1、Designation: C1872 18Standard Test Method forThermogravimetric Analysis of Hydraulic Cement1This standard is issued under the fixed designation C1872; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A num
2、ber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides a technique incorporating athermogravimetric analyzer to determine the mass changes ofhydraulic cement upon heat
3、ing in an inert gas environment.The data can be used to determine the abundance of somemineralogical components in hydraulic cement powders.1.2 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement are included in thisstandard.1.3 This test method is applica
4、ble to hydraulic cementpowders.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regu
5、latory limitations prior to use.1.5 WarningFresh hydraulic cementitious mixtures arecaustic and may cause burns to skin and tissue upon prolongedexposure. The use of gloves, protective clothing, and eyeprotection is recommended. Wash contact area with copiousamounts of water after contact. Wash eyes
6、 for a minimum of15 min. Avoid exposure of the body to clothing saturated withthe liquid phase of the unhardened material. Remove contami-nated clothing immediately after exposure.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-izat
7、ion established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:C114 Test Methods for Chemical Analysis of HydraulicCem
8、entC219 Terminology Relating to Hydraulic CementC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsE473 Terminology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Met
9、hodE1131 Test Method for Compositional Analysis by Thermo-gravimetryE1142 Terminology Relating to Thermophysical PropertiesE1582 Test Method for Temperature Calibration of Thermo-gravimetric AnalyzersE1868 Test Methods for Loss-On-Drying by Thermogravi-metryE2040 Test Method for Mass Scale Calibrati
10、on of Thermo-gravimetric AnalyzersE2402 Test Method for Mass Loss and Residue Measure-ment Validation of Thermogravimetric Analyzers3. Terminology3.1 Definitions:3.1.1 Technical terms used in this guide are defined inTerminologies C219, E473, E1142.4. Summary of Test Method4.1 Thermogravimetric anal
11、ysis of cement is performed bycontinuously monitoring mass changes of a hydraulic cementpowder specimen, in an environment with a controlled atmo-sphere as the test temperature is increased at a constant rate.Mass loss over specific temperature ranges and in a specificatmosphere can be used to suppl
12、ement the compositionalanalysis of the cement by providing estimates of the massfraction of certain mineral constituents.5. Significance and Use5.1 This test method is intended for use in acquiring,analyzing, and reporting thermogravimetric data obtained fromhydraulic cement powders.5.2 This test me
13、thod can be used to determine the calciumcarbonate content of cements with interground limestone if thecalcium carbonate content of the limestone is known.5.3 This test method can be used to determine the calciumhydroxide content of hydraulic cement powder.5.4 This test method can be used to determi
14、ne the mass lossupon heating hydraulic cement powders within a specifictemperature range.1This test method is under the jurisdiction of ASTM Committee C01 on Cementand is the direct responsibility of Subcommittee C01.23 on Compositional Analysis.Current edition approved May 15, 2018. Published June
15、2018. DOI: 10.1520/C1872-18.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles
16、 for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15.5 This test method can be used for qualitative and quan-titative characterization, under certain conditions, of varioussulfate mineral comp
17、onents including calcium sulfatedihydrate, calcium sulfate hemihydrate, and syngenite.5.6 Different kinds of thermogravimetric analyzers areavailable with different configurations and controllers.Therefore, the parameters described should be considered asguidelines. They may be altered to conform to
18、 the instrumentmanufacturers instructions, provided the changes are noted inthe report.6. Interferences6.1 This test method depends upon distinctive thermalstability ranges of the determined components as a principle ofthe test. Materials that have no well-defined thermally stablerange, or that have
19、 thermal stability ranges that are the same asother components in the cement, may create interferences.Particular examples include the following:6.1.1 Calcium silicate hydrate gel (C-S-H) releases physi-cally and chemically bound water over a continuous and broadtemperature range, typically 100 to 6
20、00C, and may beobserved even in nominally unhydrated cement powders thathave been stored in humid conditions. In specimens of partiallyhydrated cement paste, the continuous release of water byC-S-H upon heating can interfere with the measurement ofmass loss by other decomposing minerals within that
21、tempera-ture range, such as hydrated calcium sulfates and portlandite.6.1.2 In unhydrated cement powders, the conversion ofgypsum (calcium sulfate dihydrate) to calcium sulfate hemi-hydrate occurs over a temperature range, 100 to 200C, that isclose to that of the subsequent decomposition of hemihydr
22、ateto anhydrite (calcium sulfate). The two sources of mass loss aredifficult to distinguish when using an open sample container,but can be separated better by covering the container with a lidhaving a narrow slit or hole for escape of vapors.6.2 Heating rate can influence the temperature at which th
23、edecomposition of a component is detected, as well as thetemperature at which that component reaches its maximum rateof decomposition, identified readily by a peak in the firstderivative of the thermogravimetric data with respect totemperature (see Fig. 1). A difference in heating rate of5C/min can
24、change the peak temperature by as much as 50C.However, heating rates between 5 and 15C/min have anegligible influence on the total mass loss accompanying agiven decomposition event.7. Apparatus7.1 Thermogravimetric analyzer with a microbalance, tem-perature controller, and data collection device, an
25、d gas flowcontrol device all complying with the requirements of TestMethod E1131, Compositional Analysis by Thermogravimetry.7.1.1 Containers (pans, lids, and so forth), for holding thespecimen must be dimensionally stable and chemically inertwith respect to cementitious components within the temper
26、a-ture limits of this method.7.1.1.1 Aluminum oxide is suitably inert with respect tohydraulic cement to be used for containers and lids at tempera-tures exceeding 600C or when the lid need not be sealed to thepan.7.1.1.2 Aluminum is a suitable material for measurementsof the calcium sulfate hydrate
27、s and other components attemperatures less than 600C, which require the pan and lid tobe sealed with only a small slit or pinhole to allow escape ofvapors.7.1.1.3 Platinum pans can be used for analyses from ambi-ent temperature up to 1200C7.1.1.4 Pans and lids can be obtained from the manufacturerof
28、 the thermogravimetric analyzer or from a vendor recom-mended by the manufacturer.FIG. 1 Sample Thermogravimetric Curve for Unhydrated Portland CementC1872 1828. Reagents and Materials8.1 An inert compressed gas is required for this method.High-purity nitrogen gas (99.99 % N2) is sufficient. High-pu
29、rity argon or helium are also acceptable.9. Sampling, Test Specimens, and Test Units9.1 Cement powders are normally analyzed as soon aspossible after being received because they will tend to absorbmoisture and react with carbon dioxide over time. Measuringan as-received sample provides a baseline ag
30、ainst whichsubsequent measurements can be compared to assess thedegree of aging.9.2 Typical sample masses will depend on the instrumentbeing used and on the specific minerals of interest. Dependingon the instrument being used, measurement of calciumhydroxide, syngenite, and calcium carbonate typical
31、ly requireabout 50 mg of cement powder, while determination of cal-cium sulfate hydrate content in cement often require about100 mg of powder. Refer to the manufacturers instructions forguidance on the optimum mass of sample.10. Calibration10.1 Calibrate the mass signal from the apparatus accordingt
32、o Test Method E2040.10.2 Calibrate the temperature signal from the apparatusaccording to Test Method E1582.11. Procedure11.1 Turn on the flow of the inert gas and establish its flowrate.NOTE 1The appropriate flow rate depends on the type of instrumentbeing used. For example, instruments with small h
33、orizontal tube furnacestypically operate with a gas flow rate of 50 mL min. Refer to themanufacturers instructions for guidance on the appropriate flow rate.11.2 Open the apparatus and load the reference and emptysample pans. Close the apparatus.11.3 Zero the mass signal with the reference and sampl
34、epans in place.11.4 Open the apparatus to expose the specimen holder.11.5 Prepare the specimen as outlined in Section 9 andcarefully place it in the specimen holder, if this was not alreadydone as part of the sample conditions described in Section 9.11.6 Close the apparatus.11.7 Record the initial m
35、ass after any sample conditioningalready described.11.8 Initiate the user specified temperature program andcollect the data of mass and mass change versus time andtemperature. Table 1 provides typical measurement parameters.Consult the manufacturers instructions to determine optimumparameters for a
36、specific thermogravimetric analyzer.11.8.1 The mass loss profile shall be expressed in absolutemass units of milligrams or grams. Expanded scale operationmay be useful over selected temperature ranges.NOTE 2Some instrument software may default to a normalized masspercentage scale based on the origin
37、al sample mass. Absolute mass lossprofiles can be recovered from a percentage scale if the original mass isknown.11.8.2 If only one or two components of the compositionalanalysis are desired, specific, more limited temperature rangesmay be used. Similarly, several heating rates may be usedduring ana
38、lysis in those regions of greater or lesser interest.11.9 The analysis is complete when a state of constant massis obtained at the maximum temperature of interest.11.10 Calculate and report the sample composition (seeSections 12 and 13).12. Calculation and Interpretation of Results12.1 Table 2 shows
39、 the typical temperature ranges fordecomposition reactions in an open pan for common compo-nents of unhydrated cement. The temperature ranges reflectaverages of those reported in several studies, and are dependenton heating rate. In general, lower rates of heating will causedecomposition onset tempe
40、ratures to be lower.12.2 Quantitative Determination of Individual Components:12.2.1 The mass percentage of any solid component listedin Table 2 can be determined from the mass lost by thatcomponent upon its thermal decomposition.12.2.2 Each mineral component thermally decomposes overa characteristic
41、 temperature range. Approximate minimumtemperature X and maximum temperature Y for each compo-nent are indicated in Table 2.12.2.3 For some components such as calcium hydroxide,calcium sulfate hemihydrate, or syngenite, mass loss occursover a relatively narrow temperature range. Other componentsthat
42、 may be present due to significant prehydration effects,such as C-S-H gel, lose mass over a wide temperature rangeand therefore contribute to uncertainty in attributing a massloss value to a particular mineral. Normally the steps areinterpreted as a change in mass before and after the effect, sothe
43、corresponding “baseline” is horizontal. Sometimes rela-tively sharp decomposition steps occur during the decomposi-tion process. This baseline drift, possibly due to mass loss byTABLE 1 Suggested Compositional Analysis ParametersSpecimen Sample Size, mgFlow RatemL/minAPurge TimeminTemperature C Heat
44、ing RateC/minInitial MaximumUnhydrated Cement 50 50 10 25 1000 10Calcium Sulfate Hydrates orSyngenite100 50 10 25 500 10AMay differ depending on instrument design.C1872 183minerals such as C-S-H gel, may be accommodated byconstructing tangent lines to the baseline at the onset andtermination of the
45、main mass loss signal, marking the point atwhich the tangent lines depart from the curve as the onset andterminating temperatures Tiand Tf, respectively, and assigningthe mass difference m=m(Ti)m(Tf) as the mass loss dueto the component in question. Calculating and plotting thederivative of the mass
46、 loss with respect to temperature may behelpful both in identifying reaction onset/completion tempera-tures and in delineating the baseline drift.12.2.4 The mass percentage of a particular component witha narrow decomposition temperature range may be calculatedon an original mass basis, assuming tha
47、t the component isstoichiometric and pure, by using the following equation:P 5MmCmO3100 (1)where:P = mass percent of component in the original powder,M = molar mass of pure stoichiometric component in Table2 (g/mol),m = vertical distance between upper and lower tangentlines, as shown in Fig. 2 (g),C
48、 = mass loss per mole of pure stoichiometric componentin Table 2 due to thermal decomposition (g/mol), andmo= original mass of sample (g).12.2.5 Determinations of calcium sulfate dihydrate andcalcium sulfate hemihydrate are complicated by the fact thatthe dihydrate form often first decomposes to the
49、 hemihydrateform before decomposing fully to anhydrite. Therefore, thehemihydrate mass loss signal generally has contributions bothfrom original hemihydrate and from any hemihydrate formedby decomposition of dihydrate; an example is shown in Fig. 2.Referring to Fig. 2, calculations of calcium sulfate dihydrateand hemihydrate can be made according to the followingformulas, each of which is based on Eq 1 and the values inTable 2, assuming that the components are pure and stoichio-metric:PDihydrate! 56.374mT1! 2 mT2!#mo3100 (2)PHemihydrate!516.122mT2! 2 mT3
