1、Designation: C 1679 09Standard Practice forMeasuring Hydration Kinetics of Hydraulic CementitiousMixtures Using Isothermal Calorimetry1This standard is issued under the fixed designation C 1679; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f 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 hydr
3、ation 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 ofte
4、n 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 mix
5、ture 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
6、 thisstandard.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.
7、(WarningFreshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.2)2. Referenced Documents2.1 ASTM Standards:3C 125 Terminology Relating to Concrete and ConcreteAggregatesC 172 Practice for Sampling Freshly Mixed ConcreteC 219 Terminolog
8、y Relating to Hydraulic CementC 305 Practice for Mechanical Mixing of Hydraulic CementPastes and Mortars of Plastic ConsistencyC 403/C 403M Test Method for Time of Setting of ConcreteMixtures by Penetration ResistanceC511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage
9、Tanks Used in theTesting of Hydraulic Cements and ConcretesC 778 Specification for Standard SandC 1005 Specification for Reference Masses and Devices forDetermining Mass and Volume for Use in the PhysicalTesting of Hydraulic CementsC 1602/C 1602M Specification for Mixing Water Used inthe Production
10、of Hydraulic Cement Concrete2.2 Other Standard:API Specification RP 10B-2/ ISO 10426-2 RecommendedPractice for Testing Well Cements43. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, refer to Terminology C 125 and Terminology C 219.3.2 Definitions of Terms Specific to This
11、 Standard:3.2.1 baseline, 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 som
12、e supplementary cementitious materials, andcalcium-alumino-silicate glasses also occurring in somesupplementary cementitious materials, that are capable ofconsuming the sulfate phases present in hydrating cementitioussystems.1This practice is under the jurisdiction of ASTM Committee C09 on Concretea
13、nd ConcreteAggregates and is the direct responsibility of Subcommittee C09.48 onPerformance of Cementitious Materials and Admixture Combinations.Current edition approved June 15, 2009. Published July 2009. Originallyapproved in 2007. Last previous edition approved in 2008 as C 1679 08.2Section on Sa
14、fety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standards, Vol 04.02.3For referenced ASTM 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 Do
15、cument Summary page onthe ASTM website.4Available from American Petroleum Institute (API), 1220 L. St., NW, Wash-ington, DC 20005-4070, http:/api-ec.api.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
16、ohocken, PA 19428-2959, United States.3.2.3 calibration coeffcient, na factor that relates thevalue recorded by the data acquisition system to the thermalpower output.3.2.3.1 DiscussionNormally recorded data are in voltsand the calibration coefficient has units of watts per volt(W/V). Some calorimet
17、ers may have internal automatic cali-bration and will give the output in watts without the userhaving to specify the 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
18、elapsed time from initial con-tact between the cementitious materials and the mix water.3.2.6 inert 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
19、mixture.3.2.6.1 DiscussionThe output from the calorimeter is thedifference between the heat flow from 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
20、 heat flow from a specimen maintained at a constanttemperature by intimate thermal contact with a constanttemperature 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 pro
21、file, nthe thermal powerplotted as a function of hydration time, which provides anindication of the 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
22、mixture lasts forseveral hours (See Fig. 1).3.2.11 near isothermal conditions, na constant tempera-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
23、 solution, na solution of admixture in waterprepared to enable more precise volumetric addition of 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
24、 sulfatesource (such as gypsum, calcium sulfate hemihydrate, alkalisulfate) to a combined mixture to 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 sulfateaddition
25、s; in some cases where the main peak is increased insize by added sulfate, it will also be accelerated 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 p
26、lace after the main hydration peak.3.2.16.1 DiscussionThe sulfate depletion point may be-come impossible 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
27、 be used to mimic potentialconditions in the system. Among these are anhydrite, arcanite,calcium langbeinite, 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 SCM
28、s, or both, accelerate the onset ofthe main hydration peak. When a combined mixture is atsulfate balance, further addition of soluble sulfate will notincrease the size, or accelerate the onset, of the main hydrationpeak.3.2.17 thermal equilibrium time, nthe elapsed hydrationtime when the thermal pow
29、er of replicate mixtures do not differby more than 0.2 mW/g of dry material.NOTE(A) 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
30、mainly with hydration reactions contributing to setting and earlystrength development, 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 CementC16790923.2.18 thermal
31、indicator of setting time, nthe hydrationtime to reach a thermal power of 50 % of the maximum valueof the main hydration peak.3.2.19 thermal power, nheat production rate measured inwatts (W) or joules per second (J/s), usually expressed inrelation to the mass of cementitious material, as mW/g or J/s
32、/g.3.2.19.1 DiscussionThe thermal power is an indicator ofthe rate of various chemical reactions between cementitiousmaterials, other fine particles, mix water and admixtures.3.2.20 vial, ncontainer into which the freshly mixedcementitious mixture is placed for a measurement.4. Summary of Practice4.
33、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 of the vial holders and athermally inert material is placed in contact with the other
34、. 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 specimen heat flow sensor and theinert specimen heat flow sensor. Because the heat is a
35、llowed 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 prepared and introduced into anisothermal calorimeter. Isothermal calorimetry tests are per
36、-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 of different combinations ofmaterials. Calcium sulfate may be added as a probe todet
37、ermine 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 isother-mal hydration kinetics of the combined mixture of differentmaterials during th
38、e 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 early strengthdevelopment. The isothermal hydration profiles can also beused to eva
39、luate 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 to overestimatethe retardation of some mixtures containing cement, SCM, andadmixtures
40、.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 technique has been used historically tounderstand issues related to setting and slum
41、p loss, it must beemphasized that isothermal calorimetry results cannot predictconcrete performance definitely, either positively or negatively.Extensive verification in concrete at planned dosages andtemperatures, and at higher dosages, is needed. Isothermalcalorimetry is an effective tool to ident
42、ify sensitivities, so thatconcrete 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 us
43、ed to monitor thethermal power from 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 wi
44、th Practice C 172.6. Apparatus6.1 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 Speci
45、fication C 1005.FIG. 2 Example of the Effect of Soluble Calcium Sulfate Addition on the Timing of the Sulfate Depletion Point for a Type I PortlandCement Mixed with Water Only at w/c = 0.45C16790936.1.2 Graduated Cylinders shall conform to the require-ments of Specification C 1005. The permissible v
46、ariation forgraduated cylinders of less than 100-mL capacity shall be61.0 % of the rated capacity.6.1.3 Graduated Syringes of suitable capacities to containthe desired volume of liquid admixture or stock solution at 20C. The permissible variation of the measured volume shall notexceed 3 % of the vol
47、ume to be delivered. When admixturequantities required are less than 2 mL, or are viscous in nature,optionally prepare stock solutions at appropriate dilution, toavoid problems with small volumes measured volumetrically.Care shall be taken to inspect stock solutions for separation andany admixture t
48、hat is prone to separation in stock solution mustbe added in an alternative fashion, such as by analyticalsyringes.6.1.4 Mixing Apparatus:6.1.4.1 Mortar PreparationThe mixer shall comply withPractice C 305.6.1.4.2 Paste PreparationA high shear blender,5or simi-lar variable speed blender capable of m
49、aintaining a no-loadspeed of at least 15 000 r/min, with optional cooling device. Ahandheld household mixer capable of mixing paste at not lessthan 400 r/min or other mixers for paste or mortar preparationare also permitted.6.1.4.3 The repeatability of results for any mixing methodmust be measured and reported as described in 12.5.6.1.5 Vials that can be sealed and fit into the specimen vialholders of the calorimeter.6.1.6 Pipette, Funnel or Syringe to facilitate charging thesample to the vials. The neck of the device must be largeenough to avoid
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