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ACI Pg 20-21 first
| Question | Answer |
|---|---|
| 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 revolving drum mixer, what is collected and when is it taken during discharge? | In two or more portions of concrete. At regularly spaced intervals. From the middle of the 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 collecting 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 ft^3 (28 L) |
| What is the maximum allowable time between obtaining the first and final portions of the composite sample? | 15 mins |
| What action is required after the individual concrete samples have been transported to the place where tests are to be preformed? | Combine and remix the samples with a shovel |
| What should be done if the concrete contains aggregates larger than is appropriate for the size of the molds or equipment being used? | Wet sieving (screening) |
| Start the tests for slump, temperature, and air content within how many minutes after obtaining the final portion of the composite sample? | 5 mins |
| Start molding specimens for strength tests within how many minutes after fabricating the composite sample? | 15 mins |
| From what must the concrete sample be protected? | Sun, wind, rapid evaporation. Contamination. |