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specimen. Wait for 5 minutes. If both gauge readings remain constant, the system is airtight<br />
and testing may continue. If the readings decrease, the system is not airtight and adjustments<br />
must be made to the system prior to continuing testing.<br />
10.1.6 Attach the yoke with the spacers and the LVDTs to the specimen.<br />
10.2 Coefficient of Permeability for Air Flow<br />
10.2.1 Set and establish the temperature of the environmental control chamber to<br />
25 + 0.5°C.<br />
10.2.2 Open the vacuum valve and select air flow from the water-vacuum-air valve.<br />
Apply the lowest differential pressure possible (typically 50 mm of Hg) by adjusting the<br />
vacuum regulator. Record the air flow through the test specimen. Record the pressure<br />
differential reading.<br />
10.2.3 Repeat 10.2.2 for four different pressures. The pressures selected will vary<br />
depending on the void content of the specimen being tested. They may range from 50 to<br />
400 mm of Hg. It is important that a range be selected that is consistent with the air void<br />
content. A constant interval between the pressures must be selected e.g., 20, 30, 40, and<br />
50 kPa.<br />
10.2.4 Calculate the coefficient of permeability for air flow of the test specimen as<br />
described in 11.2.1 for each of the pressures. Report the average of the four results.<br />
NOTE4.--Air flow measurements should be within 10% of each other.<br />
10.2.5 Close the vacuum valve.<br />
10.3 ECS Modulus Test<br />
10.3.1 Maintain the temperature of the environmental chamber at 25 ___0.5°C.<br />
Remove the spacers from the yoke.<br />
10.3.2 Apply a static load of 130 + 25 N and an axial compressive repeated load of<br />
2200 + 25 N to the test specimen. The repeated load should be in a haversine wave form<br />
with a load duration of 0.1 s and a rest period of 0.9 s between load pulses.<br />
10.3.3 Adjust the specimen until the readings from the two LVDTs are within 15%<br />
of each other.<br />
10.3.4 If the strain is less than 50 _strain, increase the repeated load until a strain<br />
level between 50 and 100/_strain is reached. If the strain is more than 100/_strain, decrease<br />
the repeated load until a strain level between 50 and 100/_strain is reached.<br />
10.3.5 If using the ECS software, the load and deformation data for the last five<br />
cycles are collected and the ECS modulus automatically calculated when the [ESC] key is<br />
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