When the extraction of a base or binder involves larger aggregate, the sample may be specially prepared. A ratio of these portions to the total sample is used to proportion the weight of the plus half and minus half. A proprotionate amount of quartered samples are remixed for the extraction test, and this procedure assures the test sample will represent the mix. When segregation occurs before mixing, a sample from the cold feed system should be obtained in drum mixing plants. In a batch plant, a resample of the hot bins should be made.
Segregation often occurs when material is placed into the silos.
A conveyor system places the mix into a batch hopper or similar discharge system. Timing systems on these units should be set in accordance with output tonnage to keep the mix from falling straight through the batcher into the silo and causing segregation by coning. For proper operation, the mix should be discharged in small batches. The batcher gate should be operated in a pulsating manner and never completely empty during operation. For variable production rates, the gate timer should be adjusted accordingly.