ASTM C 231, Air Content – Pressure

Question 1

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.

Answer 1

Dense aggregates only

Question 2

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)

Answer 2

True

Question 3

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

Answer 3

1-1/2

Question 4

Prior to placing concrete in the measuring bowl of the pressure meter, dampen the interior of the bowl.
(T or F)

Answer 4

True

Question 5

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.

Answer 5

either rodding or vibration, depending on the measured slump

Question 6

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.

Answer 6

Only a strike-off plate

Question 7

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.

Answer 7

at least 4 inches greater than the depth of the measuring bowl but not more than 24 inches.

Question 8

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

Answer 8

3

Question 9

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

Answer 9

10 to 15

Question 10

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)

Answer 10

True

Question 11

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

Answer 11

2

Question 12

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)

Answer 12

True

Question 13

After closing both petcocks, pump air into the chamber until the dial is on the Initial Pressure Line.
(T or F)

Answer 13

False

Question 14

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.

Answer 14

Follow the strike-off procedures outlined in ASTM C 138

Question 15

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)

Answer 15

False

Question 16

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.

Answer 16

tap the sides of the bowl with the mallet to relieve local restraints.

Question 17

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.

Answer 17

release the pressure in the measuring bowl by opening both petcocks.

Question 18

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%

Answer 18

6.2 - 0.5 = 5.7%

Question 19

When consolidation is by vibration, insert the vibrator _____ time(s) per layer
A. 1
B. 2
C. 3
D. 4

Answer 19

3

Question 20

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.

Answer 20

never continue vibrating long enough to cause froth to escape from the concrete.

Question 21

What is the mallet size needed for this test?

Answer 21

1.25 lbs +/- 0.5 lbs