1、Designation: C138/C138M 10bAmerican Association StateHighway and Transportation Officials StandardAASHTO No.: T121Standard Test Method forDensity (Unit Weight), Yield, and Air Content (Gravimetric)of Concrete1This standard is issued under the fixed designation C138/C138M; the number immediately foll
2、owing the designation indicates the yearof original adoption or, in the case of revision, 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.This standard has been appro
3、ved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers determination of the density(see Note 1) of freshly mixed concrete and gives formulas forcalculating the yield, cement content, and air content of theconcrete. Yield is defined as the volume of concrete produce
4、dfrom a mixture of known quantities of the component materi-als.1.2 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 equivalents; therefore, eachsystem shall be used independently of the other. Combini
5、ngvalues from the two systems may result in non-conformancewith the standard.NOTE 1Unit weight was the previous terminology used to describethe property determined by this test method, which is mass per unitvolume.1.3 The text of this test method references notes andfootnotes that provide explanator
6、y information. These notesand footnotes (excluding those in tables) shall not be consid-ered as requirements of this test method.1.4 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
7、 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (WARNINGFresh hydraulic cementitious mixtures are caustic and maycause chemical burns to skin and tissue upon prolongedexposure.2)2. Referenced Documents2.1 ASTM Standards:3C29/C29M Tes
8、t Method for Bulk Density (“Unit Weight”)and Voids in AggregateC31/C31M Practice for Making and Curing Concrete TestSpecimens in the FieldC143/C143M Test Method for Slump of Hydraulic-CementConcreteC150 Specification for Portland CementC172 Practice for Sampling Freshly Mixed ConcreteC173/C173M Test
9、 Method for Air Content of FreshlyMixed Concrete by the Volumetric MethodC188 Test Method for Density of Hydraulic CementC231 Test Method for Air Content of Freshly Mixed Con-crete by the Pressure Method3. Terminology3.1 Symbols:A = air content (percentage of voids) in the concreteC = actual cement
10、content, lb/yd3or kg/m3Cb= mass of cement in the batch, lb or kgD = density (unit weight) of concrete, lb/ft3or kg/m3M = total mass of all materials batched, lb or kg (see Note3)Mc= mass of the measure filled with concrete, lb or kgMm= mass of the measure, lb or kgRy= relative yieldT = theoretical d
11、ensity of the concrete computed on anairfree basis, lb/ft3or kg/m3(see Note 2)Y = yield, volume of concrete produced per batch, yd3orm31This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.60 on Testin
12、g Fresh Concrete.Current edition approved Oct. 1, 2010. Published November 2010. Originallyapproved in 1938. Last previous edition approved in 2010 as C138/C138M10a.DOI: 10.1520/C0138_C0138M-10b.2See section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standard
13、s, 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 at the e
14、nd of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Yd= volume of concrete which the batch was designed toproduce, yd3or m3Yf= volume of concrete produced per batch, ft3V = total absolute volume of the component ingred
15、ientsin the batch, ft3or m3Vm= volume of the measure, ft3or m3NOTE 2The theoretical density is, customarily, a laboratory determi-nation, the value for which is assumed to remain constant for all batchesmade using identical component ingredients and proportions. It is calcu-lated from the following
16、equation:T 5 M/V (1)The absolute volume of each ingredient in cubic feet is equal to thequotient of the mass of that ingredient divided by the product of itsspecific gravity times 62.4. The absolute volume of each ingredient incubic metres is equal to the mass of the ingredient in kilograms divided
17、by1000 times its specific gravity. For the aggregate components, the bulkspecific gravity and mass should be based on the saturated, surface-drycondition. For cement, the actual specific gravity should be determined byTest Method C188.Avalue of 3.15 may be used for cements manufacturedto meet the re
18、quirements of Specification C150.NOTE 3The total mass of all materials batched is the sum of themasses of the cement, the fine aggregate in the condition used, the coarseaggregate in the condition used, the mixing water added to the batch, andany other solid or liquid materials used.4. Apparatus4.1
19、BalanceA balance or scale accurate to 0.1 lb 45 g orto within 0.3 % of the test load, whichever is greater, at anypoint within the range of use. The range of use shall beconsidered to extend from the mass of the measure empty tothe mass of the measure plus its contents at 160 lb/ft32600kg/m3.4.2 Tam
20、ping RodA round, smooth, straight steel rod, witha58 in. 16 mm 6116 in. 2 mm diameter. The length of thetamping rod shall be at least 4 in. 100 mm greater than thedepth of the measure in which rodding is being performed, butnot greater than 24 in. 600 mm in overall length (See Note 4).The rod shall
21、have the tamping end or both ends rounded to ahemispherical tip of the same diameter as the rod.NOTE 4A rod length of 16 in. 400 mm to 24 in. 600 mm meets therequirements of the following: Practice C31/C31M, Test Method C138/C138M, Test Method C143/C143M, Test Method C173/C173M and TestMethod C231.4
22、.3 Internal VibratorInternal vibrators may have rigid orflexible shafts, preferably powered by electric motors. Thefrequency of vibration shall be 7000 vibrations per minute orgreater while in use. The outside diameter or the side dimen-sion of the vibrating element shall be at least 0.75 in. 19 mma
23、nd not greater than 1.50 in. 38 mm. The length of the shaftshall be at least 24 in. 600 mm.4.4 MeasureAcylindrical container made of steel or othersuitable metal (see Note 5). The minimum capacity of themeasure shall conform to the requirements of Table 1 based onthe nominal size of aggregate in the
24、 concrete to be tested. Allmeasures, except for measuring bowls of air meters which arealso used for Test Method C138/C138M tests, shall conform tothe requirements of Test Method C29/C29M. When measuringbowls of air meters are used, they shall conform to therequirements of Test Method C231, and shal
25、l be calibrated forvolume as described in Test Method C29/C29M. The top rim ofthe air meter bowls shall be smooth and plane within 0.01 in.0.3 mm (see Note 6).NOTE 5The metal should not be readily subject to attack by cementpaste. However, reactive materials such as aluminum alloys may be usedin ins
26、tances where as a consequence of an initial reaction, a surface filmis rapidly formed which protects the metal against further corrosion.NOTE 6The top rim is satisfactorily plane if a 0.01-in. 0.3-mm feelergage cannot be inserted between the rim and a piece of14-in. 6-mm orthicker plate glass laid o
27、ver the top of the measure.4.5 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 mmgreater than the diameter of the measure with which it is to beused. The edges of the plate shall
28、be straight and smooth withina tolerance of116 in. 2 mm.4.6 MalletA mallet (with a rubber or rawhide head)having a mass of 1.25 6 0.50 lb 600 6 200 g for use withmeasures of 0.5 ft314 L or smaller, and a mallet having amass of 2.25 6 0.50 lb 1000 6 200 g for use with measureslarger than 0.5 ft3.4.7
29、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 measure.5. Sample5.1 Obtain the sample of freshly mixed concrete in accor-dance with Practice C172.6. Procedure6.1 Base the sele
30、ction of the method of consolidation on theslump, unless the method is stated in the specifications underwhich the work is being performed. The methods of consoli-dation are rodding and internal vibration. Rod concretes with aslump greater than 3 in. 75 mm. Rod or vibrate concrete witha slump of 1 t
31、o 3 in. 25 to 75 mm. Consolidate concretes witha slump less than 1 in. by vibration.NOTE 7Nonplastic concrete, such as is commonly used in themanufacture of pipe and unit masonry, is not covered by this test method.6.2 Place the concrete in the measure using the scoopdescribed in 4.7. Move the scoop
32、 around the perimeter of themeasure opening to ensure an even distribution of the concretewith minimal segregation. Fill the measure in the number oflayers required by the consolidation method (6.3 or 6.4).TABLE 1 Capacity of MeasuresNominal Maximum Sizeof Coarse AggregateCapacity of MeasureAin. mm
33、ft3L1 25.0 0.2 6112 37.5 0.4 11250 .5 4375 1 28412 112 2.5 706 150 3.5 100AThe indicated size of measure shall be used to test concrete containingaggregates of a nominal maximum size equal to or smaller than that listed. Theactual volume of the measure shall be at least 95 % of the nominal volume li
34、sted.C138/C138M 10b26.3 RoddingPlace the concrete in the measure in threelayers of approximately equal volume. Rod each layer with 25strokes of the tamping rod when nominal 0.5-ft314-L orsmaller measures are used, 50 strokes when nominal 1-ft328-L measures are used, and one stroke per 3 in.220 cm3of
35、 surface for larger measures. Rod each layer uniformly overthe cross section with the rounded end of the rod using therequired number of strokes. Rod the bottom layer throughoutits depth. In rodding this layer, use care not to damage thebottom of the measure. For each upper layer, allow the rod tope
36、netrate through the layer being rodded and into the layerbelow approximately 1 in. 25 mm.After each layer is rodded,tap the sides of the measure 10 to 15 times with the appropriatemallet (see 4.6) using such force so as to close any voids leftby the tamping rod and to release any large bubbles of ai
37、r thatmay have been trapped. Add the final layer so as to avoidoverfilling.6.4 Internal VibrationFill and vibrate the measure in twoapproximately equal layers. Place all of the concrete for eachlayer in the measure before starting vibration of that layer.Insert the vibrator at three different points
38、 for each layer. Incompacting the bottom layer, do not allow the vibrator to reston or touch the bottom or sides of the measure. In compactingthe final layer, the vibrator shall penetrate into the underlyinglayer approximately 1 in. 25 mm. Take care that the vibratoris withdrawn in such a manner tha
39、t no air pockets are left in thespecimen. The duration of vibration required will depend uponthe workability of the concrete and the effectiveness of thevibrator (see Note 8). Continue vibration only long enough toachieve proper consolidation of the concrete (see Note 9).Observe a constant duration
40、of vibration for the particular kindof concrete, vibrator, and measure involved.NOTE 8Usually, sufficient vibration has been applied as soon as thesurface of the concrete becomes relatively smooth.NOTE 9Overvibration may cause segregation and loss of appreciablequantities of intentionally entrained
41、air.6.5 On completion of consolidation the measure must notcontain a substantial excess or deficiency of concrete. Anexcess of concrete protruding approximately18 in. 3 mmabove the top of the mold is optimum. A small quantity ofconcrete may be added to correct a deficiency. If the measurecontains a
42、great excess of concrete at completion of consoli-dation, remove a representative portion of the excess concretewith a trowel or scoop immediately following completion ofconsolidation and before the measure is struck-off.6.6 Strike-OffAfter consolidation, strike-off the top sur-face of the concrete
43、and finish it smoothly using the flatstrike-off plate so that the measure is level full. Strike-off themeasure by pressing the strike-off plate on the top surface ofthe measure to cover about two thirds of the surface andwithdraw the plate with a sawing motion to finish only the areaoriginally cover
44、ed. Then place the plate on the top of themeasure to cover the original two thirds of the surface andadvance it with a vertical pressure and a sawing motion tocover the whole surface of the measure and continue toadvance it until it slides completely off the measure. Incline theplate and perform fin
45、al strokes with the edge of the plate toproduce a smooth surface.6.7 Cleaning and WeighingAfter strike-off, clean all ex-cess concrete from the exterior of the measure and determinethe mass of the concrete and measure to an accuracy consistentwith the requirements of 4.1.7. Calculation7.1 Density (U
46、nit Weight)Calculate the net mass of theconcrete in pounds or kilograms by subtracting the mass of themeasure, Mm, from the mass of the measure filled withconcrete, Mc. Calculate the density, D,ft3or yd3,by dividingthe net mass of concrete by the volume of the measure, Vmasfollows:D 5 Mc Mm!/Vm(2)7.
47、2 YieldCalculate the yield as follows:Yyd3! 5 M/D3 27! (3)orYm3! 5 M/D (4)7.3 Relative YieldRelative yield is the ratio of the actualvolume of concrete obtained to the volume as designed for thebatch (see Note 10) calculated as follows:Ry5 Y/Yd(5)NOTE 10A value for Rygreater than 1.00 indicates an e
48、xcess ofconcrete being produced whereas a value less than this indicates the batchto be “short” of its designed volume. In practice, a ratio of yield in cubicfeet per cubic yard of design concrete mixture is frequently used, forexample, 27.3 ft3/yd3.7.4 Cement ContentCalculate the actual cement cont
49、entas follows:C 5 Cb/Y (6)7.5 Air ContentCalculate the air content as follows:A 5 T 2 D!/T 3 100 (7)orA 5 Yf2 V!/Yf# 3 100 inch2pound units! (8)orA 5 Y 2 V!/Y 3 100 SI units! (9)8. Report8.1 Report the following information:8.1.1 Identification of concrete represented by the sample.8.1.2 Date of test.8.1.3 Volume of density measure to the nearest 0.001 ft30.01 L.8.1.4 Density (Unit Weight) to the nearest 0.1 lbs/ft31.0kg/m3.8.1.5 Yield, when requested, to the nearest 0.1 y
