Test Method C138: Density, Yield, and Air Content (Gravimetric) of Concrete

Question 1

The diameter of the tamping rod used in the test method is ___.

Answer 1

5/8”

Question 2

What is the required shape of the tamping end of the rod?

Answer 2

Rounded to a hemispherical tip

Question 3

What is the required minimum frequency of the vibrator used in this test method?

Answer 3

7000 vibrations per minute

Question 4

The outside diameter or side dimension of the vibrating element must be at least ___ but not greater than ___.

Answer 4

.75 inches, 1.5 inches

Question 5

A plastic container can be used for the measure in this method. T/F

Answer 5

False, measure must be steel or another suitable metal

Question 6

What is the minimum thickness of a metal strike-off plate?

Answer 6

1/4 inch

Question 7

What is the minimum thickness for a glass or acrylic strike-off plate?

Answer 7

1/2 inch

Question 8

What is the specified weight of the mallet used on measures that are 0.5 ft3 or smaller?

Answer 8

1.25 +/- .5 lb

Question 9

Measures other than air meter bowls used for this test must conform to ASTM ___.

Answer 9

C29

Question 10

Air meter bowls used for this test must conform to ASTM ___ and be calibrated for volume according to ASTM ___.

Answer 10

C231, C29

Question 11

The concrete sample must be obtained in accordance with what ASTM method?

Answer 11

C172

Question 12

What method of consolidation must be used when the slump is greater than 3 inches?

Answer 12

Rodding

Question 13

What method of consolidation must be used when the slump is less than 1 inch?

Answer 13

Vibration

Question 14

If rodding is the method of consolidation being used, the measure must be filled in how many layers?

Answer 14

3

Question 15

For a measure of 0.5 ft3, what is the required number of strokes of the tamping rod for consolidation of each layer?

Answer 15

25

Question 16

When rodding the middle and the top layers, the tamping rod should penetrate into the layer below approximately ___.

Answer 16

1 inch

Question 17

If vibration is the method of consolidation, the measure must be filled in ___ approximately equal layers.

Answer 17

2

Question 18

If, after consolidation of the final layer, the concrete level is 1/2 inch above the top of the measure, what should be done?

Answer 18

Remove a representative portion of the excess concrete with a trowel or scoop.

Question 19

After consolidation of the final layer, an excess of concrete ___ above the top of the measure is considered optimum.

Answer 19

1/8 inch

Question 20

After completing the strike-off procedure, what must be done before weighing the measure and sample?

Answer 20

Clean off any excess concrete