1、Standard Method of Test for Characterization of the Air-Void System of Freshly Mixed Concrete by the Sequential Pressure Method AASHTO Designation: TP 118-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3b TP 11
2、8-1 AASHTO Standard Method of Test for Characterization of the Air-Void System of Freshly Mixed Concrete by the Sequential Pressure Method AASHTO Designation: TP 118-1511. SCOPE 1.1. This method covers determination of the air content and system air metric (SAM) number of freshly mixed concrete from
3、 observation of the change in volume of concrete with a sequential change in test pressure. 1.2. This method is intended for use with concretes and mortars made with aggregates for which the aggregate correction factor can be satisfactorily determined by the technique described in Section 7. It is n
4、ot applicable to concretes made with light-weight aggregates, air-cooled blast-furnace slag, or other aggregates with high porosity. This test method is also not applicable to nonplastic fresh concrete such as is commonly used in the manufacture of pipe and concrete masonry units. 1.3. The text of t
5、his standard references notes and footnotes that provide explanatory information. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements for this standard. 1.4. The values stated in inch-pound units are to be regarded as the standard. 1.5. This stan
6、dard 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 and determine the applicability of regulatory limitations prior to use. WarningFresh hydraulic ceme
7、ntitious 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 a Quality Management System for Construction Materials Testing Laboratories R 39, Making and Curing Concrete Test
8、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 Concrete Test Specimens in the Field T 119M/T 119, Slump of Hydraulic Cement Concrete T 121M/T 121, Density (Unit Weight)
9、, Yield, and Air Content (Gravimetric) of Concrete T 152, Air Content of Freshly Mixed Concrete by the Pressure Method T 196M/T 196, Air Content of Freshly Mixed Concrete by the Volumetric Method 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Dupl
10、ication is a violation of applicable law.TS-3b TP 118-2 AASHTO 2.2. ASTM Standards: C192/C192M, Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory C457/C457M, Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
11、 C666/C666M, Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials D5720, Standard Practice for Static Calibration of Electronic Transducer-Based Pressure Measureme
12、nt Systems for Geotechnical Purposes E177, Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods22.3. American Concrete Institute: ACI 201.2R, Guide to Durable Concrete 2.4. Other Reference: Powers, T. C., “Void Spacing as a Basis for Producing Air-Entrained Concrete,” ACI J
13、ournal, Part 2, Proc. Vol. 50, 1954. 3. SIGNIFICANCE AND USE 3.1. This test method covers the determination of the air content and the system air metric (SAM) number of freshly mixed concrete. The test determines the air content of freshly mixed concrete exclusive of any air that exists inside voids
14、 within aggregate particles. For this reason, it is applicable only to concrete made for which the aggregate correction factor can be determined. (See Sections 7.1 and 10.1.) 3.2. This test method and T 152, T 121M/T 121, and T 196M/T 196 provide sequential pressure, static pressure, gravimetric, an
15、d volumetric procedures, respectively, for determining the air content of freshly mixed concrete. The sequential pressure procedure of this test method gives substantially the same air content as the other test methods for concrete made with dense aggregates. The sequential pressure procedure of thi
16、s test method also gives the SAM number, which can be used to estimate the freeze-thaw durability of the paste in a hardened concrete mixture. 3.3. The air content of the same hardened concrete mixture may be either higher or lower than determined by this test method. This depends upon the methods a
17、nd amount of consolidation effort applied to the concrete from which the hardened concrete specimen is taken; uniformity and stability of the air voids in the fresh and hardened concrete; accuracy of the microscopic examination to measure the hardened air content, if used; time of comparison; enviro
18、nmental exposure; stage in the delivery, placement, and consolidation processes at which the air content is determined, that is, before or after the concrete goes through a pump; and other factors. 3.4. In cases where the air content did not vary between the fresh and hardened concrete, this test me
19、thod has shown to predict freeze-thaw durability as well as the spacing factor as measured by ASTM C457/C457M. 4. APPARATUS 4.1. Air MeterA device consisting of a measuring bowl and cover assembly as shown in Figure 1 conforming to the requirements of Sections 4.2 and 4.3. The operational principle
20、of this meter consists of sequentially equalizing known volumes of air in a sealed air chamber, at a series of 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b TP 118-3 AASHTO known pressures, with
21、the unknown volume of air in the concrete sample placed in the measuring bowl. A digital pressure gauge with 0.01 psi (0.07 kPa) accuracy shall be used. Digital gauges with maximum pressures of 50.0 psi (344.7 kPa) have been used satisfactorily. The digital gauge shall be able to compute and report
22、the air content within 0.1 percent and the SAM number to 0.01 psi (0.07 kPa). The cover assembly shall be fixed to the measuring bowl with the same uniform pressure that was used during the calibration of the meter. Figure 1Schematic of the Assembled Meter 4.2. Measuring BowlThe measuring bowl shall
23、 be essentially cylindrical in shape, made of steel, hard metal, or other 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
24、a pressure-tight fit between the bowl and cover assembly. The interior surfaces of the 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 of the apparatus assembly to
25、not more than 0.1 percent of air content on the indicator scale as described in Section A1.1.1 through A1.1.5. 4.3. Cover Assembly: 4.3.1. The cover assembly shall be made of steel, hard metal, or other hard material not readily attacked by the cement paste. It shall be flanged or otherwise construc
26、ted to provide for a pressure-tight fit between bowl and cover assembly and shall have machined-smooth interior surfaces contoured to provide an air space above the level of the top of the measuring bowl. The cover shall be sufficiently rigid to limit the expansion as prescribed in Section 4.2. 4.3.
27、2. 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 design. Suitable means for clamping the cover to the bowl shall be provided to make a pressure-tight seal without en
28、trapping air at the joint between the flanges of the cover and bowl. The clamping method should provide a uniform pressure along the seal that can be verified by the user. A suitable hand pump shall be provided with the cover, either as an attachment or as an accessory. 2015 by the American Associat
29、ion of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b TP 118-4 AASHTO 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
30、air in the concrete to be tested; or, if smaller, it shall be possible to check standardization of the meter indicator at the approximate 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 th
31、e measuring bowl to check standardization, the measure shall be cylindrical in shape and of an inside depth 1/2in. (13 mm) less than that of the bowl. Note 1A satisfactory standardization vessel to place within the measure bowl may be machined from No. 16 gauge brass tubing, of a diameter to provide
32、 the volume desired, to which a brass disk 1/2in. thick is soldered to form an end. When design of the meter requires withdrawing of water from the water-filled bowl and cover assembly to check standardization, the measure may be an integral part of the cover assembly or may be a separate cylindrica
33、l measure similar to the above described cylinder. 4.5. TrowelA standard brick masons trowel. 4.6. Tamping RodA round, straight steel rod, with a 58 116-in. (16 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 be
34、ing performed but not greater than 24 in. (600 mm) in overall length (Note 2). 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 2A rod length of 16 in. (400 mm) to 24 i
35、n. (600 mm) 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. 4.7. 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 0.25 ft3(14 L) or smaller. 4.8. Strike-O
36、ff 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. 4.9. Strike-Off PlateA flat, rectangular metal plate at least 1/4in. (6 mm) thick or a glass or acrylic plate at least 1/2in. (12 mm) thick with a length and widt
37、h 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). 4.10. FunnelWith the spout fitting into a spray tube. 4.11. VibratorAs described in R 39. 4.12. ScoopOf a size la
38、rge enough so that each amount of concrete obtained from the sampling receptacle is representative and small enough that it is not spilled during placement in the measuring bowl. 5. CALIBRATION, STANDARDIZATION, AND CHECK 5.1. Unless otherwise specified, follow the requirements and intervals for equ
39、ipment calibration, standardizations, and checks in R 18. 5.2. Follow the procedures for performing equipment calibration, standardizations, and checks found in R 61. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of app
40、licable law.TS-3b TP 118-5 AASHTO 6. STANDARDIZATION OF APPARATUS 6.1. Make standardization tests in accordance with procedures prescribed in the Annex. Rough handling, change in volume, or adjustment of the clamp arms will affect the standardization of the meter. The steps described in Sections A1.
41、1.1 to A1.1.5, as applicable to the meter type under consideration, are prerequisites for the final standardization test to ensure the meter is reading accurately. Standardization shall be made as frequently as necessary to ensure the correct air content is being indicated on the air content scale.
42、The pressure gauge shall be calibrated annually in accordance with ASTM D5720 to ensure that it is reading correctly. 6.2. Standardization RecordsInformation to be maintained in the records shall include size of the standardization vessel used and the reading of the meter at the standardization test
43、 point(s). 7. DETERMINATION OF AGGREGATE CORRECTION FACTOR 7.1. ProcedureDetermine the aggregate correction factor on a combined sample of fine and coarse aggregate as directed in Sections 7.2 to 7.4. It is determined by applying 14.5 0.05 psi (100 0.3 kPa) to a sample of inundated fine and coarse a
44、ggregate in approximately the same moisture condition, amount, and proportions occurring in the concrete sample under test. 7.2. Aggregate Sample SizeCalculate the weights of fine and coarse aggregate present in the sample of fresh concrete whose air content is to be determined, as follows: Fs= S/B
45、Fb(1) Cs= S/B Cb(2) where: Fs= weight of fine aggregate in concrete sample under test, lb (kg); S = volume of concrete sample (same as volume of measuring bowl), ft3(m3); B = volume of concrete produced per batch (Note 3), ft3(m3); Fb= total weight of fine aggregate in the moisture condition used in
46、 batch, lb (kg); Cs= weight of coarse aggregate in concrete sample under test, lb (kg); and Cb= total weight of coarse aggregate in the moisture condition used in batch, lb (kg). Note 3The volume of concrete produced per batch can be determined in accordance with applicable provisions of T 121M/T 12
47、1. Note 4The term “weight” is temporarily used in this standard because of established trade usage. The word is used to mean both “force” and “mass” and care should be taken to determine which is meant in each case (SI unit for force = newton and for mass = kilogram). 7.3. Placement of Aggregate in
48、Measuring BowlMix representative samples of fine aggregate, Fs, and coarse aggregate, Cs. Place a standardization vessel approximately equivalent to the volume of air that would be contained in a typical concrete sample in the measuring bowl. Fill the measuring bowl one-third full with water. Place
49、the mixed aggregate, a small amount at a time, into the measuring bowl; if necessary, add additional water so as to inundate all of the aggregate. Add each scoopful in a manner that will entrap as little air as possible, remove accumulations of foam promptly, and lightly rod the upper 1 in. (25 mm) of the aggregate about 812 times and tap the sides of the measuring bowl. Stir after each addition of aggregate to eliminate entrapped air. Do not allow water in the standardization vessel. 7.4. Aggregate Correction
