1、Designation: C 1581 04Standard Test Method forDetermining Age at Cracking and Induced Tensile StressCharacteristics of Mortar and Concrete under RestrainedShrinkage1This standard is issued under the fixed designation C 1581; the number immediately following the designation indicates the year oforigi
2、nal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the laboratory determination ofthe age
3、at cracking and induced tensile stress characteristics ofmortar or concrete specimens under restrained shrinkage. Theprocedure can be used to determine the effects of variations inthe proportions and material properties of mortar or concreteon cracking due to both drying shrinkage and deformationsca
4、used by autogenous shrinkage and heat of hydration.1.2 This test method is not intended for expansive materials.1.3 The values stated in inch-pound units are to be regardedas standard. The values shown in parenthesis are in SI units andare given for information only.1.4 This standard does not purpor
5、t 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 to determine theapplicability of regulatory limitations prior to use.(WarningFresh hydraulic cementitious mixtures a
6、re causticand may cause chemical burns to skin and tissue uponprolonged exposure.)2. Referenced Documents2.1 ASTM Standards:2C 33 Specification for Concrete AggregatesC 138/C 138 M Test Method for Density (Unit Weight),Yield and Air Content (Gravimetric) of ConcreteC 143/C 143 M Test Method for Slum
7、p of Hydraulic-Cement MortarC 150 Specification for Portland CementC 171 Specification for Sheet Materials for Curing ConcreteC 192/C 192 M Practice for Making and Curing ConcreteTest Specimens in the LaboratoryC 387 Specification for Packaged Dry, Combined Materialsfor Mortar and ConcreteC 595 Spec
8、ification for Blended Hydraulic CementsC 1157 Performance Specification for Hydraulic CementC 1437 Test Method for Flow of Hydraulic Cement MortarF 441 Specification for Chlorinated Poly (Vinyl Chloride)(CPVC) Plastic Pipe, Schedules 40 and 802.2 ASME Standards:3B 46.1 Surface Texture (Surface Rough
9、ness, Waviness andLay)3. Summary of Test Method3.1 A sample of freshly mixed mortar or concrete is com-pacted in a circular mold around an instrumented steel ring.The compressive strain developed in the steel ring caused bythe restrained shrinkage of the mortar or concrete specimen ismeasured from t
10、he time of casting (1-6)4. Cracking of the testspecimen is indicated by a sudden decrease in the steel ringstrain. The age at cracking and the rate of tensile stressdevelopment in the test specimen are indicators of the materi-als resistance to cracking under restrained shrinkage.4. Significance and
11、 Use4.1 This test method is for relative comparison of materialsand is not intended to determine the age at cracking of mortaror concrete in any specific type of structure, configuration, orexposure.4.2 This test method is applicable to mixtures with aggre-gates of 0.5-in. (13-mm) maximum nominal si
12、ze or less.4.3 This test method is useful for determining the relativelikelihood of early-age cracking of different cementitiousmixtures and for aiding in the selection of cement-basedmaterials that are less likely to crack under retrained shrinkage.Actual cracking tendency in service depends on man
13、y variables1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.68 on Volume Change.Current edition approved July 1, 2004. Published August 2004.2For referenced ASTM standards, visit the ASTM website,
14、 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.3Available from American Society of Mechanical Engineers, 22 Law Drive,Fairfield, NJ 07007-2900.4The boldface number
15、s in parenthesis refer to the list of references at the end ofthis test method1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.including type of structure, degree of restraint, rate of propertydevelopment, construction and curing meth
16、ods, and environ-mental conditions.4.4 This test method can be used to determine the relativeeffects of material variations on induced tensile stresses andcracking potential. These variations can include, but are notlimited to, aggregate source, aggregate gradation, cement type,cement content, water
17、 content, supplementary cementing ma-terials, or chemical admixtures.4.5 For materials that have not cracked during the test, therate of tensile stress development at the time the test isterminated provides a basis for comparison of the materials.5. Apparatus5.1 Steel ringStructural steel pipe with
18、a wall thickness of0.50 6 0.05 in. (13 6 0.12 mm), an outside diameter of 13.06 0.12 in. (330 6 3.3 mm) and a height of 6.0 6 0.25 in. (1526 6 mm) (see Fig. 1). Machine the inner and outer faces toproduce smooth surfaces with a texture of 63 microinches (1.6micrometres) or finer, as defined in ASME
19、B 46.1.5.2 Strain gagesAs a minimum, use two electrical resis-tance strain gages to monitor the strain development in the steelring. Each strain gage shall be wired in a quarter-bridgeconfiguration (that is, one leg of a full Wheatstone bridge). SeeNote 1 for additional information.5.3 Data acquisit
20、ion systemThe data acquisition systemshall be compatible with the strain instrumentation and auto-matically record each strain gage independently. The resolutionof the system shall be 60.0000005 in./in. (m/m). The systemshall be capable of recording strain data at intervals not toexceed 30 minutes.N
21、OTE 1Use of a precision resistor, to balance the leg of the bridge, astrain conditioner input module, to complete the other half of the bridge,and a 16-channel interface board has been found to adequately provide therequired resolution of the system.5.4 BaseEpoxy-coated plywood or other non-absorpti
22、veand non-reactive surface.5.5 Outer ringUse one of the following alternative mate-rials as the outer ring.5.5.1 PVC pipeSchedule 80-18 PVC pipe, in accordancewith Specification F 441, with a 16.0 6 0.12-in. (406 6 3-mm)inside diameter and 6.0 6 0.25-in. (152 6 6-mm) height (seeFig. 1).5.5.2 Steel o
23、uter ring0.125-in. (3-mm) thick steel sheet-ing formed to obtain a 16.0 6 0.12-in. (406 6 3-mm) insidediameter and 6.0 6 0.25-in. (152 6 6-mm) height.5.5.3 Other materialsOther suitable non-absorptive andnon-reactive materials formed to obtain a 16.0 6 0.12-in. (4066 3-mm) inside diameter and 6.0 6
24、0.25-in. (152 6 6-mm)height.5.6 Testing environmentStore the specimens in an envi-ronmentally controlled room with constant air temperature of73.5 6 3.5 F (23.0 6 2.0 C) and relative humidity of 50 64%.6. Materials and Mixing6.1 Materials:6.1.1 CementCement shall conform to SpecificationsC 150, C 59
25、5, or C 1157.6.1.2 AggregatesAggregates shall conform to Specifica-tion C 33. The maximum nominal size of the coarse aggregateshall be 0.5-in. (13-mm) or less.6.2 Mixing:6.2.1 Concrete mixturesMachine mix the concrete asprescribed in Practice C 192/C 192M.6.2.2 Mortar mixturesMix the mortar as presc
26、ribed inSpecification C 387.7. Properties of Fresh Mixtures7.1 Concrete mixturesSamples of freshly mixed concreteshall be tested in accordance with the following methods:7.1.1 Density (unit weight) and air contentTest MethodC 138/C 138M.7.1.2 SlumpTest Method C 143/C 143M.7.2 Mortar mixturesSamples
27、of freshly mixed mortarshall be tested in accordance with the following methods:7.2.1 DensitySpecification C 387.7.2.2 FlowTest Method C 1437.8. Specimen Fabrication and Test Setup8.1 Bond two strain gages at midheight locations on theinterior surface of the steel ring along a diameter; that is, mou
28、ntthe second gage diametrically opposite the first gage. Orientthe gages to measure strain in the circumferential direction.Follow the manufacturers procedures for mounting and wa-terproofing the gages on the steel ring and connecting lead-wires to the strain gage tabs.8.2 Test specimen moldThe test
29、 specimen mold consistsof a base, an inner steel ring and an outer ring.8.2.1 Fabricate a base for each test specimen as described inSection 5.4. The top surface of each base shall minimizefrictional restraint of the specimen.NOTE 2Use of an epoxy coating or a Mylar sheet covering has beenfound to p
30、rovide a suitable surface between the test specimen and thebase.8.2.2 Secure the steel ring to the base before casting usingbolts with eccentric washers (see Fig. 1).8.2.2.1 Coat the outer surface of the steel ring with a releaseagent.8.2.3 Coat the inner surface of the outer ring with a releaseagen
31、t.8.2.4 Secure the outer ring to the base to complete the testspecimen mold using bolts with eccentric washers. Maintain a1.50 6 0.12-in. (38 6 3-mm) space between the inner steelring and the outer ring (see Fig. 1).8.3 Make and cure at least three test specimens for eachmaterial and test condition
32、following the applicable require-ments of Practice C 192/C 192 M. In making a specimen, placethe test specimen mold on a vibrating table, fill the mold in twoapproximately equal layers, rod each layer 75 times using a38-in. (10-mm) diameter rod, and vibrate each layer to consoli-date the mixture.8.4
33、 Strike-off the test specimen surface after consolidation.Finish with the minimum manipulation necessary to achieve aflat surface. Remove any fresh concrete or mortar that hasspilled inside the steel ring or outside the outer ring so that theC1581042base is clean. Transfer the test specimens to the
34、testingenvironment within 10 minutes after completion of casting.8.5 Upon transfer of the test specimens to the testingenvironment, immediately loosen the bolts with eccentricwashers and rotate the washers so they are not in contact withthe steel ring and outer ring. Within 2 minutes after loosening
35、the bolts with eccentric washers, connect the strain gagelead-wires to the data acquisition system, record the time, andbegin monitoring the strain gages at intervals not greater than30 minutes. Ensure that the strain gage connecting wires areFIG. 1 Test specimen dimensions (top), specimen mold (bot
36、tom left), and specimen (bottom right).C1581043clean of loose material before making the connections. Thetime of the first strain measurement is taken as zero age of thespecimen.NOTE 3Monitoring the strain gages soon after casting providesinformation on the internal deformations caused by autogenous
37、 shrinkageand heat of hydration (4).8.6 CuringUnless otherwise specified, test specimensshall be moist cured in the molds for 24 h at 73.5 6 3.5 F(23.0 6 2.0 C) using wet burlap covered with polyethylenefilm meeting the requirements of Specification C 171. Beginthe curing process within 5 minutes af
38、ter the first strainreading. If the curing period is longer than 24 h, remove theouter ring at 24 h and continue the curing process.8.7 At the end of curing and between strain measurements,prepare the test specimens for drying as follows. Complete thetest specimen preparation within 15 minutes.8.7.1
39、 Remove the outer ring, if it is still in place, and/orremove the polyethylene film and burlap.8.7.2 Gently remove loose material, if present, from the topsurface of the test specimen.8.7.3 Seal the top surface of the test specimen using one ofthe following alternative procedures.NOTE 4With the top
40、surface sealed, and the specimen resting on itsbase, the test specimen dries from the outer circumferential surface only.8.7.3.1 Paraffn waxCoat the top surface of the testspecimen with molten paraffin wax. Take precautions to ensurethat the outer circumference of the test specimen is not coatedwith
41、 the paraffin wax.NOTE 5Use of a 1.5-in. (38-mm) wide brush has been found to be anappropriate means of applying the paraffin wax to the top surface of thetest specimens.8.7.3.2 Adhesive aluminum-foil tapeSeal the top surfaceof the test specimen with adhesive aluminum-foil tape.8.7.4 For the calcula
42、tions outlined subsequently, the agewhen drying is initiated is the time when the first strain readingis made after the test specimens have been sealed.9. Measurement Procedure9.1 Record the time at the start of strain monitoring as statedin Section 8.5.9.2 Record ambient temperature and relative hu
43、midity ofthe testing environment every day.9.3 Monitor the strains in the steel rings at intervals not toexceed 30 minutes, recording the output of each strain gageseparately with the data acquisition system. Record both thetime and the strain at each measurement. A sudden decrease incompressive str
44、ain in one or both strain gages indicatescracking (see Note 6) (1-5). Review the strain measurementsand visually inspect the specimens for cracking at timeintervals not greater than 3 days.NOTE 6The sudden decrease in compressive strain at cracking isusually greater than 30 microstrains (see Fig. 2)
45、.9.4 Monitor and record the strain in the steel rings for atleast 28 days after initiation of drying, unless cracking occursprior to 28 days.9.5 Plot the steel ring strain for each strain gage againstspecimen age (see Fig. 2).10. Calculation10.1 Age at crackingDetermine the age at cracking as theage
46、 of each test specimen (measured from the time of casting)when a sudden decrease in strain occurs. Report the age atcracking to the nearest 0.25 day. If a test specimen does notcrack within the duration of the test, report the result as “nocracking” and record the age when the test was terminated.10
47、.1.1 Average age at crackingCalculate the average ageat cracking for the test specimens to the nearest day.FIG. 2 Steel ring strain versus specimen age.C158104410.2 Initial strainFrom the time-strain data for each straingage, record the initial strain as the strain corresponding to theage when dryin
48、g was initiated (see Fig. 2).10.2.1 Average initial strainCalculate the average initialstrain for the test specimens.NOTE 7The average initial strain indicates the net effect of deforma-tions caused by early-age autogenous shrinkage and heat of hydrationunder the restrained conditions (4).10.3 Maxim
49、um strainFrom the time-strain data for eachstrain gage on each test specimen, record the maximum strainas the strain corresponding to the age at cracking or the agewhen the test is terminated.10.3.1 When cracking occurs, the maximum strain is thestrain value just prior to the sudden decrease in strain (see Fig.2).10.4 Average maximum strain, emaxCalculate the averagemaximum strain for the test specimens.NOTE 8The average maximum strain relates to the magnitude ofstress buildup in the material under the conditions of restraint provided inth
