1、Designation: C231/C231M 17C231/C231M 17aStandard 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 revis
2、ion, the year 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.1. Scope*1.1 This test method covers determination of the air content of freshly mixed concrete from observation
3、of the change in volumeof concrete with a change in pressure.1.2 This test method is intended for use with concretes and mortars made with relatively dense aggregates for which theaggregate correction factor can be satisfactorily determined by the technique described in Section 6. It is not applicab
4、le to concretesmade with lightweight aggregates, air-cooled blast-furnace slag, or aggregates of high porosity. In these cases, Test MethodC173/C173M should be used. This test method is also not applicable to nonplastic concrete such as is commonly used in themanufacture of pipe and concrete masonry
5、 units.1.3 The text of this test method references notes and footnotes that provide explanatory information. These notes and footnotes(excluding those in tables and figures) shall not be considered as requirements of this standard.1.4 The values stated in either SI units or inch-pound units are to b
6、e regarded separately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.5 This standard does not purport to address all of
7、the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. (WarningFresh hydraulic cementitious mixtures are caustic and may cau
8、se chemical burns to skin andtissue upon prolonged exposure.2)1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations
9、issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3C31/C31M Practice for Making and Curing Concrete Test Specimens in the FieldC138/C138M Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of ConcreteC
10、143/C143M Test Method for Slump of Hydraulic-Cement ConcreteC172C172/C172M Practice for Sampling Freshly Mixed ConcreteC173/C173M Test Method for Air Content of Freshly Mixed Concrete by the Volumetric MethodC192/C192M Practice for Making and Curing Concrete Test Specimens in the LaboratoryC670 Prac
11、tice for Preparing Precision and Bias Statements for Test Methods for Construction MaterialsE177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods1 This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibilit
12、y of Subcommittee C09.60 onTesting Fresh Concrete.Current edition approved Feb. 1, 2017April 15, 2017. Published March 2017June 2017. Originally approved in 1949. Last previous edition approved in 20142017 asC231/C231M 14.17. DOI: 10.1520/C0231_C0231M-17.10.1520/C0231_C0231M-17A.2 Section on Safety
13、Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards, Vol 04.02.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Documen
14、t Summary page on the ASTM website.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 reco
15、mmends that users 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C7
16、00, West Conshohocken, PA 19428-2959. United States13. Significance and Use3.1 This test method covers the determination of the air content of freshly mixed concrete. The test determines the air contentof freshly mixed concrete exclusive of any air that may exist inside voids within aggregate partic
17、les. For this reason, it is applicableto concrete made with relatively dense aggregate particles and requires determination of the aggregate correction factor (see 6.1and 9.1).3.2 This test method and Test Method C138/C138M and C173/C173M provide pressure, gravimetric, and volumetricprocedures, resp
18、ectively, for determining the air content of freshly mixed concrete. The pressure procedure of this test methodgives substantially the same air contents as the other two test methods for concretes made with dense aggregates.3.3 The air content of hardened concrete may be either higher or lower than
19、that determined by this test method. This dependsupon the methods and amount of consolidation effort applied to the concrete from which the hardened concrete specimen is taken;uniformity and stability of the air bubbles in the fresh and hardened concrete; accuracy of the microscopic examination, if
20、used;time of comparison; environmental exposure; stage in the delivery, placement and consolidation processes at which the air contentof the unhardened concrete is determined, that is, before or after the concrete goes through a pump; and other factors.4. Apparatus4.1 Air MetersThere are available s
21、atisfactory apparatus of two basic operational designs employing the principle of Boyleslaw. For purposes of reference herein these are designated Meter Type A and Meter Type B.4.1.1 Meter Type AAn air meter consisting of a measuring bowl and cover assembly (see Fig. 1) conforming to therequirements
22、 of 4.2 and 4.3. The operational principle of this meter consists of introducing water to a predetermined height abovea sample of concrete of known volume, and the application of a predetermined air pressure over the water. The determinationconsists of the reduction in volume of the air in the concr
23、ete sample by observing the amount the water level is lowered under theapplied pressure, the latter amount being calibrated in terms of percent of air in the concrete sample.4.1.2 Meter Type BAn air meter consisting of a measuring bowl and cover assembly (see Fig. 2) conforming to therequirements of
24、 4.2 and 4.3. The operational principle of this meter consists of equalizing a known volume of air at a knownpressure in a sealed air chamber with the unknown volume of air in the concrete sample, the dial on the pressure gauge beingcalibrated in terms of percent air for the observed pressure at whi
25、ch equalization takes place. Working pressures of 50 to 205 kPa205 kPa 7.5 to 30.0 psi have been used satisfactorily.4.2 Measuring BowlThe measuring bowl shall be essentially cylindrical in shape, made of steel, hard metal, or other hardmaterial not readily attacked by the cement paste, having a min
26、imum diameter equal to 0.75 to 1.25 times the height, and a capacityof at least 6.0 L 0.20 ft3. It shall be flanged or otherwise constructed to provide for a pressure tight fit between measuring bowland cover assembly. The interior surfaces of the measuring bowl and surfaces of rims, flanges, and ot
27、her component fitted partsshall be machined smooth. The measuring bowl and cover assembly shall be sufficiently rigid to limit the expansion factor, D, ofthe apparatus assembly (Section A1.5) to not more than 0.1 % of air content on the indicator scale when under normal operatingpressure.FIG. 1 Illu
28、stration of the Pressure Method for Air ContentType-A MeterC231/C231M 17a24.3 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 a pressure-tight fit b
29、etween measuring bowl and cover assembly and shallhave machined smooth interior surfaces contoured to provide an air space above the level of the top of the measuring bowl. Thecover shall be sufficiently rigid to limit the expansion factor of the apparatus assembly as prescribed in 4.2.4.3.2 The cov
30、er assembly shall be fitted with a means of direct reading of the air content. The cover for the Type A meter shallbe fitted with a standpipe, made of a transparent graduated tube or a metal tube of uniform bore with a glass water gauge attached.In the Type B meter, the dial of the pressure gauge sh
31、all be calibrated to indicate the percent of air. Graduations shall be providedfor a range in air content of at least 8 % readable to 0.1 % as determined by the proper air pressure calibration test.4.3.3 The cover assembly shall be fitted with air valves, air bleeder valves, and petcocks for bleedin
32、g off or through which watermay be introduced as necessary for the particular meter design. Suitable means for clamping the cover to the measuring bowl shallbe provided to make a pressure-tight seal without entrapping air at the joint between the flanges of the cover and measuring bowl.A suitable ha
33、nd pump shall be provided with the cover either as an attachment or as an accessory.4.4 Calibration VesselA measure having an internal volume equal to a percent of the volume of the measuring bowlcorresponding to the approximate percent of air in the concrete to be tested; or, if smaller, it shall b
34、e possible to check calibrationof the meter indicator at the approximate percent of air in the concrete to be tested by repeated filling of the measure. When thedesign of the meter requires placing the calibration vessel within the measuring bowl to check calibration, the measure shall becylindrical
35、 in shape.NOTE 1A satisfactory calibration vessel to place within the measuring bowl 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. in thickness is soldered to form an end. When design of the meter requires withdrawingof
36、 water from the water-filled measuring bowl and cover assembly, to check calibration, the measure may be an integral part of the cover assembly ormay be a separate cylindrical measure similar to the above-described cylinder.4.5 The designs of various available types of air meters are such that they
37、differ in operating techniques; therefore, all of theitems described in 4.6 4.16 may not be required. The items required shall be those necessary for use with the particular designof apparatus used to satisfactorily determine air content in accordance with the procedures prescribed herein.4.6 Coil S
38、pring or Other Device for Holding Calibration Cylinder in Place.4.7 Spray TubeA brass tube of appropriate diameter, which may be an integral part of the cover assembly, or which may beprovided separately. It shall be so constructed that when water is added to the container, it is sprayed to the wall
39、s of the cover insuch a manner as to flow down the sides causing a minimum of disturbance to the concrete.4.8 TrowelA standard brick masons trowel.4.9 Tamping RodA round, smooth, straight steel rod, with a 16 mm 58 in. 6 2 mm 116 in. diameter. The length of thetamping rod shall be at least 100 mm 4
40、in. greater than the depth of the measuring bowl in which rodding is being performed,FIG. 2 Schematic DiagramType-B MeterC231/C231M 17a3but not greater than 600 mm 24 in. in overall length (see Note 2). The rod shall have the tamping end or both ends rounded toa hemispherical tip of the same diamete
41、r as the rod.NOTE 2Arod length of 400 mm 16 in. to 600 mm 24 in. meets the requirements of the following: Practice C31/C31M, Test Method C138/C138M,Test Method C143/C143M, Test Method C173/C173M, and Test Method C231/C231M.4.10 MalletA mallet (with a rubber or rawhide head) weighing approximately 0.
42、60 6 0.25 kg 1.25 6 0.50 lb for use withmeasures of 14 L 0.5 ft 3 or smaller, and a mallet weighing approximately 1.0 6 0.25 kg 2.25 6 0.50 lb for use with measureslarger than 14 L 0.5 ft3.4.11 Strike-Off BarA flat straight bar of steel or other suitable metal at least 3 mm 18 in. thick and 20 mm 34
43、 in. wide by300 mm 12 in. long.4.12 Strike-Off PlateAflat rectangular metal plate at least 6 mm 14 in. thick or a glass or acrylic plate at least 13 mm 12 in.thick with a length and width at least 50 mm 2 in. greater than the diameter of the measure with which it is to be used. The edgesof the plate
44、 shall be straight and smooth within a tolerance of 1.5 mm 116 in.4.13 Funnel, with the spout fitting into spray tube.4.14 Measure for Water, having the necessary capacity to fill the indicator with water from the top of the concrete to the zeromark.4.15 Vibrator, as described in Practice C192/C192M
45、.4.16 Sieves, 37.5-mm (112-in.) with not less than 0.2 m2 2 ft 2 ft2 of sieving area.4.17 Scoopof a size large enough so each amount of concrete obtained from the sampling receptacle is representative andsmall enough so it is not spilled during placement in the measuring bowl.5. Calibration of Appar
46、atus5.1 Make calibration tests in accordance with procedures prescribed in the annex. Rough handling will affect the calibration ofboth Types A and B meters. Changes in barometric pressure will affect the calibration of Type A meter but not Type B meter. Thesteps described Sections A1.2 A1.6, as app
47、licable to the meter type under consideration, are prerequisites for the final calibrationtest to determine the operating pressure, P, on the pressure gauge of the TypeAmeter as described in Section A1.7, or to determinethe accuracy of the graduations indicating air content on the dial face of the p
48、ressure gauge of the Type B meter as described inSection A1.9. The steps in Sections A1.2 A1.6 need be made only once (at the time of initial calibration), or only occasionallyto check volume constancy of the calibration cylinder and measuring bowl. The calibration test described in Sections A1.7 an
49、dA1.9, as applicable to the meter type being checked, must be made as frequently as necessary and at intervals not to exceed threemonths to ensure that the proper gauge pressure, P, is being used for the Type A meter or that the correct air contents are beingindicated on the pressure gauge air content scale for the Type B meter. A change in elevation of more than 180 m 600 ft fromthe location at which a Type A meter was last calibrated will require recalibration in accordance with Section A1.7.5.2 Ca
