1、Designation: C 173/C 173M 08aStandard Test Method forAir Content of Freshly Mixed Concrete by the VolumetricMethod1This standard is issued under the fixed designation C 173/C 173M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, th
2、e 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers de
3、termination of the air contentof freshly mixed concrete containing any type of aggregate,whether it be dense, cellular, or lightweight.1.2 The values stated in either inch-pound or SI units shallbe regarded separately as standard. The SI units are shown inbrackets. The values stated are not exact eq
4、uivalents; thereforeeach system must be used independently of the other. Com-bining values from the two units may result in nonconfor-mance.1.3 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 t
5、o 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 prolonged exposure.2)2. Referenced Documents2.1 ASTM Standards:3C
6、29/C 29M Test Method for Bulk Density (“Unit Weight”)and Voids in AggregateC 172 Practice for Sampling Freshly Mixed ConcreteC 231 Test Method for Air Content of Freshly MixedConcrete by the Pressure MethodC 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction Ma
7、terials3. Significance and Use3.1 This test method covers the determination of the aircontent of freshly mixed concrete. It measures the air containedin the mortar fraction of the concrete, but is not affected by airthat may be present inside porous aggregate particles.3.1.1 Therefore, this is the a
8、ppropriate test to determine theair content of concretes containing lightweight aggregates,air-cooled slag, and highly porous or vesicular natural aggre-gates.3.2 This test method requires the addition of sufficientisopropyl alcohol, when the meter is initially being filled withwater, so that after
9、the first or subsequent rollings little or nofoam collects in the neck of the top section of the meter. Ifmore foam is present than that equivalent to 2 % air above thewater level, the test is declared invalid and must be repeatedusing a larger quantity of alcohol. Addition of alcohol to dispelfoam
10、any time after the initial filling of the meter to the zeromark is not permitted.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 amounts of consolidation effortapplied to the concrete from which the hard
11、ened concretespecimen is taken; uniformity 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 unhar
12、dened concreteis determined, that is, before or after the concrete goes througha pump; and other factors.4. Apparatus4.1 Air MeterAn air meter consisting of a bowl and a topsection (Fig. 1) conforming to the following requirements:4.1.1 The bowl and top sections shall be of sufficientthickness and r
13、igidity to withstand rough field use. Thematerial shall not be attacked by high pH cement paste, deformwhen stored at high temperatures in closed spaces, or becomebrittle or crack at low temperatures. A watertight seal must beobtained when the top section is attached to the bowl.4.1.2 BowlThe bowl s
14、hall have a diameter equal to 1 to1.25 times the height and be constructed with a flange at ornear the top surface. Bowls shall not have a capacity of lessthan 0.075 ft32.0 L.1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct respon
15、sibility of SubcommitteeC09.60 on Testing Fresh Concrete.Current edition approved Dec. 15, 2008. Published January 2009. Originallyapproved in 1942. Last previous edition approved in 2008 as C 173/C 173M 08.2Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM
16、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 Changes section appears a
17、t the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.3 Top SectionThe top section shall have a capacity atleast 20 % larger than the bowl and shall be equipped with aflexible gasket and a device to attach the
18、 top section to thebowl. The top section shall be equipped with a transparentscale, graduated in increments not greater than 0.5 % from 0 atthe top to 9 %, or more, of the volume of the bowl. Graduationsshall be accurate to 60.1 % by volume of the bowl. The upperend of the neck shall have a watertig
19、ht cap that will maintaina watertight seal when the meter is inverted and rolled.4.2 FunnelA funnel with a spout of a size permitting it tobe inserted through the neck of the top section and long enoughto extend to a point just above the bottom of the top section.The discharge end of the spout shall
20、 be so constructed thatwhen water is added to the container there will be a minimumdisturbance of the concrete.4.3 Tamping RodA round, smooth, straight58 6116-in.16 6 2-mm diameter rod at least 12 in. 300 mm long withboth ends rounded to a hemispherical tip of the same diameter.The rod shall be made
21、 of steel, high-density polyethylene, orother plastic of equal or greater abrasion resistance.4.4 Strike-off BarA flat, straight steel bar at least18 by34by 12 in. 3 by 20 by 300 mm or a flat, straight high-densitypolyethylene bar, or other plastic of equal or greater abrasionresistance, at least14
22、by34 by 12 in. 6 by 20 by 300 mm.4.5 Calibrated CupA metal or plastic cup either having acapacity of or being graduated in increments equal to 1.00 60.04 % of the volume of the bowl of the air meter. Thecalibrated cup is only to be used to add water when theconcrete air content exceeds 9 % or the ca
23、librated range of themeter.4.6 Measuring Vessel for Isopropyl AlcoholA vessel witha minimum capacity of at least 1 pt 500 mL with graduationsnot larger than 4 oz 100 mL for measuring a quantity ofisopropyl alcohol.4.7 SyringeA rubber syringe having a capacity of at least2 oz 50 mL.4.8 Pouring Vessel
24、 for WaterA container of approxi-mately 1 qt 1 L capacity.4.9 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 bowl.4.10 Isopropyl AlcoholUse 70 % by volume isopropylalcohol (ap
25、proximately 65 % by weight) (Note 1). Otherfoam-dispersing agents are permitted if tests demonstrate thatthe use of the agent does not change the indicated air content,in the amounts being used, by more than 0.1 % or if correctionfactors are developed similar to those in Table 1. When otherdispersin
26、g agents are used, a copy of the records documentingthe testing or calculations shall be available in the laboratory.NOTE 1Seventy percent isopropyl alcohol is commonly available asrubbing alcohol. More concentrated grades can be diluted with water tothe required concentration.4.11 MalletA mallet (w
27、ith a rubber or rawhide head) witha mass of approximately 1.25 6 0.5 lb 600 6 200 g.FIG. 1 Apparatus for Measuring Air Content of Fresh Concrete byVolumetric MethodTABLE 1 Correction for the Effect of Isopropyl Alcohol onC 173/C 173M Air Meter Reading70 % Isopropyl Alcohol Used CorrectionPints Fluid
28、OuncesLitres (Subtract)A0.5 8 0.2 0.0B1.0 16 0.5 0.0B1.5 24 0.7 0.0B2.0 32 0.9 0.0B3.0 48 1.4 0.254.0 64 1.9 0.505.0 80 2.4 0.75ASubtract from final meter reading.BCorrections less than 0.125 are not significant and are to be applied only when2.5 pt 1.2 L or more alcohol is used. The effect occurs w
29、hen the meter is invertedafter being filled with an alcohol-water solution which then becomes further dilutedwhen it is mixed with the water in the concrete. The values given are for air metersthat have a bowl volume of 0.075 ft32.1 L and a top section that is 1.2 times thevolume of the bowl.C 173/C
30、 173M 08a25. Calibration5.1 Calibrate the meter and calibrated cup initially andannually or whenever there is reason to suspect damage ordeformation of the meter or calibrated cup.5.2 Determine the volume of the bowl with an accuracy ofat least 0.1 % by determining the mass of water required to fill
31、it at room temperature and dividing it by the density of thewater at the same temperature. Follow the calibration proce-dure outlined in Test Method C 29/C 29M.5.3 Determine the accuracy of the graduations on the neckof the top section of the air meter by filling the assembledmeasuring bowl and top
32、section with water to the level of themark for highest air content graduation.5.3.1 Add water in increments of 1.0 % of the volume of thebowl to check accuracy throughout the graduated range of aircontent. The error at any point throughout the graduated rangeshall not exceed 0.1 % of air.5.4 Determi
33、ne the volume of the calibrated cup using waterat 70 F 21.1 C by the method outlined in 5.2.Aquick checkcan be made by adding one or more calibrated cups of water tothe assembled apparatus and observing the increase in theheight of the water column after filling to a given level.6. Sampling6.1 Obtai
34、n the sample of freshly mixed concrete in accor-dance with Practice C 172. If the concrete contains coarseaggregate particles that would be retained on a 112-in.37.5-mm sieve, wet sieve a representative sample over a 1-in.25-mm sieve to yield somewhat more than enough material tofill the measuring b
35、owl. The wet sieving procedure is describedin Practice C 172. Carry out the wet sieving operation with theminimum practicable disturbance of the mortar. Make noattempt to wipe adhering mortar from coarse aggregate par-ticles retained on the sieve.7. Procedure7.1 Rodding and TappingWet the inside of
36、the bowl anddry it to a damp but not shiny appearance. Using the scoopdescribed in 4.9, fill the bowl with freshly mixed concrete intwo layers of equal depth. While placing the concrete in thebowl, move the scoop around the perimeter of the bowlopening to ensure an even distribution of the concrete
37、withminimal segregation. Rod each layer 25 times with the tampingrod. Do not forcibly strike the bottom of the bowl whenrodding the first layer. When rodding the second layer, pen-etrate the prior layer about 1 in. 25 mm. After each layer isrodded, tap the sides of the bowl 10 to 15 times with the m
38、alletto close any voids left by the tamping rod and to release anylarge bubbles of air that may have been trapped. After tappingthe final layer, a slight excess of concrete,18 in. 3 mm or less,above the rim is acceptable. Add or remove a representativesample of concrete if necessary to obtain the re
39、quired amountof concrete.7.2 Striking OffAfter rodding and tapping of the secondlayer, strike off the excess concrete with the strike-off bar untilthe surface is flush with the top of the bowl. Wipe the flange ofthe bowl clean.7.3 Adding Water and AlcoholWet the inside of the topsection of the meter
40、, including the gasket. Attach the topsection to the bowl and insert the funnel. Add at least 1 pt 0.5L of water followed by the selected amount (Note 2)ofisopropyl alcohol. Record the amount of isopropyl alcoholadded. Continue adding water until it appears in the graduatedneck of the top section (N
41、ote 3). Remove the funnel.Adjust theliquid level until the bottom of the meniscus is level with thezero mark. A rubber syringe is useful for this purpose. Attachand tighten the watertight cap.NOTE 2The amount of isopropyl alcohol necessary to obtain a stablereading and a minimum of foam at the top o
42、f the water column willdepend upon a number of factors. Many concretes made with less than 500lb/yd3300 kg/m3 of cement and air contents less than 4 % may requireless than 0.5 pt 200 mL of alcohol. Some high-cement mixes made withsilica fume that have air contents of 6 % or more may require more tha
43、n3 pt 1400 mL of alcohol. The amount required will vary with theconcrete air content, the amount and type of air-entraining admixture, thecement content and cement alkali content, and perhaps other factors.Generally, the amount of alcohol necessary can be established for givenmixture proportions and
44、 should not change greatly during the course of ajob.NOTE 3When, if ever, it is necessary to use more than 4 or 4.5 pt 2.0L of isopropyl alcohol, it may be necessary to restrict the amount of wateradded initially to avoid overfilling the meter. However, it is desirable toadd at least some water init
45、ially to aid in mixing the alcohol and limit thecontact of the concentrated alcohol with the top surface of the concrete.7.4 Displacing the Volume of Air in the Concrete SpecimenUsing These Procedures:7.4.1 Free the Concrete from the Base Quickly invert themeter, shake the base horizontally, and ret
46、urn the meter to theupright position. To prevent the aggregate from lodging in theneck of the unit, do not keep it inverted for more than 5 s at atime. Repeat the inversion and shaking process for a minimumof 45 s and until the concrete has broken free and the aggregatecan be heard moving in the met
47、er as it is inverted.7.4.2 RollingPlace one hand on the neck of the meter andthe other on the flange. Using the hand on the neck, tilt the topof the meter approximately 45 from the vertical position withthe bottom edge of the base of the meter resting on the floor oron the work surface. Maintain thi
48、s position through theprocedures described in this section. Using the hand on theflange to rotate the meter, vigorously roll the meter14 to12 turnforward and back several times, quickly starting and stoppingthe roll. Turn the base of the meter about13 turn and repeat therolling procedure as stated p
49、reviously. Continue the turningand rolling procedures for approximately 1 min. The aggregatemust be heard sliding in the meter during this process.7.4.2.1 If, at any time, during the inversion and rollingprocedures liquid is found to be leaking from the meter, the testis invalid and a new test shall be started as in 6.1.7.4.2.2 Set the unit upright and loosen the top to allow anypressure to stabilize. Allow the meter to stand while the airrises to the top and until the liquid level stabilizes. The liquid
