What defines the total mix time?

• A. The total time from plant startup to shutdown.
• B. The time from weighbox discharge until the close of the pugmill discharge gate.
• C. The time required to weigh all materials for a batch.
• D. The time from pugmill start to finished batch discharge.

Answer: (B)

Total mix time measures the entire processing window for a single batch from when the batch contents leave the weigh box until the batch is discharged and the discharge gate closes. This includes weighing, transferring to the pugmill, actual mixing, and final discharge of the finished mix. That end point—the closing of the pugmill discharge gate—signals that the batch has completed its processing cycle.

Why this fits best: it captures all the steps that define a batch’s processing duration in the pugmill, from the moment the materials are weighed and released to the moment the batch is fully discharged. Other options either start or end at points that exclude parts of the cycle (for example, weighing only, starting after the pugmill has begun, or spanning the plant from startup to shutdown), so they don’t represent the full batch processing time.