AASHTO T 121M T 121-2017 Standard Method of Test for Density (Unit Weight) Yield and Air Content (Gravimetric) of Concrete.pdf

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1、Standard Method of Test for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete AASHTO Designation: T 121M/T 121-17 Technical Section: 3b, Fresh Concrete Release: Group 1 (April 2017) ASTM Designation: C138/C138M-10a American Association of State Highway and Transportation Offici

2、als 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3b T 121M/T 121-1 AASHTO Standard Method of Test for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete AASHTO Designation: T 121M/T 121-17 Technical Section: 3b, Fresh Concrete Release: Group 1 (April 2017)

3、ASTM Designation: C138/C138M-10a 1. SCOPE 1.1. This method covers determination of the density (see Note 1) of freshly mixed concrete and gives formulas for calculating the yield, cement content, and the air content of the concrete. Yield is defined as the volume of concrete produced from a mixture

4、of known quantities of the component materials. 1.2. Nonplastic concrete, such as is commonly used in the manufacture of pipe and unit masonry, is not covered by this test method. 1.3. The values stated in either SI or inch-pound units shall be regarded separately as standard. The inch-pound units a

5、re shown in brackets. The values stated might not be exact equivalents; therefore, each system must be used independently of the other. Note 1Unit weight was the previous terminology used to describe the property determined by this test method, which is mass per unit volume. 1.4. The text of this te

6、st method references notes and footnotes that provide explanatory information. These notes and footnotes (excluding those in tables) shall not be considered as requirements of this test method. 1.5. This standard may involve hazardous materials, operations, and equipment. This standard does not purp

7、ort to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. WarningFresh hydraulic cementitious mixtures are caust

8、ic and may cause chemical burns to skin and tissue upon prolonged exposure. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 85, Portland Cement R 18, Establishing and Implementing a Quality Management System for Construction Materials Testing Laboratories R 60, Sampling Freshly Mixed Concrete R 61,

9、 Establishing Requirements for Equipment Calibrations, Standardizations, and Checks 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 121M/T 121-2 AASHTO T 19M/T 19, Bulk Density (“Unit Weight”) an

10、d Voids in Aggregate T 23, Making and Curing Concrete Test Specimens in the Field T 119M/T 119, Slump of Hydraulic Cement Concrete T 133, Density of Hydraulic Cement T 152, Air Content of Freshly Mixed Concrete by the Pressure Method T 196M/T 196, Air Content of Freshly Mixed Concrete by the Volumet

11、ric Method 2.2. ASTM Standards: C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 3. TERMINOLOGY 3.1. Definitions: 3.1.1. Symbols: A = air content (percentage of voids) in the concrete; C = actual cement content, kg/m3lb/yd3; Cb= mass of

12、cement in the batch, kg lb; D = density (unit weight) of concrete, kg/m3lb/ft3; M = total mass of all materials batched, kg lb (see Section 3.4); Mc= mass of the measure filled with concrete, kg lb; Mm= mass of the measure, kg lb; Ry= relative yield; T = theoretical density of the concrete computed

13、on an airfree basis, kg/m3lb/ft3 (see Section 3.1.2); V = total absolute volume of the component ingredients in the batch, m3ft3 (see Section 3.1.3); Vm= volume of the measure; Y = yield, volume of concrete produced per batch, m3 or yd3. Yd= yield, volume of concrete that the batch was designed to p

14、roduce, m3yd3; and Yf= yield, volume of concrete produced per batch, ft33.1.2. theoretical density (T)The theoretical density is, customarily, a laboratory determination. The value for the theoretical density is assumed to remain constant for all batches made using identical component ingredients an

15、d proportions. It is calculated from the equation: =T MV (1) 3.1.3. absolute volume (V)The absolute volume of each ingredient in cubic yards is equal to the quotient of the mass of the ingredient divided by the product of its specific gravity times 62.4. The absolute volume of each ingredient in cub

16、ic meters is equal to the mass of the ingredient in kilograms divided by 1000 times its specific gravity. 3.1.4. bulk specific gravity and massFor the aggregate components, the bulk specific gravity and mass should be based on the saturated surface-dry condition. For cement, the actual specific grav

17、ity should be determined by T 133. A value of 3.15 may be used for cements manufactured to meet the requirements of M 85. 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 121M/T 121-3 AASHTO 3.1.5

18、. total mass (M)The total mass of all materials batched is the sum of the masses of the cement, the fine aggregate in the condition used, the coarse aggregate in the condition used, the mixing water added to the batch, and any other solid or liquid materials used. 4. APPARATUS 4.1. BalanceA balance

19、or scale accurate to within 45 g 0.1 lb or 0.3 percent of the test load, whichever is greater, at any point within the range of use. The range of use shall be considered to extend from the mass of the measure empty to the mass of the measure plus its contents at 2600 kg/m3 160 lb/ft3. 4.2. Tamping R

20、odA round, straight steel rod, with a 16 2-mm 58 116-in. diameter. The length of the tamping rod shall be at least 100 mm 4 in. greater than the depth of the measure in which rodding is being performed but not greater than 600 mm 24 in. in overall length (see Note 2). The length tolerance for the ta

21、mping rod shall be 4 mm 18in. The rod shall have the tamping end or both ends rounded to a hemispherical tip of the same diameter as the rod. Note 2A rod length of 400 mm 16 in. to 600 mm 24 in. meets the requirements of the following AASHTO Test Methods: T 23, T 119M/T 119, T 121M/T 121, T 152, and

22、 T 196M/T 196. 4.3. Internal VibratorInternal vibrators may have rigid or flexible shafts, preferably powered by electric motors. The frequency of vibration shall be 117 Hz 7000 vibrations per min or greater while in use. The outside diameter or the side dimension of the vibrating element shall be a

23、t least 19 mm 0.75 in. and not greater than 38 mm 1.50 in. The length of the shaft shall be at least 610 mm 24 in. 4.4. MeasureA cylindrical container made of steel or other suitable metal (Note 3). The minimum capacity of the measure shall conform to the requirements of Table 1 based on the nominal

24、 size of aggregate in the concrete to be tested. All measures, except for measuring bowls of air meters, which are also used for T 121M/T 121 tests, shall conform to the requirements of T 19M/T 19. When measuring bowls of air meters are used, they shall conform to the requirements of T 152 and shall

25、 be standardized for volume as described in T 19M/T 19. The top rim of the air meter bowls shall be smooth and plane within 0.25 mm 0.01 in. Note 3The metal should not be readily subject to attack by cement paste. However, reactive materials such as aluminum alloys may be used in instances where, as

26、 a consequence of an initial reaction, a surface film is rapidly formed that protects the metal against further corrosion. Note 4The top rim is satisfactorily plane if a 0.25-mm 0.01-in. feeler gauge cannot be inserted between the rim and a piece of 6 mm0.25 in. or thicker plate glass laid over the

27、top of the measure. Note 5Standardization is a critical step to ensure accurate test results when using this apparatus. Failure to perform the standardization procedures as described herein will produce inaccurate or unreliable test results. 4.5. Strike-Off PlateA flat rectangular metal plate at lea

28、st 6 mm 1/4in. thick or a glass or acrylic plate at least 13 mm 1/2in. 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 edges of the plate shall be straight and smooth within a tolerance of 1.6 mm 1/16in. 4.6. MalletA mallet

29、 (with a rubber or rawhide head) having a mass of 600 200 g 1.25 0.50 lb for use with measures 14 L 0.5 ft3 or smaller and a mallet having a mass of 1000 200 g 2.25 0.50 lb for use with measures larger than 0.014 m3 0.5 ft3. 2017 by the American Association of State Highway and Transportation Offici

30、als.All rights reserved. Duplication is a violation of applicable law.TS-3b T 121M/T 121-4 AASHTO Table 1Capacity of Measures Nominal Maximum Size of Coarse AggregateaCapacity of Measureamm in. L ft325.0 1 6 0.2 37.5 1.5 11 0.4 50 2 14 0.5 75 3 28 1.0 112 4.5 70 2.5 150 6 100 3.5 aThe indicated size

31、 of measure shall be used to test concrete containing aggregates of a nominal maximum size equal to or smaller than that listed. The actual volume of the measure shall be at least 95 percent of the nominal volume listed. 4.7. ScoopA scoop of a size large enough so each amount of concrete obtained fr

32、om the sampling receptacle is representative and small enough so it is not spilled during placement in the measure. 5. CALIBRATION, STANDARDIZATION, AND CHECK 5.1. Unless otherwise specified, follow the requirements and intervals for equipment calibrations, standardizations, and checks in R 18. 5.2.

33、 Follow the procedures for performing equipment calibration, standardizations, and checks found in R 61. 6. SAMPLE 6.1. Obtain the sample of freshly mixed concrete in accordance with R 60. 7. PROCEDURE 7.1. Dampen the interior of the measuring bowl and place it on a flat, level, firm surface. Using

34、the scoop described in Section 4.7, place a representative sample of the concrete in the measuring bowl in equal layers. Consolidate each layer by the rodding procedure (see Section 7.3) or by vibration (see Section 7.4). Self-Consolidating Concrete (SCC) prohibits rodding and internal vibration (se

35、e Section 7.5). 7.2. Rod concretes with a slump greater than 75 mm 3 in. Rod or vibrate concrete with a slump of 25 to 75 mm 1 to 3 in. Consolidate concretes with a slump less than 25 mm 1 in. by vibration. 7.3. RoddingPlace the concrete in the measure in three layers of approximately equal volume u

36、sing the scoop described in Section 4.7. During concrete placement, move the scoop around the perimeter of the measure opening to ensure an even distribution of the concrete with minimal segregation. Rod each layer with 25 strokes of the tamping rod when the 0.014 m3 0.5 ft3 or smaller measures are

37、used and 50 strokes when the 0.028 m3 1 ft3 measure is used. Rod the bottom layer throughout its depth but the rod shall not forcibly strike the bottom of the measure. Distribute the strokes uniformly over the cross section of the measure and for the top two layers; penetrate about 25 mm 1 in. into

38、the underlying layer. After each layer is rodded, tap around the perimeter of the measure smartly 10 to 15 times with the appropriate mallet (see Section 4.6) using 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of appli

39、cable law.TS-3b T 121M/T 121-5 AASHTO such force so as to close any voids left by the tamping rod and to release any large bubbles of air that may have been trapped. Add the final layer so as to avoid overfilling. 7.4. Internal VibrationPlace the concrete in the measure in two layers of approximatel

40、y equal volume using the scoop described in Section 4.7. Place all of the concrete for each layer in the measure before starting vibration of that layer. During concrete placement, move the scoop around the perimeter of the measure opening to ensure an even distribution of the concrete with minimal

41、segregation. Insert the vibrator at three different points of each layer. In compacting the bottom layer, do not allow the vibrator to rest on or touch the bottom or side of the measure. In compacting the final layer, allow the vibrator to penetrate into the underlying layer approximately 25 mm 1 in

42、. Ensure that the vibrator is withdrawn in such a manner so that no air pockets are left in the specimen. The duration of vibration required will depend on the workability of the concrete and the effectiveness of the vibrator (Note 6). Continue vibration only long enough to achieve proper consolidat

43、ion of the concrete (Note 7). Observe a constant duration of vibration for the particular kind of concrete, vibrator, and measure involved. After each layer is vibrated, tap the sides of the measure smartly 10 to 15 times with the appropriate mallet (see Section 4.6) using such force so as to close

44、any voids left by the vibrator and to release any large bubbles of air that may have been trapped. Note 6Usually, sufficient vibration has been applied as soon as the surface of the concrete becomes relatively smooth. Note 7Overvibration may cause segregation and loss of appreciable quantities of in

45、tentionally entrained air. 7.5. Self-Consolidating ConcreteSlightly overfill the measure and fill in one continuous lift. Rodding, tapping the sides of the measure, and vibrating of SCC is prohibited. 7.6. The filled measure must not contain a substantial excess or deficiency of concrete. An excess

46、of concrete protruding approximately 3 mm1/8in. above the top of the mold is optimum. A small quantity of concrete may be added to correct a deficiency. If the measure contains a great excess of concrete at completion of consolidation, remove a representative portion of the excess concrete with a tr

47、owel or scoop immediately following completion of consolidation and before the measure is struck off. 7.7. Strike-OffStrike off the top surface of the concrete and finish it smoothly with the flat strike-off plate so that the measure is level full. Strike off the concrete by pressing the strike-off

48、plate on the top surface of the measure to cover about two thirds of the surface and withdraw the plate with a sawing motion to finish only the area originally covered. Then place the plate on the top of the measure to cover the original two thirds of the surface and advance it with a vertical press

49、ure and a sawing motion to cover the whole surface of the measure. Hold the plate at an incline and apply the final strokes to produce a smooth finished surface. 7.8. Mass DeterminationClean all excess concrete from the exterior of the measure and determine the net mass of the concrete in the measure with a balance that meets the requirements of Section 4.1. 8. CALCULATIONS 8.1. Density (Unit Mass)Calculate the net mass of the c