1、Designation: C231/C231M 10Standard Test Method forAir Content of Freshly Mixed Concrete by the PressureMethod1This standard is issued under the fixed designation C231/C231M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () 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 test method covers determina
3、tion of the air contentof freshly mixed concrete from observation of the change involume of concrete with a change in pressure.1.2 This test method is intended for use with concretes andmortars made with relatively dense aggregates for which theaggregate correction factor can be satisfactorily deter
4、mined bythe technique described in Section 6. It is not applicable toconcretes made with lightweight aggregates, air-cooled blast-furnace slag, or aggregates of high porosity. In these cases, TestMethod C173/C173M should be used. This test method is alsonot applicable to nonplastic concrete such as
5、is commonly usedin the manufacture of pipe and concrete masonry units.1.3 The text of this test method references notes andfootnotes that provide explanatory information. These notesand footnotes (excluding those in tables and figures) shall notbe considered as requirements of this standard.1.4 The
6、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 equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the stan
7、dard.1.5 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. (WarningF
8、reshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.)22. Referenced Documents2.1 ASTM Standards:3C31/C31M Practice for Making and Curing Concrete TestSpecimens in the FieldC138/C138M Test Method for Density (Unit Weight),Yield, and A
9、ir Content (Gravimetric) of ConcreteC143/C143M Test Method for Slump of Hydraulic-CementConcreteC172 Practice for Sampling Freshly Mixed ConcreteC173/C173M Test Method for Air Content of FreshlyMixed Concrete by the Volumetric MethodC192/C192M Practice for Making and Curing ConcreteTest Specimens in
10、 the LaboratoryC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods3. Significance and Use3.1 This test method covers the determination of the aircontent of freshly mixed concrete
11、. The test determines the aircontent of freshly mixed concrete exclusive of any air that mayexist inside voids within aggregate particles. For this reason, itis applicable to concrete made with relatively dense aggregateparticles and requires determination of the aggregate correctionfactor (see 6.1
12、and 9.1).3.2 This test method and Test Method C138/C138M andC173/C173M provide pressure, gravimetric, and volumetricprocedures, respectively, for determining the air content offreshly mixed concrete. The pressure procedure of this testmethod gives substantially the same air contents as the othertwo
13、test methods for concretes made with dense aggregates.3.3 The air content of hardened concrete may be eitherhigher or lower than that determined by this test method. This1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibil
14、ity of SubcommitteeC09.60 on Testing Fresh Concrete.Current edition approved Oct. 1, 2010. Published November 2010. Originallyapproved in 1949. Last previous edition approved in 2009 as C231/C231M09b.DOI: 10.1520/C0231_C0231M-10.2Section on Safety Precautions, Manual of Aggregate and Concrete Testin
15、g,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 ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Cha
16、nges section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.depends upon the methods and amount of consolidation effortapplied to the concrete from which the hardened concretespecimen is taken; uni
17、formity and stability of the air bubbles inthe fresh and hardened concrete; accuracy of the microscopicexamination, if used; time of comparison; environmentalexposure; stage in the delivery, placement and consolidationprocesses at which the air content of the unhardened concreteis determined, that i
18、s, before or after the concrete goes througha pump; and other factors.4. Apparatus4.1 Air MetersThere are available satisfactory apparatusof two basic operational designs employing the principle ofBoyles law. For purposes of reference herein these aredesignated Meter Type A and Meter Type B.4.1.1 Me
19、ter Type AAn air meter consisting of a measuringbowl and cover assembly (see Fig. 1) conforming to therequirements of 4.2 and 4.3. The operational principle of thismeter consists of introducing water to a predetermined heightabove a sample of concrete of known volume, and theapplication of a predete
20、rmined air pressure over the water. Thedetermination consists of the reduction in volume of the air inthe concrete sample by observing the amount the water level islowered under the applied pressure, the latter amount beingcalibrated in terms of percent of air in the concrete sample.4.1.2 Meter Type
21、 BAn air meter consisting of a measuringbowl and cover assembly (see Fig. 2) conforming to therequirements of 4.2 and 4.3. The operational principle of thismeter consists of equalizing a known volume of air at a knownpressure in a sealed air chamber with the unknown volume ofair in the concrete samp
22、le, the dial on the pressure gauge beingcalibrated in terms of percent air for the observed pressure atwhich equalization takes place. Working pressures of 50 to 205kPa 7.5 to 30.0 psi have been used satisfactorily.4.2 Measuring BowlThe measuring bowl shall be essen-tially cylindrical in shape, made
23、 of steel, hard metal, or otherhard material not readily attacked by the cement paste, havinga minimum diameter equal to 0.75 to 1.25 times the height, anda capacity of at least 6.0 L 0.20 ft3. It shall be flanged orotherwise constructed to provide for a pressure tight fitbetween measuring bowl and
24、cover assembly. The interiorsurfaces of the measuring bowl and surfaces of rims, flanges,and other component fitted parts shall be machined smooth.The measuring bowl and cover assembly shall be sufficientlyrigid to limit the expansion factor, D, of the apparatus assembly(Annex A1.5) to not more than
25、 0.1 % of air content on theindicator scale when under normal operating pressure.4.3 Cover Assembly:4.3.1 The cover assembly shall be made of steel, hard metal,or other hard material not readily attacked by the cement paste.It shall be flanged or otherwise constructed to provide for apressure-tight
26、fit between measuring bowl and cover assemblyand shall have machined smooth interior surfaces contoured toprovide an air space above the level of the top of the measuringbowl. The cover shall be sufficiently rigid to limit the expan-sion factor of the apparatus assembly as prescribed in 4.2.4.3.2 Th
27、e cover assembly shall be fitted with a means ofdirect reading of the air content. The cover for the Type Ameter shall be fitted with a standpipe, made of a transparentgraduated tube or a metal tube of uniform bore with a glasswater gauge attached. In the Type B meter, the dial of thepressure gauge
28、shall be calibrated to indicate the percent of air.Graduations shall be provided for a range in air content of atleast 8 % readable to 0.1 % as determined by the proper airpressure calibration test.4.3.3 The cover assembly shall be fitted with air valves, airbleeder valves, and petcocks for bleeding
29、 off or through whichwater may be introduced as necessary for the particular meterdesign. Suitable means for clamping the cover to the measuringbowl shall be provided to make a pressure-tight seal withoutentrapping air at the joint between the flanges of the cover andmeasuring bowl. A suitable hand
30、pump shall be provided withthe cover either as an attachment or as an accessory.4.4 Calibration VesselA measure having an internal vol-ume equal to a percent of the volume of the measuring bowlcorresponding to the approximate percent of air in the concreteto be tested; or, if smaller, it shall be po
31、ssible to checkcalibration of the meter indicator at the approximate percent ofair in the concrete to be tested by repeated filling of themeasure. When the design of the meter requires placing thecalibration vessel within the measuring bowl to check calibra-tion, the measure shall be cylindrical in
32、shape.NOTE 1Asatisfactory calibration vessel to place within the measuringbowl may be machined from No. 16 gauge brass tubing, of a diameter toprovide the volume desired, to which a brass disk 13 mm 12 in. inthickness is soldered to form an end. When design of the meter requireswithdrawing of water
33、from the water-filled measuring bowl and coverassembly, to check calibration, the measure may be an integral part of thecover assembly or may be a separate cylindrical measure similar to theabove-described cylinder.4.5 The designs of various available types of air meters aresuch that they differ in
34、operating techniques; therefore, all ofthe items described in 4.6-4.16 may not be required. The itemsrequired shall be those necessary for use with the particulardesign of apparatus used to satisfactorily determine air contentin accordance with the procedures prescribed herein.4.6 Coil Spring or Oth
35、er Device for Holding CalibrationCylinder in Place.4.7 Spray TubeA brass tube of appropriate diameter,which may be an integral part of the cover assembly, or whichmay be provided separately. It shall be so constructed thatwhen water is added to the container, it is sprayed to the wallsof the cover i
36、n such a manner as to flow down the sides causinga minimum of disturbance to the concrete.4.8 TrowelA standard brick masons trowel.4.9 Tamping RodAround, smooth, straight steel rod, witha16mm58 in. 6 2mm116 in. diameter. The length of thetamping rod shall be at least 100 mm 4 in. greater than thedep
37、th of the measuring bowl in which rodding is beingperformed, but not greater than 600 mm 24 in. in overalllength (See Note 2). The rod shall have the tamping end or bothends rounded to a hemispherical tip of the same diameter as therod.NOTE 2Arod length of 400 mm 16 in. to 600 mm 24 in. meets thereq
38、uirements of the following: Practice C31/C31M, Test Method C138/C138M, Test Method C143/C143M, Test Method C173/C173M, and TestMethod C231/C231M.C231/C231M 1024.10 MalletA mallet (with a rubber or rawhide head)weighing approximately 0.60 6 0.25 kg 1.25 6 0.50 lb foruse with measures of 14 L 0.5 ft3
39、or smaller, and a malletweighing approximately 1.0 6 0.25 kg 2.25 6 0.50 lb for usewith measures larger than 14 L 0.5 ft3.4.11 Strike-Off BarA flat straight bar of steel or othersuitable metal at least 3 mm 18 in. thick and 20 mm 34 in.wide by 300 mm 12 in. long.4.12 Strike-Off PlateA flat rectangul
40、ar metal plate at least6mm14 in. thick or a glass or acrylic plate at least 13 mm 12in. thick with a length and width at least 50 mm 2 in. greaterthan the diameter of the measure with which it is to be used.The edges of the plate shall be straight and smooth within atolerance of 1.5 mm 116 in.4.13 F
41、unnel, with the spout fitting into spray tube.4.14 Measure for Water, having the necessary capacity tofill the indicator with water from the top of the concrete to thezero mark.4.15 Vibrator, as described in Practice C192/C192M.4.16 Sieves, 37.5-mm (112-in.) with not less than 0.2 m22ft2 of sieving
42、area.FIG. 1 Illustration of the Pressure Method for Air ContentType-A MeterFIG. 2 Schematic DiagramType-B MeterC231/C231M 1034.17 Scoopof a size large enough so each amount ofconcrete obtained from the sampling receptacle is representa-tive and small enough so it is not spilled during placement inth
43、e measuring bowl.5. Calibration of Apparatus5.1 Make calibration tests in accordance with proceduresprescribed in the annex. Rough handling will affect thecalibration of both Types A and B meters. Changes in baro-metric pressure will affect the calibration of Type A meter butnot Type B meter. The st
44、eps describedA1.2-A1.6, as applicableto the meter type under consideration, are prerequisites for thefinal calibration test to determine the operating pressure, P,onthe pressure gauge of the TypeAmeter as described inA1.7,orto determine the accuracy of the graduations indicating aircontent on the di
45、al face of the pressure gauge of the Type Bmeter as described in A1.9. The steps in A1.2-A1.6 need bemade only once (at the time of initial calibration), or onlyoccasionally to check volume constancy of the calibrationcylinder and measuring bowl. The calibration test described inA1.7 and A1.9, as ap
46、plicable to the meter type being checked,must be made as frequently as necessary and at intervals not toexceed three months to ensure that the proper gauge pressure,P, is being used for the Type A meter or that the correct aircontents are being indicated on the pressure gauge air contentscale for th
47、e Type B meter. A change in elevation of more than180 m 600 ft from the location at which a Type A meter waslast calibrated will require recalibration in accordance withA1.7.5.2 Calibration RecordsInformation to be maintained inthe records shall include determination of expansion factor;size of the
48、calibration vessel used; and the reading of the meterat the calibration test point(s).6. Determination of Aggregate Correction Factor6.1 ProcedureDetermine the aggregate correction factoron a combined sample of fine and coarse aggregate as directedin 6.2 to 6.4. It is determined independently by app
49、lying thecalibrated pressure to a sample of inundated fine and coarseaggregate in approximately the same moisture condition,amount, and proportions occurring in the concrete sampleunder test.6.2 Aggregate Sample SizeCalculate the weights of fineand coarse aggregate present in the sample of fresh concretewhose air content is to be determined, as follows:Fs5 S/B! 3 Fb(1)Cs5 S/B! 3 Cb(2)where:Fs= mass of fine aggregate in concrete sample under test,kg lb,S = volume of concrete sample (same as volume ofmeas
