in Section 12.
4.1 General—The bonding compound shall be a film form-
6. Sampling
ing, non-oxidizing, non-toxic, non-flammable composition
6.1 Take a sample of not less than 1 kg from each shipment
suitable for application by brush, roller, and spray. The
or consignment for analysis and tests. Except in special cases,
take the sample from not less than three separate containers,
This specification is under the jurisdiction of ASTM Committee C11 on
chosen at random. In addition, take samples from containers
Gypsum and Related Building Materials and Systems and is the direct responsibility
that appear to be nonrepresentative, and test separately. Imme-
of Subcommittee C11.02 on Specifications and Test Methods for Accessories and
diately place the samples in airtight glass containers and
Related Products.
transport to the testing laboratory in these containers. Take
Current edition approved Oct. 10, 1995. Published December 1995. Originally
published as C 631 – 88. Last previous edition C 631 – 95.
precautions to reduce evaporation or drying to a minimum.
Annual Book of ASTM Standards, Vol 04.01.
*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.
C 631
Thoroughly mix the bonding compound in the container if
there is a tendency for liquid phase separation.
7. Apparatus
7.1 Moist Cabinet—Specification C 511.
7.2 Oven—A forced draft type oven, having a temperature
controlled at 140 6 5°F (60 6 3°C) for high temperature tests
and 100 6 5°F (38 6 3°C) for drying of the briquets.
7.3 Freezer—A freezer having a controlled temperature
of−10 6 2°F (−23 6 1°C).
7.4 Balance—A balance capable of weighing at least 2500 g
at a precision of 0.1 g.
7.5 Timing Device—A standard clock or watch with second
hand.
7.6 Tamper—A tamper made up of a nonabsorptive, non-
abrasive, non-brittle material and having a cross section of ⁄2
in. by 1 in. (13 by 25 mm) and approximately 5 to 6 in. (130
to 150 mm) long. The tamping face shall be flat and at right
angles to the length of the tamper.
7.7 Straight Edge—A steel straight edge not less than 4 in.
(100 mm) long and not less than ⁄16 in. (1.6 mm) nor more than
⁄8 in. (3.2 mm) in thickness.
7.8 Spatula—A spatula with a metal blade 6 in. (150 mm) in
length and ⁄2in. (13 mm) in width, with straight edges.
7.9 Paint Brush—A standard 1 in. (25 mm) wide brush,
with natural or synthetic bristles.
7.10 Testing Machine—Any type that is of sufficient capac-
ity and that is capable of applying the load continuously and
without shock at the rate of 0.05 in. (1.27 mm)/min, with
NOTE 1—1 in. = 25.4 mm
provision for adjustment of the rate of loading.
FIG. 2 Briquet Specimen for Tensile Strength Test
7.11 Briquet Molds—The molds for making test specimens
shall be made of metal not attacked by the plaster mortar and
7.13 Clips for Briquet Testing Machine— The clips for
shall have sufficient material in the sides to prevent spreading
holding the tension test specimen shall be in accordance with
during molding. Gang molds, when used, shall be of the type
Fig. 3.
shown in Fig. 1. The dimensions of the briquet molds shall
8. Conditioning
conform to the following requirements: width of mold, be-
tween inside faces, at waist line of the briquet, 1 in. (25.4 mm)
8.1 Room Temperature and Humidity— Maintain the air
with permissible variations of 60.01 in. (0.25 mm) for molds
temperature in the vicinity of the mixing and testing area, 70 6
in use and 60.005 in. (0.13 mm) for new molds; thickness of
5°F (21 6 3°C). Maintain the relative humidity at 50 6 2%.
molds measured at the point of greatest thickness on either side
8.2 Temperature of the Mixing Water—72 6 2°F (22 6
of the mold at the waist line, 1 in. (25.4 mm) with permissible
1°C).
variations of + 0.004 in. (0.10 mm) and − 0.002 in. (0.05 mm)
9. High Temperature Test
for new molds and − 0.02 in. (0.5 mm) for molds in use. The
inside faces at the waist line shall have a vertical slot 0.03 in. 9.1 Significance and Use—This test method provides pro-
(0.75 mm) wide by 0.06 in. (1.5 mm) deep to accept the cedures for evaluating the bond strength of adhesives after
divider. The briquet specimens shall conform to the dimen- being exposed to accelerated aging at high temperature.
sional requirements shown in Fig. 2. 9.2 Specimen Preparation—For each test specimen, transfer
7.12 Divider—Sheet brass 0.02 in. (0.05 mm) thick, 1.1 in. the bonding compound, taken from the sample obtained, into a
(27.8 mm) wide by 1 in. (25.4 mm) high. standard 1 pt (400 mL) glass container.
FIG. 1 Briquet Gang Mold
C 631
NOTE 1—1 in. = 25.4 mm
FIG. 3 Clips for Briquet Testing Machine
9.3 Procedure—Place the specimen in the oven for 30 days. 10.4 Tests and Retests—Bonding compound that fails to be
Remove the container, allow the compound to cool to room remixed to a uniform consistency shall be considered to have
temperature, mix the compound to a uniform consistency, and failed the test.
test as specified in Section 12. 10.5 Report—Determine the extent of settling and separa-
9.4 Test and Retests—Test six briquets and report the tion by measuring, and report as a percentage of the height of
average of the test results. If the result of any one of the six the specimen in the clear glass container, represented by the
tests varied more than 15 % from the average, reject it and location of the liquid/solid interface.
report the average of the other five tests. If the results from 10.6 Precision and Bias—No information is presented
more than two tests vary more than 15 % from the average, about either the precision or bias of the degradation test for
reject the series and retest. m
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