How soon should tests for slump, temperature, and air content begin after obtaining the final portion of the composite sample?

The correct timeframe for beginning tests for slump, temperature, and air content after obtaining the final portion of the composite sample is 5 minutes. This duration is critical because it ensures the properties of the concrete are evaluated while the material remains consistent with its freshly mixed state. Conducting these tests promptly helps to achieve accurate representations of the concrete's workability, temperature, and air content, which are vital for quality control in construction.

If tests are conducted too soon, the concrete may not have settled or reached a stable state, leading to unreliable results. Conversely, waiting too long can result in changes to the concrete due to initial setting or environmental factors, ultimately affecting the test outcomes. Thus, adhering to the 5-minute guideline allows for a balance between timing and the integrity of the measurements.