Lesson 6/Learning Event 4
NOTE: When operations begin it may be necessary to make adjustments
of the cold feed gate openings. Several adjustments may be necessary to
maintain a balanced flow of aggregates to the gradation unit.
Step 12. Check All Settings.
(1) Once the mixing plant has been calibrated, all settings must be checked to insure
accuracy. When it is verified that all settings are correct, the mixing operation may begin.
(2) At the start of the mixing operation, a Marshall Stability test and an extraction test should
be taken by the plant laboratory using samples of the finished mix. The plant is operated only
long enough to mix four truck loads. Four samples are then taken (one from each truck load to
obtain a representative sample). The plant is then shut down until the results of the Marshall and
extraction tests can be compared with the mix design for compliance with specifications. If
necessary, proper adjustments are made to secure a conforming mix. If adjustments are made,
four additional truck loads are mixed, sampled, and tested. When it is determined that the plant
mix conforms to specifications, the plant may be placed in continuous operation.
NOTE: The plant must not be placed in continuous operation until the
variations in test properties are within allowable tolerances.