1、Designation: C 138/C 138M 09American 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 C 138/C 138M; the number immediately f
2、ollowing 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 ap
3、proved 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 prod
4、ucedfrom 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. Comb
5、iningvalues 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 explana
6、tory information. These notesand footnotes (excluding those in tables) shall not be consid-ered as requirements of this test method.2. Referenced Documents2.1 ASTM Standards:2C 29/C 29M Test Method for Bulk Density (“Unit Weight”)and Voids in AggregateC 31/C 31M Practice for Making and Curing Concre
7、te TestSpecimens in the FieldC 143/C 143M Test Method for Slump of Hydraulic-Cement ConcreteC 150 Specification for Portland CementC 172 Practice for Sampling Freshly Mixed ConcreteC 173/C 173M Test Method for Air Content of FreshlyMixed Concrete by the Volumetric MethodC 188 Test Method for Density
8、 of Hydraulic CementC 231 Test Method for Air Content of Freshly MixedConcrete by the Pressure Method3. Terminology3.1 Symbols:A = air content (percentage of voids) in the concreteC = actual cement content, lb/yd3or kg/m3Cb= mass of cement in the batch, lb or kgD = density (unit weight) of concrete,
9、 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 density of the concrete computed on anairfree basis, lb/ft3or kg/m3(see Note 2)Y = yield, volume of con
10、crete produced per batch, yd3orm3Yd= volume of concrete which the batch was designed toproduce, yd3or m3Yf= volume of concrete produced per batch, ft3V = total absolute volume of the component ingredientsin the batch, ft3or m3Vm= volume of the measure, ft3or m3NOTE 2The theoretical density is, custo
11、marily, 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 equation:T 5 M/V (1)The absolute volume of each ingredient in cubic feet is equal to thequotient of t
12、he 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 by1000 times its specific gravity. For the aggregate components, the bulk1This test method is under t
13、he 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 1938. Last previous edition approved in 2008 as C 138/C 138M 08.
14、2For 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 end of this sta
15、ndard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.specific gravity and mass should be based on the saturated, surface-drycondition. For cement, the actual specific gravity should be determined byTest Method C 188. A value of 3.15
16、may be used for cements manufac-tured to meet the requirements of Specification C 150.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
17、other solid or liquid materials used.4. Apparatus4.1 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 mea
18、sure plus its contents at 160 lb/ft32600kg/m3.4.2 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. 100 mm greater than the depth of themeasure in which rodding is being performed, but not greaterthan 24 in. 600 mm
19、in overall length (See Note 4). The lengthtolerance for the tamping rod shall be 618 in. 4 mm. The rodshall 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: Pra
20、ctice 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 231.4.3 Internal VibratorInternal vibrators may have rigid orflexible shafts, preferably powered by electric motors. Thefrequency of vibration shall be 7000 vibrations per minute orgreater
21、 while in use. The outside diameter or the side dimen-sion of the vibrating element shall be at least 0.75 in. 19 mmand 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 min
22、imum capacity of themeasure shall conform to the requirements of Table 1 based onthe nominal size of aggregate in the concrete to be tested. Allmeasures, except for measuring bowls of air meters which arealso used for Test Method C 138/C 138M tests, shall conformto the requirements of Test Method C
23、29/C 29M. When mea-suring bowls of air meters are used, they shall conform to therequirements of Test Method C 231, and shall be calibrated forvolume as described in Test Method C 29/C 29M. The top rimof the air meter bowls shall be smooth and plane within 0.01 in.0.3 mm (see Note 6).NOTE 5The metal
24、 should not be readily subject to attack by cementpaste. However, reactive materials such as aluminum alloys may be usedin instances 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 p
25、lane 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 over 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 an
26、d 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 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
27、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 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 me
28、asure.5. Sample5.1 Obtain the sample of freshly mixed concrete in accor-dance with Practice C 172.6. Procedure6.1 Base the selection 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
29、 rodding and internal vibration. Rod concretes with aslump greater than 3 in. 75 mm. Rod or vibrate concrete witha slump of 1 to 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 ma
30、sonry, is not covered by this test method.6.2 Place the concrete in the measure using the scoopdescribed in 4.7. Move the scoop 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 c
31、onsolidation method (6.3 or 6.4).6.3 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
32、 in.220 cm3of 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
33、 the rod topenetrate 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
34、bubbles of air thatmay have been trapped. Add the final layer so as to avoidoverfilling.TABLE 1 Capacity of MeasuresNominal Maximum Sizeof Coarse AggregateCapacity of MeasureAin. mm 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
35、 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 listed.C 138/C 138M 0926.4 Internal VibrationFill and vibrate the measure in twoapproximately equal layers. Place all of
36、 the concrete for eachlayer in the measure before starting vibration of that layer.Insert the vibrator at three different points 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
37、shall penetrate into the underlyinglayer approximately 1 in. 25 mm. Take care that the vibratoris withdrawn in such a manner that 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
38、8). Continue vibration only long enough toachieve proper consolidation of the concrete (see Note 9).Observe a constant duration 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 b
39、ecomes relatively smooth.NOTE 9Overvibration may cause segregation and loss of appreciablequantities of intentionally entrained 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 mma
40、bove the top of the mold is optimum. A small quantity ofconcrete may be added to correct a deficiency. If the measurecontains a great excess of concrete at completion of consoli-dation, remove a representative portion of the excess concretewith a trowel or scoop immediately following completion ofco
41、nsolidation and before the measure is struck-off.6.6 Strike-OffAfter consolidation, strike-off the top sur-face of the concrete and finish it smoothly with the flatstrike-off plate using great care to leave the measure just levelfull. The strike-off is best accomplished by pressing thestrike-off pla
42、te on the top surface of the measure to cover abouttwo thirds of the surface and withdrawing the plate with asawing motion to finish only the area originally covered. Thenplace the plate on the top of the measure to cover the originaltwo thirds of the surface and advance it with a vertical pressurea
43、nd a sawing motion to cover the whole surface of the measureand continue to advance it until it slides completely off themeasure. Several final strokes with the inclined edge of theplate will produce a smooth finished surface.6.7 Cleaning and WeighingAfter strike-off, clean all ex-cess concrete from
44、 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 (Unit Weight)Calculate the net mass of theconcrete in pounds or kilograms by subtracting the mass of themeasure, Mm, from the mass of the mea
45、sure 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)7.2 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
46、 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 excess ofconcrete being produced whereas a value less than this indicates the batchto be “short” of its designed volume. In practice, a rati
47、o 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 contentas 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
48、! (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
49、, when requested, to the nearest 0.1 yd30.1 m3.8.1.6 Relative Yield, when requested, to the nearest 0.01.8.1.7 Cement Content, when requested, to the nearest 1.0 lb0.5 kg.8.1.8 Air Content, when requested, to the nearest 0.1 per-cent.9. Precision and Bias9.1 The following estimates of precision for this test methodare based on a collection of data from various locations by theNational Ready Mixed Concrete Association.3The data repre-sent concrete mixtures with slump
