1、Standard Method of Test for Determining Air Content of Hardened Portland Cement Concrete by High-Pressure Air Meter AASHTO Designation: T 356-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3c T 356-1 AASHTO Sta
2、ndard Method of Test for Determining Air Content of Hardened Portland Cement Concrete by High-Pressure Air Meter AASHTO Designation: T 356-1511. SCOPE 1.1. This test method covers laboratory determination of the air content of hardened portland cement concrete with the use of the high-pressure air m
3、eter. This determination is made from the observation of change in linear piston movement with a specimen in the test chamber from that of the linear piston movement with no specimen in the test chamber. This change is due to a replacement of specific volume of compressible air by a specific volume
4、of incompressible water. 1.2. This procedure may involve hazardous materials, operations, and equipment. This procedure does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this procedure to consult and establish appropriate safety a
5、nd health practices and determine the applicability of regulatory limitation prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: T 121M/T 121, Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete T 152, Air Content of Freshly Mixed Concrete by the Pressure Method 3. TERMI
6、NOLOGY 3.1. Definitions: 3.1.1. linear piston movement (LPM)the travel of the hydraulic piston with a specimen in the test chamber. 3.1.2. initial value (INIT)the stabilized travel of the hydraulic piston with no specimen in the test chamber. 3.1.3. saturated surface-dry (SSD)the saturated surface-d
7、ry mass (weight) of the specimen. 4. SIGNIFICANCE AND USE 4.1. This test method covers determination of the air content of hardened concrete exclusive of any air that may be inside voids within aggregate particles. Therefore, determination of an aggregate correction factor, in accordance with the ap
8、plicable requirements of T 152, is required. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-2 AASHTO 5. APPARATUS 5.1. High-Pressure Air Meter (see Figure 1): 5.1.1. Hydraulic Pump and Hydra
9、ulic CylinderA specially designed unit combining a hydraulic pump and a hydraulic cylinder employed to supply the 34 470 kPa (5000 psi) load required to force water into a concrete specimen in the test chamber. The unit is supplied hydraulic pressure, which is converted to water pressure by movement
10、 of the hydraulic piston. 5.1.2. Test Chamber (Figures 2, 3, and 4)A specially designed stainless steel seamless tube secured with a stainless steel plate at the bottom and a stainless steel lid at the top. This chamber is designed to contain water under pressure. 5.1.3. The SystemThe cylinder, of k
11、nown volume, is attached to the test chamber, of known volume, that is completely filled with deionized water. This is done in order to enable load from the hydraulic pump to be applied to the test chamber. The system is equipped with a dial gauge accurate to 0.0254 mm (0.001 in.), in order to measu
12、re the movement of the hydraulic piston. Volume displacement is determined by the measured movement of the hydraulic piston. Note: Not to scale Figure 1High-Pressure Air Meter (Plan View) 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication
13、is a violation of applicable law.TS-3c T 356-3 AASHTO Note: Not to scale. Figure 2Test Chamber 280 mmWing Nutand BarGraduatedCylinder40 mm15 mm 15 mm25 mm25 mm255 mm305 mm40 mm480 mm525 mm 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication
14、 is a violation of applicable law.TS-3c T 356-4 AASHTO Note: Not to scale. Figure 3Test Chamber (Front View) 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-5 AASHTO Note: Not to scale Figure
15、 4Test Chamber Lid 6. SAMPLING 6.1. Obtain a sound concrete sample free of steel reinforcement. The sample must be of suitable size to fit into the test chamber. The diameter of the stainless steel lid is 173 mm (6.8 in.) and the depth of the seamless tube is 480 mm (18.9 in.). 7. PREPARATION OF THE
16、 TEST SPECIMENS 7.1. Oven DryingOven-dry the specimens for 72 h at 138 to 149C (280 to 300F). 7.2. SaturationAfter the specimens have been oven dried, saturate in 21 6C (70 10F) water for a period of 40 to 48 h. 7.3. Unit Mass (Weight)Determine the unit mass (weight) of the concrete sample in accord
17、ance with T 121M/T 121. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-6 AASHTO 8. PREPARATION OF TEST EQUIPMENT 8.1. Preconditioning the Water: 8.1.1. Prior to opening the test chamber, clo
18、se all valves except the valve positioned between the test chamber and the hydraulic cylinder. Remove the lid of the test chamber by loosening the wing nut at the top, thereby releasing the steel crossbar used to secure the lid. Tilt the lid and remove it from the chamber by aligning the flat sides
19、of the lid with the flat sides of the test chamber. 8.1.2. Completely fill the test chamber with deionized water. Remove the pressure gauge and replace it with a plug capable of withstanding a 101 kPa (30 in Hg) vacuum. Apply Teflontape to the plug, prior to installation. Place the vacuum lid over t
20、he top of the test chamber. It may be necessary to apply vacuum grease to the O-ring of the vacuum lid to prevent leakage. 8.1.3. Engage the vacuum by turning on the power and opening the valves connecting the vacuum lid to the vacuum hose and the vacuum hose to the vacuum. The vacuum gauge should r
21、ead approximately 91 kPa (27 in Hg). Apply the vacuum until air bubbles being pulled to the surface are no longer visible; this may be done overnight. The vacuum is applied to remove as much air as possible prior to the determination of an initial value. 8.1.4. Disengage the vacuum by closing the va
22、lves previously opened and turning off the power. The gauge should return to zero. Apply Teflontape to the pressure gauge and replace the plug with the pressure gauge. Replace the vacuum lid with the test chamber lid; do not secure the lid. 8.2. Bleeding the SystemThe system is bled to remove all en
23、trapped air bubbles that may have developed throughout the workings of the high-pressure air meter. This is done by forcing water through the system. 8.2.1. Close the valve positioned between the test chamber and the hydraulic cylinder. Open the drainage valve positioned at the bottom of the test ch
24、amber. Allow water to freely flow from the drainage hose to ensure no entrapped air. Close drainage valve, and secure chamber lid by placing the crossbar over the top of the lid and tightening the wing nut. 8.2.2. Open the valve connected to the graduated cylinder located at the top of the test cham
25、ber. Fill the graduated cylinder with water. Open the valve opposite this valve and allow gravity to force water through the test chamber. Do not allow water to splatter onto the high-pressure air meter. Continue until no air bubbles are visible and the height of the water in the graduated cylinder
26、reads 50 mL or below. Do not allow the water to completely drain. If this does occur, repeat Section 8.2.1. Close the valve opposite of the valve attached to the graduated cylinder. 8.2.3. Open the valve positioned between the test chamber and the hydraulic cylinder. Use the hydraulic pump, in the l
27、oad position, to force water through the system. Water will be forced into the graduated cylinder; continue in the load position until the graduated cylinder is filled. Reverse the hydraulic pump to the release position and drain the graduated cylinder. Continue the process until no air bubbles appe
28、ar in the graduated cylinder. Close the valve attached to the graduated cylinder. The valve positioned between the test chamber and the hydraulic cylinder must remain open. 9. PROCEDURE 9.1. Determination of Initial Value: 9.1.1. Place the hydraulic pump in the load position. Apply the load until th
29、e pressure in the test chamber is exactly 34 470 kPa (5000 psi). Record the initial value read from the dial indicator attached to 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-7 AASHTO the
30、 hydraulic ram in Figure 5. Release the load very slowly; if the load is released quickly, the well holding the hydraulic fluid will overflow. Bleed the system as described in Section 8.2.2. 9.1.2. Repeat this process until the difference in subsequent movement is 0.0762 mm (0.003 in.) or less. This
31、 value is considered the INIT. Record all readings on the data sheet given in Figure 5. Method of Test for High-Pressure Air Content of Hardened Portland Cement Concrete INIT DETERMINATION OPERATOR RECORDER DATE INIT LPM TIME COMMENTS Figure 5Initial Value Determination (Data Record) 2016 by the Ame
32、rican Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-8 AASHTO 9.2. Testing Hardened Concrete Specimen: 9.2.1. Remove the lid of the test chamber. Open the drainage valve to release a volume of water approximatel
33、y equal to the volume of the test specimen. Place the test specimen in the test chamber using forceps; it is crucial that the water in the test chamber is disturbed as little as possible. This is to prevent introduction of air into water within the test chamber. Bleed the system as identified in Sec
34、tion 8.2, beginning at Section 8.2.2. Place the lid on the test chamber and secure it. 9.2.2. Check all valves, except the valve positioned between the test chamber and the hydraulic cylinder, to make certain that they are tightly closed. The valve positioned between the test chamber and the hydraul
35、ic cylinder must remain open. Apply load until pressure in the test chamber is exactly 34 470 kPa (5000 psi). 9.2.3. Immediately record the value read from the dial indicator identifying the LPM. Record the time of the reading and hold the 34 470 kPa (5000 psi) load. The LPM measured via the dial in
36、dicator must be recorded at 5-min intervals. This value should only be read when the pressure in the test chamber is at 34 470 kPa (5000 psi). 9.2.4. It will be necessary to reapply the pressure lost due to the compression of air, in the test specimen, within the first 5 min of testing. It may be ne
37、cessary to reapply pressure at subsequent 5-min time intervals to maintain the 34 470 kPa (5000 psi) load. Maintain the 34 470 (5000 psi) load until the movement of the piston remains the same for 15 min. Record this stabilized value on the data sheet given in Figure 6. 9.2.5. Record the INIT value
38、obtained in Figure 5. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-9 AASHTO Method of Test for High-Pressure Air Content of Hardened Portland Cement Concrete AIR CONTENT DETERMINATION OPER
39、ATOR RECORDER DATE LAB # INIT LPM TIME COMMENTS Figure 6Air Content Determination (Data Record) 10. COMPLETION OF THE TEST PROCEDURE 10.1. Open the lid of the test chamber and remove the specimen from the test chamber. 10.1.1. If the testing is complete, replace the water removed from the test chamb
40、er and close the lid of the test chamber. 10.1.2. If additional testing is required, repeat the process beginning with Section 8.2. 11. CALCULATIONS 11.1. Compute the volume of this test specimen to the nearest one decimal place according to the requirements of the data form given in Figure 7. 2016
41、by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-10 AASHTO Method of Test for COMPUTING VOLUME OF TEST SPECIMEN Metric volume(s) = kg / kg/m3* (1000 mm/m)3SSD Unit mass (weight) Volume(s) = mm3Engl
42、ish volume(s) = kg / 0.4535924 kg/lb * (12 in./ft)3 / pcf SSD Unit mass (weight) Volume(s) = in.3Figure 7Volume of Test Specimen (Data Form) 11.2. Compute the hardened air content of the test specimen according to the procedure given in data form in Figure 8. The values are to be calculated to the n
43、earest one decimal place. Method of Test for COMPUTING HARDENED AIR CONTENT OF TEST SPECIMEN Metric air content = 462121.65 * ( ) / + 1.46 LPM INIT Volume Agg. correction Air content = % English air content = 716.29 * ( ) / + 1.46 LPM INIT Volume Agg. correction Air content = % Note: The coefficient
44、 1.46 is a calibration factor based on Report No. 6-286, Corps of Engineers, U.S. Army Engineer Waterways Experiment Station. Figure 8Hardened Air Content of Test Specimen (Data Form) 11.3. Calculate the plastic air content of the specimen as follows in Equation 1: plastic air content = (hardened ai
45、r content 1.53)/0.9 (1) 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 356-11 AASHTO 12. REPORT 12.1. Report the hardened concrete air content to the nearest percent. 13. PRECISION AND BIAS 13.1
46、. No precision or bias statements are available at this time. 14. KEYWORDS 14.1. Air content; hardened portland cement concrete. 1Formerly AASHTO Provisional Standard TP 59. First published as a full standard in 2015. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
