1、Designation: C138/C138M 12aC138/C138M 13 American 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 im
2、mediately following 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
3、has been approved 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 the concrete. Yield is defined as the volume of
4、concrete produced froma mixture of known quantities of the component materials.1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of t
5、he other. Combining values from thetwo systems may result in non-conformance with the standard.NOTE 1Unit weight was the previous terminology used to describe the property determined by this test method, which is mass per unit volume.1.3 The text of this test method references notes and footnotes th
6、at provide explanatory information. These notes and footnotes(excluding those in tables) shall not be considered as requirements of this test method.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this
7、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 cause chemical burns to skinand tissue upon prolonged exposure.2)2. Referenced Documents2.1 ASTM Stan
8、dards:3C29/C29M Test Method for Bulk Density (“Unit Weight”) and Voids in AggregateC31/C31M Practice for Making and Curing Concrete Test Specimens in the FieldC143/C143M Test Method for Slump of Hydraulic-Cement ConcreteC150 Specification for Portland CementC172 Practice for Sampling Freshly Mixed C
9、oncreteC173/C173M Test Method for Air Content of Freshly Mixed Concrete by the Volumetric MethodC188 Test Method for Density of Hydraulic CementC231 Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method3. Terminology3.1 Symbols:A = air content (percentage of voids) in the conc
10、reteC = actual cement content, kg/m3 lb/yd3Cb = mass of cement in the batch, kg lb1 This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregatesand is the direct responsibility of Subcommittee C09.60 onTesting Fresh Concrete.Current edition approved Dec. 1, 20
11、12May 1, 2013. Published December 2012June 2013. Originally approved in 1938. Last previous edition approved in 2012 asC138/C138M12.12a. DOI: 10.1520/C0138_C0138M-12a.10.1520/C0138_C0138M-13.2 See section on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards,
12、 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 Document Summary page on the ASTM website.This document is not an ASTM standard and is inte
13、nded 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 recommends that users consult prior editions as appropriate. In all cases only the curre
14、nt 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 C700, West Conshohocken, PA 19428-2959. United States1D = density (unit weight) of con
15、crete, kg/m3 lb/ft3M = total mass of all materials batched, kg lb (see Note 3)Mc = mass of the measure filled with concrete, kg lb orMm = mass of the measure, kg lbRy = relative yieldT = theoretical density of the concrete computed on an airfree basis, kg/m3 lb/ft3 (see Note 2)Y = yield, volume of c
16、oncrete produced per batch, m3 yd3Yd = volume of concrete which the batch was designed to produce, m3 yd3Yf = volume of concrete produced per batch, m3 ft3V = total absolute volume of the component ingredients in the batch, m3 ft3Vm = volume of the measure, m3 ft3NOTE 2The theoretical density is, cu
17、stomarily, a laboratory determination, the value for which is assumed to remain constant for all batches madeusing identical component ingredients and proportions.NOTE 3The total mass of all materials batched is the sum of the masses of the cement, the fine aggregate in the condition used, the coars
18、e aggregatein the condition used, the mixing water added to the batch, and any other solid or liquid materials used.4. Apparatus4.1 BalanceA balance or scale accurate to 45 g 0.1 lb or to within 0.3 % of the test load, whichever is greater, at any pointwithin the range of use. The range of use shall
19、 be considered to extend from the mass of the measure empty to the mass of themeasure plus its contents at 2600 kg/m3 160 lb/ft3.4.2 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 in. greater than t
20、he depth of the measure in which rodding is being performed, but notgreater than 600 mm 24 in. in overall length (See Note 4). The rod shall have the tamping end or both ends rounded to ahemispherical tip of the same diameter as the rod.NOTE 4Arod length of 400 mm 16 in. to 600 mm 24 in. meets the r
21、equirements of the following: Practice C31/C31M, Test Method C138/C138M,Test Method C143/C143M, Test Method C173/C173M and Test Method C231.4.3 Internal VibratorInternal vibrators may have rigid or flexible shafts, preferably powered by electric motors. The frequencyof vibration shall be 7000 vibrat
22、ions per minute or greater while in use. The outside diameter or the side dimension of the vibratingelement shall be at least 19 mm 0.75 in. and not greater than 38 mm 1.50 in. The length of the shaft shall be at least 600 mm24 in.4.4 MeasureAcylindrical container made of steel or other suitable met
23、al (see Note 5). The minimum capacity of the measureshall conform to the requirements of Table 1 based on the nominal size of aggregate in the concrete to be tested. All measures,except for measuring bowls of air meters which are also used for Test Method C138/C138M tests, shall conform to therequir
24、ements of Test Method C29/C29M. When measuring bowls of air meters are used, they shall conform to the requirementsof Test Method C231, and shall be calibrated for volume as described in Test Method C29/C29M. The top rim of the air meterbowls shall be smooth and plane within 0.01 in. 0.3 mm (see Not
25、e 6).NOTE 5The metal should not be readily subject to attack by cement paste. However, reactive materials such as aluminum alloys may be used ininstances where as a consequence of an initial reaction, a surface film is rapidly formed which protects the metal against further corrosion.NOTE 6The top r
26、im is satisfactorily plane if a 0.3-mm 0.01-in. feeler gage cannot be inserted between the rim and a piece of 6-mm 14-in. or thickerplate glass laid over the top of the measure.4.5 Strike-Off PlateA flat rectangular metal plate at least 6 mm 14 in. thick or a glass or acrylic plate at least 12 mm 12
27、 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 shall be straight and smooth within a tolerance of 2 mm 116 in.4.6 MalletA mallet (with a rubber or rawhide head) having a mass of 600 6 200 g 1.25 6 0.5
28、0 lb for use with measuresof 14 L 0.5 ft3 or smaller, and a mallet having a mass of 1000 6 200 g 2.25 6 0.50 lb for use with measures larger than 14L 0.5 ft3.TABLE 1 Capacity of MeasuresNominal Maximum Size of CoarseAggregate Capacity of MeasureAmm in. L ft325.0 1 6 0.237.5 112 11 0.450 2 14 0.575 3
29、 28 1.0112 412 70 2.5150 6 100 3.5A The 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 listed.C138/C138M 1324.7 Scoopof a size l
30、arge enough so each amount of concrete obtained from the sampling receptacle is representative and smallenough so it is not spilled during placement in the measure.5. Sample5.1 Obtain the sample of freshly mixed concrete in accordance with Practice C172.6. Procedure6.1 Base the selection of the meth
31、od of consolidation on the slump, unless the method is stated in the specifications under whichthe work is being performed. The methods of consolidation are rodding and internal vibration. Rod concretes with a slump greaterthan 75 mm 3 in. Rod or vibrate concrete with a slump of 25 to 75 mm 1 to 3 i
32、n. Consolidate concretes with a slump lessthan 25 mm 1 in. by vibration.NOTE 7Nonplastic concrete, such as is commonly used in the manufacture of pipe and unit masonry, is not covered by this test method.6.2 Dampen the interior of the measure and place it on a flat, level, firm surface. Remove any s
33、tanding water from the bottomof the measure. Place the concrete in the measure using the scoop described in 4.7. Move the scoop around the perimeter of themeasure opening to ensure an even distribution of the concrete with minimal segregation. Fill the measure in the number of layersrequired by the
34、consolidation method (6.3 or 6.4).6.3 RoddingPlace the concrete in the measure in three layers of approximately equal volume. Rod each layer with 25 strokesof the tamping rod when nominal 14-L 0.5-ft3 or smaller measures are used, 50 strokes when nominal 28-L 1-ft3 measuresare used, and one stroke p
35、er 20 cm2 3 in.2 of surface for larger measures. Rod each layer uniformly over the cross section withthe rounded end of the rod using the required number of strokes. Rod the bottom layer throughout its depth. In rodding this layer,use care not to damage the bottom of the measure. For each upper laye
36、r, allow the rod to penetrate through the layer being roddedand into the layer below approximately 25 mm 1 in. After each layer is rodded, tap the sides of the measure 10 to 15 times withthe appropriate mallet (see 4.6) using such force so as to close any voids left by the tamping rod and to release
37、 any large bubblesof air that may have been trapped. Add the final layer so as to avoid overfilling.6.4 Internal VibrationFill and vibrate the measure in two approximately equal layers. Place all of the concrete for each layerin the measure before starting vibration of that layer. Insert the vibrato
38、r at three different points for each layer. In compacting thebottom layer, do not allow the vibrator to rest on or touch the bottom or sides of the measure. In compacting the final layer, thevibrator shall penetrate into the underlying layer approximately 25 mm 1 in. . Take care that the vibrator is
39、 withdrawn in sucha manner that no air pockets are left in the specimen. The duration of vibration required will depend upon the workability of theconcrete and the effectiveness of the vibrator (see Note 8). Continue vibration only long enough to achieve proper consolidationof the concrete (see Note
40、 9). Observe a constant duration of vibration for the particular kind of concrete, vibrator, and measureinvolved.NOTE 8Usually, sufficient vibration has been applied as soon as the surface of the concrete becomes relatively smooth.NOTE 9Overvibration may cause segregation and loss of appreciable qua
41、ntities of intentionally entrained air.6.5 On completion of consolidation the measure must not contain a substantial excess or deficiency of concrete. An excess ofconcrete protruding approximately 3 mm 18 in. above the top of the mold is optimum.Asmall quantity of concrete may be addedto correct a d
42、eficiency. If the measure contains a great excess of concrete at completion of consolidation, remove a representativeportion of the excess concrete with a trowel or scoop immediately following completion of consolidation and before the measureis struck-off.6.6 Strike-OffAfter consolidation, strike-o
43、ff the top surface of the concrete and finish it smoothly using the flat strike-off plateso that the measure is level full. Strike-off the measure by pressing the strike-off plate on the top surface of the measure to coverabout two thirds of the surface and withdraw the plate with a sawing motion to
44、 finish only the area originally covered. Then placethe plate on the top of the measure to cover the original two thirds of the surface and advance it with a vertical pressure and asawing motion to cover the whole surface of the measure and continue to advance it until it slides completely off the m
45、easure.Incline the plate and perform final strokes with the edge of the plate to produce a smooth surface.6.7 Cleaning and WeighingAfter strike-off, clean all excess concrete from the exterior of the measure and determine the massof the concrete and measure to an accuracy consistent with the require
46、ments of 4.1.7. Calculation7.1 Density (Unit Weight)Calculate the net mass of the concrete in pounds or kilograms by subtracting the mass of themeasure, Mm, from the mass of the measure filled with concrete, Mc. Calculate the density, D, kg/m3 lb/ft3 , by dividing the netmass of concrete by the volu
47、me of the measure, Vm as follows:D 5Mc 2Mm!/Vm (1)7.2 Theoretical DensityCalculate the theoretical density as follows:T 5M/V (2)C138/C138M 1337.2.1 The absolute volume of each ingredient in cubic meters is equal to the mass of the ingredient in kilograms divided by 1000times its specific gravity. Th
48、e absolute volume of each ingredient in cubic feet is equal to the quotient of the mass of that ingredientdivided by the product of its specific gravity times 62.4 lb/ft3. For the aggregate components, base the specific gravity and masson the saturated, surface-dry condition. For cement, determine t
49、he actual specific gravity using Test Method C188. Using a valueof 3.15 is permitted for cements manufactured to meet the requirements of Specification C150.7.3 YieldCalculate the yield as follows:Yyd3!5M/D 327! (3)orYm3!5M/D (4)7.4 Relative YieldRelative yield is the ratio of the actual volume of concrete obtained to the volume as designed for the batch(see Note 10) calculated as follows:Ry 5Y/Yd (5)NOTE 10A value for
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