AASHTO T 356:15(2019) Standard Method of Test for Determining Air Content of Hardened Portland Cement Concrete by High-Pressure Air Meter.
8.1.1. Prior to opening the test chamber, close all valves except the valve positioned between the test chamber and thc 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 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.l-lg) vacuum. Apply TeflonR tape to the plug, prior to installation. Place the vacuum lid over the top of the test chamber. It may be necessary to apply vacuum grease to the 0-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 read 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 valves previously opened and turning off the power. The gauge should return to zero. Apply Teflon’ tape 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 i/ic’ Si’sreni—The system is bled to remove all entrapped 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 chamber. Allow water to freely how 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 chamber. 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 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 load 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 appear 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.AASHTO T 356 pdf download.