Astm c 563 17

Designation C563 − 17 Standard Guide for Approximation of Optimum SO3 in Hydraulic Cement1 This standard is issued under the fixed designation C563; the number immediately following the designation in[.]

Designation: C563−17

Standard Guide for

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 SO3for maximum performance as a result of

substi-tuting 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 SO3content 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 MethodsC114

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

appro-priate safety and health practices and determine the

applica-bility of regulatory limitations prior to use.

2 Referenced Documents

2.1 ASTM Standards:2

C39/C39MTest Method for Compressive Strength of

Cylin-drical Concrete Specimens

C78Test Method for Flexural Strength of Concrete (Using

Simple Beam with Third-Point Loading)

C109/C109MTest Method for Compressive Strength of

Hydraulic Cement Mortars (Using 2-in or [50-mm] Cube

Specimens)

C114Test Methods for Chemical Analysis of Hydraulic

Cement

C150Specification for Portland Cement

C192Practice for Making and Curing Concrete Test

Speci-mens in the Laboratory

C204Test Methods for Fineness of Hydraulic Cement by Air-Permeability Apparatus

C305Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency

C430Test Method for Fineness of Hydraulic Cement by the 45-µm (No 325) Sieve

C465Specification for Processing Additions for Use in the Manufacture of Hydraulic Cements

C471MTest Methods for Chemical Analysis of Gypsum and Gypsum Products (Metric)

C595Specification for Blended Hydraulic Cements

C596Test Method for Drying Shrinkage of Mortar Contain-ing Hydraulic Cement

C1157Performance Specification for Hydraulic Cement

C1437Test Method for Flow of Hydraulic Cement Mortar

C1702Test 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 SO3content 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 Specifica-tions C150,C595, andC1157

3.2 The SO3content of a cement giving maximum perfor-mance is different at different ages, with different perforperfor-mance criteria and with different materials such supplementary ce-mentitious 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

N OTE 1—Typically, the optimum SO3content is higher the later the age.

3.3 This guide indicates optimum SO3content for cement in mortar made and cured at a standard temperature of 23.0 6 2.0°C (73.5 6 3.5°F) The optimum SO3 increases with increasing temperature and may increase when water-reducing admixtures are used

3.4 It should not be assumed that the optimum SO3 esti-mated in this guide is the same SO3 content for optimum performance of a concrete prepared from the cement

3.5 The guide is applicable to cements specified in Specifi-cations C150,C595, and C1157

1 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 Feb 1, 2017 Published March 2017 Originally

approved in 1965 Last previous edition approved in 2016 as C563 – 16 DOI:

10.1520/C0563-17.

2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or

contact ASTM Customer Service at service@astm.org 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

4 Apparatus

4.1 Use the apparatus as specified in Test Methods C109/

C109M,C192,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

SO3content 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,

and at least 800 m2/kg Blaine fineness (Test MethodC204) If

the SO3content of the calcium sulfate is unknown, analyze it

in accordance with Test Methods C471M

N OTE 2—The calcium sulfate source can impact the optimum sulfate

result due in part to differences in 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.

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 m2/kg for every 1 % calcium

sulfate addition is permitted, as shown in equationEq 1

F A,X 5 F M,X2 10·~SO3,X 2 SO3,median!

where:

SO3,CS = percentage of SO3in the calcium sulfate,

SO3,median = SO3percentage of the sample with the median

SO3of the samples tested,

SO3,X = SO3percentage of cement sample X,

F M,X = measured fineness of cement sample X, and

F A,X = adjusted fineness of cement sample X

N OTE 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.

N OTE 4—As an example, consider the case of one cement sample with

an SO3content of 2.7 % and a fineness of 380 m 2 /kg, which is the sample

with the median SO3content, and another sample with an SO3content of

3.7 % and a fineness of 405 m 2 /kg The second sample has a 1.0% higher

SO3 content, or 2.2 % more calcium sulfate addition, assuming the

calcium sulfate was 45 % SO3 The adjusted cement fineness of the second

sample would be reduced by 22 m 2 /kg (10 × 2.2) to 383 m 2 /kg by using

Equation Eq 1 as shown in Eq 2 This value of 383 m2/kg is within

13 m 2 /kg of the fineness of 380 m 2 /kg, and thus is acceptable for testing.

F A,X5 405 210·~3.7 2 2.7!

45 100

5.2.2 Determine the percentage of the following analytes by

Test Method C114 for each cement tested: silicon dioxide

(SiO2), aluminum oxide (Al2O3), ferric oxide (Fe2O3), calcium oxide (CaO), magnesium oxide (MgO), sulfur trioxide (SO3), loss on ignition, insoluble residue, sodium oxide (Na2O), and potassium oxide (K2O) Calculate the potential percentages of the following compounds for portland cements according to Specification C150: tricalcium silicate, dicalcium silicate, tri-calcium aluminate and tetratri-calcium aluminoferrite When applicable, report the amount of limestone and Specification

C465inorganic processing additions according to Specification

C150 Determine the fineness of each cement tested according

to Test Methods C204andC430

N OTE 5—The amount of material retained on the 45-µm sieve has been used as an indication of the clinker fineness When high efficiency separators are used, the amount retained on a 20-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 SO3contents are to be at least 0.20 % different unless more than five different SO3 contents are being tested The maximum and minimum SO3content of the blended samples must differ by at least 2.0 % SO3content

N OTE 6—The same mixture design and materials shall be used when comparing different SO3contents 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 SO3

in the blended sample of cement and calcium sulfate:

SO3-Total5 M calcium sulfate

M calciumsulfate 1M cememnt3SO3-calcium sulfate

M calciumsulfate 1M cement3SO3-cement (3)

where:

M calcium sulfate = the mass of the calcium sulfate,

SO3-cement sulfate = the percent by mass of SO3in the calcium

sulfate, and

SO3-cement = the percent by mass of the SO3 in the

cement

N OTE 7—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 SO3contents Use one or more of the following test methods to evaluate the performance:

6.2.1 Mortar compressive strength—Determine mortar

com-pressive strength at each sulfate level at the age of 24 61⁄4h,

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

110 6 5 for one of the mixtures using 25 drops of the table as

determined in the section on Procedures in Test MethodC1437

Use that same amount of water (constant w/cm) for each

mixture with different sulfate levels

N OTE 8—The mixture with the median sulfate level or lowest sulfate

level is often used to determine the water content.

6.2.2 Heat of hydration—Determine heat of hydration at

each sulfate level at the age of 24 6 1⁄4h, 3 days 6 1 h, or

7 days 6 3 h in accordance with Test MethodC1702except as

follows:

6.2.2.1 Add the calcium sulfate to the water, unless the

calcium sulfate addition has been previously ground and mixed

with the cement;

6.2.2.2 Additions of other materials typically used in

concrete, such as supplementary cementitious materials and

chemical admixtures, can be used

6.2.2.3 Mortars are allowed to be used in addition to pastes

When testing with mortars use the same sand content for each

different mixture

6.2.2.4 Testing at temperatures besides 23°C is allowed Use

the same temperature for each different mixture

6.2.3 Concrete Strength—Prepare all material according to

Practice C192except as follows:

6.2.3.1 Add the calcium sulfate to the water, unless the

calcium sulfate addition has been previously ground and mixed

with the cement

6.2.3.2 When applicable, determine compressive strength

according to Test MethodC39/C39M When applicable,

deter-mine flexural strength according to Test Method C78

6.2.3.3 Testing at concrete and curing temperatures other

than specified is allowed Use the same material temperature

(all mixtures within 10°C range) and the same curing

tempera-ture (all curing temperatempera-tures within 4°C range) for each of the

different mixtures

6.2.4 Drying Shrinkage of Mortar—Prepare all material

according to PracticeC596 except as follows:

6.2.4.1 When mixing in accordance with the section on

Procedure for Mixing Mortars 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

6.2.4.2 Instead of using the amount of mixing water

suffi-cient to produce a flow of 110 6 5, use the amount of mixing

water to produce a flow of 110 6 5 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

N OTE 9—The mixture with the median sulfate level or lowest sulfate

level is often used to determine the water content.

7 Interpretation of Results

7.1 Approximate the SO3content which gives the maximum performance by one of the following methods:

N OTE 10—See the appendix for an example of how this interpretation

is done for each method described below Depending on which method is chosen the results may differ.

7.1.1 Visual Fit—Plot the performance level versus SO3

content and interpolate the sulfate level at the peak

7.1.2 Least Squares Parabolic Fit.

7.1.2.1 Determine the equation of a least squares fit accord-ing to follow equation:

Performance Level 5 a~SO3!21bSO31c

where a, b, and c are fitting coefficients.

N OTE 11—Spreadsheet and graphing programs have the capability to calculate the least squares parabolic fit.

7.1.2.2 Approximate the optimum SO3by calculating vertex

of the parabolic least squares fit from the following equation:

Optimum SO3approximation = 2 b⁄~2 a!

where a and b are coefficients of the parabolic least squares

fit

7.1.3 Asymmetric Fit—In cases where the performance level

versus SO3is skewed to the right or left of the peak a fit using

an asymmetric distribution function may provide a better fit than parabolic fit

N OTE 12—Mathematical and statistics software programs are useful in doing such fits.

N OTE 13—The sulfate level for the maximum performance may or may

be not the SO3content that one of the tests was conducted at.

8 Retest

8.1 If the approximate optimum sulfate level is greater or lower than all the SO3contents tested, then test at additional sulfate levels until at least one SO3content is greater than or less than approximate optimum SO3 content Repeat the interpretation of results in Section7and report on that final set

of results

9 Report

9.1 Report the method(s) and ages used to determine per-formance

9.2 Report any variations in the method(s) from the standard 9.3 Report of the approximate optimum SO3 value as required

9.4 Report if calcium sulfate was added to the cement samples to achieve various levels of SO3

9.5 Report the results of chemical and physical analysis, as required by5.2.2, for the cement sample(s) used

10 Keywords

10.1 blended hydraulic cement; calcium sulfate; cement; compressive strength; gypsum; hydraulic cement; optimum sulfate content (of cement); portland cement; strength (of cement); sulfate content (of cement)

APPENDIXES (Nonmandatory Information) X1 DISCUSSION OF THE TERM “OPTIMUM”

X1.1 The scope statement notes that this test method

deter-mines the optimum SO3 content in cements in mortar at a

particular temperature and age Usually, but not always, the

SO3 content that produces the highest 24-h strength at 23°C

also produces approximately the lowest expansion in water and

the lowest contraction in air at that temperature

X1.2 The “optimum” determined by this test is

approxi-mate The “optimum” SO3content will vary with changes in

mortar proportions; between cement paste, mortars and

con-crete; will vary with the source of SO3; with the age of test;

with the use of chemical admixtures; and with the use of

supplementary cementitious materials Thus, the term

“opti-mum SO3” refers to an approximate value

X1.3 The age for determining the optimum is typically

chosen by the manufacturer based on experience with local

concrete materials

X1.4 For convenience, the method uses the compressive strength of specimens at three different SO3contents for the cement If the strength results are plotted against SO3content, the three points are assumed to give a curve in the shape of a parabola, and the calculation used assumes this shape If more points are used with smaller SO3content increments, the shape

of the curve is seen to be that of a “sawtooth,” with a decreasing slope up to the apex at maximum strength, followed

by a precipitous fall in strength immediately after the apex The apex represents the actual optimum SO3 content, and is typically higher than that calculated using three points Therefore, this affords a small “cushion” when targeting the calculated optimum SO3(determined using three points) dur-ing manufacture to allow for variation in the process

X2 INTERPRETATION OF RESULTS EXAMPLE

X2.1 The following shows an example of how the

interpre-tation is done in three different ways: visual fit, least squares

parabolic fit, and asymmetric fit with the set of data in Table

X2.1

X2.2 Note that each one these interpretation methods gives

a slightly different approximation for optimum SO3: 2.9, 3.1,

and 3.0 % In many cases additional testing can further

increase the precision of each interpretation and help determine

if a symmetric (parabolic) or asymmetric least squares fitting is

more appropriate if it is not apparent with the initial tests

X2.2.1 Example of Visual Fit—The plot of the compressive

strength versus SO3 level is seen in Fig X2.1 The plot

indicates that the optimum is between the 2.65 and 3.25 % SO3

points, close to the 2.94 % SO3data point Thus one

interpre-tation is that the optimum SO3is approximately 2.9 % SO3

X2.2.2 Example of Least Squares Parabolic Fit—Many

spreadsheet, statistical and graphing programs have the

capa-bility to calculate the least squares parabolic fit from a set of data In some spreadsheet programs the LINEST function canbe used for this calculation by utilizing the form of the equation

in 7.1.2.1, a parabola Another option would be to use the graphing interface of some programs which also have the capability to calculate the equation for a least squares parabola The data is graphed with the SO3level on the x-axis and the performance on the y-axis (compressive strength in this case)

as seen inFig X2.1and the fitting function is applied The least squares parabolic fit calculates the following coefficients for this data which are applied to the equations in 7.1.2

a = -1.09

TABLE X2.1 Data for Interpretation of Results Example

SO 3 level (%) Strength (MPa) Calculated natural log

of SO 3 level

FIG X2.1 Plot of Compressive Strength Versus SO 3 Level

b = 6.83

c = 13.13 The calculated coefficients are applied to the equation in

7.1.2.2to calculate the approximate optimum SO3

Optimum SO 3approximation = -b/(2a) = -6.83/(2 × -1.09) = 3.1 %

X2.2.3 Example Of Asymmetric Fit—The data set may not

always be represented best by a symmetric fit such as a

parabola and an asymmetric may be more representative of the

data set The following is an example of how to do an

asymmetric fit with a natural log transformation There are

many other methods asymmetric fitting functions that could be

used depending on the data set First the SO3 levels are

transformed using the natural log function (the values are

shown in Table X2.1) In a similar manner described by the

least squares parabolic fit example a parabolic fit of the

compressive strength versus natural log of SO3is calculated for

the equation below

Strength 5 a~ln~SO3!!21bln~SO3!1c

Again this calculation can be done by graphing, spreadsheet

or statistical software capable of calculate a least squares parabolic fit A graph of this data and fit can be seen in Fig X2.3 Both plots inFig X2.3are the same data but (a) shows the natural log transformation of the SO3level and (b) shows asymmetric fit where SO3is on a linear scale The calculated coefficients from the program (shown below) can then be applied to the equation (shown below) to determine the vertex

of a parabola in Fig X2.3(a)

a = -10.08

b = 22.12

c = 11.71 ln(Optimum SO 3) = -b/(2a) = -22.12/(2 × -10.08) = 1.10 The natural log of optimum SO3is then transformed using the exponential of base e, 2.718, to determine the optimum SO3 level with the following equation:

Approximate Optimum SO35 e ln ~optimum SO3! 5 2.718 1.11 5 3.0 %

FIG X2.2 Example of Parabolic Least Squares Fit of Compressive

Strength Versus SO 3 Level

SUMMARY OF CHANGES

CommitteeC01has identified the location of selected changes to this standard since the last issue (C563 – 16)

that may impact the use of this standard (Approved Feb 1, 2017)

(1) Revised title of this guide from “Standard Guide for

Approximation of Optimum SO3in Hydraulic Cement Using

Compressive Strength” to “Standard Guide for Approximation

of Optimum SO3in Hydraulic Cement.”

(2) Revised 1,3.1,3.2, and4.1

(3) Revised and made additions to Sections5 – 7, and 9

(4) Added Test MethodsC39/C39M,C78,C430,C595,C596,

C1702, PracticeC192, and SpecificationC465

(5) Added Appendix X2

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FIG X2.3 Example of Asymmetric Curve Fitting (a) Strength Versus Natural Log of SO 3 (b) Strength Versus SO3 With Least Squares Fit Line of Strength

Versus Natural Log of SO 3