1、Designation: C 1679 08Standard 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 calibration coeffcient, na factor that relates thevalue recorded by the data acquisition system to the thermalpower output.3.2.2.1 DiscussionNormally recorded data are in voltsand the ca
12、libration coefficient has units of watts per volt(W/V). Some calorimeters may have internal automatic cali-bration and will give the output in watts without the userhaving to specify the calibration coefficient.1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand ConcreteAgg
13、regates and is the direct responsibility of Subcommittee C09.48 onPerformance of Cementitious Materials and Admixture Combinations.Current edition approved June 1, 2008. Published July 2008. Originally approvedin 2007. Last previous edition approved in 2007 as C 1679 07.2Section on Safety Precaution
14、s, 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 Document Summary
15、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 Conshohocken, PA 194
16、28-2959, United States.3.2.3 combined mixture, ncombination of all the materialsthat are introduced into the calorimeter for measuring hydra-tion kinetics.3.2.4 hydration time, nthe elapsed time from initial con-tact between the cementitious materials and the mix water.3.2.5 inert specimen, nspecime
17、n 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.3.2.5.1 DiscussionThe output from the calorimeter is thedifference between the heat flow from the test specime
18、n and theinert specimen. The use of an inert specimen substantiallydecreases the noise and drift of the measured heat flow.3.2.6 isothermal calorimeter, na calorimeter that mea-sures heat flow from a specimen maintained at a constanttemperature by intimate thermal contact with a constanttemperature
19、heat sink.3.2.7 isothermal calorimetry, nan experimental techniqueto monitor the thermal power output from a specimen kept atnear isothermal conditions.3.2.8 isothermal hydration profile, nthe thermal powerplotted as a function of hydration time, which provides anindication of the rate of hydration
20、over time at a giventemperature.3.2.9 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).3.2.10 near isothermal conditions, na constant tempera-ture with a permissi
21、ble variation of 6 1.0 C.3.2.11 specimen holder, ncontainer within the isothermalcalorimeter that conducts the heat from the specimen in the vialto the heat flow sensor.3.2.12 stock solution, na solution of admixture in waterprepared to enable more precise volumetric addition of smallquantities of a
22、dmixture, typically made by pipetting knownvolumes of admixture into a volumetric flask and diluting it tothe flasks fixed volume.3.2.13 sulfate addition, nthe addition of a soluble sulfatesource (such as gypsum, calcium sulfate hemihydrate, alkalisulfate) to a combined mixture to investigate whethe
23、r a givencombination of materials is in sulfate balance.3.2.14 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 accelerated in time.3.2.15 s
24、ulfate depletion point, nthe onset of acceleratedaluminate activity that for a portland cement in absence ofsupplementary cementitious material (SCM) and admixturemay take place after the main hydration peak.3.2.15.1 DiscussionThe sulfate depletion point may be-come impossible to detect without furt
25、her addition of gypsumor plaster for certain cements and more often in combinedmixtures with admixtures or SCMs, or both. In some casesother sources of sulfate might be used to mimic potentialconditions in the system. Among these are anhydrite, arcanite,calcium langbeinite, aphthitalite, syngenite,
26、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 atsulfate balance, further addition of soluble s
27、ulfate will notincrease the size, or accelerate the onset, of the main hydrationpeak.3.2.16 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.3.2.17 thermal indicator of setting time, nthe hydrationtim
28、e to reach a thermal power of 50 % of the maximum valueof the main hydration peak.3.2.18 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/g.3.2.18.1 DiscussionThe thermal power is a
29、n indicator ofthe rate of various chemical reactions between cementitiousmaterials, other fine particles, mix water and admixtures.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-co
30、ntrolled hydration: (C) main hydration peak associated mainly with hydration reactions contributing to setting and earlystrength development, with maximum at (D); and (E) sulfate depletion point,6followed by (F) accelerated aluminate activity.FIG. 1 Example of Thermal Power Curve for Isothermal Hydr
31、ation of Portland CementC16790823.2.19 vial, ncontainer into which the freshly 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
32、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. Theheat of hydration released by the reacting cementitious speci-men is transferred and passes across a heat flow sensor. Thecalorimeter outp
33、ut is calculated from the difference betweenthe outputs from the test specimen 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 w
34、ith cement, SCM, admixtures, water andoptional fine aggregate are prepared 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 graphi
35、cal and mathematical means to evaluateretarding and accelerating effects 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.
36、 Significance and Use5.1 Thermal power curves are used to evaluate the isother-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 ch
37、aracteristics, compat-ibility of different materials, sulfate balance and 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 eva
38、luating extended retardationwith paste specimens, which have been shown to 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 chem
39、ical admixture changes the kineticsof cement hydration.5.3 Although this 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
40、.Extensive verification in concrete at planned dosages andtemperatures, and at higher dosages, is needed. Isothermalcalorimetry is an effective tool to identify sensitivities, so thatconcrete testing can be efficiently planned and performed.5.4 This practice provides a means of assessing the relativ
41、ehydration 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 from pastes and mortars alone or in combinationwith chemical admixtures.5.6 The isothermal calorimeter described
42、 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 C 172.6. Apparatus6.1 Devices for mixing to produce a homogeneous mixtureof cement, SCM, admixtures, water and optional other finem
43、aterials or aggregate and devices for charging the mixtureinto the specimen vial.6.1.1 Weights and Weighing Devices shall conform to therequirements of Specification C 1005.6.1.2 Graduated Cylinders shall conform to the require-ments of Specification C 1005. The permissible variation forgraduated cy
44、linders 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 volume to be delivered. Whe
45、n 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.FIG. 2 Example of the Effect of Soluble Calcium Sulfate Addition on the Timing of the Sulfate Depletion
46、Point for a Type I PortlandCement Mixed with Water Only at w/c = 0.45C1679083Care shall be taken to inspect stock solutions for separation andany admixture that 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
47、.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 maintaining a no-loadspeed of at least 15 000 r/min, with optional cooling device. Ahandheld household mixer capable of mixing paste at not less
48、than 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
49、or Syringe to facilitate charging thesample to the vials. The neck of the device must be largeenough to avoid sample segregation.6.2 Calorimeter and Data Acquisition System of suitablecapacity and calibrated to monitor the thermal power of mortaror paste in a repeatable fashion. The actual design of anindividual instrument, whether commercial or custom-built,may vary, but it shall meet the following criteria, and shall beverified to do so on a yearly basis or at any time that equipmentis modified.6.2.1 The standard deviation in thermal power for si
