1、Designation: C 31/C 31M 08aStandard Practice forMaking and Curing Concrete Test Specimens in the Field1This standard is issued under the fixed designation C 31/C 31M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This practice covers procedures for mak
3、ing and curingcylinder and beam specimens from representative samples offresh concrete for a construction project.1.2 The concrete used to make the molded specimens shallbe sampled after all on-site adjustments have been made to themixture proportions, including the addition of mix water andadmixtur
4、es. This practice is not satisfactory for making speci-mens from concrete not having measurable slump or requiringother sizes or shapes of specimens.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact
5、 equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard. The SI units are shown in brackets.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its u
6、se. 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 cementitious mixtures are caustic and may causechemical burns to exposed skin and tissue upon
7、 prolongedexposure.2)1.5 The text of this standard references notes which provideexplanatory material. These notes shall not be considered asrequirements of the standard.2. Referenced Documents2.1 ASTM Standards:3C 125 Terminology Relating to Concrete and ConcreteAggregatesC 138/C 138M Test Method f
8、or Density (Unit Weight),Yield, and Air Content (Gravimetric) of ConcreteC 143/C 143M Test Method for Slump of Hydraulic-Cement ConcreteC 172 Practice for Sampling Freshly Mixed ConcreteC 173/C 173M Test Method for Air Content of FreshlyMixed Concrete by the Volumetric MethodC 231 Test Method for Ai
9、r Content of Freshly MixedConcrete by the Pressure MethodC 330 Specification for Lightweight Aggregates for Struc-tural ConcreteC 403/C 403M Test Method for Time of Setting of ConcreteMixtures by Penetration ResistanceC 470/C 470M Specification for Molds for Forming Con-crete Test Cylinders Vertical
10、lyC511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and ConcretesC 617 Practice for Capping Cylindrical Concrete Speci-mensC 1064/C 1064M Test Method for Temperature of FreshlyMixed Hydraulic-Cement Concrete2.2 American C
11、oncrete Institute Publication:4CP-1 Concrete Field Testing Technician, Grade I309R Guide for Consolidation of Concrete3. Terminology3.1 For definitions of terms used in this practice, refer toTerminology C 125.4. Significance and Use4.1 This practice provides standardized requirements formaking, cur
12、ing, protecting, and transporting concrete testspecimens under field conditions.4.2 If the specimens are made and standard cured, asstipulated herein, the resulting strength test data when thespecimens are tested are able to be used for the followingpurposes:4.2.1 Acceptance testing for specified st
13、rength,1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand Concrete Aggregates and is the direct responsibility of Subcommittee C09.61on Testing for Strength.Current edition approved April 1, 2008. Published May 2008. Originallyapproved in 1920. Last previous edition approv
14、ed in 2008 as C 31/C 31M-08.2See Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standards, 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 ASTMStandard
15、s volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American Concrete Institute (ACI), P.O. Box 9094, FarmingtonHills, MI 48333-9094, http:/www.aci-int.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM Internationa
16、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2.2 Checking adequacy of mixture proportions forstrength, and4.2.3 Quality control.4.3 If the specimens are made and field cured, as stipulatedherein, the resulting strength test data when the specimens areteste
17、d are able to be used for the following purposes:4.3.1 Determination of whether a structure is capable ofbeing put in service,4.3.2 Comparison with test results of standard cured speci-mens or with test results from various in-place test methods,4.3.3 Adequacy of curing and protection of concrete in
18、 thestructure, or4.3.4 Form or shoring removal time requirements.5. Apparatus5.1 Molds, General Molds for specimens or fasteningsthereto in contact with the concrete shall be made of steel, castiron, or other nonabsorbent material, nonreactive with concretecontaining portland or other hydraulic ceme
19、nts. Molds shallhold their dimensions and shape under all conditions of use.Molds shall be watertight during use as judged by their abilityto hold water poured into them. Provisions for tests of waterleakage are given in the Test Methods for Elongation, Absorp-tion, and Water Leakage section of Spec
20、ification C 470/C 470M. A suitable sealant, such as heavy grease, modelingclay, or microcrystalline wax shall be used where necessary toprevent leakage through the joints. Positive means shall beprovided to hold base plates firmly to the molds. Reusablemolds shall be lightly coated with mineral oil
21、or a suitablenonreactive form release material before use.5.2 Cylinder Molds Molds for casting concrete test speci-mens shall conform to the requirements of SpecificationC 470/C 470M.5.3 Beam MoldsBeam molds shall be of the shape anddimensions required to produce the specimens stipulated in 6.2.The
22、inside surfaces of the molds shall be smooth. The sides,bottom, and ends shall be at right angles to each other and shallbe straight and true and free of warpage. Maximum variationfrom the nominal cross section shall not exceed18 in. 3 mmfor molds with depth or breadth of 6 in. 150 mm or more.Molds
23、shall produce specimens at least as long but not morethan116 in. 2 mm shorter than the required length in 6.2.5.4 Tamping Rod A round, straight steel rod with thedimensions conforming to those in Table 1, having the tampingend or both ends rounded to a hemispherical tip of the samediameter as the ro
24、d.5.5 VibratorsInternal vibrators shall be used. The vibratorfrequency shall be at least 7000 vibrations per minute 150 Hzwhile the vibrator is operating in the concrete. The diameter ofa round vibrator shall be no more than one-fourth the diameterof the cylinder mold or one-fourth the width of the
25、beam mold.Other shaped vibrators shall have a perimeter equivalent to thecircumference of an appropriate round vibrator. The combinedlength of the vibrator shaft and vibrating element shall exceedthe depth of the section being vibrated by at least 3 in. 75mm. The vibrator frequency shall be checked
26、periodicallywith a vibrating-reed tachometer or other suitable device.NOTE 1For information on size and frequency of various vibratorsand a method to periodically check vibrator frequency see ACI 309R.5.6 MalletA mallet with a rubber or rawhide head weigh-ing 1.25 6 0.50 lb 0.6 6 0.2 kg shall be use
27、d.5.7 Placement Toolsof a size large enough so eachamount of concrete obtained from the sampling receptacle isrepresentative and small enough so concrete is not spilledduring placement in the mold. For placing concrete in acylinder mold, the acceptable tool is a scoop. For placingconcrete in a beam
28、mold, either a shovel or scoop is permitted.5.8 Finishing Toolsa handheld float or a trowel.5.9 Slump Apparatus The apparatus for measurement ofslump shall conform to the requirements of Test MethodC 143/C 143M.5.10 Sampling ReceptacleThe receptacle shall be a suit-able heavy gage metal pan, wheelba
29、rrow, or flat, clean nonab-sorbent board of sufficient capacity to allow easy remixing ofthe entire sample with a shovel or trowel.5.11 Air Content ApparatusThe apparatus for measuringair content shall conform to the requirements of Test MethodsC 173/C 173M or C 231.5.12 Temperature Measuring Device
30、sThe temperaturemeasuring devices shall conform to the applicable require-ments of Test Method C 1064/C 1064M.6. Testing Requirements6.1 Cylindrical SpecimensCompressive or splitting ten-sile strength specimens shall be cylinders cast and allowed toset in an upright position. The number and size of
31、cylinderscast shall be as directed by the specifier of the tests. In addition,the length shall be twice the diameter and the cylinder diametershall be at least 3 times the nominal maximum size of thecoarse aggregate. When the nominal maximum size of thecoarse aggregate exceeds 2 in. 50 mm, the concr
32、ete sampleshall be treated by wet sieving through a 2-in. 50-mm sieveas described in Practice C 172. For acceptance testing forspecified compressive strength, cylinders shall be 6 by 12 in.150 by 300 mm or 4 3 8 in. 100 3 200 mm (Note 2).NOTE 2When molds in SI units are required and not available,eq
33、uivalent inch-pound unit size mold should be permitted.6.2 Beam Specimens Flexural strength specimens shall bebeams of concrete cast and hardened in the horizontal position.The number of beams cast shall be as directed by the specifierof the tests. The length shall be at least 2 in. 50 mm greatertha
34、n three times the depth as tested. The ratio of width to depthas molded shall not exceed 1.5. The standard beam shall be 6by 6 in. 150 by 150 mm in cross section, and shall be used forconcrete with nominal maximum size coarse aggregate up to 2in. 50 mm. When the nominal maximum size of the coarseagg
35、regate exceeds 2 in. 50 mm, the smaller cross sectionalTABLE 1 Tamping Rod RequirementsDiameter of Cylinder or Width ofBeam in. mmRod DimensionsADiameterin. mmLength of Rodin. mm8 200 3 or more equal depths,each not to exceed6 in. 150 mm.see 9.3TABLE 4 Molding Requirements by VibrationSpecimen Typea
36、nd SizeNumber ofLayersNumber ofVibratorInsertionsper LayerApproximate Depth ofLayer, in. mmCylinders:Diameter, in. mm4 100 2 1 one-half depth of specimen6 150 2 2 one-half depth of specimen9 225 2 4 one-half depth of specimenBeams:Width, in. mm6 150 to 8 200 1 see 9.4.2 depth of specimenover 8 200 2
37、 or more see 9.4.2 8 200 as near aspracticableC 31/C 31M 08a3and ends of beam molds with a trowel or other suitable tool.Underfilled molds shall be adjusted with representative con-crete during consolidation of the top layer. Overfilled moldsshall have excess concrete removed.9.4.2 VibrationMaintain
38、 a uniform duration of vibrationfor the particular kind of concrete, vibrator, and specimen moldinvolved. The duration of vibration required will depend uponthe workability of the concrete and the effectiveness of thevibrator. Usually sufficient vibration has been applied as soonas the surface of th
39、e concrete has become relatively smooth andlarge air bubbles cease to break through the top surface.Continue vibration only long enough to achieve proper con-solidation of the concrete (see Note 4). Fill the molds andvibrate in the required number of approximately equal layers.Place all the concrete
40、 for each layer in the mold before startingvibration of that layer. In compacting the specimen, insert thevibrator slowly and do not allow it to rest on the bottom orsides of the mold. Slowly withdraw the vibrator so that no largeair pockets are left in the specimen. When placing the finallayer, avo
41、id overfilling by more than14 in. 6 mm.NOTE 4Generally, no more than5sofvibration should be requiredfor each insertion to adequately consolidate concrete with a slump greaterthan 3 in. 75 mm. Longer times may be required for lower slumpconcrete, but the vibration time should rarely have to exceed 10
42、 s perinsertion.9.4.2.1 CylindersThe number of insertions of the vibratorper layer is given in Table 4. When more than one insertion perlayer is required distribute the insertion uniformly within eachlayer. Allow the vibrator to penetrate through the layer beingvibrated, and into the layer below, ab
43、out 1 in. 25 mm. Aftereach layer is vibrated, tap the outsides of the mold at least 10times with the mallet, to close holes that remain and to releaseentrapped air voids. Use an open hand to tap cardboard andsingle-use metal molds that are susceptible to damage if tappedwith a mallet.9.4.2.2 BeamsIn
44、sert the vibrator at intervals not exceed-ing 6 in. 150 mm along the center line of the long dimensionof the specimen. For specimens wider than 6 in., use alternat-ing insertions along two lines.Allow the shaft of the vibrator topenetrate into the bottom layer about 1 in. 25 mm. After eachlayer is v
45、ibrated, tap the outsides of the mold sharply at least 10times with the mallet to close holes left by vibrating and torelease entrapped air voids.9.5 FinishingPerform all finishing with the minimummanipulation necessary to produce a flat even surface that islevel with the rim or edge of the mold and
46、 that has nodepressions or projections larger than18 in. 3.3 mm.9.5.1 CylindersAfter consolidation, finish the top surfacesby striking them off with the tamping rod where the consis-tency of the concrete permits or with a handheld float or trowel.If desired, cap the top surface of freshly made cylin
47、ders with athin layer of stiff portland cement paste which is permitted toharden and cure with the specimen. See section on CappingMaterials of Practice C 617.9.5.2 BeamsAfter consolidation of the concrete, use ahandheld float or trowel to strike off the top surface to therequired tolerance to produ
48、ce a flat, even surface.9.6 Identification Mark the specimens to positively iden-tify them and the concrete they represent. Use a method thatwill not alter the top surface of the concrete. Do not mark theremovable caps. Upon removal of the molds, mark the testspecimens to retain their identities.10.
49、 Curing10.1 Standard Curing Standard curing is the curingmethod used when the specimens are made and cured for thepurposes stated in 4.2.10.1.1 StorageIf specimens cannot be molded at the placewhere they will receive initial curing, immediately afterfinishing move the specimens to an initial curing place forstorage. The supporting surface on which specimens are storedshall be level to within14 in. per ft 20 mm per m. If cylindersin the single use molds are moved, lift and support th
