1、Standard Method of Test for Air Content of Freshly Mixed Concrete by the Volumetric Method AASHTO Designation: T 196M/T 196-11 (2015) ASTM Designation: C173/C173M-10 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-
2、3b T 196M/T 196-1 AASHTO Standard Method of Test for Air Content of Freshly Mixed Concrete by the Volumetric Method AASHTO Designation: T 196M/T 196-11 (2015) ASTM Designation: C173/C173M-10 1. SCOPE 1.1. This test method covers determination of the air content of freshly mixed concrete containing a
3、ny type of aggregate, whether it be dense, cellular, or lightweight. 1.2. The values stated in either inch-pound or SI units shall be regarded separately as standard. The inch-pound units are shown in brackets. The values stated are not exact equivalents; therefore each system must be used independe
4、ntly of the other. Combining values from the two units may result in nonconformance. 1.3. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices
5、and determine the applicability of regulatory limitations prior to use. WarningFresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 60, Sampling Freshly Mixed Concrete T 19M/T 19, B
6、ulk Density (“Unit Weight”) and Voids in Aggregate T 23, Making and Curing Concrete Test Specimens in the Field T 119M/T 119, Slump of Hydraulic Cement Concrete T 121M/T 121, Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete T 152, Air Content of Freshly Mixed Concrete by the P
7、ressure Method 2.2. ASTM Standard: C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 3. SIGNIFICANCE AND USE 3.1. This test covers the determination of the air content of freshly mixed concrete. It measures the air contained in the mortar
8、 fraction of the concrete but is not affected by air that may be present inside porous aggregate particles. Therefore, this is the appropriate test to determine the air content of concretes containing lightweight aggregates, air-cooled slag, and highly porous or vesicular natural aggregates. 2016 by
9、 the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 196M/T 196-2 AASHTO 3.2. This test method requires the addition of sufficient isopropyl alcohol, when the meter is initially being filled with water, so t
10、hat after the first or subsequent rolling, little or no foam collects in the neck of the top section of the meter. If more foam is present than that equivalent to 2 percent air above the water level, the test is declared invalid and must be repeated using a larger quantity of alcohol. Addition of al
11、cohol to dispel foam any time after the initial filling of the meter to the zero mark is not permitted. 3.3. The air content of hardened concrete may be either higher or lower than that determined by this test method. This depends upon the methods and amounts of consolidation effort applied to the c
12、oncrete from which the hardened concrete specimen is taken; uniformity and stability of the air bubbles in the fresh and hardened concrete; accuracy of the microscopic examination, if used; time of comparison; environmental exposure; stage in the delivery, placement, and consolidation processes at w
13、hich the air content of the unhardened concrete is determined, that is, before or after the concrete goes through a pump; and other factors. 4. APPARATUS 4.1. Air MeterAn air meter consisting of a bowl and a top section (Figure 1) conforming to the following requirements: 4.1.1. The bowl and top sec
14、tions shall be of sufficient thickness and rigidity to withstand rough field use. The material shall not be attacked by high pH cement paste, deform when stored at high temperatures in closed spaces, or become brittle or crack at low temperatures. A watertight seal must be obtained when the top sect
15、ion is attached to the bowl. Figure 1Apparatus for Measuring Air Content of Fresh Concrete by Volumetric Method 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 196M/T 196-3 AASHTO 4.1.2. BowlThe
16、bowl shall have a diameter equal to 1 to 1.25 times the height and be constructed with a flange at or near the top surface. Bowls shall not have a capacity of less than 2.0 L 0.075 ft3. 4.1.3. Top SectionThe top section shall have a capacity at least 20 percent larger than the bowl and shall be equi
17、pped with a flexible gasket and a device to attach the top section to the bowl and make a watertight connection. The top section shall be equipped with a transparent scale, graduated in increments not greater than 0.5 percent from zero at the top, to 9 percent or more of the volume of the bowl. Grad
18、uations shall be accurate to 0.1 percent by volume of the bowl. The upper end of the neck shall have a watertight cap that will maintain a seal when the meter is inverted and rolled. 4.2. FunnelA funnel with a spout of a size permitting it to be inserted through the neck of the top section and long
19、enough to extend to a point just above the bottom of the top section. The discharge end of the spout shall be so constructed that when water is added to the container there will be a minimum disturbance of the concrete. 4.3. Tamping RodA round, straight steel rod, with a 16 2-mm 58in. 116-in. diamet
20、er. 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 1). The length tolerance for the tamping rod shall be 4 mm 18in. The rod shall have the tamping en
21、d or both ends rounded to a hemispherical tip of the same diameter as the rod. Note 1A 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 T 196M/T 196. 4.4. Strike-Off BarA flat, straight steel bar a
22、t least 3 by 20 by 300 mm 0.125 by 0.75 by 12 in., or a flat, straight, high-density polyurethane bar, or other plastic of equal or greater abrasion resistance, at least 6 by 20 by 300 mm1/4by 3/4by 12 in. 4.5. Calibrated CupA metal or plastic cup either having a capacity of or being graduated in in
23、crements equal to 1.0 0.04 percent of the volume of the bowl of the air meter. The calibrated cup is only to be used to add water when the concrete air content exceeds 9 percent or the calibrated range of the meter. 4.6. Measuring Vessel for Isopropyl AlcoholA vessel with a minimum capacity of 500 m
24、L 1 pt with graduations not larger than 100 mL 4 oz for measuring a quantity of isopropyl alcohol. 4.7. SyringeA rubber syringe having a capacity of at least 50 mL 2 oz. 4.8. Pouring Vessel for WaterA container of approximately 1 L 1 qt capacity. 4.9. ScoopOf a size large enough so each amount of co
25、ncrete obtained from the sampling receptacle is representative and small enough so it is not spilled during placement in the bowl. 4.10. Isopropyl AlcoholUse 70 percent by volume isopropyl alcohol (approximately 65 percent by mass) (Note 2). Other foam-dispersing agents are permitted if tests demons
26、trate that the use of the agent does not change the indicated air content, in the amounts being used, by more than 0.1 percent or if correction factors are developed similar to those in Table 1. When other dispersing agents are used, a copy of the records documenting the testing or calculations shal
27、l be available in the laboratory. Note 2Seventy percent isopropyl alcohol is commonly available as rubbing alcohol. More concentrated grades can be diluted with water to the required concentration. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Du
28、plication is a violation of applicable law.TS-3b T 196M/T 196-4 AASHTO Table 1Correction for the Effect of Isopropyl Alcohol on Air Meter Reading 70% Isopropyl Alcohol Used Correction (Subtract)apt oz L 0.5 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 0.3 4.0 64 1.9 0.6 5.0 80 2
29、.4 0.9 aSubtract from final meter reading. bCorrections less than 0.125 are not significant and are to be applied only when 1.2 L 2.5 pt or more alcohol is used. The effect occurs when the meter is inverted after being filled with an alcohol-water solution, which then becomes further diluted when it
30、 is mixed with the water in the concrete. The values given are for air meters that have a bowl volume of 2.1 L 0.075 ft3 and a top section that is 1.2 times the volume of the bowl. 4.11. MalletA mallet (with a rubber or rawhide head) with a mass of approximately 600 200 g 1.25 0.5 lb. 5. CALIBRATION
31、 5.1. Calibrate the meter and calibrated cup initially and at three-year intervals or whenever there is reason to suspect damage or deformation of the meter or calibrated cup. 5.2. Determine the volume of the bowl, with an accuracy of at least 0.1 percent, by determining the mass of water required t
32、o fill it at room temperature and dividing this weight by the density of water at the same temperature. Follow the calibration procedure outlined in T 19M/T 19. 5.3. Determine the accuracy of the graduations on the neck of the top section of the air meter by filling the assembled measuring bowl and
33、top section with water to a preselected air content graduation and then determining the quantity of 21.1C 70F water required to fill the meter to the zero mark. The quantity of water added shall equal the preselected air content graduation within 0.1 volume percent of the measuring bowl. Repeat the
34、procedure to check a minimum of three gradations within the expected range of use. 5.3.1. Add water in increments of 1.0 percent of the volume of the bowl to check accuracy throughout the graduated range of air content. The error at any point throughout the graduated range shall not exceed 0.1 perce
35、nt of air. 5.4. Determine the volume of the calibrated cup using water at 21.1C 70F by the method outlined in Section 5.2. A quick check can be made by adding one or more calibrated cups of water to the assembled apparatus and observing the increase in the height of the water column after filling to
36、 a given level. 6. SAMPLING 6.1. Obtain the sample of freshly mixed concrete in accordance with R 60. If the concrete contains coarse aggregate particles that would be retained on a 37.5-mm 11/2-in. sieve, wet-sieve a representative sample over a 25-mm 1-in. sieve to yield somewhat more than enough
37、material to fill the measuring bowl. The wet-sieving procedure is described in R 60. Carry out the wet-sieving operation with the minimum practicable disturbance of the mortar. Make no attempt to wipe adhering mortar from coarse aggregate particles retained on the sieve. 2016 by the American Associa
38、tion of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 196M/T 196-5 AASHTO 7. PROCEDURE 7.1. Rodding and TappingWet the inside of the bowl and dry it to a damp, not shiny, appearance. Using the scoop described in Section 4.9, fill
39、 the bowl with freshly mixed concrete in two layers of equal depth. Rod each layer 25 times uniformly over the cross section with the tamping rod. Do not forcibly strike the bottom of the bowl when rodding the first layer. When rodding the second layer, penetrate the prior layer approximately 25 mm
40、1 in. After each layer is rodded, tap the sides of the measure 10 to 15 times with the mallet to close any voids left by the tamping rod and to release any large bubbles of air that may have been trapped. After tapping the final layer, a slight excess of concrete, 3 mm 1/8 in. or less, above the rim
41、 is acceptable. Add or remove a representative sample of concrete if necessary to obtain the required amount of concrete. 7.2. Striking OffAfter rodding and tapping of the second layer, strike off the excess concrete with the strike-off bar until the surface is flush with the top of the bowl. Wipe t
42、he flange of the bowl clean. 7.3. Adding WaterWet the inside of the top section of the meter, including the gasket. Attach the top section into position on the bowl, and then insert the funnel. Add at least 0.5 L 1 pt of water followed by the selected amount (Note 3) of isopropyl alcohol. Record the
43、 amount of isopropyl alcohol added. Continue adding water until it appears in the graduated neck of the top section (Note 4). Remove the funnel. Adjust the liquid level until the bottom of the meniscus is level with the zero mark. A rubber syringe is useful for this purpose. Attach and tighten the w
44、atertight cap. Note 3The amount of isopropyl alcohol necessary to obtain a stable reading and a minimum of foam at the top of the water column will depend upon a number of factors. Many concretes made with less than 300 kg/m3500 lb/yd3 of cement and air contents less than 4 percent may require less
45、than 200 mL 0.5 pt of alcohol. Some high-cement mixes made with silica fume that have air contents of 6 percent or more may require more than 1400 mL 3 pt of alcohol. The amount required will vary with the concrete air content, the amount and type of air-entraining admixture, the cement content and
46、cement alkali content, and perhaps other factors. Generally, the amount of alcohol necessary can be established for given mixture proportions and should not change greatly during the course of a job. Note 4When, if ever, it is necessary to use more than 2.0 L 4 to 4.5 pt of isopropyl alcohol, it may
47、 be necessary to restrict the amount of water added initially to avoid overfilling the meter. However, it is desirable to add at least some water initially to aid in mixing the alcohol and limit the contact of the concentrated alcohol with the top surface of the concrete. 7.4. Displace the volume of
48、 air in the concrete specimen using these procedures: 7.4.1. Free the Concrete from the BaseQuickly invert the meter, shake the base horizontally, and return the meter to the upright position. To prevent the aggregate from lodging in the neck of the unit, do not keep it inverted for more than 5 s at
49、 a time. Repeat the inversion and shaking process for a minimum of 45 s and until the concrete has broken free and the aggregate can be heard moving in the meter as it is inverted. 7.4.2. RollingPlace one hand on the neck of the meter and the other on the flange. Using the hand on the neck, tilt the top of the meter approximately 45 degrees from the vertical position with the bottom edge of the base of the meter resting on the floor or on the work surface. Maintain this
