Section 1: Sampling Fresh Concrete Flashcards
What must occur before a sample of concrete can be taken from a revolving drum mixer?
All water and admixtures must be added to the mixer
When sampling from a stationary or a revolving drum mixer, what is collected and when is taken during discharge?
- Two or more portions of concrete
- Regularly spaced intervals
- Middle of Batch
How are the sample portions obtained from the discharge stream of a stationary or revolving drum mixer?
- Repeatedly pass a receptacle through the entire discharge stream
- Completely divert the discharge stream into a sample container
Describe the procedure for collection a sample from a paving mixer
- Discharge the contents of the paving mixer
- Obtain samples from at least five different portions of the pile
What is the minimum size for a sample when strength test specimens are to be molded?
1 cubic foot [28 L]
What is the maximum allowable time between obtaining the first and final portions of the composite sample?
15 min
What action is required after the individual concrete samples have been transported to the place where tests are to be performed?
Combine and remix the samples with a shovel
What should be done if the concrete contains aggregate larger than is appropriate for the size of the molds or equipment being used?
Wet sieving (screening)
Slump, temperature, and air content tests must be started within how many minutes after obtaining the final portion of the composite sample?
5 minutes
Molds for Strength tests must be started within how many minutes after fabricating the composite sample?
15 minutes
From what must the concrete sample be protected from?
Sun, Wind, Rapid Evaporation, and Contamination
What types of equipment does this cover sampling from?
- Stationary mixers
- Paving Mixers
- Revolving Truck Mixers
- Continuous Mixers
When sampling from a paving mixer, obtain samples from how portions of the pile must be sampled?
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