Which mixer type requires sampling from at least five portions of the pile to form a composite sample for testing?

• A. Paving mixer
• B. Stationary mixer
• C. Revolving drum truck mixer
• D. All of the above

Answer: (A)

Sampling from a pile to form a composite sample is about capturing variability across the material stockpile. For paving mixes, the material can differ across different parts of the pile in moisture, gradation, or contaminants, so taking samples from multiple portions and combining them gives a test material that truly represents the whole pile. That’s why the guideline specifies sampling from at least five portions—the more portions you collect from different areas, the less bias you introduce and the more reliable the test results will be. In contrast, stationary mixers and revolving drum truck mixers operate more like batch or continuous processes where the material already blends within the equipment, so sampling is taken from the batch or discharge rather than from multiple pile portions.