1、Standard Method of Test for Air Content of Freshly Mixed Concrete by the Pressure Method AASHTO Designation: T 152-17 Technical Section: 3b, Fresh Concrete Release: Group 1 (April 2017) ASTM Designation: C231/C231M-14 American Association of State Highway and Transportation Officials 444 North Capit
2、ol Street N.W., Suite 249 Washington, D.C. 20001 TS-3b T 152-1 AASHTO Standard Method of Test for Air Content of Freshly Mixed Concrete by the Pressure Method AASHTO Designation: T 152-17 Technical Section: 3b, Fresh Concrete Release: Group 1 (April 2017) ASTM Designation: C231/C231M-14 1. SCOPE 1.1
3、. This method covers determination of the air content of freshly mixed concrete from observation of the change in volume of concrete with a change in pressure. 1.2. This method is intended for use with concretes and mortars made with relatively dense aggregates for which the aggregate correction fac
4、tor can be satisfactorily determined by the technique described in Section 7. It is not applicable to concretes made with lightweight aggregates, air-cooled blast-furnace slag, or aggregates of high porosity. In these cases, T 196M/T 196 should be used. This test method is also not applicable to non
5、plastic concrete such as is commonly used in the manufacture of pipe and concrete masonry units. 1.3. The text of this standard references notes and footnotes that provide explanatory information. These notes and footnotes (excluding those in tables and figures) shall not be considered as requiremen
6、ts for this standard. 1.4. The values stated in inch-pound units are to be regarded as the standard. 1.5. 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 h
7、ealth practices 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 18, Establishing and Implementing
8、 a Quality Management System for Construction Materials Testing Laboratories R 39, Making and Curing Concrete Test Specimens in the Laboratory R 60, Sampling Freshly Mixed Concrete R 61, Establishing Requirements for Equipment Calibrations, Standardizations, and Checks T 23, Making and Curing Concre
9、te Test Specimens in the Field T 119M/T 119, Slump of Hydraulic Cement Concrete 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 152-2 AASHTO T 121M/T 121, Density (Unit Weight), Yield, and Air Co
10、ntent (Gravimetric) of Concrete T 196M/T 196, Air Content of Freshly Mixed Concrete by the Volumetric Method 2.2. ASTM Standards: C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials E177, Standard Practice for Use of the Terms Precision and
11、 Bias in ASTM Test Methods13. SIGNIFICANCE AND USE 3.1. This test method covers the determination of the air content of freshly mixed concrete. The test determines the air content of freshly mixed concrete exclusive of any air that exists inside voids within aggregate particles. For this reason, it
12、is applicable to concrete made with relatively dense aggregate particles and requires determination of the aggregate correction factor. (See Sections 7.1 and 10.1.) 3.2. This test method and T 121M/T 121 and T 196M/T 196 provide pressure, gravimetric, and volumetric procedures, respectively, for det
13、ermining the air content of freshly mixed concrete. The pressure procedure of this test method gives substantially the same air content as the other two test methods for concrete made with dense aggregates. 3.3. The air content of hardened concrete may be either higher or lower than that determined
14、by this test method. This depends on the methods and amount of consolidation effort applied to the concrete 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 co
15、mparison; environmental exposure; stage in the delivery, placement, and consolidation processes at which the air is determined, that is, before or after the concrete goes through a pump; and other factors. 4. APPARATUS 4.1. Air MetersThere are available satisfactory apparatus of two basic operationa
16、l designs employing the principle of Boyles Law. For purposes of reference herein these are designated Meter Type A and Meter Type B. 4.1.1. Meter Type AAn air meter consisting of a measuring bowl and cover assembly (Figure 1) conforming to the requirements of Sections 4.2 and 4.3. The operational p
17、rinciple of this meter consists of introducing water to a predetermined height above a sample of concrete of known volume and the application of a predetermined air pressure over the water. The determination consists of the reduction in volume of the air in the concrete sample by observing the amoun
18、t the water level is lowered under the applied pressure, the latter amount being standardized in terms of percent of air in the concrete sample. Note 1Standardization is a critical step to ensure accurate test results when using this apparatus. Failure to perform the standardization procedures as de
19、scribed herein will produce inaccurate or unreliable test results. 4.1.2. Meter Type BAn air meter consisting of a measuring bowl and cover assembly (Figure 2) conforming to the requirements of Sections 4.2 and 4.3. The operational principle of this meter consists of equalizing a known volume of air
20、 at a known pressure in a sealed air chamber with the unknown volume of air in the concrete sample, the dial on the pressure gauge being standardized in terms of percent air for the observed pressure at which equalization takes place. Working pressures of 7.5 to 30.0 psi (51 to 207 kPa) have been us
21、ed satisfactorily. 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 152-3 AASHTO 4.2. Measuring BowlThe measuring bowl shall be essentially cylindrical in shape, made of steel, hard metal, or othe
22、r hard material not readily attacked by the cement paste, having a minimum diameter equal to 0.75 to 1.25 times the height, and a capacity of at least 0.20 ft3(5.7 L). It shall be flanged or otherwise constructed to provide for a pressure-tight fit between the measuring bowl and cover assembly. The
23、interior surfaces of the measuring bowl and surfaces of rims, flanges, and other component fitted parts shall be machined smooth. The measuring bowl and cover assembly shall be sufficiently rigid to limit the expansion factor, D, of the apparatus assembly (Annex A1.5) to not more than 0.1 percent of
24、 air content on the indicator scale when under normal operating pressure. . Note: A1= h1 h2when measuring bowl contains concrete as shown in this figure; when measuring bowl contains only aggregate and water, h1 h2= G (aggregate correction factor). A1 G = A (entrained air content of concrete). Figur
25、e 1Illustration of the Pressure Method for Air Content: Type A Meter ZeroPressureMarkAir PumpPressure Gauge(Indicating OperatingPressure P)WaterClamph1(Reading atPressure P)Pressure LowersLevel of Concreteand Water in TubeConcreteZeroPressureh2(Reading atZero Pressureafter Releaseof Pressure P)A B C
26、0000123456700A1h1h2 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 152-4 AASHTO Figure 2Schematic Diagram: Type B Meter 4.3. Cover Assembly: 4.3.1. The cover assembly shall be made of steel, har
27、d metal, or other hard material not readily attacked by the cement paste. It shall be flanged or otherwise constructed to provide for a pressure-tight fit between measuring bowl and cover assembly and shall have machined-smooth interior surfaces contoured to provide an air space above the level of t
28、he top of the measuring bowl. The cover shall be sufficiently rigid to limit the expansion factor of the apparatus assembly as prescribed in Section 4.2. 4.3.2. The cover assembly shall be fitted with a means of direct reading of the air content. The cover for the Type A meter shall be fitted with a
29、 standpipe, which may be a transparent graduated tube or may be a metal tube of uniform bore with a glass water gauge attached. In the Type B meter, the dial of the pressure gauge shall be standardized to indicate the percent of air. Graduations shall be provided for a range in air content of at lea
30、st 8 percent, easily readable to 0.1 percent, as determined by the proper air pressure standardization test. 4.3.3. The cover assembly shall be fitted with air valves, air bleeder valves, and petcocks for bleeding off or through which water may be introduced as necessary for the particular meter des
31、ign. Suitable means for clamping the cover to the measuring bowl shall be provided to make a pressure-tight seal without entrapping air at the joint between the flanges of the cover and measuring bowl. A suitable hand pump shall be provided with the cover, either as an attachment or as an accessory.
32、 4.4. Standardization VesselA measure having an internal volume equal to a percent of the volume of the measuring bowl corresponding to the approximate percent of air in the concrete to be tested; or, if smaller, it shall be possible to check standardization of the meter indicator at the approximate
33、 percent of air in the concrete to be tested by repeated filling of the measure. When the design of the meter requires placing the standardization vessel within the measuring bowl to check standardization, the measure shall be cylindrical in shape and of an inside depth 1/2in. (13 mm) less than that
34、 of the measuring bowl. Note 2A satisfactory standardization vessel to place within the measuring bowl may be machined for No. 16 gauge brass tubing, of a diameter to provide the volume desired, to which a 2017 by the American Association of State Highway and Transportation Officials.All rights rese
35、rved. Duplication is a violation of applicable law.TS-3b T 152-5 AASHTO brass disk 1/2in. thick is soldered to form an end. When design of the meter requires withdrawing of water from the water-filled measuring bowl and cover assembly to check standardization, the measure may be an integral part of
36、the cover assembly or may be a separate cylindrical measure similar to the above described cylinder. 4.5. The designs of various available types of air meters are such that they differ in operating techniques and, therefore, all of the items described in Sections 4.6 through 4.16 may not be required
37、. The items required shall be those necessary for use with the particular design of apparatus used to satisfactorily determine air content in accordance with the procedures prescribed herein. 4.6. Coil Spring or Other Devicefor Holding Standardization Cylinder in Place. 4.7. Spray TubeA brass tube o
38、f appropriate diameter, which may be an integral part of the cover assembly or which may be provided separately. It shall be so constructed that when water is added to the container, it is sprayed to the walls of the cover in such a manner as to flow down the sides causing a minimum of disturbance t
39、o the concrete. 4.8. TrowelA standard brick masons trowel. 4.9. Tamping RodA round, straight steel rod, with a 58in. 116-in. (16 mm 2-mm) diameter. The length of the tamping rod shall be at least 4 in. (100 mm) greater than the depth of the measure in which rodding is being performed but not greater
40、 than 24 in. (600 mm) in overall length (see Note 3). The length tolerance for the tamping rod shall be 18in. (4 mm). The rod shall have the tamping end or both ends rounded to a hemispherical tip of the same diameter as the rod. Note 3A rod length of 16 in. (400 mm) to 24 in. (600 mm) meets the req
41、uirements of the following AASHTO Test Methods: T 23, T 119M/T 119, T 121M/T 121, T 152, and T 196M/T 196. 4.10. MalletA mallet (with a rubber or rawhide head) weighing approximately 1.25 0.50 lb (0.57 0.23 kg) for use with measures of 0.5 ft3(14L) or smaller and a mallet weighing approximately 2.25
42、 0.50 lb (1.02 0.23 kg) for use with measures larger than 0.5 ft3(14 L). 4.11. Strike-Off BarA flat straight bar of steel or other suitable metal at least 1/8in. (3 mm) thick and 3/4in. (20 mm) wide by 12 in. (300 mm) long. 4.12. Strike-Off PlateA flat rectangular metal plate at least 1/4in. (6 mm)
43、thick or a glass or acrylic plate at least 1/2in. (12 mm) thick with a length and width at least 2 in. (50 mm) 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 1/16in. (1.5 mm). 4.13. FunnelWith the spout
44、fitting into a spray tube. 4.14. Measure for WaterHaving the necessary capacity to fill the indicator with water from the top of the concrete to the zero mark. 4.15. VibratorAs described in R 39. 4.16. Sieves11/2 in. (37.5 mm) with not less than 2 ft2(0.19 m2) of sieving area. 4.17. ScoopOf a size l
45、arge enough so each amount of concrete obtained from the sampling receptacle is representative and small enough so it is not spilled during placement in the measuring bowl. 2017 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation
46、of applicable law.TS-3b T 152-6 AASHTO 5. CALIBRATIONS, STANDARDIZATIONS, AND CHECKS 5.1. Unless otherwise specified, follow the requirements and intervals for equipment calibrations, standardizations, and checks in R 18. 5.2. Follow the procedures for performing equipment calibrations, standardizat
47、ions, and checks found in R 61. 6. STANDARDIZATION OF APPARATUS 6.1. Make standardization tests in accordance with procedures prescribed in the annex. Rough handling will affect the standardization of both Type A and Type B meters. Changes in barometric pressure will affect the standardizations of t
48、he Type A meter but not the Type B meter. The steps described in Sections A1.2 to A1.6, as applicable to the meter type under consideration, are prerequisites for the final standardization test to determine the operating pressure, P, on the pressure gauge of the Type A meter as described in Section
49、A1.7 or to determine the accuracy of the graduations indicating air content on the dial face of the pressure gauge of the Type B meter. Normally, the steps in Sections A1.2 to A1.6 need be made only once (at the time of initial standardization) or only occasionally to check volume constancy of the standardization cylinder and measuring bowl. On the other hand, the standardization test described in Sections A1.8 and A1.9, as applicable to the meter type being standardized, must be made as frequently as necessary to ensu
