ASTM C1698-2009(2014) Standard Test Method for Autogenous Strain of Cement Paste and Mortar《水泥浆和水泥砂浆自应力的标准试验方法》.pdf

1、Designation: C1698 09 (Reapproved 2014)Standard Test Method forAutogenous Strain of Cement Paste and Mortar1This standard is issued under the fixed designation C1698; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last

2、 revision. A number 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 measures the bulk strain of a sealedcement paste or mortar specimen, including those containingadmixtures

3、, various supplementary cementitious materials(SCM), and other fine materials, at constant temperature andnot subjected to external forces, from the time of final settinguntil a specified age. This strain is known as autogenous strain.Autogenous strain is most significant in concrete with lowwater-c

4、ementitious materials ratio (w/cm) (See Note 1).NOTE 1A low water-cementitious materials ratio (w/cm) can beconsidered to be a water to cement ratio of 0.40 or lower for this test.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstand

5、ard.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. (WarningFr

6、eshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.2)2. Referenced Documents2.1 ASTM Standards:3C125 Terminology Relating to Concrete and Concrete Ag-gregatesC157/C157M Test Method for Length Change of HardenedHydraulic-Cement Mortar

7、 and ConcreteC191 Test Methods for Time of Setting of Hydraulic Cementby Vicat NeedleC192/C192M Practice for Making and Curing Concrete TestSpecimens in the LaboratoryC219 Terminology Relating to Hydraulic CementC305 Practice for Mechanical Mixing of Hydraulic CementPastes and Mortars of Plastic Con

8、sistencyC403/C403M Test Method for Time of Setting of ConcreteMixtures by Penetration ResistanceC1005 Specification for Reference Masses and Devices forDetermining Mass and Volume for Use in the PhysicalTesting of Hydraulic Cements2.2 API Specification4RP 10B-2/ISO 10426-2 Recommended Practice for T

9、estingWell Cements3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, referto Terminologies C125 and C219.3.2 Definitions of Terms Specific to This Standard:3.2.1 autogenous strain, nthe bulk strain of a sealedspecimen of a cementitious mixture, not subjected to ex

10、ternalforces and under constant temperature, measured from the timeof final setting until a specified age; negative strain correspondsto shrinkage and positive strain corresponds to expansion.4. Summary of Test Method4.1 A specimen of freshly mixed paste or mortar is preparedusing a corrugated mold

11、that offers little resistance to lengthchange of the specimen. The mold is sealed to prevent moistureloss and the specimen is stored at constant temperature.Starting at the time of final setting, the length of the specimenis measured using a dilatometer. The change in length isrecorded at regular ti

12、me intervals until the designated age. Thechange in length and original length of the specimen are usedto compute the autogenous strain.5. Significance and Use5.1 Autogenous strain is the self-created bulk strain ofcement paste, mortar, or concrete during hardening at constanttemperature. In convent

13、ional concrete, autogenous shrinkagestrain is generally negligible, but in concrete with low water-cementitious materials ratio (w/cm) or with silica fume it may1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of Su

14、bcommitteeC09.68 on Volume Change.Current edition approved Oct. 1, 2014. Published November 2014. Originallyapproved in 2009. Last previous edition approved in 2009 as C1698-09. DOI:10.1520/C1698-09R14.2Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Stand

15、ards, 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 page onthe ASTM website.4Available from American Petroleum Institute

16、 (API), 1220 L. St., NW,Washington, DC 20005-4070, http:/www.api.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1be considerable (1).5Restraint of the autogenous strain byaggregates or adjoining structural members may result infor

17、mation of micro and macro cracks that impair strength,durability and aesthetics. Cracks may also be a problem withregard to hygienic cleaning of surfaces.5.2 An accurate measurement of the autogenous strain ofcementitious mixtures with low w/cm is important for evalu-ating the risk of early-age crac

18、king of concrete structures.Measurements of autogenous strain have been carried out usingeither volumetric or linear methods. Both methods may showevidence of significant artifacts (1); therefore, results of thetwo methods may disagree considerably if not carried outproperly.5.3 A sealed, flexible c

19、orrugated mold system (2) combinesthe advantages of linear and volumetric measurement ofautogenous strain, while avoiding most of their disadvantages.The mold effectively prevents moisture loss and minimizesrestraint to volume change during hardening. Moreover, resultsobtained with the corrugated mo

20、ld system agree with thosefrom the volumetric method, once some artifacts, in particularwater absorption through the membrane used to contain the testspecimen, have been eliminated in the latter (3,4). The corru-gated mold system is easier to use and shows better repeatabil-ity than the volumetric t

21、echnique (3,4). Measurements with thecorrugated mold system are in good agreement with unre-strained length change measurements obtained using TestMethod C157/C157M with sealed specimens (5); however,Test Method C157/C157M does not allow measurement of theshrinkage occurring before 24 h (5).5.4 This

22、 test method can be used to evaluate the effects ofcementitious materials, admixtures, and mixture proportionson autogenous shrinkage strain of paste or mortar specimens.5.5 The autogenous shrinkage strain of mortar specimenswill be less than that of paste specimens for the same w/cm.The autogenous

23、shrinkage strain of concrete will be less thanthat of mortar for the same w/cm. The nominal maximumaggregate size for mortar used in this test method is 4.75 mm.6. Apparatus6.1 The apparatus to measure autogenous strain is com-posed of a corrugated mold with two end plugs, a dilatometerbench, a leng

24、th measuring gauge, and a reference bar (see Fig.1).6.2 MoldsThe molds consist of corrugated plastic tubes,having a length of 420 6 5 mm and an outer diameter of 29 60.5 mm (see Note 2). The plastic tubes are made of 0.5 60.2-mm thick low-density polyethylene (PE) and havetriangular-shaped corrugati

25、ons in order to minimize restraint inthe longitudinal direction (see Fig. 2). The distance betweencorrugations is 5.8 6 0.2 mm. The mold is tightly closed withtwo tapered end plugs having a length of 19 6 0.5 mm. Thediameter of the plastic end plugs tapers from 21 6 0.1 mm to22.4 6 0.1 mm (see Fig.

26、3).NOTE 2The small diameter of the molds limits the temperaturedifferences that may arise during hydration of the cementitious materials.Typical maximum temperature increase in the center of the test specimen,due to heat of hydration of cement paste or mortar has been determined tobe 2 C. The maximu

27、m longitudinal restraint stress exerted by the moldshas been determined to be 0.001 MPa (6).6.3 Dilatometer BenchThe dilatometer bench consists ofthree stainless steel rods with a diameter of 20 6 1.0 mm andtwo stainless steel end plates. Technical drawings of a suitabledilatometer bench are shown i

28、n Fig. 4. During measurement,the test specimen is positioned horizontally and is supportedlongitudinally by the two upper rods.6.4 Length Measuring GaugeA gauge measures lengthchanges at one end of the specimen. The measuring range ofthe gauge shall be at least 10 mm and the resolution shall be at5T

29、he boldface numbers in parentheses refer to a list of references at the end ofthis standard.NOTE 1In the foreground a corrugated PE-mold with two specially shaped end plugs and a 425 mm reference bar. In the background the dilatometerbench with a test specimen placed for length measurement. To the r

30、ight a digital length gauge with remote control.FIG. 1 A Suitable Dilatometer Bench with AccessoriesC1698 09 (2014)2least 0.0025 mm, corresponding to a resolution of about 6m/m for the calculated strain.6.5 Reference BarMeasurements in the dilatometer areperformed relative to the length of the refer

31、ence bar. The bar ismade of Invar with a length of 425 6 0.5 mm and a diameterof 20 6 1.0, tapering to 10 6 1.0 mm at both ends as shownin Fig. 5. The actual length of the reference bar shall be markedpermanently on the bar to the nearest 0.01 mm. Two plasticrings with an external diameter 30 6 0.5

32、mm are mounted onthe reference bar, as shown in Fig. 1.6.6 Reference Masses and Devices for Determining Massand Volume shall conform to the requirements of SpecificationC1005.6.7 Support Tube used to support the corrugated moldduring specimen fabrication. The support tube has a length of400 6 5 mm a

33、nd an inside diameter of 32 6 1 mm (see Fig.6). The tube is attached to a base that can be fixed to a vibratingtable.6.8 Vibrating Table as described in Practice C192/C192M.6.9 Tamping Rod for consolidation of the paste or mortar. Itshall be made of a rigid, non-absorptive material that does notreac

34、t with the cementitious mixture. The length of the rod shallbe at least 500 mm and the diameter shall be 6 6 1 mm. Theends may be flat or hemispherical.7. Procedure7.1 Number of SpecimensThree replicate specimens shallbe tested for each cement paste or mortar (see Note 3).7.1.1 MixingMix cement past

35、es and mortars according toPractice C305. Record the time when the cementitious mate-rials are added to the water.7.1.2 Mixing Apparatus7.1.2.1 Mortar PreparationThe mixer shall comply withthe sequence in Practice C305.7.1.2.2 Paste PreparationA high shear blender,6or simi-lar variable speed blender

36、 capable of maintaining a no-loadspeed of at least 15 000 r/min, with optional cooling device. A6Mixing devices described in API Specification RP 10B-2/ISO 10426-2.FIG. 2 Corrugated Polyethylene MoldNOTE 1Plastic Tube Wall Thickness 0.5 6 0.2 mm.FIG. 3 Outer Dimensions (mm) of Corrugated Low-Density

37、 Polyethylene Mold and End PlugC1698 09 (2014)3hand-held household mixer capable of mixing paste at not lessthan 400 r/min or other mixers for paste or mortar preparationare also permitted.NOTE 3About 185 mL of cement paste or mortar are needed to filleach corrugated mold. For a paste with a water-c

38、ement ratio of 0.4, thiscorresponds to approximately 360 g of paste.7.2 Filling and Closing of MoldsClamp the mountingbase of the support tube to a vibrating table. Measure thelengths of the plugs to be used for each specimen. Place a pluginto one end of the mold, and position the mold, with the clo

39、sedend down, inside the support tube. If the cementitious mixtureis pourable, slowly pour the mixture into the corrugated moldwith the vibrating table turned on (see Fig. 7). For a semi-fluidmixture, fill the mold in four equal layers and compact eachlayer 5 times with the tamping rod before each su

40、bsequentlayer is cast. The rod shall just penetrate the underlying layer.For a stiff mixture, hand prepare rolled sections of thecementitious mixture, drop them into the mold, and consolidatewith the tamping rod. To ensure that the cast specimens haveapproximately the same length, do not stretch or

41、compress thecorrugated mold during filling. For fluid mixtures, the corru-gated mold shall be held only by the support tube duringcasting. For semi-fluid and stiff mixtures, manually maintainthe initial length of the mold during compaction. Fill the moldto approximately 15 mm below the top end of th

42、e mold toallow room for the top end plug. Before mounting the top endplug, gently compress the corrugated mold to bring the cementpaste or mortar in contact with the end plug. Mount the endplug during relief of the compression of the corrugated mold.Use a screwing motion of the end plug to ease the

43、mountingoperation. Immediately after casting, carefully wipe the surfaceof the corrugated mold with a dry cloth to remove any cementpaste, mortar, or water.NOTE 1All dimensions are in mm (tolerance 6 0.5 %).FIG. 4 Technical Drawing of the Dilatometer Bench Shown in Fig. 1Top: Plan View. Bottom: Elev

44、ation View of End PlateNOTE 1All dimensions are in mm and tolerances given in the text.FIG. 5 Technical Drawing of the Reference Bar Shown in Fig. 1C1698 09 (2014)47.3 Measuring RoomTo minimize the influence of tem-perature variations, both the specimens and the dilatometershall be kept in a thermos

45、tatically controlled room or cabinet atall times during the test. Maintain the surrounding air tempera-ture at 23.0 6 1.0 C, unless otherwise specified (see Note 4).Do not store specimens in a water bath due to possible watertransport through the corrugated molds.NOTE 4The measurement can be perform

46、ed at any temperaturespecified by the user, provided that the temperature in the measuring roomor cabinet is maintained constant during the test with a tolerance of 6 1.0C.7.4 Specimen StorageAfter filling and sealing the molds,store the specimens horizontally on a smooth surface, to avoidany restra

47、int to length change. Support specimens along theirentire length to avoid damage and to ensure they remainstraight (see Note 5). Maintain a separation of at least 30 mmbetween specimens during the first day of measurement toallow dispersion of their heats of hydration.NOTE 5Corrugated plastic sheets

48、 as shown in Fig. 8 or other suitablematerials can be used to support the molded specimens.7.5 Time of First MeasurementStart length measurementsat the time of final setting. Determine times of setting usingTest Method C191 for paste or Test Method C403/C403M formortar on specimens made with the sam

49、e mixture used to moldNOTE 1All dimensions are in mm. The base of the support tube allows clamping to a vibration table.FIG. 6 Suitable Dimensions of the Support Tube That is Used During Filling of the Corrugated MoldsNOTE 1An empty corrugated mold, closed at one end with an endplug, is inserted into the support tube and positioned vertically on avibrating table. The fresh mixture is slowly poured into the corrugatedmold during vibration, until the mold is filled.FIG. 7 How to Fill the Corrugated MoldsC1698 09 (2014)5the autogenous shrinkage specime