ACI ASTM C231 - Air Content: Pressure Method 2019
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- Опубликовано: 22 май 2019
- Air Content: Pressure Method
ACI Technician Workbook CP-1
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* Aggregate Testing Limitations *
This test method cannot be used for testing lightweight concrete because the aggregate in lightweight is too porous. See ASTM C173 Air Content by Volumetric Method.
* Two types of Air *
1. Entrapped (naturally occurring in the mix)
2. Entrained (intentionally added to the mix)
Remember, entrained air is necessary for concrete that will be directly exposed to freeze-thaw cycles throughout its lifetime. The air voids allow for collected moisture to expand and contract through freezing without causing the concrete to spall.
And as air increases, the ultimate strength of the concrete decreases, just as the increase of water decreases strength.
* Two types of Pressure Method Air Meters *
Type A: Not commonly used - uses pressure to displace water into concrete.
Type B: Most commonly used. Uses equalization to determine air content in the concrete.
Once the valve is depressed and held, equalization occurs when the known air in the air chamber releases into the unknown air content in the concrete sample in the bowl below. The apparatus equalizes and provides you with an air reading (how much air it took to equalize the system).
* Additional Important Information *
Maximum 2" aggregate permitted for use with the Type B bowl size
Pressure gauge should read to the nearest 0.1 percent
Mallet mass same as described under ASTM C138
Tamping rod dimensions same as described under ASTM C143
Strike-Off bar made of metal at least 1/8-inch thick, 3/4-inch wide, and 12-inches long OR Strike-Off plate that is at least 2-inches wider than diameter of bowl AND Metal, at least 1/4-inch thick OR Glass or acrylic, at least 1/2-inch thick
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Good video. I passed the exam on Nov 11,2021.
Great video sir. Straight to the point and clearly explained
Helped me pass my ACI. Thank you
Just took this test on 09/21/19 and failed my first attempt for not asking for the correction factor at the end so please do not forget to ask that!!!
@@aulajomaa6286If you are taking the ACI Grade One test, your company should provide you with the relevant ASTM standards. You will need to know slump, temperature, air content, and cylinders. You will need to know proper sampling. You will also need to know the dreaded roll-meter, which is used to determine air content for lightweight concrete. I've been doing testing for 15 years and I've only used a roll-meter on (2) jobs.
@@aulajomaa6286 I work in Ohio and needed Grade I ACI to test concrete in the field. We had a written portion and then had to run all the tests in a lab (2 types of air tests, temps, slump, make cylinders).
@@JSSTyger how do you know what the initial pressure is?
@@ZootedSnakeThe initial pressure for a new pot is in print on the neck of the top piece. Sometimes the pot needs re-calibrated and the initial pressure would be determined during calibration. The IP should always be marked somewhere on the pot.
JSSTyger ok thank you
Excellent very educative and informative Thanks.
Great video can someone help me to give me an advice how to calibrate my air pot
Great
I appreciate all the skipping past the first part, but I struggle with knocking every bit of air out of the vessel before taking the compression test. It seems to me that if it was in a controlled area that it would maintain that air?? or am I wrong
This is why the test emphasizes the flat surface of concrete in the first half of the test / the start of this video. A flat surface of concrete will be right up against the bottom of the pressure chamber. That is also why you put the water into the petcocks. Once water is standing in both petcocks there is no non entrenched air inside of the pot. The concrete is right up against the bottom of the top piece (top of the chamber) and any air that is trapped is pushed out by the water introduced.
You then pressurize the top valve with air - then until you press the air valve on top and hit the side of the pot there is no connection between the air in the top and the pot, therefore there is no air introduced to the lower chamber until the time where the test is taken.
Why need ip until 2 not zero
Nice video I just passed the exam Nov 16, 2021
Do they time this test ?
@@PrometheanFrErunning no they don’t the only test that they time is the slump and it’s 2:30 min
Why do you pump it up with petcocks open? How’s it hold the air?
The air chamber is closed off to the rest of the air meter bowl. Whether the petcocks are open or closed it doesn't change anything. Once he depresses the main air valve, it raises a pin inside the air chamber that releases the air into the air meter bowl.
@@witherskeletonfilms2851 thank ya
You didn’t release all the pressure in the chamber before putting the lid on the pot. That makes your tests not uniform
Why did u not show the first steps?? Filling the pot with concrete, 3 layers rodding 25 times each tap 10-15 times each etc. If you’re gonna show the test show the whole thing
That’s a different ASTM
He made an individual video for that
@0:10 🤨🤔😂 pay attention.
Should be in there. Its all part of ACI test.