Test Method C231: Air Content of Freshly Mixed Concrete by the Pressure Method

Question 1

The pressure method of determining air content can be used on concrete containing ___ ___ aggregate.

Answer 1

Relatively dense

Question 2

The pressure method of determining air content cannot be used on concrete containing the following types of aggregates: ____, ____, ____

Answer 2

Lightweight, air-cooled blast furnace slag, or aggregates of high porosity

Question 3

What is the minimum allowable capacity of the measuring bowl used in this test method?

Answer 3

6 L (0.2 ft3)

Question 4

What are the required characteristics of the tamping rod used in this test method?

Answer 4

Round, straight steel rod, with a 16 mm [5/8 in.] +- 2 mm [1/16 in.] diameter, length at least 100 mm [4 in.] greater than the depth of the measuring bowl, but not greater than 600 mm [24 in.] in overall length, with the tamping end rounded to a hemispherical tip of the same diameter as the rod.

Question 5

What is the specified size of the mallet required for this test method when the measuring bowl has the capacity of 14 L (0.5 ft3) or less?

Answer 5

0.60 +- 0.25 kg (1.25 +- 0.5 lb)

Question 6

The sample of concrete used for this test is to be obtained in accordance with what ASTM Standard?

Answer 6

C172

Question 7

The max size aggregate allowed for this test method is ____.

Answer 7

2 inches (50mm)

Question 8

If the concrete contains aggregate larger than the max allowed for this test, the sample must be _____.

Answer 8

Wet sieved over a 1.5 in sieve

Question 9

If the concrete sample is to be consolidated by rodding, the measure is filled in ___ layers.

Answer 9

3 equal

Question 10

If the concrete sample is to be consolidated by vibration, the measure is filled in ___ layers.

Answer 10

2 equal

Question 11

When rodding the concrete sample, what is the number of strokes required for each layer?

Answer 11

25

Question 12

Vibration of the concrete sample is not allowed when the slump of concrete exceeds ____.

Answer 12

75 mm (3 inches)

Question 13

In rodding the sample, how deep should the rod penetrate each layer?

Answer 13

1 inch into previous layer

Question 14

After rodding each layer, what should be done to the measure before adding another layer of concrete?

Answer 14

Tap the sides of the measure smartly 10 to 15 times with the mallet.

Question 15

When consolidating the concrete by vibration, how many times should the vibrator be inserted into each layer?

Answer 15

3

Question 16

What tools may be used to strike off the top surface of the concrete following consolidation of the final layer?

Answer 16

A strike-off bar, a metal, glass, or acrylic plate

Question 17

What must be done if there is a slight deficiency in the quantity of concrete in the measure of consolidation of final layer?

Answer 17

Add a quantity of representative concrete before strike off

Question 18

What must be done if there is an excessive amount of concrete in measure following consolidation of the final layer?

Answer 18

Remove a representative quantity of concrete with the scoop or trowel before the strike off