Incorporation of Recycled Asphalt Products in a Drum Mix Plant

Recycled asphalt products (RAP) can be incorporated into hot mix asphalt produced in a drum mixing plant up to a rate of approximately 30%. Aggregates are superheated in the dryer drum section to provide the energy required to dry and heat the RAP upon addition.

All systems incorporate the BG RAP feed bin specifically designed to handle materials with poor flow characteristics:

RAP Bin and Feeder

The recycle bin is available in a range of capacities to suit the particular application. All feature a vertical discharge end bin wall with the opposing wall at 15° from vertical and two sloping side walls at 70°. The self-relieving discharge opening onto the belt feeder the bin is designed to promote clean discharge of the RAP material. Bin spill plates extend the sides of the RAP bin and enclose three sides of the optional inclined grizzly therefore preventing spillage when loading.

The bolt-on type belt feeder features include a vulcanised endless belt, lagged head drum, spiral tail drum, screw tensioning at the tailend and 100mm diameter intermediate rollers. Direct drive to head shaft is by an IE2 thermistor protected bevel helical gearbox which provides high torque starting and high efficiency operation.

The outlet of the bin is fitted with an adjustable sliding gate to control the depth of material on to the belt.

From the RAP bin material is conveyed to the drum recycle breaching via an inclined conveyor incorporating an inline weigh bridge to accurately measure addition rates.

Drum Recycle Breaching

The BG drum recycle breaching is installed within the drying drum to allow cold RAP material to be incorporated within the dried aggregates prior to the addition of bitumen. RAP is introduced in a continuous stream to the lined breaching feed chute. The chute is fitted with a tipping valve to seal the breaching when not in use and prevent excess air entering the drying process. RAP is collected within the external scroll and guided through slots in the shell section. Internal flights lift the dry aggregates over the internal breaching arrangement and promote the incorporation of the RAP material within the hot virgin aggregate.

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