ASTM C472-20

Standard Test Methods for Physical Testing of Gypsum, Gypsum Plasters, and Gypsum Concrete

ABSTRACT
These test methods cover the physical testing of gypsum, gypsum plasters, and gypsum concrete. Test methods are detailed for the following: precautions for physical tests, reagents and materials, free water, fineness, normal consistency of gypsum plaster and gypsum concrete, setting time, setting time (temperature rise method), compressive strength, and density. Materials include distilled or deionized water and standard sand. For each test method, the following are specified: significance and use, apparatus, and procedure.
SCOPE
1.1 These test methods cover the physical testing of gypsum, gypsum plasters, and gypsum concrete.  
1.2 The test methods appear in the following sections:    
Precautions for Physical Tests  
4  
Reagents and Materials  
5  
Free Water  
6  
Fineness  
7  
Normal Consistency of Gypsum Plaster  
8  
Normal Consistency of Gypsum Concrete  
9  
Setting Time  
10  
Setting Time (Temperature Rise Method)  
11  
Compressive Strength  
12  
Density  
13  
1.3 The values regarded as standard are either in inch-pound units or SI (metric). The values stated first shall be regarded as the standard. The values given in parentheses are mathematical conversions that are provided for information only and are not considered standard.  
1.4 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) are not requirements of the standard.  
1.5 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. For a specific precautionary statement, see X1.2.1.  
1.6 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

• Status: Published
• Publication Date: 31-Mar-2020
• ICS: 91.100.10 - Cement. Gypsum. Lime. Mortar
• Technical Committee: C11 - Gypsum and Related Building Materials and Systems
• Drafting Committee: C11.01 - Specifications and Test Methods for Gypsum Products

Relations

• Replaces: ASTM C472-99(2014) - Standard Test Methods for Physical Testing of Gypsum, Gypsum Plasters and Gypsum Concrete
• Effective Date: 01-Apr-2020
• Refers: ASTM C11-18a - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Oct-2018
• Refers: ASTM C11-18 - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Jun-2018
• Refers: ASTM C11-17a - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Oct-2017
• Refers: ASTM C11-17 - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 15-May-2017
• Refers: ASTM C11-16 - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 15-May-2016
• Refers: ASTM C11-15a - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Oct-2015
• Refers: ASTM C11-15 - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Apr-2015
• Refers: ASTM E11-13 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-Oct-2013
• Refers: ASTM C778-13 - Standard Specification for Standard Sand
• Effective Date: 01-Jun-2013
• Refers: ASTM C11-13 - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Mar-2013
• Refers: ASTM C778-12 - Standard Specification for Standard Sand
• Effective Date: 01-May-2012
• Refers: ASTM C11-10a - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Aug-2010
• Refers: ASTM C11-10 - Standard Terminology Relating to Gypsum and Related Building Materials and Systems
• Effective Date: 01-Jan-2010
• Refers: ASTM E11-09e1 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-May-2009

Overview

ASTM C472-20: Standard Test Methods for Physical Testing of Gypsum, Gypsum Plasters, and Gypsum Concrete provides comprehensive procedures for evaluating the key physical properties of gypsum-based materials. Developed by ASTM International, this standard is essential for assessing the quality and performance of gypsum, gypsum plasters, and gypsum concrete used in construction and related industries. The methods outlined ensure consistency, reliability, and compliance with applicable specifications, contributing to the integrity of building materials.

Key Topics

ASTM C472-20 details the standardized approaches for determining the following physical properties:

• Free Water Content: Assesses the moisture present in gypsum materials before further testing.
• Fineness: Evaluates the particle size distribution using standard sieves or, for finer materials, the alcohol wash method.
• Normal Consistency: Establishes the required water content for mixing gypsum plaster or concrete to achieve standard plasticity for subsequent tests.
• Setting Time: Measures the period required for gypsum plaster and gypsum concrete to transition from a fluid to a hardened state, both by penetration (Vicat apparatus) and by monitoring temperature rise (hydration setting).
• Compressive Strength: Determines the load-bearing capability of gypsum materials by measuring the force needed to crush cured specimens.
• Density: Calculates the mass-to-volume ratio, a critical factor for structural and insulation considerations in construction.

The standard also covers:

• Apparatus and materials (such as distilled/deionized water and standard sand)
• Detailed test procedures and precautions to avoid contamination and ensure accuracy
• Reporting formats for test results

Applications

The physical testing methods under ASTM C472-20 are widely used by:

• Building Material Manufacturers: To monitor product quality, ensure batch consistency, and meet market or regulatory requirements for gypsum and gypsum-based products.
• Construction Professionals: For pre-construction material qualification, quality assurance, and compliance with building codes.
• Testing Laboratories: To conduct standardized physical tests for gypsum, gypsum plasters, and gypsum concrete as part of third-party certification or validation processes.
• Specifiers and Architects: To verify that materials meet project specifications and performance standards, especially related to workability, strength, and setting times.

By following ASTM C472-20, organizations benefit from reproducible test results and greater confidence in the physical properties of their gypsum materials, supporting safety and structural performance in building applications.

Related Standards

To ensure complete and accurate physical testing of gypsum materials, ASTM C472-20 references and aligns with several related standards, including:

• ASTM C11: Terminology Relating to Gypsum and Related Building Materials and Systems
• ASTM C778: Specification for Standard Sand, used in testing mixtures
• ASTM E11: Specification for Woven Wire Test Sieve Cloth and Test Sieves, which provides requirements for sieve sizes and quality

These related documents provide essential definitions, material specifications, and equipment requirements that complement the procedures outlined in ASTM C472-20.

Practical Value

Adhering to ASTM C472-20 enables manufacturers, builders, and testing laboratories to:

• Standardize testing protocols for gypsum, plaster, and concrete, ensuring accuracy and reproducibility across facilities.
• Demonstrate regulatory compliance with internationally recognized quality benchmarks.
• Enhance product reliability by identifying physical property variations before application in the field.
• Support product innovation by providing validated test methods for new gypsum formulations.

By implementing the physical test methods from ASTM C472-20, organizations ensure the quality and durability of gypsum-based construction materials, leading to safer, more resilient built environments.

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: C472 − 20
Standard Test Methods for
Physical Testing of Gypsum, Gypsum Plasters, and Gypsum
Concrete
This standard is issued under the fixed designation C472; 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* 2. Referenced Documents
1.1 These test methods cover the physical testing of 2.1 ASTM Standards:
gypsum, gypsum plasters, and gypsum concrete. C11 Terminology Relating to Gypsum and Related Building
Materials and Systems
1.2 The test methods appear in the following sections:
C778 Specification for Standard Sand
Precautions for Physical Tests 4
E11 Specification for Woven Wire Test Sieve Cloth and Test
Reagents and Materials 5
Free Water 6
Sieves
Fineness 7
Normal Consistency of Gypsum Plaster 8
3. Terminology
Normal Consistency of Gypsum Concrete 9
Setting Time 10
3.1 Definitions:
Setting Time (Temperature Rise Method) 11
Compressive Strength 12 3.1.1 For useful definitions refer to Terminology C11.
Density 13
1.3 Thevaluesregardedasstandardareeitherininch-pound 4. Precautions for Physical Tests
units or SI (metric). The values stated first shall be regarded as
4.1 Gypsum products are greatly affected by small amounts
the standard.The values given in parentheses are mathematical
of impurities introduced by careless laboratory manipulation.
conversions that are provided for information only and are not
In order to obtain accurate results, it is absolutely essential to
considered standard.
observe the following precautions:
1.4 The text of this standard references notes and footnotes
4.1.1 Keep all apparatus thoroughly clean. Remove all
which provide explanatory material. These notes and footnotes
traces of set plaster.
(excluding those in tables and figures) are not requirements of
NOTE 1—For mixing pastes and mortars, a 500 mL rubber dental bowl
the standard.
is a convenience.
NOTE 2—Use care when drying gypsum, gypsum plasters, or gypsum
1.5 This standard does not purport to address all of the
concrete. Exceeding the specified drying temperatures may calcine the
safety concerns, if any, associated with its use. It is the
specimens, which will cause inaccurate test results.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
5. Reagents and Materials
mine the applicability of regulatory limitations prior to use.
5.1 Distilled or Deionized Water—free of chlorides and
For a specific precautionary statement, see X1.2.1.
sulfates at a temperature of 21 6 1 °C (70 6 2 °F).
1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
5.2 Calcium chloride.
ization established in the Decision on Principles for the
5.3 Petroleum jelly.
Development of International Standards, Guides and Recom-
5.4 Reagent grade sodium citrate.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
5.5 Standard Sand—Specification C778, 20–30 sand.
5.6 Mineral oil.
These test methods are under the jurisdiction of ASTM Committee C11 on
Gypsum and Related Building Materials and Systems and are the direct responsi-
bility of Subcommittee C11.01 on Specifications and Test Methods for Gypsum
Products. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2020. Published April 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1961. Last previous edition approved in 2014 as C472 – 99 (2014). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C0472-20. the ASTM website.
*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
C472 − 20
(No. 325) sieve, see Appendix X1.
6. Free Water
NOTE 4—The sizes of the sieves to be used are given in the specifica-
6.1 Significance and Use—This test method determines the
tions of ASTM covering the particular product in question.
free water contained in gypsum, gypsum plasters, and gypsum
NOTE 5—When sieving by hand through a 150 µm (No. 100) sieve, use
a lateral motion, and tap the side of the sieve with the palm of the hand.
concrete samples, and prepares the sample for subsequent
Continuewithoutbrushinguntilnotmorethan0.5gpassesthroughduring
testing.
1 min of sieving. If the sieve openings become clogged, transfer the
6.2 Apparatus: retained material temporarily to another vessel, invert the sieve over a
sheet of paper on the table and tap it sharply against the table. Then
6.2.1 Balance, capable of weighing not less than 500 g at
transfer all the retained material back into the sieve and continue sieving.
a precision of 0.1 g.
7.4 Report—Report the percent by weight retained on each
6.2.2 Drying Oven, set at 45 6 3 °C.
sieve or passing particular sieves in accordance with the
6.2.3 Desiccator, containing calcium chloride or equiva-
material specification to the nearest full percentage point.
lent desiccant.
7.5 Precision and Bias—The precision and bias of the
6.3 Procedure:
fineness test method have not been determined.
6.3.1 Weigh a sample of not less than 500 g of the material
as received to the nearest 0.1 g and spread it to a thin layer in
8. Normal Consistency of Gypsum Plaster
a suitable-vessel. Place in an oven (6.2.2) and dry for 2 h; then
cool in a desiccator (6.2.3) and weigh again.
8.1 Significance and Use—This test method is used to
6.3.2 Retain the dried sample in an airtight container until determine the volume of water required for mixing gypsum
used for the fineness test (Section 7). plaster when performing the setting time and compressive
strength tests.
6.4 Report—Report the loss in weight as a percentage of the
original weight of the sample as received to a precision of 8.2 Apparatus:
0.1 %. 8.2.1 Modified Vicat Apparatus—The modified Vicat appa-
ratus (Fig. 1) shall consist of a bracket, A, bearing a movable
6.5 Precision and Bias—The precision and bias of the free
brassrod,B,6.3mmindiameterandofsuitablelengthtofitthe
water test method have not been determined.
Vicat Bracket. A conical plunger made of aluminum with an
7. Fineness apex angle of 53° 08 min and a height of 45 mm shall be
attachedtothelowerendoftherod.Thetotalweightoftherod
7.1 Significance and Use—This test method covers a proce-
andplungershallbe35g.Ameansshallbeprovidedforadding
dure for determining the fineness of gypsum and gypsum
a weight, G, to the rod, increasing the total weight to 50 g. The
plasters and is used to determine compliance with gypsum and
rod shall be capable of being held in any position by a screw,
gypsum plaster specifications. The degree of correlation be-
E. The rod shall have a mark, D, midway between the ends
tween the results of this test method and service performance
which moves under a scale, F, graduated in millimetres,
has not been determined.
attached to the bracket, A.
7.2 Apparatus:
8.2.2 Mold—The conical ring mold shall be made of a
7.2.1 Sieves, as required by a particular gypsum or gypsum
noncorroding, nonabsorbent material, and shall have an inside
plaster specification, in accordance with Specification E11.
diameter of 60 mm at the base and 70 mm at the top and a
7.2.2 Balance, capable of weighing not less than 1000 g at
height of 40 mm.
a precision of 0.1 g.
8.2.3 Base Plate—The base plate for supporting the ring
7.2.3 Mechanical Sieving Machine:
mold shall be of plate glass and about 100 mm square.
8.2.4 Balance, capable of weighing not less than 500 g at a
7.3 Procedure:
7.3.1 Determine fineness by sieving a known weight of the precision of 0.1 g.
8.2.5 Graduated Cylinder, shall be made to deliver the
dried sample through sieves of the specified sizes (Note 3 and
Note 4). The size of the sample to be used in determining indicated volume at 20 °C (68 °F) and shall be subdivided to
not less than 1 mL.
fineness depends upon the particle size of the material. If the
material will pass a 6.3 mm ( ⁄4-in.) sieve, a 100 g sample will
8.3 Procedure:
besufficient;ifthelargestparticlesaremorethan25mm(1in.)
8.3.1 Clean the plunger, mold, and base plate of the modi-
in diameter, use not less than a 1000 g sample. With these
fied Vicat apparatus. Apply a thin coat of petroleum jelly or
limitations the size of sample to be used is left to the discretion
other suitable lubricant to the upper surface of the base plate in
of the operator. Shake the sample through each sieve with as
order to prevent leaks during the test.
little abrasion as possible (Note 5). Weigh the amount of
8.3.2 Sift a weighed quantity of the sample (200 to 300 g as
material retained on each sieve and calculate the fineness,
required to fill the mold) into a known volume of water (see
expressed as a percentage of the weight of the original sample.
5.1). If the plaster is unretarded, add to the mixing water 0.2 g
7.3.2 If a mechanical sieving machine is used, make a series
of sodium citrate per 100 g of sample. After allowing the
of tests at one minute intervals, with each type of material and
sample to soak for 2 min, stir the mixture for 1 min to an even
sieve size combination to be used. When not more than 0.5 g
passes each sieve in a one minute interval, use that time as the
This method is described by Kuntze, R. A., “An Improved Method for the
standard sieving time for that test procedure on that machine.
Normal Consistency of Gypsum Plasters,” ASTM Bulletin No. 246, ASTM
NOTE 3—For suggested method of sieving gypsum through a 45 µm International, May 1960, p. 35.
C472 − 20
8.5 Precision and Bias—The precision and bias of the test
method for normal consistency of gypsum plaster have not
been determined.
9. Normal Consistency of Gypsum Concrete
9.1 Significance and Use—This test method is used to
determine the volume of water required for mixing gypsum
concrete when performing the setting time and compressive
strength tests.
9.2 Apparatus:
9.2.1 Consistometer (Fig. 2)—The consistometer consists of
a conical vessel made of noncorroding, nonabsorbent material,
and having an inside diameter of 9 in. (229 mm) at the top and
3 1
1 ⁄4 in. (44.5 mm) at the bottom, and a height of 5 ⁄2 in.
(139.7 mm). It shall be provided with a sliding gate at the
bottom and supported so that the bottom is 4 in. (102 mm)
above the base plate.The base plate shall be of plate glass, free
of scratches and about 18 in. (457 mm) square.
9.2.2 Balance, capable of weighing not less than 2000 g at
a precision of 1 g.
9.3 Procedure:
9.3.1 Cleananddrytheconsistometerandthebaseplateand
close the sliding gate.
9.3.2 Sift 2000 g of the sample into a known volume of
water (see 5.1) to which 1.0 g of sodium citrate has previously
been added. After allowing the sample to soak for 1 min, stir
the mixture for 3 min to an even fluidity. Pour the mixture into
A—Hinged support bracket D—Graduation mark
B—Plunger support rod E—Lock screw the consistometer until level with the top. Then rapidly and
C—Conical plunger F—Modified scale
completely open the sliding gate, allowing the mixture to run
G—Weight
out onto the base plate. When the sliding gate is opened, take
FIG. 1 Modified Vicat Apparatus (Conical Plunger Method) care to avoid jarring the consistometer.
9.3.3 Measure the resulting patty along its major and minor
axes and determine the average diameter.
9.3.4 Test gypsum concrete with different amounts of water
fluidity. Pour this sample into the ring mold, work slightly to
until a patty diameter of 380 6 13 mm (15 6 ⁄2 in.) is
remove air bubbles, and then strike off flush with the top of the
obtained.
mold. Wet the plunger of the modified Vicat apparatus and
lowerittothesurfaceofthesampleatapproximatelythecenter
9.4 Report—Report the normal consistency as the number
of the mold. Read the scale and release the plunger immedi-
of millilitres of water to the nearest whole millilitre required to
ately.After the rod has settled, read the scale again. Make three
be added to 100 g of the gypsum concrete.
determinations on each mix, care being taken to have the mold
9.5 Precision and Bias—The precision and bias of the test
completely filled and the plunger clean and wet.
method for normal consistency of gypsum concrete have not
8.3.3 Test gypsum molding plaster and gypsum gauging
been determined.
plasterwithdifferentamountsofwateruntilapenetrationof30
6 2 mm is obtained. Use the rod and plunger for this 10. Setting Time
determination weighing 35 g.
10.1 Significance and Use—This test method is used to
8.3.4 Test all gypsum mixtures containing aggregates with
determine the setting time of gypsum plaster and gypsum
different amounts of water until a penetration of 20 62mmis
concrete, and is used to determine compliance with gypsum
obtained. Add weight to the rod and plunger to bring the total
plaster and gypsum concrete specifications. Since variable job
weight to 50 g for these determinations.
conditions influence the setting time, the degree of correlation
8.3.5 Mix gypsum neat plaster with standard sand (see 5.5)
between this test method and service performance has not been
in the ratio of 200 g of sand to 100 g of plaster before testing
determined.
for normal consistency.
10.1.1 This test method does not determine the time of
8.4 Report—Report the normal consistency as the average complete hydration of gypsum plaster or gypsum concrete. To
number of millilitres of water required to be added to 100 g of determine the time of complete hydration see Setting Time
the dry mixture to the nearest whole millilitre. (Temperature Rise Method) Section 11.
C472 − 20
FIG. 2 Consistometer
NOTE 6—Automatic setting time apparatus are commercially available
10.2 Apparatus:
and may be used provided they can be shown to give the same results as
10.2.1 Vicat Apparatus—The Vicat apparatus (Fig. 3) shall
the specified apparatus and procedure.
consist of a frame, A, bearing a movable rod, B, weighing
10.2.3 Balance, capable of weighing not less than 500 g at
300 g, one end, C, the plunger end, being 10 mm in diameter
a precision of 0.1 g.
for a distance of not less than 50 mm, the other end having a
removable needle, D, 1 mm in diameter and 50 mm in length. 10.2.4 Stopwatch or Clock, for determining setting time.
The rod, B, shall be reversible, shall be able to be held in any
10.2.5 Temperature and Humidity Controlled Cabinet, ca-
position by a screw, E, and shall have an adjustable indicator,
pable of maintaining a temperature of 21 6 1 °C (70 6 2 °F)
F, that moves over a scale (graduated in millimetres) attached
and a relative humidity of not less than 85 %.
to the frame, A. The paste shall be held in a rigid conical ring,
10.3 Procedure:
G, resting on a glass plate, H, about 100 mm square. The ring
10.3.1 Gypsum Concrete and All Gypsum Plasters, Except
shall be made of a noncorroding, nonabsorbent material and
Gypsum Neat Plaster—Start the timing of the test approxi-
shall have an inside diameter of 70 mm at the base and 60 mm
mately at the moment of contact of the dry material with the
at the top, and a height of 40 mm.
water (see 5.1). Mix enough paste to fill the conical ring. For
10.2.2 In addition, the Vicat apparatus shall conform to the
the quantity of water and directions for mixing, see Section 8,
following requirements:
but do not add retarder. Place the conical ring on the base plate
Weight of plunger 300 ± 0.5 g
and fill the ring with the paste level with the top of the ring.
Diameter of larger end of plunger 10 ± 0.05 mm
Diameter of needle 1 ± 0.05 mm Position the end of the needle so that it just touches the top
Inside diameter of ring at bottom 70±3mm
surface of the paste and tighten the screw. Release the screw so
Inside diameter of ring at top 60±3mm
that the needle falls freely into the paste. After each
Height of ring 40±1mm
penetration,wipetheneedleclean,andmovethebaseplateand
Graduated scale The graduated scale, when
compared with a standard
ring slightly so that the needle will not strike the same place
scale accurate to within 0.1
twice. Test the sample at intervals in accordance with the table
mm at all points, shall not
show a deviation at any point in 10.3.3. Setting time is complete when the needle no longer
greater than 0.25 mm.
penetrates to the bottom of the paste. When setting times are
C472 − 20
FIG. 3 Vicat Apparatus
expected to be longer than ⁄2 h, store the test specimens in the 11. Setting Time (Temperature Rise Method)
cabinet described in 10.2.5.
11.1 Significance and Use:
10.3.2 Gypsum Neat Plaster—Test gypsum neat plaster for
11.1.1 This test method determines the hydration time by
setting time as mixed with three parts by weight of standard
measuring the maximum temperature rise of gypsum plaster or
sand (see 5.5). Mix dry a 100 g sample of the gypsum neat
gypsum concrete. The temperature rise is caused by the
plaster and 300 g of the sand, and then add sufficient water to
reaction of
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C472 − 99 (Reapproved 2014) C472 − 20
Standard Test Methods for
Physical Testing of Gypsum, Gypsum Plasters, and Gypsum
Concrete
This standard is issued under the fixed designation C472; 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 Scope*
1.1 These test methods cover the physical testing of gypsum, gypsum plasters, and gypsum concrete.
1.2 The test methods appear in the following sections:
Precautions for Physical Tests 4
Reagents and Materials 5
Free Water 6
Fineness 7
Normal Consistency of Gypsum Plaster 8
Normal Consistency of Gypsum Concrete 9
Setting Time 10
Setting Time (Temperature Rise Method) 11
Compressive Strength 12
Density 13
Sections
Precautions for Physical Tests 4
Reagents and Materials 5
Free Water 6
Fineness 7
Normal Consistency of Gypsum Plaster 8
Normal Consistency of Gypsum Concrete 9
Setting Time 10
Setting Time (Temperature Rise Method) 11
Compressive Strength 12
Density 13
1.3 The values regarded as the standard are either in inch-pound units or SI (metric). The values stated first shall be regarded
as the standard. Values following The values given in parentheses are approximate and mathematical conversions that are provided
for information purposes only.only and are not considered standard.
1.4 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) are not requirements of the standard.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For a specific precautionary statement, see X1.2.1.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
C11 Terminology Relating to Gypsum and Related Building Materials and Systems
These test methods are under the jurisdiction of ASTM Committee C11 on Gypsum and Related Building Materials and Systems and are the direct responsibility of
Subcommittee C11.01 on Specifications and Test Methods for Gypsum Products.
Current edition approved April 1, 2014April 1, 2020. Published April 2014April 2020. Originally approved in 1961. Last previous edition approved in 20092014 as
C472 – 99 (2009).(2014). DOI: 10.1520/C0472-99R14.10.1520/C0472-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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
C472 − 20
C778 Specification for Standard Sand
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
3. Terminology
3.1 Definitions:
3.1.1 For useful definitions refer to Terminology C11.
4. Precautions for Physical Tests
4.1 Gypsum products are greatly affected by small amounts of impurities introduced by careless laboratory manipulation. In
order to obtain accurate results, it is absolutely essential to observe the following precautions:
4.1.1 Keep all apparatus thoroughly clean. Remove all traces of set plaster.
NOTE 1—For mixing pastes and mortars, a 500-ml500 mL rubber dental bowl is a convenience.
NOTE 2—Use care when drying gypsum, gypsum plasters, or gypsum concrete. Exceeding the specified drying temperatures may calcine the specimens,
which will cause inaccurate test results.
5. Reagents and Materials
5.1 Distilled or Deionized Water—free of chlorides and sulfates at a temperature of 21 6 1°C1 °C (70 6 2°F).2 °F).
5.2 Calcium chloride.
5.3 Petroleum jelly.
5.4 Reagent grade sodium citrate.
5.5 Standard Sand—Specification C778, 20–30 sand.
5.6 Mineral oil.
6. Free Water
6.1 Significance and Use—This test method determines the free water contained in gypsum, gypsum plasters, and gypsum
concrete samples, and prepares the sample for subsequent testing.
6.2 Apparatus:
6.2.1 Balance, capable of weighing not less than 500 g at a precision of 0.1 g.
6.2.2 Drying Oven, set at 45 6 3°C.3 °C.
6.2.3 Desiccator, containing calcium chloride or equivalent desiccant.
6.3 Procedure:
6.3.1 Weigh a sample of not less than 500 g of the material as received to the nearest 0.1 g and spread it to a thin layer in a
suitable-vessel. Place in an oven (6.2.2) and dry for 2 h; then cool in a desiccator (6.2.3) and weigh again.
6.3.2 Retain the dried sample in an airtight container until used for the fineness test (Section 7).
6.4 Report—Report the loss in weight as a percentage of the original weight of the sample as received to a precision of
0.1%.0.1 %.
6.5 Precision and Bias—The precision and bias of the free water test method have not been determined.
7. Fineness
7.1 Significance and Use—This test method covers a procedure for determining the fineness of gypsum and gypsum plasters and
is used to determine compliance with gypsum and gypsum plaster specifications. The degree of correlation between the results of
this test method and service performance has not been determined.
7.2 Apparatus:
7.2.1 Sieves, as required by a particular gypsum or gypsum plaster specification, in accordance with Specification E11.
7.2.2 Balance, capable of weighing not less than 1000 g at a precision of 0.1 g.
7.2.3 Mechanical Sieving MachineMachine:
7.3 Procedure:
7.3.1 Determine fineness by sieving a known weight of the dried sample through sieves of the specified sizes (Note 3 and Note
4). The size of the sample to be used in determining fineness depends upon the particle size of the material. If the material will
pass a 6.3-mm6.3 mm ( ⁄4-in.) sieve, a 100-g 100 g sample will be sufficient; if the largest particles are more than 25 mm (1 in.)
in diameter, use not less than a 1000-g 1000 g sample. With these limitations the size of sample to be used is left to the discretion
of the operator. Shake the sample through each sieve with as little abrasion as possible (Note 5). Weigh the amount of material
retained on each sieve and calculate the fineness, expressed as a percentage of the weight of the original sample.
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7.3.2 If a mechanical sieving machine is used, make a series of tests at one minute intervals, with each type of material and sieve
size combination to be used. When not more than 0.5 g passes each sieve in a one minute interval, use that time as the standard
sieving time for that test procedure on that machine.
NOTE 3—For suggested method of sieving gypsum through a 45-μm 45 μm (No. 325) sieve, see Appendix X1.
NOTE 4—The sizes of the sieves to be used are given in the specifications of ASTM covering the particular product in question.
NOTE 5—When sieving by hand through a 150-μm 150 μm (No. 100) sieve, use a lateral motion, and tap the side of the sieve with the palm of the
hand. Continue without brushing until not more than 0.5 g passes through during 1 min of sieving. If the sieve openings become clogged, transfer the
retained material temporarily to another vessel, invert the sieve over a sheet of paper on the table and tap it sharply against the table. Then transfer all
the retained material back into the sieve and continue sieving.
7.4 Report—Report the percent by weight retained on each sieve or passing particular sieves in accordance with the material
specification to the nearest full percentage point.
7.5 Precision and Bias—The precision and bias of the fineness test method have not been determined.
8. Normal Consistency of Gypsum Plaster
8.1 Significance and Use—This test method is used to determine the volume of water required for mixing gypsum plaster when
performing the setting time and compressive strength tests.
8.2 Apparatus:
8.2.1 Modified Vicat Apparatus—The modified Vicat apparatus (Fig. 1) shall consist of a bracket, A, bearing a movable brass
rod, B, 6.3 mm in diameter and of suitable length to fit the Vicat Bracket. A conical plunger made of aluminum with an apex angle
of 53° 08 min and a height of 45 mm shall be attached to the lower end of the rod. The total weight of the rod and plunger shall
be 35 g. A means shall be provided for adding a weight, G, to the rod, increasing the total weight to 50 g. The rod shall be capable
A—Hinged support bracket D—Graduation mark
B—Plunger support rod E—Lock screw
C—Conical plunger F—Modified scale
G—Weight
FIG. 1 Modified Vicat Apparatus (Conical Plunger Method)
This method is described by Kuntze, R. A., “An Improved Method for the Normal Consistency of Gypsum Plasters,” ASTM Bulletin No. 246, ASTM, ASTM International,
May 1960, p. 35.
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of being held in any position by a screw, E. The rod shall have a mark, D, midway between the ends which moves under a scale,
F, graduated in millimetres, attached to the bracket, A.
8.2.2 Mold—The conical ring mold shall be made of a noncorroding, nonabsorbent material, and shall have an inside diameter
of 60 mm at the base and 70 mm at the top and a height of 40 mm.
8.2.3 Base Plate—The base plate for supporting the ring mold shall be of plate glass and about 100 mm square.
8.2.4 Balance, capable of weighing not less than 500 g at a precision of 0.1 g.
8.2.5 Graduated Cylinder, shall be made to deliver the indicated volume at 20°C (68°F)20 °C (68 °F) and shall be subdivided
to not less than 1 mL.
8.3 Procedure:
8.3.1 Clean the plunger, mold, and base plate of the modified Vicat apparatus. Apply a thin coat of petroleum jelly or other
suitable lubricant to the upper surface of the base plate in order to prevent leaks during the test.
8.3.2 Sift a weighed quantity of the sample (200 to 300 g as required to fill the mold) into a known volume of water (See(see
5.15.1).). If the plaster is unretarded, add to the mixing water 0.2 g of sodium citrate per 100 g of sample. After allowing the sample
to soak for 2 min, 2 min, stir the mixture for 1 min to an even fluidity. Pour this sample into the ring mold, work slightly to remove
air bubbles, and then strike off flush with the top of the mold. Wet the plunger of the modified Vicat apparatus and lower it to the
surface of the sample at approximately the center of the mold. Read the scale and release the plunger immediately. After the rod
has settled, read the scale again. Make three determinations on each mix, care being taken to have the mold completely filled and
the plunger clean and wet.
8.3.3 Test gypsum molding plaster and gypsum gauging plaster with different amounts of water until a penetration of 30 6 2
mm is obtained. Use the rod and plunger for this determination weighing 35 g.
8.3.4 Test all gypsum mixtures containing aggregates with different amounts of water until a penetration of 20 6 2 mm is
obtained. Add weight to the rod and plunger to bring the total weight to 50 g for these determinations.
8.3.5 Mix gypsum neat plaster with standard sand (see 5.25.5) in the ratio of 200 g of sand to 100 g of plaster before testing
for normal consistency.
8.4 Report: Report—Report the normal consistency as the average number of millilitres of water required to be added to 100
g of the dry mixture to the nearest whole millilitre.
8.5 Precision and Bias—The precision and bias of the test method for normal consistency of gypsum plaster have not been
determined.
9. Normal Consistency of Gypsum Concrete
9.1 Significance and Use—This test method is used to determine the volume of water required for mixing gypsum concrete
when performing the setting time and compressive strength tests.
9.2 Apparatus:
9.2.1 Consistometer (Fig. 2)—The consistometer consists of a conical vessel made of noncorroding, nonabsorbent material, and
3 1
having an inside diameter of 9 in. (229 mm) at the top and 1 ⁄4 in. (44.5 mm) at the bottom, and a height of 5 ⁄2 in. (139.7 mm).
(139.7 mm). It shall be provided with a sliding gate at the bottom and supported so that the bottom is 4 in. (102 mm) above the
base plate. The base plate shall be of plate glass, free of scratches and about 18 in. (457 mm) square.
9.2.2 Balance, capable of weighing not less than 2000 g at a precision of 1 g.
9.3 Procedure:
9.3.1 Clean and dry the consistometer and the base plate and close the sliding gate.
9.3.2 Sift 2000 g of the sample into a known volume of water (see 5.1) to which 1.0 g of sodium citrate has previously been
added. After allowing the sample to soak for 1 min, stir the mixture for 3 min to an even fluidity. Pour the mixture into the
consistometer until level with the top. Then rapidly and completely open the sliding gate, allowing the mixture to run out onto the
base plate. When the sliding gate is opened, take care to avoid jarring the consistometer.
9.3.3 Measure the resulting patty along its major and minor axes and determine the average diameter.
9.3.4 Test gypsum concrete with different amounts of water until a patty diameter of 380 6 13 mm (15 6 ⁄2 in.) is obtained.
9.4 Report—Report the normal consistency as the number of millilitres of water to the nearest whole millilitre required to be
added to 100 g of the gypsum concrete.
9.5 Precision and Bias—The precision and bias of the test method for normal consistency of gypsum concrete have not been
determined.
10. Setting Time
10.1 Significance and Use—This test method is used to determine the setting time of gypsum plaster and gypsum concrete, and
is used to determine compliance with gypsum plaster and gypsum concrete specifications. Since variable job conditions influence
the setting time, the degree of correlation between this test method and service performance has not been determined.
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FIG. 2 Consistometer
10.1.1 This test method does not determine the time of complete hydration of gypsum plaster or gypsum concrete. To determine
the time of complete hydration see Setting Time,Time (Temperature Rise Method,)Method) Section 11.
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10.2 Apparatus:
10.2.1 Vicat Apparatus—The Vicat apparatus (Fig. 3) shall consist of a frame, A, bearing a movable rod, B, weighing 300 g,
300 g, one end, C, the plunger end, being 10 mm in diameter for a distance of not less than 50 mm, the other end having a
removable needle, D, 1 mm in diameter and 50 mm in length. The rod, B, shall be reversible, shall be able to be held in any position
by a screw, E, and shall have an adjustable indicator, F, that moves over a scale (graduated in millimetres) attached to the frame,
A. The paste shall be held in a rigid conical ring, G, resting on a glass plate, H, about 100 mm square. The ring shall be made of
a noncorroding, nonabsorbent material and shall have an inside diameter of 70 mm at the base and 60 mm at the top, and a height
of 40 mm.
10.2.2 In addition, the Vicat apparatus shall conform to the following requirements:
Weight of plunger 300 ± 0.5 g
Diameter of larger end of plunger 10 ± 0.05 mm
Diameter of needle 1 ± 0.05 mm
Inside diameter of ring at bottom 70 ± 3 mm
Inside diameter of ring at top 60 ± 3 mm
Height of ring 40 ± 1 mm
Graduated scale The graduated scale, when
compared with a standard
scale accurate to within 0.1
mm at all points, shall not
show a deviation at any point
greater than 0.25 mm.
NOTE 6—Automatic setting time apparatus are commercially available and may be used provided they can be shown to give the same results as the
specified apparatus and procedure.
10.2.3 Balance, capable of weighing not less than 500 g at a precision of 0.1 g.
10.2.4 Stopwatch or Clock, for determining setting time.
10.2.5 Temperature and Humidity Controlled Cabinet, capable of maintaining a temperature of 21 6 1°C1 °C (70 6 2°F)2 °F)
and a relative humidity of not less than 85 %.
10.3 Procedure:
10.3.1 Gypsum Concrete and All Gypsum Plasters, Except Gypsum Neat Plaster—Start the timing of the test approximately at
the moment of contact of the dry material with the water (see 5.1). Mix enough paste to fill the conical ring. For the quantity of
water and directions for mixing, see Section 8, but do not add retarder. Place the conical ring on the base plate and fill the ring
with the paste level with the top of the ring. Position the end of the needle so that it just touches the top surface of the paste and
FIG. 3 Vicat Apparatus
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tighten the screw. Release the screw so that the needle falls freely into the paste. After each penetration, wipe the needle clean,
and move the base plate and ring slightly so that the needle will not strike the same place twice. Test the sample at intervals
according to in accordance with the table in 10.3.3. Setting time is complete when the needle no longer penetrates to the bottom
of the paste. When setting times are expected to be longer than ⁄2 h, store the test specimens in the cabinet described in 10.2.5.
10.3.2 Gypsum Neat Plaster—Test gypsum neat plaster for setting time as mixed with three parts by weight of standard sand
(see 5.25.5). Mix dry a 100-g 100 g sample of the gyp
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