1、Designation: C 1698 09Standard Test Method forAutogenous Strain of Cement Paste and Mortar1This standard is issued under the fixed designation C 1698; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A num
2、ber 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, various supple
3、mentary 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-cementitious mate
4、rials 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 thisstandard.1.3 This sta
5、ndard 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. (WarningFreshhydraulic cem
6、entitious 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 and ConcreteC19
7、1 Test Methods for Time of Setting of HydraulicCement by Vicat NeedleC192/C192M Practice for Making and Curing ConcreteTest Specimens in the LaboratoryC219 Terminology Relating to Hydraulic CementC305 Practice for Mechanical Mixing of Hydraulic CementPastes and Mortars of Plastic ConsistencyC403/C40
8、3M 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 TestingWell Cemen
9、ts3. 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 externalforces and
10、 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 that offers litt
11、le 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 time intervals unt
12、il 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 conventional concrete,
13、autogenous shrinkagestrain is generally negligible, but in concrete with low water-cementitious materials ratio (w/cm) or with silica fume it maybe considerable (1).5Restraint of the autogenous strain by1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggrega
14、tes and is the direct responsibility of SubcommitteeC09.68 on Volume Change.Current edition approved Oct. 1, 2009. Published November 2009. DOI:10.1520/C1698-09.2Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standards, Vol. 04.02.3For referenced ASTM sta
15、ndards, 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 (API), 1220 L. St., NW, Wash-ington, DC
16、20005-4070, http:/www.api.org.5The boldface numbers in parentheses refer to a list of references at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.aggregates or adjoining structural members may result informa
17、tion 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 cracki
18、ng 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 cor
19、rugated 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 mold
20、 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 tec
21、hnique (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 t
22、est 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 sh
23、rinkage 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 length
24、 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 corrugation
25、s 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. 3)
26、.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 maximum
27、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 in
28、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 atleas
29、t 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 reference bar. The bar ismade of Invar with a length of 425 6 0.5 mm and a diameterNOTEIn the foreground a corrugated PE-mold
30、 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 right a digital length gauge with remote control.FIG. 1 A Suitable Dilatometer Bench with AccessoriesC1698092of 20 6 1.0, tapering to 10
31、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 mm are mounted onthe reference bar, as shown in Fig. 1.6.6 Reference Masses and Devices for Determining Ma
32、ssand 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 and an inside diameter of 32 6 1 mm (see Fig.6). The tube is attached to a base that can be fixed to a vibr
33、atingtable.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 notreact with the cementitious mixture. The length of the rod shallbe at least 500 mm and the diameter shall be 6
34、 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 pastes and mortars according toPractice C305. Record the time when the cementitious mate-rials are added to th
35、e 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 capable of maintaining a no-loadspeed of at least 15 000 r/min, with optional cooling device. Ahand-held
36、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-cement ratio of 0.4, this6Mixing devices described in API
37、Specification RP 10B-2/ISO 10426-2.FIG. 2 Corrugated Polyethylene MoldNOTEPlastic Tube Wall Thickness 0.5 6 0.2 mm.FIG. 3 Outer Dimensions (mm) of Corrugated Low-Density Polyethylene Mold and End PlugC1698093corresponds to approximately 360 g of paste.7.2 Filling and Closing of MoldsClamp the mounti
38、ngbase 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 closedend down, inside the support tube. If the cementitious mixtureis pourable, slowly pour the mixture into the corru
39、gated 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 subsequentlayer is cast. The rod shall just penetrate the underlying layer.For a stiff mixture, hand prepare rolled se
40、ctions 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 compress thecorrugated mold during filling. For fluid mixtures, the corru-gated mold shall be held only by the suppo
41、rt 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 the mold toallow room for the top end plug. Before mounting the top endplug, gently compress the corrugated mold to br
42、ing 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 mountingoperation. Immediately after casting, carefully wipe the surfaceNOTEAll dimensions are in mm (tolerance 6 0.
43、5 %).FIG. 4 Technical Drawing of the Dilatometer Bench Shown in Fig. 1Top: Plan View. Bottom: Elevation View of End PlateNOTEAll dimensions are in mm and tolerances given in the text.FIG. 5 Technical Drawing of the Reference Bar Shown in Fig. 1C1698094of the corrugated mold with a dry cloth to remov
44、e any cementpaste, mortar, or water.7.3 Measuring RoomTo minimize the influence of tem-perature variations, both the specimens and the dilatometershall be kept in a thermostatically controlled room or cabinet atall times during the test. Maintain the surrounding air tempera-ture at 23.0 6 1.0 C, unl
45、ess 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 performed at any temperaturespecified by the user, provided that the temperature in the measuring roomor cabinet is maintained constant
46、 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 restraint to length change. Support specimens along theirentire length to avoid damage and to ensure they remainstraight (see Note 5).
47、 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 as shown in Fig. 8 or other suitablematerials can be used to support the molded specimens.7.5 Time of First MeasurementStart le
48、ngth 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 same mixture used to moldthe autogenous shrinkage specimens and cured at the sametemperature as for the autogenous strain measureme
49、nt. Protectthe specimens used for determination of setting times frommoisture loss during the measurement.7.6 Length MeasurementInsert the reference bar in thedilatometer bench and bring the measuring gauge in contactwith the end of the bar. Reset the measuring gauge so that itreads zero with the reference bar in position (see Note 6).Remove the reference bar and insert a specimen in thedilatometer bench. Measure the length of the specimen with thegauge (see Note 6). Remove the specimen and measure thelength of the next specimen.NOTE 6A number of digital
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