ASPHALT DRUM MIX PLANT

In a asphalt drum mix plant Rotating drum is divided into two sections: (1) a primary or radiation (heating) zone. (2) a secondary or convention/coating (Mixing) zone. The aggregate is not only dried and heated within the drum, but it is also mixed with the Bitumen (asphalt cement). In a drum mix plant, there are no gradation screens, hot bins, weigh-hoppers or Pugmill. Aggregate gradation is controlled at the bin feeder. The basic plant consists of a cold feed system, a rotating drum dryer, an asphalt proportioning and dispensing system, and a surge silo. The ease of setup and operation of the drum mix plant makes it the ideal machine for operations. Weight the virgin aggregates individually from the cold feed bins gate, with variable, continuous, and automatic speed of belt in the proportion indicated by the control systems. The aggregates that have been weighed are transferred to the dryer by charging conveyor. Aggregates enter the primary zone where heat from the burner dries and heats them. Then the aggregate moves to the secondary zone where asphalt is added, and aggregates and asphalt are thoroughly blended. Continued drying also occurs in the secondary zone. Drum-mixers are equipped with flights to direct the aggregate flow and spread the aggregates into a veil across the cross section of the drum. The aggregates must not only rotate with the revolving motion of the drum but must also spread out sufficiently to make heating and drying of all particles quick and efficient. The drum mix plant produces the asphalt concrete mix on a continuous basis thus a temporary holding bin or surge silo is used to convert the continuous flow of material. Several different types of conveying devices can be employed to carry the asphalt concrete from the discharge end of the drum mixer to the holding bin or surge silo. Bucket elevators, drag slat conveyors, and belt conveyors are the three most common means of transport. Each device has its own advantages and disadvantages.