ASTM C563-20

Standard Guide for Approximation of Optimum SO<inf>3</inf> in Hydraulic Cement

SIGNIFICANCE AND USE
3.1 The purpose of this guide is to estimate the SO3 content for a hydraulic cement that gives maximum performance. The value obtained is one way to establish an appropriate level of sulfate in the manufacture of cements specified in Specifications C150/C150M, C595/C595M, and C1157/C1157M.  
3.2 The SO3 content of a cement giving maximum performance is different at different ages, with different performance criteria and with different materials such supplementary cementitious materials and chemical admixtures. A manufacturer can choose the performance criteriato determine optimum SO3 content. This optimum SO3 content may be a compromise between different ages and different performance criteria.
Note 1: Typically, the optimum SO3 content is higher the later the age.  
3.3 This guide indicates optimum SO3 content for cement, optionally in presence of supplementary cementitious materials and admixtures. Several alternate methods are allowed: compressive strength of concrete or mortar, heat of hydration of paste or mortar, and drying shrinkage of mortar.  
3.4 It should not be assumed that the optimum SO3 estimated in this guide is the same SO3 content for optimum performance of a concrete prepared in the field using the same materials. The optimum SO3 is influenced by parameters such as ambient and fresh concrete temperature, admixtures, and supplementary cementitious materials.  
3.5 The guide is applicable to cements specified in Specifications C150/C150M, C595/C595M, and C1157/C1157M.
SCOPE
1.1 This guide describes the determination of approximate optimum SO3 for maximum performance as a result of substituting calcium sulfate for a portion of the cement.  
1.2 This guide refers to the sulfur trioxide (SO3) content of the cement only. Slag cements and occasionally other hydraulic cements can contain sulfide or other forms of sulfur. The determination of SO3 content by rapid methods may include these other forms, and may therefore produce a significant error. If a significant error occurs, analyze the cement for SO3 content using the reference test method of Test Methods C114 for sulfur trioxide.  
1.3 Values stated as SI units are to be regarded as 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

• Status: Published
• Publication Date: 31-May-2020
• ICS: 91.100.10 - Cement. Gypsum. Lime. Mortar
• Technical Committee: C01 - Cement
• Drafting Committee: C01.28 - Sulfate Content

Relations

• Refers: ASTM C471M-24 - Standard Test Methods for Chemical Analysis of Gypsum and Gypsum Products (Metric)
• Effective Date: 01-Apr-2024
• Refers: ASTM C204-24 - Standard Test Methods for Fineness of Hydraulic Cement by Air-Permeability Apparatus
• Effective Date: 01-Jan-2024
• Refers: ASTM C109/C109M-23 - Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 50 mm [2 in.] Cube Specimens)
• Effective Date: 15-Dec-2023
• Refers: ASTM C39/C39M-23 - Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
• Effective Date: 01-Dec-2023
• Refers: ASTM C596-23 - Standard Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement
• Effective Date: 01-Dec-2023
• Refers: ASTM C114-23 - Standard Test Methods for Chemical Analysis of Hydraulic Cement
• Effective Date: 01-Oct-2023
• Refers: ASTM C305-20 - Standard Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency
• Effective Date: 15-Jul-2020
• Refers: ASTM C150/C150M-19 - Standard Specification for Portland Cement
• Effective Date: 01-Apr-2019
• Refers: ASTM C596-18 - Standard Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement
• Effective Date: 01-Dec-2018
• Refers: ASTM C465-18 - Standard Specification for Processing Additions for Use in the Manufacture<brk/> of Hydraulic Cements
• Effective Date: 01-Apr-2018
• Refers: ASTM C430-17 - Standard Test Method for Fineness of Hydraulic Cement by the 45-&#x3bc;m (No. 325) Sieve
• Effective Date: 01-Dec-2017
• Refers: ASTM C471M-17a - Standard Test Methods for Chemical Analysis of Gypsum and Gypsum Products (Metric)
• Effective Date: 01-Oct-2017
• Refers: ASTM C39/C39M-17b - Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
• Effective Date: 01-Aug-2017
• Refers: ASTM C1157/C1157M-17 - Standard Performance Specification for Hydraulic Cement
• Effective Date: 15-Jun-2017
• Refers: ASTM C471M-17e1 - Standard Test Methods for Chemical Analysis of Gypsum and Gypsum Products (Metric)
• Effective Date: 01-Jun-2017

Overview

ASTM C563-20: Standard Guide for Approximation of Optimum SO₃ in Hydraulic Cement provides guidance for determining the appropriate level of sulfur trioxide (SO₃) content in hydraulic cements, such as portland and blended cements. The guide supports manufacturers and laboratories in optimizing SO₃ levels to enhance cement and concrete performance while considering the specific types of cement, supplementary cementitious materials, and chemical admixtures used. The document is relevant to cements specified by ASTM C150/C150M, C595/C595M, and C1157/C1157M, outlining methods to achieve maximum performance.

Key Topics

• Purpose and Scope: The guide estimates the optimum SO₃ content needed to maximize performance in hydraulic cement by partially substituting cement with calcium sulfate.
• SO₃ Variability: The optimum SO₃ content may vary depending on materials used, age of the cement, performance criteria, and use of admixtures or supplementary cementitious materials (SCMs).
• Test Methods: The guide permits several test methods for evaluating performance at differing SO₃ levels, such as:
  • Compressive strength tests (ASTM C109/C109M for mortars, C39/C39M for concrete)
  • Heat of hydration measurements (ASTM C1702)
  • Drying shrinkage of mortar (ASTM C596)
• Sample Preparation: Procedures for dosing and blending calcium sulfate into cement are specified to accurately create samples with varying SO₃ content.
• Data Interpretation: Includes instructions for visual and mathematical interpretation of test results to identify the SO₃ level that delivers optimal performance.
• Reporting Requirements: Standardized format for reporting results, methodologies, and any variations from the guide’s specified procedures.
• Safety and Compliance: Users are responsible for safety, health, and environmental practices, and adhering to local regulations during testing.

Applications

The procedures in ASTM C563-20 are vital in the following contexts:

• Cement Manufacturing: Enables cement producers to determine the optimal proportion of SO₃-typically introduced via gypsum or other calcium sulfate sources-enhancing early and long-term strength, workability, and durability.
• Product Optimization: Assists manufacturers in balancing various performance factors (strength, setting behavior, shrinkage) across different ages and field conditions.
• Laboratory Testing: Allows researchers to approximate optimum sulfate content under controlled laboratory conditions before scaling up for field application.
• Quality Assurance: Supports quality control by providing reproducible methods for performance assessment and SO₃ optimization, aligning with ASTM C150, C595, and C1157 cement specifications.
• Formulation of Blended Cements: Facilitates development of cement mixtures containing SCMs or chemical admixtures by providing guidance on how these materials interact with SO₃ content.

Related Standards

ASTM C563-20 references and complements several standards critical to cement and concrete testing, including:

• ASTM C114: Test Methods for Chemical Analysis of Hydraulic Cement (particularly for accurate SO₃ analysis)
• ASTM C150/C150M: Specification for Portland Cement
• ASTM C595/C595M: Specification for Blended Hydraulic Cements
• ASTM C1157/C1157M: Performance Specification for Hydraulic Cement
• ASTM C109/C109M: Compressive Strength of Hydraulic Cement Mortars
• ASTM C39/C39M: Compressive Strength of Concrete Cylinders
• ASTM C1702: Measurement of Heat of Hydration
• ASTM C596: Drying Shrinkage of Mortar
• ASTM C204 / C430: Fineness of Hydraulic Cement

Practical Value

ASTM C563-20 brings practical value across the cement and concrete industry by standardizing the process of approximating optimum SO₃ content for enhanced product performance. The guide ensures that manufacturers can reliably:

• Adjust and test sulfate levels for optimal results,
• Address variability due to material sources and admixtures,
• Comply with leading ASTM specifications for hydraulic cement products,
• Improve cement durability, strength, and long-term performance in application.

Adopting ASTM C563-20 supports high-quality cement production and greater confidence in concrete construction projects through evidence-based, standardized methods for sulfate optimization.

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: C563 − 20
Standard Guide for
Approximation of Optimum SO in Hydraulic Cement
This standard is issued under the fixed designation C563; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* C114Test Methods for Chemical Analysis of Hydraulic
Cement
1.1 This guide describes the determination of approximate
C150/C150MSpecification for Portland Cement
optimum SO for maximum performance as a result of substi-
C192/C192MPractice for Making and Curing ConcreteTest
tuting calcium sulfate for a portion of the cement.
Specimens in the Laboratory
1.2 This guide refers to the sulfur trioxide (SO ) content of
C204Test Methods for Fineness of Hydraulic Cement by
thecementonly.Slagcementsandoccasionallyotherhydraulic
Air-Permeability Apparatus
cements can contain sulfide or other forms of sulfur. The
C305Practice for Mechanical Mixing of Hydraulic Cement
determination of SO content by rapid methods may include
Pastes and Mortars of Plastic Consistency
these other forms, and may therefore produce a significant
C430Test Method for Fineness of Hydraulic Cement by the
error. If a significant error occurs, analyze the cement for SO
45-µm (No. 325) Sieve
content using the reference test method of Test Methods C114
C465Specification for Processing Additions for Use in the
for sulfur trioxide.
Manufacture of Hydraulic Cements
1.3 Values stated as SI units are to be regarded as standard.
C471MTestMethodsforChemicalAnalysisofGypsumand
Gypsum Products (Metric)
1.4 This standard does not purport to address all of the
C595/C595MSpecification for Blended Hydraulic Cements
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- C596Test Method for Drying Shrinkage of Mortar Contain-
ing Hydraulic Cement
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. C1157/C1157MPerformance Specification for Hydraulic
1.5 This international standard was developed in accor- Cement
dance with internationally recognized principles on standard-
C1437Test Method for Flow of Hydraulic Cement Mortar
ization established in the Decision on Principles for the C1679Practice for Measuring Hydration Kinetics of Hy-
Development of International Standards, Guides and Recom-
draulic Cementitious Mixtures Using Isothermal Calorim-
mendations issued by the World Trade Organization Technical
etry
Barriers to Trade (TBT) Committee.
C1702Test Method for Measurement of Heat of Hydration
of Hydraulic Cementitious Materials Using Isothermal
2. Referenced Documents
Conduction Calorimetry
2.1 ASTM Standards:
C39/C39MTest Method for Compressive Strength of Cylin-
3. Significance and Use
drical Concrete Specimens
3.1 The purpose of this guide is to estimate the SO content
C78/C78MTest Method for Flexural Strength of Concrete
for a hydraulic cement that gives maximum performance. The
(Using Simple Beam with Third-Point Loading)
value obtained is one way to establish an appropriate level of
C109/C109MTest Method for Compressive Strength of
sulfate in the manufacture of cements specified in Specifica-
Hydraulic Cement Mortars (Using 2-in. or [50 mm] Cube
tions C150/C150M, C595/C595M, and C1157/C1157M.
Specimens)
3.2 The SO content of a cement giving maximum perfor-
mance is different at different ages, with different performance
This guide is under the jurisdiction of ASTM Committee C01 on Cement and
criteria and with different materials such supplementary ce-
is the direct responsibility of Subcommittee C01.28 on Sulfate Content
CurrenteditionapprovedJune1,2020.PublishedJuly2020.Originallyapproved
mentitious materials and chemical admixtures.Amanufacturer
in 1965. Last previous edition approved in 2019 as C563–19. DOI: 10.1520/
can choose the performance criteriato determine optimum SO
C0563-20.
content. This optimum SO content may be a compromise
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM between different ages and different performance criteria.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. NOTE1—Typically,theoptimumSO contentishigherthelatertheage.
*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
C563 − 20
3.3 This guide indicates optimum SO content for cement,
SO =SO percentage of the sample with the median
3,median 3
optionallyinpresenceofsupplementarycementitiousmaterials
SO of the samples tested,
and admixtures. Several alternate methods are allowed: com-
SO =SO percentage of cement sample X,
3,X 3
pressive strength of concrete or mortar, heat of hydration of F = measured fineness of cement sample X, and
M,X
paste or mortar, and drying shrinkage of mortar. F = adjusted fineness of cement sample X.
A,X
NOTE 3—Differences in the mill conditions between samples of
3.4 It should not be assumed that the optimum SO esti-
different sulfate levels should be minimized. For this reason samples are
mated in this guide is the same SO content for optimum
normally taken during the same production campaign. Strategies should
performance of a concrete prepared in the field using the same
be employed to minimize the differences in fineness of the clinker when
materials. The optimum SO is influenced by parameters such
3 taking samples, such as targeting a specific sieve size range and adjusting
around that target within reasonable tolerances. Since calcium sulfate is
as ambient and fresh concrete temperature, admixtures, and
softer, and thus easier to grind than clinker, increases in calcium sulfate
supplementary cementitious materials.
content will elevate the fineness of the cement without a change in the
3.5 The guide is applicable to cements specified in Specifi-
grinding energy or the fineness of the clinker.
cations C150/C150M, C595/C595M, and C1157/C1157M.
NOTE 4—As an example, consider the case of one cement sample with
an SO content of 2.7% and a fineness of 380 m /kg, which is the sample
with the median SO content, and another sample with an SO content of
4. Apparatus 3 3
3.7% and a fineness of 405 m /kg.The second sample has a 1.0 % higher
4.1 Use the apparatus as specified in Test Methods C109/
SO content, or 2.2% more calcium sulfate addition, assuming the
C109M, C192/C192M, C596,or C1702. calciumsulfatewas45%SO .Theadjustedcementfinenessofthesecond
2 2
sample would be reduced by 22 m /kg (10 × 2.2) to 383 m /kg by using
2 2
Eq 1 as shown in Eq 2.This value of 383 m /kg is within 13m /kg of the
5. Materials
fineness of 380 m /kg, and thus is acceptable for testing.
5.1 CalciumSulfate—Usecalciumsulfateforadditiontothe
10·~3.7 2 2.7!
cement that is either a high-grade natural gypsum having an
F 5 405 2 5 383 mg ⁄kg (2)
A,X
SO content of at least 46%, or the calcium sulfate from the
source used for the intended plant production. Grind the
calcium sulfate to 100% passing the 75 µm (No. 200) sieve,
5.2.2 Determinethepercentageofthefollowinganalytesby
and at least 800 m /kg Blaine fineness (Test Method C204). If
Test Method C114 for each cement tested: silicon dioxide
the SO content of the calcium sulfate is unknown, analyze it
(SiO ),aluminumoxide(Al O ),ferricoxide(Fe O ),calcium
2 2 3 2 3
in accordance with Test Methods C471M.
oxide (CaO), magnesium oxide (MgO), sulfur trioxide (SO ),
NOTE 2—The calcium sulfate source can impact the optimum sulfate
loss on ignition, insoluble residue, sodium oxide (Na O), and
result due in part to differences in surface area and form of the calcium
potassium oxide (K O). Calculate the potential percentages of
sulfate(forexample,gypsum,calciumsulfatehemi-hydrate,oranhydrous
calcium sulfate). Temperatures in cement finish mills during production
the following compounds for portland cements according to
can reach levels to partially or completely change the form of calcium
Specification C150/C150M: tricalcium silicate, dicalcium
sulfate in cement, while laboratory grinding of calcium sulfate may alter
silicate, tricalcium aluminate, and tetracalcium aluminoferrite.
its reactivity through increased fineness and partial change of the form of
When applicable, report the amount of limestone and Specifi-
thecalciumsulfate.Differentclinkersmayreactdifferentlytotheeffectof
sulfateforms.Inparticular,ifthedissolutionrateofsulfateduringcement cationC465inorganicprocessingadditionsaccordingtoSpeci-
hydration is at any time lower than the sulfate consumption rate of the
fication C150/C150M. Determine the fineness of each cement
aluminates, the sulfate in solution may become temporarily depleted,
tested according to Test Methods C204 and C430.
resultinginelevatedaluminatereactivityandsignificantreductionsinalite
reactivity. Elevated aluminate reactivity may lead to loss of workability
NOTE 5—The amount of material retained on the 45 µm sieve has been
and admixture performance as well as reduced rate of strength develop-
used as an indication of the clinker fineness. When high efficiency
ment and setting behavior that has a relatively low degree of repeatability
separators are used, the amount retained on a 20 µm sieve has also been
and reproducibility. On the other hand, if the dissolution rate of sulfate
used as an indicator of clinker fineness.
before placing of concrete is higher than the sulfate consumption rate of
the aluminates, precipitation of secondary gypsum may cause loss of
workability and false set. 6. Procedure
5.2 Cement—Make cements of different sulfate levels at a
6.1 Sulfate Levels to Test—Test at least five different sulfate
single production site. Make the cements so that the amount of
levels.
calcium sulfate added, and the subsequent dilution effects, are
6.1.1 SO contents are to be at least 0.20% different unless
the only difference in constituent materials.
more than five different SO contents are being tested. The
5.2.1 Grind samples to a fineness within 13 m /kg of the
maximum and minimum SO content of the blended samples
other samples when tested in accordance with Test Method
must differ by at least 2.0% SO content.
C204. Since calcium sulfate sources are typically softer than
clinker, an adjustment of 10 m /kg for every 1% calcium
NOTE 6—The same mixture design and materials shall be used when
comparing different SO contents. Use one or more of the following test
sulfate addition is permitted, as shown in Eq 1.
methods to evaluate the performance:
10· SO 2 SO
~ !
3,X 3,median
F 5 F 2 (1)
A,X M,X
6.1.1.1 When adding calcium sulfate it is considered as part
SO ⁄ 100
3,CS
of the mass of cement for proportioning.
where:
6.1.1.2 UsethefollowingequationtocalculatethetotalSO
SO = percentage of SO in the calcium sulfate,
3,CS 3
in the blended sample of cement and calcium sulfate:
C563 − 20
M 6.2.2.2 Additions of other materials typically used in
calciumsulfate
SO 5 3SO
3-total 3-calciumsulfate
M 1M concrete, such as supplementary cementitious materials and
calciumsulfate cement
chemical admixtures, can be used, provided that the content of
M
cement
1 3SO (3)
3-cement
supplementarycementitiousmaterials,chemicaladmixtures,or
M 1M
calciumsulfate cement
both are kept the same for each different mixture.
where:
6.2.2.3 When testing with mortars use the same sand con-
M = the mass of the calcium sulfate,
calcium sulfate tent for each different mixture.
M = the mass of the cement,
cement
6.2.2.4 Testing at temperatures besides 23 °C is allowed.
SO = thepercentbymassofSO inthecalcium
3-cement sulfate 3
Use the same temperature for each different mixture.
sulfate, and
SO = the percent by mass of the SO in the NOTE 10—Experience shows that mixing cement paste externally and
3-cement 3
transferringasubsetofpasteormortartothesamplevialgenerateshigher
cement.
variability because of increased variability of the masses of cement and
calcium sulfate transferred from the external mixing vial to the sample
NOTE 7—As an example, consider the case of a cement with a SO
vial. If using cement paste with additions of calcium sulfate powder not
content of 2.7% and calcium sulfate with SO content of 45% where
alreadyintergroundinthecement,itisrecommendedtoweighandmixall
594g of cement are mixed with 6g calcium sulfate. The total SO of the
materials inside the sample vial without removing any material from the
blendofcementandcalciumsulfatewouldbe3.1%asshowninequation
sample vial after mixing.
Eq 4 below:
NOTE 11—Blending of two industrially produced cement samples as
6 594
describedin5.2,producedwithinthesamedaywithalowandahighSO
SO 5 345 %1 32.7 % 5 3.1 % (4)
3-total
61594 61594 content to obtain a series of sub samples with varying SO contents, is
known to give good results, provided that the clinker fineness and the
NOTE 8—More sulfate levels may be tested to help improve the
clinker reactivity are similar.Alternatively, the addition of calcium sulfate
precision of the interpretation of the results. Extremely high and low
powdertoasingleindustrialcementsampleallowsfortestingtheeffectof
sulfate levels can give results that deviate from the typical peak behavior
differentsulfateformsandmayyieldalessvariableapproximateoptimum
whichmayneedtobetreatedasoutlierswhenusingamathematicalfitting
sulfatelevelasthesulfatelevelistheonlyparameterthatvariesinthetest.
procedure.
6.2.2.5 Any thermal power measured prior to the minimum
6.2 The same mixture design and materials shall be used
at point (B) observed prior to the onset of the main hydration
whencomparingdifferentSO contents.Useoneormoreofthe
peak (C), Fig. 1, shall be excluded from the calculated heat of
following test methods to evaluate the performance:
hydration.
6.2.1 Mortar Compressive Strength—Determine mortar
compressive strength at each sulfate level at the age of 24 6
NOTE 12—Experience shows that optimum SO estimated at a given
⁄4h, 3 days 6 1 h, or 7 days 6 3 h in accordance with Test age using isothermal conduction calorimetry with cement paste is similar
to the optimum SO estimated using compressive strength of mortar in
Method C109/C109M except as follows: 3
Guide C1679. The early heat measurements before the minimum B, Fig.
6.2.1.1 When mixing in accordance with the “Procedure for
1, are typically subject to high levels of variability and influenced by
Mixing Mortars” section of Practice C305, add the calcium
relatively small differences in calorimeter and material temperatures, and
sulfate to the water, unless the calcium sulfate addition has are therefore excluded.
been previously ground and mixed with the cement; then start
6.2.2.6 Composition of Test Mixture—Adjust the mass of
the mixer and mix at slow speed (140 6 5 rpm) for 15 s; then
solids and water as needed to obtain a suitable mix size, with
stop the mixer and add the cement to the water; then start the
theoptionaladditionofsandandothermaterialstypicallyused
mixer and mix at slow speed (140 6 5 rpm) for 30 s.
in concrete. Ensure that the total masses of cement and cement
6.2.1.2 Usetheamountofmixingwatertoproduceaflowof
plus calcium sulfate differ by no more than 5% within a given
105 to 115% for one of the mixtures using 25 drops of the
test series. Weigh or determine volumetrically a fixed and
table as determined in the section on Procedures in Test
sufficient amount of water to completely wet and easily mix
Method C1437. Use that same amount of water (constant
each individual mixture.
w/cm) for each mixture with different sulfate levels.
6.2.2.7 Use the same mixing method for all samples to be
compared.
NOTE 9—The mixture with the median sulfate level or lowest sulfate
level is often used to determine the water content.
NOTE 13—Several paste mixing methods are known to give suitable
results, including: Internal mixing using a disposable impeller left inside
6.2.2 Heat of Hydration—Determine heat of hydration at
thesamplevialaftermixing;externalmixingusingadisposablespoonleft
each sulfate level at the desired ages in accordance with Test
inside the sample vial after mixing; external mixing using vibration or
Method C1702 except as follows:
ultrasound contacting the outside of the sample vial, external mechanical
6.2.2.1 If making calcium sulfate powder additions to an mixing of paste or mortar which is then added to the sample vial.
However, better reproducibility can be achieved when the mixing is done
industrially produced cement sample, add the cement and
withinthecalorimetersamplevial,aserrorduetodifferentsamplingfrom
calcium sulfate powder directly into the calorimetry sample
a separate mixing bowl to sample vial is avoided, and mixing temperature
vial and dry mix the solids inside the calorimetry sample vial
conditions are easier to control within the sample vial.
to ensure that the calcium sulfate is blended with the cement
6.2.2.8 TestDuration—Continuecollectingcalorimetrydata
prior to water addition. If using industrially-produced cement
for the period over which sulfate optimization is desired to be
sampleswiththecalciumsulfateadditionsalreadyinterground,
achieved.
follow the procedure for Test Method C1702 Method A or B
except as follows.Alternatively, produce a mortar as described
NOTE 14—Generally optimum SO levels are found to be higher when
6.2.1. the degree of cement hydration is higher. Accordingly it is useful to
C563 − 20
(A) Initial thermal power by dissolution of cement and initial cement hydration; (B) Dormant period associated with very low thermal power indicatingslowand
well-controlled hydration; (C) Main hydration peak associated
...

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: C563 − 19 C563 − 20
Standard Guide for
Approximation of Optimum SO in Hydraulic Cement
This standard is issued under the fixed designation C563; 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.
1. Scope*
1.1 This guide describes the determination of approximate optimum SO for maximum performance as a result of substituting
calcium sulfate for a portion of the cement.
1.2 This guide refers to the sulfur trioxide (SO ) content of the cement only. Slag cements and occasionally other hydraulic
cements can contain sulfide or other forms of sulfur. The determination of SO content by rapid methods may include these other
forms, and may therefore produce a significant error. If a significant error occurs, analyze the cement for SO content using the
reference test method of Test Methods C114 for sulfur trioxide.
1.3 Values stated as SI units are to be regarded as 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.
2. Referenced Documents
2.1 ASTM Standards:
C39/C39M Test Method for Compressive Strength of Cylindrical Concrete Specimens
C78/C78M Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)
C109/C109M Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50 mm] Cube Specimens)
C114 Test Methods for Chemical Analysis of Hydraulic Cement
C150/C150M Specification for Portland Cement
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C204 Test Methods for Fineness of Hydraulic Cement by Air-Permeability Apparatus
C305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency
C430 Test Method for Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve
C465 Specification for Processing Additions for Use in the Manufacture of Hydraulic Cements
C471M Test Methods for Chemical Analysis of Gypsum and Gypsum Products (Metric)
C595/C595M Specification for Blended Hydraulic Cements
C596 Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement
C1157/C1157M Performance Specification for Hydraulic Cement
C1437 Test Method for Flow of Hydraulic Cement Mortar
C1679 Practice for Measuring Hydration Kinetics of Hydraulic Cementitious Mixtures Using Isothermal Calorimetry
C1702 Test Method for Measurement of Heat of Hydration of Hydraulic Cementitious Materials Using Isothermal Conduction
Calorimetry
3. Significance and Use
3.1 The purpose of this guide is to estimate the SO content for a hydraulic cement that gives maximum performance. The value
obtained is one way to establish an appropriate level of sulfate in the manufacture of cements specified in Specifications
C150/C150M, C595/C595M, and C1157/C1157M.
This guide is under the jurisdiction of ASTM Committee C01 on Cement and is the direct responsibility of Subcommittee C01.28 on Sulfate Content
Current edition approved Oct. 1, 2019June 1, 2020. Published November 2019July 2020. Originally approved in 1965. Last previous edition approved in 20182019 as
C563 – 18a.C563 – 19. DOI: 10.1520/C0563-19.10.1520/C0563-20.
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
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C563 − 20
3.2 The SO content of a cement giving maximum performance is different at different ages, with different performance criteria
and with different materials such supplementary cementitious materials and chemical admixtures. A manufacturer can choose the
performance criteriato determine optimum SO content. This optimum SO content may be a compromise between different ages
3 3
and different performance criteria.
NOTE 1—Typically, the optimum SO content is higher the later the age.
3.3 This guide indicates optimum SO content for cement, optionally in presence of supplementary cementitious materials and
admixtures. Several alternate methods are allowed: compressive strength of concrete or mortar, heat of hydration of paste or
mortar, and drying shrinkage of mortar.
3.4 It should not be assumed that the optimum SO estimated in this guide is the same SO content for optimum performance
3 3
of a concrete prepared in the field using the same materials. The optimum SO is influenced by parameters such as ambient and
fresh concrete temperature, admixtures, and supplementary cementitious materials.
3.5 The guide is applicable to cements specified in Specifications C150/C150M, C595/C595M, and C1157/C1157M.
4. Apparatus
4.1 Use the apparatus as specified in Test Methods C109/C109M, C192/C192M, C596, or C1702.
5. Materials
5.1 Calcium Sulfate—Use calcium sulfate for addition to the cement that is either a high-grade natural gypsum having an SO
content of at least 46 %, or the calcium sulfate from the source used for the intended plant production. Grind the calcium sulfate
to 100 % passing the 75-μm 75 μm (No. 200) sieve, and at least 800 m /kg Blaine fineness (Test Method C204). If the SO content
of the calcium sulfate is unknown, analyze it in accordance with Test Methods C471M.
NOTE 2—The calcium sulfate source can impact the optimum sulfate result due in part to differences in surface area and form of the calcium sulfate
(for example, gypsum, calcium sulfate hemi-hydrate, or anhydrous calcium sulfate). Temperatures in cement finish mills during production can reach
levels to partially or completely change the form of calcium sulfate in cement, while laboratory grinding of calcium sulfate may alter its reactivity through
increased fineness and partial change of the form of the calcium sulfate. Different clinkers may react differently to the effect of sulfate forms. In particular,
if the dissolution rate of sulfate during cement hydration is at any time lower than the sulfate consumption rate of the aluminates, the sulfate in solution
may become temporarily depleted, resulting in elevated aluminate reactivity and significant reductions in alite reactivity. Elevated aluminate reactivity
may lead to loss of workability and admixture performance as well as reduced rate of strength development and setting behavior that has a relatively low
degree of repeatability and reproducibility. On the other hand, if the dissolution rate of sulfate before placing of concrete is higher than the sulfate
consumption rate of the aluminates, precipitation of secondary gypsum may cause loss of workability and false set.
5.2 Cement—Make cements of different sulfate levels at a single production site. Make the cements so that the amount of
calcium sulfate added, and the subsequent dilution effects, are the only difference in constituent materials.
5.2.1 Grind samples to a fineness within 13 m /kg of the other samples when tested in accordance with Test Method C204. Since
calcium sulfate sources are typically softer than clinker, an adjustment of 10 m /kg for every 1 % calcium sulfate addition is
permitted, as shown in Eq 1.
10·~SO 2 SO !
3,X 3,median
F 5 F 2 (1)
A,X M,X
SO ⁄ 100
3,CS
10· SO 2 SO
~ !
3,X 3,median
F 5 F 2 (1)
A,X M,X
SO ⁄ 100
3,CS
where:
SO = percentage of SO in the calcium sulfate,
3,CS 3
SO = percentage of SO in the calcium sulfate,
3,CS 3
SO = SO percentage of the sample with the median SO of the samples tested,
3,median 3 3
SO = SO percentage of the sample with the median SO of the samples tested,
3,median 3 3
SO = SO percentage of cement sample X,
3,X 3
F = measured fineness of cement sample X, and
M,X
F = adjusted fineness of cement sample X.
A,X
NOTE 3—Differences in the mill conditions between samples of different sulfate levels should be minimized. For this reason samples are normally taken
during the same production campaign. Strategies should be employed to minimize the differences in fineness of the clinker when taking samples, such
as targeting a specific sieve size range and adjusting around that target within reasonable tolerances. Since calcium sulfate is softer, and thus easier to
grind than clinker, increases in calcium sulfate content will elevate the fineness of the cement without a change in the grinding energy or the fineness
of the clinker.
NOTE 4—As an example, consider the case of one cement sample with an SO content of 2.7 % and a fineness of 380 m /kg, which is the sample with
the median SO content, and another sample with an SO content of 3.7 % and a fineness of 405 m /kg. The second sample has a 1.0%1.0 % higher SO
3 3 3
content, or 2.2 % more calcium sulfate addition, assuming the calcium sulfate was 45 % SO . The adjusted cement fineness of the second sample would
2 2 2 2
be reduced by 22 m /kg (10 × 2.2) to 383 m /kg by using Eq 1 as shown in Eq 2. This value of 383 m /kg is within 13 m /kg of the fineness of 380
m /kg, and thus is acceptable for testing.
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10· 3.7 2 2.7
~ !
F 5 405 2 5 383 m ⁄kg (2)
A,X
10· 3.7 2 2.7
~ !
F 5 405 2 5 383 mg ⁄kg (2)
A,X
5.2.2 Determine the percentage of the following analytes by Test Method C114 for each cement tested: silicon dioxide (SiO ),
aluminum oxide (Al O ), ferric oxide (Fe O ), calcium oxide (CaO), magnesium oxide (MgO), sulfur trioxide (SO ), loss on
2 3 2 3 3
ignition, insoluble residue, sodium oxide (Na O), and potassium oxide (K O). Calculate the potential percentages of the following
2 2
compounds for portland cements according to Specification C150/C150M: tricalcium silicate, dicalcium silicate, tricalcium
aluminate, and tetracalcium aluminoferrite. When applicable, report the amount of limestone and Specification C465 inorganic
processing additions according to Specification C150/C150M. Determine the fineness of each cement tested according to Test
Methods C204 and C430.
NOTE 5—The amount of material retained on the 45-μm45 μm sieve has been used as an indication of the clinker fineness. When high efficiency
separators are used, the amount retained on a 20-μm20 μm sieve has also been used as an indicator of clinker fineness.
6. Procedure
6.1 Sulfate Levels to Test—Test at least five different sulfate levels.
6.1.1 SO contents are to be at least 0.20 % different unless more than five different SO contents are being tested. The
3 3
maximum and minimum SO content of the blended samples must differ by at least 2.0 % SO content.
3 3
NOTE 6—The same mixture design and materials shall be used when comparing different SO contents. Use one or more of the following test methods
to evaluate the performance:
6.1.1.1 When adding calcium sulfate it is considered as part of the mass of cement for proportioning.
6.1.1.2 Use the following equation to calculate the total SO in the blended sample of cement and calcium sulfate:
M M
calciumsulfate cement
SO 5 3SO 1 3SO (3)
3-Total 3-calciumsulfate 3-cement
M 1M M 1M
calcium sulfate cememnt calciumsulfate cement
M M
calcium sulfate cement
SO 5 3SO 1 3SO (3)
3-total 3-calcium sulfate 3-cement
M 1M M 1M
calcium sulfate cement calcium sulfate cement
where:
M = the mass of the calcium sulfate,
calcium sulfate
M = the mass of the cement,
cement
SO = the percent by mass of SO in the calcium sulfate, and
3-cement sulfate 3
SO = the percent by mass of the SO in the cement.
3-cement 3
NOTE 7—As an example, consider the case of a cement with a SO content of 2.7 % and calcium sulfate with SO content of 45 % where 594 g of
3 3
cement are mixed with 6 g calcium sulfate. The total SO of the blend of cement and calcium sulfate would be 3.1 % as shown in equation Eq 4 below:
6 594
SO 5 345 %1 32.7 %5 3.1 % (4)
32Total
61594 61594
6 594
SO 5 345 %1 32.7 %5 3.1 % (4)
3-total
61594 61594
NOTE 8—More sulfate levels may be tested to help improve the precision of the interpretation of the results. Extremely high and low sulfate levels
can give results that deviate from the typical peak behavior which may need to be treated as outliers when using a mathematical fitting procedure.
6.2 The same mixture design and materials shall be used when comparing different SO contents. Use one or more of the
following test methods to evaluate the performance:
6.2.1 Mortar compressive strength—Compressive Strength—Determine mortar compressive strength at each sulfate level at the
age of 24 6 ⁄4 h, 3 days 6 1 h, or 7 days 6 3 h in accordance with Test Method C109/C109M except as follows:
6.2.1.1 When mixing in accordance with the “Procedure for Mixing Mortars” section of Practice C305, add the calcium sulfate
to the water, unless the calcium sulfate addition has been previously ground and mixed with the cement; then start the mixer and
mix at slow speed (140 6 5 rpm) for 15 s; then stop the mixer and add the cement to the water; then start the mixer and mix at
slow speed (140 6 5 rpm) for 30 s.
6.2.1.2 Use the amount of mixing water to produce a flow of 105 to 115 % for one of the mixtures using 25 drops of the table
as determined in the section on Procedures in Test Method C1437. Use that same amount of water (constant w/cm) for each mixture
with different sulfate levels.
NOTE 9—The mixture with the median sulfate level or lowest sulfate level is often used to determine the water content.
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6.2.2 Heat of hydration—Hydration—Determine heat of hydration at each sulfate level at the desired ages in accordance with
Test Method C1702 except as follows:
6.2.2.1 If making calcium sulfate powder additions to an industrially produced cement sample, add the cement and calcium
sulfate powder directly into the calorimetry sample vial and dry mix the solids inside the calorimetry sample vial to ensure that
the calcium sulfate is blended with the cement prior to water addition. If using industrially-produced cement samples with the
calcium sulfate additions already interground, follow the procedure for Test Method C1702 Method A or B except as follows.
Alternatively, produce a mortar as described 6.2.1.
6.2.2.2 Additions of other materials typically used in concrete, such as supplementary cementitious materials and chemical
admixtures, can be used, provided that the content of supplementary cementitious materials, chemical admixtures, or both are kept
the same for each different mixture.
6.2.2.3 When testing with mortars use the same sand content for each different mixture.
6.2.2.4 Testing at temperatures besides 23°C23 °C is allowed. Use the same temperature for each different mixture.
NOTE 10—Experience shows that mixing cement paste externally and transferring a subset of paste or mortar to the sample vial generates higher
variability because of increased variability of the masses of cement and calcium sulfate transferred from the external mixing vial to the sample vial. If
using cement paste with additions of calcium sulfate powder not already interground in the cement, it is recommended to weigh and mix all materials
inside the sample vial without removing any material from the sample vial after mixing.
NOTE 11—Blending of two industrially produced cement samples as described in 5.2, produced within the same day with a low and a high SO content
to obtain a series of sub samples with varying SO contents, is known to give good results, provided that the clinker fineness and the clinker reactivity
are similar. Alternatively, the addition of calcium sulfate powder to a single industrial cement sample allows for testing the effect of different sulfate forms
and may yield a less variable approximate optimum sulfate level as the sulfate level is the only parameter that varies in the test.
6.2.2.5 Any thermal power measured prior to the minimum at point (B) observed prior to the onset of the main hydration peak
(C), Fig. 1, shall be excluded from the calculated heat of hydration.
NOTE 12—Experience shows that optimum SO estimated at a given age using isothermal conduction calorimetry with cement paste is similar to the
optimum SO estimated using compressive strength of mortar in Standard Guide C1679. The early heat measurements before the minimum B, Fig. 1,
are typically subject to high levels of variability and influenced by relatively small differences in calorimeter and material temperatures, and are therefore
excluded.
6.2.2.6 Composition of Test Mixture—Adjust the mass of solids and water as needed to obtain a suitable mix size, with the
optional addition of sand and other materials typically used in concrete. Ensure that the total masses of cement and cement plus
calcium sulfate differ by no more than 5 % within a given test series. Weigh or determine volumetrically a fixed and sufficient
amount of water to completely wet and easily mix each individual mixture.
6.2.2.7 Use the same mixing method for all samples to be compared.
NOTE 13—Several paste mixing methods are known to give suitable results, including: Internal mixing using a disposable impeller left inside the sample
vial after mixing; external mixing using a disposable spoon left inside the sample vial after mixing; external mixing using vibration or ultrasound
contacting the outside of the sample vial, external mechanical mixing of paste or mortar which is then added to the sample vial. However, better
(A) Initial thermal power by dissolution of cement and initial cement hydration; (B) Dormant period associated with very low thermal power indicating slow and
well-controlled hydration; (C) Main hydration peak associated mainly with hydration reactions contributing to setting and early strength development, with maximum at (D);
and (E) Sulfate depletion point, followed by (F) Accelerated calcium aluminate activity. In this example the approximate time of onset of the main hydration peak is 1 h
45 min.
FIG. 1 (A) initial thermal power by dissolution of cement and initial cement hydration; (B) dormant period associated with very low
thermal power indicating slow and well-controlled hydration; (C) main hydration peak associated mainly with hydration reactions con-
tributing to setting and early strength development, with maximum at (D); and (E) sulfate depletion point, followed by (F) accelerated
calcium aluminate activity. In this example the approximate time of onset of the main hydration peak is 1 h 45 min.Heat Evolution Over
Hydration Time
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reproducibility can be achieved when the mixing is done within the calorimeter sample vial, as error due to different sampling from a separate mixing
bowl to sample vial is avoided, and mixing temperature conditions are easier to control within the sample vial.
6.2.2.8 Test Duration—Continue collectin
...