1、Designation: C1679 13C1679 14Standard 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
2、case of 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 for measuring relative differences
3、in hydration kinetics of hydrauliccementitious mixtures, either in paste or mortar (See(see Note 1), including those containing admixtures, various supplementarycementitious materials (SCM), and other fine materials by measuring the thermal power using an isothermal calorimeter.NOTE 1Paste specimens
4、 are often preferred for mechanistic research when details of individual reaction peaks are important or for particularcalorimetry configurations. Mortar specimens may give results that have better correlation with concrete setting and early strength development and areoften preferred to evaluate di
5、fferent mixture proportions for concrete. Both paste and mortar studies have been found to be effective in evaluating concretefield problems due to incompatibility of materials used in concrete mixtures.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement a
6、re included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations p
7、rior to use. (WarningFresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin andtissue upon prolonged exposure.2Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin andtissue upon prolonged exposure.)2. Referenced Documents2.1 ASTM Sta
8、ndards:3C125 Terminology Relating to Concrete and Concrete AggregatesC172 Practice for Sampling Freshly Mixed ConcreteC219 Terminology Relating to Hydraulic CementC305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic ConsistencyC403/C403M Test Method for Time of Setti
9、ng of Concrete Mixtures by Penetration ResistanceC511 Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of HydraulicCements and ConcretesC778 Specification for SandC1005 Specification for Reference Masses and Devices for Determining Mass and Vol
10、ume for Use in the Physical Testing ofHydraulic CementsC1602/C1602M Specification for Mixing Water Used in the Production of Hydraulic Cement Concrete2.2 Other Standard:API Specification RP 10B-2/ ISO 10426-2 Recommended Practice for Testing Well Cements43. Terminology3.1 DefinitionsFor definitions
11、of terms used in this practice, refer to Terminology C125 and Terminology C219.3.2 Definitions of Terms Specific to This Standard:3.2.1 baseline, nthe signal from the calorimeter when there is an inert specimen in the instrument.1 This practice is under the jurisdiction of ASTM Committee C09 on Conc
12、rete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.48 onPerformance of Cementitious Materials and Admixture Combinations.Current edition approved Dec. 15, 2013June 1, 2014. Published January 2014June 2014. Originally approved in 2007. Last previous edition approved in
13、20092013 asC1679 09.C1679 13. DOI: 10.1520/C1679-13.10.1520/C1679-14.2 Section on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards, Vol 04.02.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm
14、.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 Available from American Petroleum Institute (API), 1220 L. St., NW, Washington, DC 20005-4070, http:/api-ec.api.org.This document is not an ASTM standard and is intended only
15、 to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versio
16、nof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 calcium aluminate, nvarious alumina
17、te phases including but not limited to the tricalcium aluminate and ferrite phasesin portland cement clinker, calcium aluminate phases occurring in some supplementary cementitious materials, and calcium-alumino-silicate glasses also occurring in some supplementary cementitious materials, that are ca
18、pable of consuming the sulfatephases present in hydrating cementitious systems.3.2.3 calibration coeffcient, na factor that relates the value recorded by the data acquisition system to the thermal poweroutput.3.2.3.1 DiscussionNormally recorded data are in volts and the calibration coefficient has u
19、nits of watts per volt (W/V). Some calorimeters may haveinternal automatic calibration and will give the output in watts without the user having to specify the calibration coefficient.3.2.4 combined mixture, ncombination of all the materials that are introduced into the calorimeter for measuring hyd
20、rationkinetics.3.2.5 hydration time, nthe elapsed time from initial contact between the cementitious materials and the mix water.3.2.6 inert specimen, nspecimen placed within the isothermal calorimeter made of a non-reactive material of similar thermalproperties (mainly heat capacity) as the reactin
21、g specimen made of the cementitious test mixture.3.2.6.1 DiscussionThe output from the calorimeter is the difference between the heat flow from the test specimen and the inert specimen. The useof an inert specimen substantially decreases the noise and drift of the measured heat flow.3.2.7 isothermal
22、 calorimeter, na calorimeter that measures heat flow from a specimen maintained at a constant temperatureby intimate thermal contact with a constant temperature heat sink.3.2.8 isothermal calorimetry, nan experimental technique to monitor the thermal power output from a specimen kept at nearisotherm
23、al conditions.3.2.9 isothermal hydration profile, nthe thermal power plotted as a function of hydration time, which provides an indicationof the rate of hydration over time at a given temperature.3.2.10 main hydration peak, nthe broadest peak in the isothermal hydration profile that starts at the en
24、d of the dormant periodand for a well-balanced mixture lasts for several hours (See(see Fig. 1).3.2.11 near isothermal conditions, na constant temperature with a permissible variation of 6 1.0 C.3.2.12 specimen holder, ncontainer within the isothermal calorimeter that conducts the heat from the spec
25、imen in the vial tothe heat flow sensor.3.2.13 stock solution, na solution of admixture in water prepared to enable more precise volumetric addition of smallquantities of admixture, typically made by pipetting known volumes of admixture into a volumetric flask and diluting it to theflasks fixed volu
26、me.NOTE 1(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 mainly with hydration reactions contributing to setting and earlystreng
27、th development, with maximum at (D); and (E) sulfate depletion point,6 followed by (F) accelerated calcium aluminate activity.FIG. 1 Example of Thermal Power Curve for Isothermal Hydration of Portland CementC1679 1423.2.14 sulfate addition, nthe addition of a soluble sulfate source (such as gypsum,
28、calcium sulfate hemihydrate, alkali sulfate)to a combined mixture to investigate whether a given combination of materials is in sulfate balance.3.2.15 sulfate balance of mixture, nthe situation when the size of the main hydration peak is not increased by sulfate additions;in some cases where the mai
29、n peak is increased in size by added sulfate, it will also be accelerated in time.3.2.16 sulfate depletion point, nthe onset of accelerated calcium aluminate activity that for a portland cement in absence ofsupplementary cementitious material (SCM) and admixture may take place after the main hydrati
30、on peak.3.2.16.1 DiscussionThe sulfate depletion point may become impossible to detect without further addition of soluble calcium sulfate for certain cementsand more often in combined mixtures with admixtures or SCMs, or both. In some cases other sources of sulfate might be used tomimic potential c
31、onditions in the system. Among these are anhydrite, arcanite, calcium langbeinite, aphthitalite, syngenite, andothers. Fig. 2 shows an example of the effect of added sulfate on the sulfate depletion point.Added sulfate may, in some combinedmixtures with admixtures or SCMs, or both, accelerate the on
32、set of the main hydration peak. When a combined mixture is at sulfatebalance, further addition of soluble sulfate will not increase the size, or accelerate the onset, of the main hydration peak.3.2.17 thermal equilibrium time, nthe elapsed hydration time when the thermal power of replicate mixtures
33、do not differ bymore than 0.2 mW/g of dry material.3.2.18 thermal indicator of setting time, n the hydration time to reach a thermal power of 50 % of the maximum value of themain hydration peak.3.2.19 thermal mass, nthe amount of thermal energy that can be stored by a material (J/K).3.2.19.1 Discuss
34、ionThe thermal mass of a given material is calculated by multiplying the mass by the specific heat capacity of the material. For thepurpose of calculating the thermal mass used in this standard, the following specific heat capacities can be used: The specific heatcapacity of a typical unhydrated por
35、tland cement and water is 0.75 and 4.18 J/(gK), respectively. Thus a mixture ofAg of cementand B g of water has a thermal mass of (0.75 A + 4.18 B) J/K. The specific heat capacity of typical quartz and limestone is0.75 and 0.84 J/(gK), respectively. The specific heat capacity of most amorphous suppl
36、ementary cementitious material such as flyash or slag is approximately 0.8 J/(gK).3.2.20 thermal power, nheat production rate measured in watts (W) or joules per second (J/s), usually expressed in relationto the mass of cementitious material, as mW/g or J/s/g.3.2.20.1 DiscussionThe thermal power is
37、an indicator of the rate of various chemical reactions between cementitious materials, other fine particles,mix water and admixtures.3.2.21 vial, ncontainer into which the freshly mixed cementitious mixture is placed for a measurement.FIG. 2 Example of the Effect of Soluble Calcium Sulfate Addition
38、on the Timing of the Sulfate Depletion Point for a Type I Portland Ce-ment Mixed with Water Only at w/c = 0.45C1679 1434. Summary of Practice4.1 An isothermal calorimeter consists of heat sink with a thermostat, two heat flow sensors and a specimen vial holder attachedto each sensor. A vial containi
39、ng a freshly prepared mixture is placed in contact with one of the vial holders and a thermally inertmaterial is placed in contact with the other. The heat of hydration released by the reacting cementitious specimen is transferredand passes across a heat flow sensor. The calorimeter output is calcul
40、ated from the difference between the outputs from the testspecimen heat flow sensor and the inert specimen heat flow sensor. Because the heat is allowed to flow away from the specimen,the measurement will take place at essentially constant temperature (isothermal conditions).4.2 Mixtures with cement
41、, SCM, admixtures, water and optional fine aggregate are prepared and introduced into an isothermalcalorimeter. Isothermal calorimetry tests are performed on a series of different mixtures for relative comparison of the hydrationkinetics. The output of the calorimeter is evaluated by graphical and m
42、athematical means to evaluate retarding and acceleratingeffects of different combinations of materials. Calcium sulfate may be added as a probe to determine if the addition of admixture,SCMs, or both have increased the mixtures demand for sulfate beyond that which is available in the cement.5. Signi
43、ficance and Use5.1 Thermal power curves are used to evaluate the isothermal hydration kinetics of the combined mixture of different materialsduring the early period after being mixed with water.These isothermal power curves, or hydration profiles, may provide indicationsrelative to setting character
44、istics, compatibility of different materials, sulfate balance and early strength development. Theisothermal hydration profiles can also be used to evaluate the effects of compositions, proportions, and time of addition of materialsas well as curing temperature. Special care must be used in evaluatin
45、g extended retardation with paste specimens, which have beenshown to overestimate the retardation of some mixtures containing cement, SCM, and admixtures.5.2 This procedure can be used to measure the effect of chemical admixtures on the cement hydration profile. In many cases,the addition of chemica
46、l admixture changes the kinetics of cement hydration.5.3 Although this technique has been used historically to understand issues related to setting and slump loss, it must beemphasized that isothermal calorimetry results cannot predict concrete performance definitely, either positively or negatively
47、.Extensive verification in concrete at planned dosages and temperatures, and at higher dosages, is needed. Isothermal calorimetryis an effective tool to identify sensitivities, so that concrete testing can be efficiently planned and performed.5.4 This practice provides a means of assessing the relat
48、ive hydration 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 the thermal power from pastes and mortars alone or in combinationwith chemical admixtures.5.6 The isothermal calorimeter descr
49、ibed here can be used to measure the thermal power and heat of hydration of mortarsprepared independently or obtained by wet sieving from concrete in accordance with Practice C172.6. Apparatus6.1 Devices for mixing to produce a homogeneous mixture of cement, SCM, admixtures, water and optional other fine materialsor aggregate and devices for charging the mixture into the specimen vial.6.1.1 Weights and Weighing Devices shall conform to the requirements of Specification C1005.6.1.2 Graduated Cylinders shall conform to the requirements o
