Section 1: Sampling of Fresh Concrete

Study Questions for sampling of fresh concrete.

Collecting a representative sample of concrete to be tested is as important as executing the test method to obtain …..

accurate results

This practice covers sampling from four types of equipment, which are …..

stationary mixers, paving mixers, revolving truck mixers, continuous mixers

The elapsed time between obtaining the first and final portions of a composite sample shall not exceed …..

15 minutes

True or False: Portions of a composite sample shall be thoroughly remixed before beginning tests on the sample

True. Thorough remixing ensures uniformity in the sample and accurate test results.

Start tests for slump, temperature, and air content within ..… after obtaining the final portion of the composite sample.

15 minutes

Start molding specimens for strength tests within ….. after fabricating the composite sample.

15 minutes

The concrete sample must be protected from contamination and …..

evaporation

The minimum size sample for making strength samples is …..

1 cubic foot

When sampling from a stationary mixer, the batch must be sampled at ….. or more regularly spaced intervals during discharge of the middle portion of the batch.

Two

When sampling from a paving mixer, obtain samples from at least ….. different portions of the pile and combine them into one composite sample for test purposes,

Five

When sampling from a revolving truck mixer, sample the concrete by collecting ….. different portions taken at regularly spaced intervals during discharge of the middle portion of the batch.

Two

True or False: Concrete samples from a revolving truck mixer must be obtained before any water or admixtures are added to the mixer at the job site.

False. The sample must be obtained after all adjustments including any additional water or admixtures have been added and thoroughly mixed a minimum of 30 mixing revolutions.

When concrete contains aggregate larger than that permitted for a particular test method, the sample must be ….. before making the test.

When screened (wet sieved)