1、Designation: C1679 17Standard Practice forMeasuring Hydration Kinetics of Hydraulic CementitiousMixtures Using Isothermal Calorimetry1This standard is issued under the fixed designation C1679; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice describes the apparatus and procedure formeasuring relative differences in hydrat
3、ion kinetics of hydrau-lic cementitious mixtures, either in paste or mortar (see Note1), including those containing admixtures, various supplemen-tary cementitious materials (SCM), and other fine materials bymeasuring the thermal power using an isothermal calorimeter.NOTE 1Paste specimens are often
4、preferred for mechanistic researchwhen details of individual reaction peaks are important or for particularcalorimetry configurations. Mortar specimens may give results that havebetter correlation with concrete setting and early strength developmentand are often preferred to evaluate different mixtu
5、re proportions forconcrete. Both paste and mortar studies have been found to be effective inevaluating concrete field problems due to incompatibility of materialsused in concrete mixtures.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in t
6、hisstandard.1.3 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 and health practices and determine the applica-bility of regulatory limitations prior to use. (W
7、arningFreshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.2)1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for th
8、eDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3C125 Terminology Relating to Concrete and Concrete Ag-gregatesC172/C172M Practice for Sampling Freshly Mix
9、ed Con-creteC219 Terminology Relating to Hydraulic CementC305 Practice for Mechanical Mixing of Hydraulic CementPastes and Mortars of Plastic ConsistencyC403/C403M Test Method for Time of Setting of ConcreteMixtures by Penetration ResistanceC511 Specification for Mixing Rooms, Moist Cabinets,Moist R
10、ooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and ConcretesC778 Specification for Standard SandC1005 Specification for Reference Masses and Devices forDetermining Mass and Volume for Use in the PhysicalTesting of Hydraulic CementsC1602/C1602M Specification for Mixing Water Us
11、ed in theProduction of Hydraulic Cement ConcreteC1738/C1738M Practice for High-Shear Mixing of Hydrau-lic Cement Pastes3. Terminology3.1 DefinitionsFor definitions of terms used in thispractice, refer to Terminology C125 and Terminology C219.3.2 Definitions of Terms Specific to This Standard:3.2.1 b
12、aseline, nthe signal from the calorimeter whenthere is an inert specimen in the instrument.3.2.2 calcium aluminate, nvarious aluminate phases in-cluding but not limited to the tricalcium aluminate and ferritephases in portland cement clinker, calcium aluminate phasesoccurring in some supplementary c
13、ementitious materials, andcalcium-alumino-silicate glasses also occurring in some1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand ConcreteAggregates and is the direct responsibility of Subcommittee C09.48 onPerformance of Cementitious Materials and Admixture Combinations
14、.Current edition approved Dec. 1, 2017. Published January 2018. Originallyapproved in 2007. Last previous edition approved in 2014 as C1679 14. DOI:10.1520/C1679-17.2Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standards, Vol 04.02.3For referenced ASTM
15、standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM In
16、ternational, 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 for theDevelopment of International Standard
17、s, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1supplementary cementitious materials, that are capable ofconsuming the sulfate phases present in hydrating cementitioussystems.3.2.3 calibration coeffcient, na factor that relates theval
18、ue recorded by the data acquisition system to the thermalpower output.3.2.3.1 DiscussionNormally recorded data are in volts andthe calibration coefficient has units of watts per volt (W/V).Some calorimeters may have internal automatic calibration andwill give the output in watts without the user hav
19、ing to specifythe calibration coefficient.3.2.4 combined mixture, ncombination of all the materialsthat are introduced into the calorimeter for measuring hydra-tion kinetics.3.2.5 hydration time, nthe elapsed time from initial con-tact between the cementitious materials and the mix water.3.2.6 inert
20、 specimen, nspecimen placed within the iso-thermal calorimeter made of a non-reactive material of similarthermal properties (mainly heat capacity) as the reactingspecimen made of the cementitious test mixture.3.2.6.1 DiscussionThe output from the calorimeter is thedifference between the heat flow fr
21、om the test specimen and theinert specimen. The use of an inert specimen substantiallydecreases the noise and drift of the measured heat flow.3.2.7 isothermal calorimeter, na calorimeter that mea-sures heat flow from a specimen maintained at a constanttemperature by intimate thermal contact with a c
22、onstanttemperature heat sink.3.2.8 isothermal calorimetry, nan experimental techniqueto monitor the thermal power output from a specimen kept atnear isothermal conditions.3.2.9 isothermal hydration profile, nthe thermal powerplotted as a function of hydration time, which provides anindication of the
23、 rate of hydration over time at a giventemperature.3.2.10 main hydration peak, nthe broadest peak in theisothermal hydration profile that starts at the end of thedormant period and for a well-balanced mixture lasts forseveral hours (see Fig. 1).3.2.11 near isothermal conditions, na constant tempera-
24、ture with a permissible variation of 6 1.0 C.3.2.12 specimen holder, ncontainer within the isothermalcalorimeter that conducts the heat from the specimen in the vialto the heat flow sensor.3.2.13 stock solution, na solution of admixture in waterprepared to enable more precise volumetric addition of
25、smallquantities of admixture, typically made by pipetting knownvolumes of admixture into a volumetric flask and diluting it tothe flasks fixed volume.3.2.14 sulfate addition, nthe addition of a soluble sulfatesource (such as gypsum, calcium sulfate hemihydrate, alkalisulfate) to a combined mixture t
26、o investigate whether a givencombination of materials is in sulfate balance.3.2.15 sulfate balance of mixture, nthe situation when thesize of the main hydration peak is not increased by sulfateadditions; in some cases where the main peak is increased insize by added sulfate, it will also be accelera
27、ted in time.3.2.16 sulfate depletion point, nthe onset of acceleratedcalcium aluminate activity that for a portland cement inabsence of supplementary cementitious material (SCM) andadmixture may take place after the main hydration peak.3.2.16.1 DiscussionThe sulfate depletion point may be-come impos
28、sible to detect without further addition of solublecalcium sulfate for certain cements and more often in com-bined mixtures with admixtures or SCMs, or both. In somecases other sources of sulfate might be used to mimic potentialconditions in the system. Among these are anhydrite, arcanite,calcium la
29、ngbeinite, aphthitalite, syngenite, and others. Fig. 2shows an example of the effect of added sulfate on the sulfatedepletion point. Added sulfate may, in some combined mix-tures with admixtures or SCMs, or both, accelerate the onset ofthe main hydration peak. When a combined mixture is atNOTE 1(A)
30、initial thermal power by dissolution of cement and initial cement hydration; (B) dormant period associated with very low thermal powerindicating slow and well-controlled hydration: (C) main hydration peak associated mainly with hydration reactions contributing to setting and earlystrength developmen
31、t, with maximum at (D); and (E) sulfate depletion point,6followed by (F) accelerated calcium aluminate activity.FIG. 1 Example of Thermal Power Curve for Isothermal Hydration of Portland CementC1679 172sulfate balance, further addition of soluble sulfate will notincrease the size, or accelerate the
32、onset, of the main hydrationpeak.3.2.17 thermal equilibrium time, nthe elapsed hydrationtime when the thermal power of replicate mixtures do not differby more than 0.2 mW/g of dry material.3.2.18 thermal indicator of setting time, n the hydrationtime to reach a thermal power of 50 % of the maximum v
33、alueof the main hydration peak.3.2.19 thermal mass, nthe amount of thermal energy thatcan be stored by a material (J/K).3.2.19.1 DiscussionThe thermal mass of a given materialis calculated by multiplying the mass by the specific heatcapacity of the material. For the purpose of calculating thethermal
34、 mass used in this standard, the following specific heatcapacities can be used: The specific heat capacity of a typicalunhydrated portland cement and water is 0.75 and 4.18 J/(gK),respectively. Thus a mixture ofAg of cement andBgofwaterhas a thermal mass of (0.75 A + 4.18 B) J/K. The specificheat ca
35、pacity of typical quartz and limestone is 0.75 and 0.84J/(gK), respectively. The specific heat capacity of most amor-phous supplementary cementitious material such as fly ash orslag is approximately 0.8 J/(gK).3.2.20 thermal power, nheat production rate measured inwatts (W) or joules per second (J/s
36、), usually expressed inrelation to the mass of cementitious material, as mW/g or J/s/g.3.2.20.1 DiscussionThe thermal power is an indicator ofthe rate of various chemical reactions between cementitiousmaterials, other fine particles, mix water and admixtures.3.2.21 vial, ncontainer into which the fr
37、eshly mixedcementitious mixture is placed for a measurement.4. Summary of Practice4.1 An isothermal calorimeter consists of heat sink with athermostat, two heat flow sensors and a specimen vial holderattached to each sensor. A vial containing a freshly preparedmixture is placed in contact with one o
38、f the vial holders and athermally inert material is placed in contact with the other. Theheat of hydration released by the reacting cementitious speci-men is transferred and passes across a heat flow sensor. Thecalorimeter output is calculated from the difference betweenthe outputs from the test spe
39、cimen heat flow sensor and theinert specimen heat flow sensor. Because the heat is allowed toflow away from the specimen, the measurement will take placeat essentially constant temperature (isothermal conditions).4.2 Mixtures with cement, SCM, admixtures, water andoptional fine aggregate are prepare
40、d and introduced into anisothermal calorimeter. Isothermal calorimetry tests are per-formed on a series of different mixtures for relative comparisonof the hydration kinetics. The output of the calorimeter isevaluated by graphical and mathematical means to evaluateretarding and accelerating effects
41、of different combinations ofmaterials. Calcium sulfate may be added as a probe todetermine if the addition of admixture, SCMs, or both haveincreased the mixtures demand for sulfate beyond that whichis available in the cement.5. Significance and Use5.1 Thermal power curves are used to evaluate the is
42、other-mal hydration kinetics of the combined mixture of differentmaterials during the early period after being mixed with water.These isothermal power curves, or hydration profiles, mayprovide indications relative to setting characteristics, compat-ibility of different materials, sulfate balance and
43、 early strengthdevelopment. The isothermal hydration profiles can also beused to evaluate the effects of compositions, proportions, andtime of addition of materials as well as curing temperature.Special care must be used in evaluating extended retardationwith paste specimens, which have been shown t
44、o overestimatethe retardation of some mixtures containing cement, SCM, andadmixtures.5.2 This procedure can be used to measure the effect ofchemical admixtures on the cement hydration profile. In manycases, the addition of chemical admixture changes the kineticsof cement hydration.5.3 Although this
45、technique has been used historically tounderstand issues related to setting and slump loss, it must beemphasized that isothermal calorimetry results cannot predictconcrete performance definitely, either positively or negatively.Extensive verification in concrete at planned dosages andFIG. 2 Example
46、of the Effect of Soluble Calcium Sulfate Addition on the Timing of the Sulfate Depletion Point for a Type I Portland Ce-ment Mixed with Water Only at w/c = 0.45C1679 173temperatures, and at higher dosages, is needed. Isothermalcalorimetry is an effective tool to identify sensitivities, so thatconcre
47、te testing can be efficiently planned and performed.5.4 This practice provides a means of assessing the relativehydration performance of various test mixtures compared withcontrol mixtures that are prepared in a similar manner.5.5 The procedure and apparatus can be used to monitor thethermal power f
48、rom pastes and mortars alone or in combinationwith chemical admixtures.5.6 The isothermal calorimeter described here can be usedto measure the thermal power and heat of hydration of mortarsprepared independently or obtained by wet sieving fromconcrete in accordance with Practice C172/C172M.6. Appara
49、tus6.1 Devices for mixing to produce a homogeneous mixtureof cement, SCM, admixtures, water and optional other finematerials or aggregate and devices for charging the mixtureinto the specimen vial.6.1.1 Weights and Weighing Devices shall conform to therequirements of Specification C1005.6.1.2 Graduated Cylinders shall conform to the require-ments of Specification C1005. The permissible variation forgraduated cylinders of less than 100-mL capacity shall be61.0 % of the rated capacity.6.1.3 Graduated Syringes of suitable capacities to contain
