ACI Class

Question 1

What must occur before a sample of concrete can be taken from a revolving drum mixer?

Answer 1

All water and admixtures must be added to the mixer.

Question 2

When sampling from a stationary or revolving drum mixer, what is collected and when is it taken during discharge?

Answer 2

• In two or more portions of concrete

• At regularly spaced intervals

• From the middle of the batch

Question 3

How are the sample portions obtained from the discharge stream of a stationary or revolving drum mixer?

Answer 3

• Repeatedly pass a receptacle through the entire discharge stream

• Completely divert the discharge stream into a sample container

Question 4

Describe the procedure for collecting a sample from a paving mixer.

Answer 4

• discharge the contents of the paving mixer

• obtain samples from at least five different portions of the pile

Question 5

What is the minimum size for a sample when strength test specimens are to be molded?

Answer 5

1 cu.ft [28 L]

Question 6

What is the maximum allowable time between obtaining the first and final portions of the composite sample?

Answer 6

• 15 min

Question 7

What action is required after the individual concrete samples have been transported to the place where tests are to be performed?

Answer 7

• Combine and remix the samples with a shovel

Question 8

What should be done if the concrete contains aggregate larger than is appropriate for the size of the molds or equipment being used?

Answer 8

• Wet sieving (screening)

Question 9

Start the tests for slump, temperature, and air content within how many minutes after obtaining the final portion of the composite sample?

Answer 9

5 min

Question 10

Start molding specimens for strength tests within how many minutes after fabricating the composite sample?

Answer 10

• 15 min

Question 11

From what must a concrete sample be protected?

Answer 11

• sun, wind, and rapid evaporation

• contamination