ASTM C512 C512M-2015 Standard Test Method for Creep of Concrete in Compression《混凝土压缩蠕变的标准试验方法》.pdf

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1、Designation: C512/C512M 10C512/C512M 15Standard Test Method forCreep of Concrete in Compression1This standard is issued under the fixed designation C512/C512M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last revisi

2、on. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the creep of molded concrete cylinders subjected to sustained longitudinalcompressiv

3、e load. This test method is limited to concrete in which the maximum aggregate size does not exceed 50 mm 2 in.1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system

4、shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the 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

5、appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C39/C39M Test Method for Compressive Strength of Cylindrical Concrete SpecimensC125 Terminology Relating to Concrete and Concrete AggregatesC192/C1

6、92M Practice for Making and Curing Concrete Test Specimens in the LaboratoryC470/C470M Specification for Molds for Forming Concrete Test Cylinders VerticallyC617 Practice for Capping Cylindrical Concrete SpecimensC670 Practice for Preparing Precision and Bias Statements for Test Methods for Construc

7、tion Materials3. Terminology3.1 For definitions of terms used in this test method refer to Terminology C125.4. Significance and Use4.1 This test method measures the load-induced time-dependent compressive strain at selected ages for concrete under anarbitrary set of controlled environmental conditio

8、ns.4.2 This test method can be used to compare creep potentials of different concretes. A procedure is available, using thedeveloped equation (or graphical plot), for calculating stress from strain data within massive non-reinforced concrete structures.For most specific design applications, the test

9、 conditions set forth herein must be modified to more closely simulate the anticipatedcuring, thermal, exposure, and loading age conditions for the prototype structure. Current theories and effects of material andenvironmental parameters are presented inACI SP-9,SP-135, Symposium on Creep of Concret

10、e.and Shrinkage of Concrete: Effectof Materials and Environment.34.3 In the absence of a satisfactory hypothesis governing creep phenomena, a number of assumptions have been developed thathave been generally substantiated by test and experience.4.3.1 Creep is proportional to stress from 0 to 40 % of

11、 concrete compressive strength.1 This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.61 onTesting for Strength.Current edition approved Dec. 1, 2010Oct. 1, 2015. Published January 2011December 2015.

12、 Originally approved in 1963. Last previous edition approved in 20022010as C512C512/C512M02.10. DOI: 10.1520/C0512_C0512M-10.10.1520/C0512_C0512M-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standa

13、rdsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available SP-135 is currently out of print, however, the individual papers contained in the publication are available from American Concrete Institute (ACI), P.O. Box9094, Farmington Hills, MI 48333-9094, http:

14、/www.concrete.org.This document is not an ASTM standard and is intended only 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

15、 consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.3.2 Creep has been conclusiv

16、ely shown to be directly proportional to paste content throughout the range of paste contentsnormally used in concrete. Thus, the creep characteristics of concrete mixtures containing aggregate of maximum size greater than50 mm 2 in. may be determined from the creep characteristics of the minus 50-m

17、m minus 2-in. fraction obtained by wet-sieving.Multiply the value of the characteristic by the ratio of the cement paste content (proportion by volume) in the full concrete mixtureto the paste content of the sieved sample.4.4 The use of the logarithmic expression (Section 89) does not imply that the

18、 creep strain-time relationship is necessarily anexact logarithmic function; however, for the period of one year, the expression approximates normal creep behavior with sufficientaccuracy to make possible the calculation of parameters that are useful for the purpose of comparing concretes.4.5 There

19、are no data that would support the extrapolation of the results of this test to tension or torsion.5. Apparatus5.1 MoldsMolds shall be cylindrical conforming to the provisions of Practice C192/C192M, or to the provisions ofSpecification C470/C470M. If required, provisions shall be made for attaching

20、 gauge studs and inserts, and for affixing integralbearing plates to the ends of the specimen as it is cast.5.1.1 Horizontal molds shall conform to the requirements of the section on horizontal molds for creep test cylinders of PracticeC192/C192M. A horizontal mold that has proven satisfactory is sh

21、own in Fig. 1.5.2 Loading Frame, capable of applying and maintaining the required load on the specimen, despite any change in thedimension of the specimen. In its simplest form the loading frame consists of header plates bearing on the ends of the loadedspecimens, a load-maintaining element that is

22、either a spring or a hydraulic capsule or ram, and threaded rods to take the reactionof the loaded system. Bearing surfaces of the header plates shall not depart from a plane by more than 0.025 mm 0.001 in. Inany loading frame, it is not prohibited to stack several specimens for simultaneous loading

23、. The length between header plates shallnot exceed 1780 mm 70 in. When a hydraulic load-maintaining element is used, several frames may be loaded simultaneouslythrough a central hydraulic pressure-regulating unit consisting of an accumulator, a regulator, indicating gages, and a source of highpressu

24、re, such as a cylinder of nitrogen or a high-pressure pump. Springs such as railroad car springs may be used to maintain theload in frames similar to those described above; the initial compression shall be applied by means of a portable jack or testingmachine. When springs are used, care should be t

25、aken to provide a spherical head or ball joint, and end plates rigid enough toensure uniform loading of the cylinders. Fig. 2 shows an acceptable spring-loaded frame. Means shall be provided for measuringthe load to the nearest 2 % of total applied load. It is not prohibited to use a permanently ins

26、talled hydraulic pressure gauge or ahydraulic jack and a load cell inserted in the frame when the load is applied or adjusted.5.3 Strain-Measuring DeviceSuitable apparatus shall be provided for the measurement of longitudinal strain in the specimento the nearest 10 millionths. It is not prohibited f

27、or the apparatus to be embedded, attached, or portable. If a portable apparatusis used, gauge points shall be attached to the specimen in a positive manner. Attached gages relying on friction contact are notpermissible. If an embedded device is used, it shall be situated so that its strain movement

28、occurs along the longitudinal axis ofthe cylinder. If external devices are used, strains shall be measured on not less than two gauge lines spaced uniformly around theperiphery of the specimen. The gages may be instrumented so that the average strain on all gauge lines can be read directly. Theeffec

29、tive gauge length shall be at least three times the maximum size of aggregate in the concrete. The strain-measuring deviceshall be capable of measuring strains for at least 1 year without change in calibration.FIG. 1 Horizontal Mold for Creep SpecimensC512/C512M 152NOTE 1Systems in which the varying

30、 strains are compared with a constant-length standard bar are considered most reliable, but unbonded electricalstrain gages are satisfactory.6. Test Specimens6.1 Specimen SizeThe diameter of each specimen shall be 150 6 1.5 mm 6 6 0.6 in., and the length shall be at least 290mm 11.5 in. When the end

31、s of the specimen are in contact with steel bearing plates, the specimen length shall be at least equalto the gauge length of the strain-measuring apparatus plus the diameter of the specimen. When the ends of the specimen are inFIG. 2 Spring-Loaded Creep FrameC512/C512M 153contact with other concret

32、e specimens similar to the test specimen, the specimen length shall be at least equal to the gauge lengthof the strain-measuring apparatus plus 40 mm 1.5 in. Between the test specimen and the steel bearing plate at each end of a stack,a supplementary noninstrumented cylinder whose diameter is equal

33、to that of the test cylinders and whose length is at least halfits diameter shall be installed.6.2 Fabricating SpecimensThe maximum size of aggregate shall not exceed 50 mm 2 in. (Section 34). Vertically castcylinders shall be fabricated in accordance with the provisions of Practice C192/C192M. The

34、ends of each cylinder shall meet theplaneness requirements described in the scope of Practice C617 (Note 2). Horizontally cast specimens shall be consolidated by themethod appropriate to the consistency of the concrete as indicated in the methods of consolidation section of PracticeC192/C192M. Care

35、must be taken to ensure that the rod or vibrator does not strike the strain meter. When vibration is used, theconcrete shall be placed in one layer and the vibrating element shall not exceed 35 mm 1.3 in. in diameter. When rodding is used,the concrete shall be placed in two approximately equal layer

36、s and each layer shall be rodded 25 times evenly along each side ofthe strain meter. After consolidation, the concrete shall be struck off with trowel or float then trowelled the minimum amount toform the concrete in the opening concentrically with the rest of the specimen. It is not prohibited to u

37、se a template curved in theradius of the specimen as a strikeoff to shape and finish the concrete more precisely in the opening. When cylinders are to bestacked, lapping of ends is strongly recommended.NOTE 2Requirements for planeness may be met by capping, lapping, or, at the time of casting, fitti

38、ng the ends with bearing plates normal to the axisof the cylinder.6.3 Number of SpecimensNo fewer than six specimens (Note 3) shall be made from a given batch of concrete for each testcondition; two shall be tested for compressive strength, two shall be loaded and observed for total deformation, and

39、 two shallremain unloaded for use as controls to indicate deformations due to causes other than load. Each strength and control specimenshall undergo the same curing and storage treatment as the loaded specimen.NOTE 3It is recommended that specimens be tested in triplicate although duplicate specime

40、ns are acceptable.7. Curing and Storage of Specimens7.1 Standard CuringBefore removal from the molds, specimens shall be stored at 23.0 6 2.0 C 73.5 6 3.5 F and coveredto prevent evaporation. The specimens shall be removed from the molds not less than 20 nor more than 48 h after molding andstored in

41、 a moist condition at a temperature of 23.0 6 2.0 C 73.5 6 3.5 F until the age of 7 days. A moist condition is thatin which free water is maintained on the surfaces of the specimens at all times. Specimens shall not be exposed to a stream ofrunning water nor be stored in water. After the completion

42、of moist curing the specimens shall be stored at a temperature of 23.06 1.0 C 73.5 6 1.5 F and at a relative humidity of 50 6 4 % until completion of the test.7.2 Basic Creep CuringIf it is desired to prevent the gain or loss of water during the storage and test period, specimens shallat the time of

43、 fabrication or stripping be enclosed and sealed in moistureproof jackets (for example, copper or butyl rubber) toprevent loss of moisture by evaporation and shall remain sealed throughout the period of storage and testing.7.3 Variable Curing Temperature RegimenWhen it is desired to introduce the ef

44、fect of temperature on the elastic and inelasticproperties of a concrete (as, for example, the adiabatic temperature conditions existing in massive concrete or temperatureconditions to which concrete is subjected during accelerated curing), temperatures within the specimen storage facility shall bec

45、ontrolled to correspond to the desired temperature history. The user shall be responsible for establishing the time-temperaturehistory to be followed and the permissible range of deviation therefrom.7.4 Other Curing ConditionsOther test ages and ambient storage conditions may be substituted when inf

46、ormation is requiredfor specific applications. The storage conditions shall be carefully detailed in the report.8. Procedure8.1 Age at LoadingWhen the purpose of the test is to compare the creep potential of different concretes, initially load thespecimens at an age of 28 days. When the complete cre

47、ep behavior of a given concrete is desired, prepare the specimens for initialloading in the following ages: 2, 7, 28, and 90 days, and 1 year. If information is desired for other ages of loading, include theage in the report.8.2 Loading DetailsImmediately before loading the creep specimens, determin

48、e the compressive strength of the strengthspecimens in accordance with Test Method C39/C39M. At the time unsealed creep specimens are placed in the loading frame,cover the ends of the control cylinders to prevent loss of moisture (Note 4). Load the specimens at an intensity of not more than40 % of t

49、he compressive strength at the age of loading. Take strain readings immediately before and after loading, 2 to 6 h later,then daily for 1 week, weekly until the end of 1 month, and monthly until the end of 1 year. Before taking each strain reading,measure the load. If the load varies more than 2 % from the correct value, it must be adjusted (Note 5). Take strain readings onthe control specimens on the same schedule as the loaded specimens.NOTE 4In placing creep specimens in the frame, take care in aligning the specimens to avo