C172/C172M - 17 Sampling Freshly Mixed Concrete

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 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 a 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

28 L [1 ft squared]

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

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 the concrete sample be protected?

Answer 11

Sun, wind and rapid evaporation

Contamination