1、Designation: C 231 09Standard Test Method forAir Content of Freshly Mixed Concrete by the PressureMethod1This standard is issued under the fixed designation C 231; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript 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 determination of th
3、e 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 determined byth
4、e 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 C 173/C 173M should be used. This test method isalso not applicable to nonplastic concrete such as is commo
5、nlyused in 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 values s
6、tated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its
7、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 cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolon
8、ged exposure.)22. Referenced Documents2.1 ASTM Standards:3C 31/C 31M Practice for Making and Curing Concrete TestSpecimens in the FieldC 138/C 138M Test Method for Density (Unit Weight),Yield, and Air Content (Gravimetric) of ConcreteC 143/C 143M Test Method for Slump of Hydraulic-Cement ConcreteC 1
9、72 Practice for Sampling Freshly Mixed ConcreteC 173/C 173M Test Method for Air Content of FreshlyMixed Concrete by the Volumetric MethodC 192/C 192M Practice for Making and Curing ConcreteTest Specimens in the LaboratoryC 231 Test Method for Air Content of Freshly MixedConcrete by the Pressure Meth
10、odC 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsE 177 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. The test
11、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 and 9.1).3.
12、2 This test method and Test Method C 138/C 138M andC 173/C 173M 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 test me
13、thods 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. Thisdepends upon the methods and amount of consolidation effortapplied to the concrete from which the hardened concretespecimen is taken; uni
14、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 concrete1This test method is
15、under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.60 on Testing Fresh Concrete.Current edition approved June 1, 2009. Published July 2009. Originally approvedin 1949. Last previous edition approved in 2008 as C 231 08c
16、.2Section 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 ASTMStandards volume information, refer to t
17、he standards Document Summary page onthe ASTM website.1*A Summary of Changes 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.is determined, that is, before or after the concrete goes through
18、a 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 Meter Type AAn air meter consisting of a measu
19、ringbowl 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 predetermined air pressure over the water. Thedeter
20、mination 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 BAn air meter consisting of a measuringbowl
21、 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 sample, the dial on the pressure gauge beingcali
22、brated in terms of percent air for the observed pressure atwhich equalization takes place. Working pressures of 7.5 to30.0 psi (51 to 207 kPa) have been used satisfactorily.4.2 Measuring BowlThe measuring bowl shall be essen-tially cylindrical in shape, made of steel, hard metal, or otherhard materi
23、al 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 0.20 ft3(5.7 L). It shall be flanged orotherwise constructed to provide for a pressure tight fitbetween measuring bowl and cover assembly. The interiorsurfaces of t
24、he 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 0.1 % of air content on theindicator sca
25、le 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 fit between measuring bowl and cover asse
26、mblyand 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 The cover assembly shall be fitted with a m
27、eans 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 shall be calibrated to indicate the perce
28、nt 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 off or through whichwater may be introdu
29、ced 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 pump shall be provided withthe cover eith
30、er 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 possible to checkcalibration of the meter i
31、ndicator 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 shape and of an insidedepth12 in. (13 mm)
32、 less than that of the measuring bowl.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 disk12 in. in thickness issoldered to form an end. When design of the meter requ
33、ires withdrawingof water from the water-filled measuring bowl and cover assembly, tocheck calibration, the measure may be an integral part of the coverassembly or may be a separate cylindrical measure similar to theabove-described cylinder.4.5 The designs of various available types of air meters are
34、such that they differ in 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 here
35、in.4.6 Coil Spring or Other 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 t
36、o the wallsof the cover in 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 RodA round, straight steel rod, with a58 in.(16 mm) 6116 in. (2 mm) diameter. The length of the tampingrod shall be at least 4 in. (
37、100 mm) greater than the depth of themeasuring bowl in which rodding is being performed, but notgreater than 24 in. (600 mm) in overall length (See Note 2).The length tolerance for the tamping rod shall be 618 in. (4mm). The rod shall have the tamping end or both ends roundedto a hemispherical tip o
38、f the same diameter as the rod.NOTE 2Arod length of 16 in. (400 mm) to 24 in. (600 mm) meets therequirements of the following: Practice C 31/C 31M, Test Method C 138/C 138M, Test Method C 143/C 143M, Test Method C 173/C 173M, andTest Method C 231.4.10 MalletA mallet (with a rubber or rawhide head)we
39、ighing approximately 1.25 6 0.50 lb (0.57 6 0.23 kg) foruse with measures of 0.5 ft3(14 L) or smaller, and a malletweighing approximately 2.25 6 0.50 lb (1.02 6 0.23 kg) foruse with measures larger than 0.5 ft3(14 L).C2310924.11 Strike-Off BarA flat straight bar of steel or othersuitable metal at le
40、ast18 in. (3 mm) thick and34 in. (20 mm)wide by 12 in. (300 mm) long.4.12 Strike-Off PlateA flat rectangular metal plate at least14 in. (6 mm) thick or a glass or acrylic plate at least12 in. (12mm) thick with a length and width at least 2 in. (50 mm)greater than the diameter of the measure with whi
41、ch it is to beused. The edges of the plate shall be straight and smooth withina tolerance of116 in. (1.5 mm).4.13 Funnel, 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 Vib
42、rator, as described in Practice C 192/C 192M.4.16 Sieves,112-in. (37.5-mm) with not less than 2 ft2(0.19m2) of sieving area.4.17 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 inthe
43、 measuring bowl.FIG. 1 Illustration of the Pressure Method for Air ContentType-A MeterFIG. 2 Schematic DiagramType-B MeterC2310935. 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
44、 meters. Changes in baro-metric pressure will affect the calibration of Type A meter butnot Type B meter. The steps 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 t
45、he TypeAmeter as described inA1.7,orto determine the accuracy of the graduations indicating aircontent on the dial 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 volum
46、e constancy of the calibrationcylinder and measuring bowl. The calibration test described inA1.7 and A1.9, as applicable 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 th
47、e Type A meter or that the correct aircontents are being indicated on the pressure gauge air contentscale for the Type B meter. A change in elevation of more than600 ft (183 m) from the location at which a Type-A meter waslast calibrated will require recalibration in accordance withA1.7.5.2 Calibrat
48、ion RecordsInformation to be maintained inthe records shall include determination of expansion factor;size of the 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 facto
49、ron a combined sample of fine and coarse aggregate as directedin 6.2 to 6.4. It is determined independently by applying 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 u
