ASTM C 231, Air Content – Pressure Flashcards
It is permissible to use ASTM C 231 to determine the air content of fresh concrete made with
A. dense aggregates only.
B. lightweight aggregates only.
C. either dense or lightweight aggregates.
D. only highly porous aggregates.
Dense aggregates only
It is permissible to use the measuring bowl of the pressure meter to determine the density of a concrete mixture per ASTM C 138, so long as the coarse aggregate is of an appropriate size.
(T or F)
True
When the coarse aggregate of a concrete mixture can be retained on a 2 inch sieve, wet sieve a sufficient amount of material for the air content test (ASTM C 231) over a _____ inch sieve.
A. 3/4
B. 1
C. 1‐1/2
D. 2
1-1/2
Prior to placing concrete in the measuring bowl of the pressure meter, dampen the interior of the bowl.
(T or F)
True
Consolidation of concrete in the measuring bowl of a Type B pressure meter is accomplished by
A. rodding only.
B. vibration only.
C. striking the bowl 25 times with the mallet.
D. either rodding or vibration, depending on the measured slump.
either rodding or vibration, depending on the measured slump
When testing only for air content, strike‐off the top surface of the concrete using
A. only a strike‐off bar.
B. only a strike‐off plate.
C. only the tamping rod.
D. either the strike‐off bar or strike‐off plate.
Only a strike-off plate
The length of a tamping rod shall be
A. no less than 12 inches.
B. no more than 16 inches.
C. 24 inches.
D. at least 4 inches greater than the depth of the measuring bowl but not more than 24 inches.
at least 4 inches greater than the depth of the measuring bowl but not more than 24 inches.
When consolidation is by rodding, place the concrete in the measuring bowl of a Type B pressure meter in_____ layer(s) of approximately equal volume.
A. 1
B. 2
C. 3
D. 4
3
After each layer of concrete in a Type B pressure meter is rodded, tap the sides of the measuring bowl _____times with the mallet.
A. no more than 10
B. 10 to 15
C. at least 15
D. 25
10 to 15
When rodding a layer of concrete in a Type B pressure meter, rod through the layer and penetrate the layer below by approximately 1 inch.
(T or F)
True
When consolidation is by vibration , place the concrete in the measuring bowl of a Type B pressure meter in _____ layer(s) of approximately equal volume.
A. 1
B. 2
C. 3
D. 4
2
The test for air content by the pressure method is to be conducted by placing the measuring bowl on a flat, level, and firm surface.
(T or F)
True
After closing both petcocks, pump air into the chamber until the dial is on the Initial Pressure Line.
(T or F)
False
If the strike‐off plate is used to remove excess concrete
A. follow the strike‐off procedures outlined in ASTM C 138.
B. with the plate on its edge, move the plate across the measuring bowl in a sawing motion.
C. us any technique to finish the top surface, just so long as it ends up being smooth and level.
D. there cannot be more than 1/4 inch of concrete above the rim of the bowl.
Follow the strike-off procedures outlined in ASTM C 138
After consolidating a layer of concrete by vibration, strike the measuring bowl 10 to 15 times with the mallet to close the voids left by the vibrator and to release any large air bubbles
(T or F)
False
After opening the main air valve between the air chamber and measuring bowl of a Type B pressure meter,
A. jar the meter to determine if air will be expelled from the petcock valves.
B. read the final air content to the nearest .25%.
C. read the air content, pump air back into the air chamber, release the air into the bowl and check to see
that both air readings are within 0.25% of each other.
D. tap the sides of the bowl with the mallet to relieve local restraints.
tap the sides of the bowl with the mallet to relieve local restraints.
After completion of the air test,
A. release the pressure in the measuring bowl by opening both petcocks.
B. remove the cover, dump the concrete from the base, and check for any undisturbed concrete.
C. open the main air valve while releasing the pressure from the measuring bowl.
D. re‐assemble the top and re‐run the test.
release the pressure in the measuring bowl by opening both petcocks.
Assume that the reading from the dial gage is 6.2% and the Aggregate Correction Factor for the concrete mixture is 0.5%. The final air content for this mixture is then
A. 6.2 + 0.5 = 6.7%.
B. 6.2 – 0.5 = 5.7%
C. 6.2 x 0.5 = 3.1%
D. 6.2%
6.2 - 0.5 = 5.7%
When consolidation is by vibration, insert the vibrator _____ time(s) per layer
A. 1
B. 2
C. 3
D. 4
3
When consolidation is by vibration,
A. never continue vibrating long enough to cause froth to escape from the concrete.
B. continue vibrating until large air bubbles begin to develop on the surface of the concrete.
C. insert the vibrator for no more than 5 seconds.
D. insert the vibrator for at least 5 seconds.
never continue vibrating long enough to cause froth to escape from the concrete.
What is the mallet size needed for this test?
1.25 lbs +/- 0.5 lbs
