UniDrum® Counterflow Dryer/Drum Mixer

The UniDrum mixer offers asphalt pavement producers a heavy-duty drum that generates high quality mix.

The UniDrum is a high quality counterflow design that is offered in both portable and stationary arrangements. The UniDrum mixer is offered as part of complete new plants and also for retrofit applications, with a range of production capacities from 200 to 600 tons per hour (182 to 544 tonnes per hour) with 5% moisture.

With an extra-long drum, the UniDrum mixer is uniquely capable of producing quality hot mix at a high production rate with a high percentage of recycle. The extra-long drum length maximizes mixing and drying times to reduce fuel consumption and provide superior mixing.

Features & Benefits

  • Portable and Stationary available
  • Range of capacities from 200 to 600 TPH
  • Can process mix with up to 50% RAP
  • V-Flights produce a more even aggregate veil to facilitate heat transfer
  • Single-Point Trunnion Alignment saves time and ensures proper equipment operation

UniDrum Relocatable (Up to 50% RAP*)

Drum Size Mixing Chamber TPH (MTPH)
7.5’ x 50’ (2.3m x15.2m) 17’ (5.2m) 300 TPH (272 MTPH)
8.5’ x 50’ (2.6m x15.2m) 19’ (5.8m) 400 TPH (363 MTPH)
9.5’ x 54’ (2.9m x16.5m) 19’ (5.8m) 500 TPH (454 MTPH)
10.5’ x 60’ (3.2m x18.3m) 24’ (7.3m) 500 TPH (454 MTPH)

UniDrum Portable (Up to 50% RAP*)

Drum Size Mixing Chamber TPH (MTPH)
7.5’ x 50’ (2.3m x15.2m) 17’ (5.2m) 300 TPH (272 MTPH)
8.5’ x 50’ (2.6m x15.2m) 19’ (5.8m) 400 TPH (363 MTPH)
9.5’ x 52’ (2.9m x15.8m) 19’ (5.8m) 500 TPH (454 MTPH)

*50% RAP is achieved with patented V-Pac™


As aggregate enters the drum from the conveyor, it passes through the entry gate, which minimizes air leakage into the drum. From there, it passes through a series of flights that veil aggregate through the burner’s gas stream, transfering heat from the burner to the aggregate. The aggregate continues along the drum behind the extended nose burner where dust, RAP, filler, additives, and liquid AC are added sequentially in a flame-free environment. In this zone, the constituents are mixed for the remainder of the drum length before exiting to the drag conveyor.

Extra Long Drum

A diverter is integrated at the entry point to prevent aggregate from entering the drum during calibration or when changing mix design.

Sealed Aggregate Entry

A sealed aggregate entry chute minimizes air in the baghouse. Minimizing the amount of air that enters the baghouse helps maintain production by reducing the chance of baghouse mudding. You have the choice to configure the drum with either a gravity feed chute or a slinger feeder. Gravity feed is standard on the relocatable. A slinger feeder is standard on the portable.


A diverter is integrated at the entry point to prevent aggregate from entering the drum during calibration or when changing mix design.

1.) Virgin Material Enters | 2.) Baghouse Dust Entry | 3.) Recycle Entry | 4.) Liquid Asphalt Cement Entry | 5.) Final Mix Exits

Optional Slinger Feeder
Recycle Entry
Baghouse Dust Entry
Final Mix Exit


Drying of the virgin aggregate is the first step in the mix process and takes place in the first portion of the drum. The drying process begins when the virgin aggregate enters the inner drum through a sealed aggregate entry chute. The sealed chute restricts air entry into the drum while allowing the aggregate to pass through. The angle of the ceramic-lined inlet chute keeps material flowing freely into the drum. State-of-the art flights move the material through the drying zones. Once dried and heated, the aggregate leaves the drying zone of the drum and moves past the burner nozzle and into the mixing zone of the drum.

Extended Nose Burners

The extended nose puts the flame up close to the aggregate, maximizing drying, while keeping the flame away from the RAP and liquid AC, minimizing oxidation and drum fires.

1.) Feeder Flights

Move material into the drying portion of the drum.

Feeder flights guide aggregate as it enters the drum, helping it move efficiently toward the v-flights.

2.) V-Flights

Provide greater uniformity of aggregate veiling through the gas stream during the drying process, across a wide variety of mix designs and tonnage rates.

The v-shaped notch allows material to start pouring out of the bucket at the beginning of each revolution. The material in the bucket continues to pour out until the rotation is complete. This is what provides an even veil of material. The v-flight is also larger than a traditional flight, allowing it to carry the same amount of aggregate even with the notch.

U.S. Patent No. 9,835,374

3.) Combustion Flights

Prevent aggregate from impinging on the flame, while spreading the material to maximize radiant heat transfer.

The combustion flights are made of stainless steel, which lasts longer than traditional carbon steel. The flights overlap one another, creating a shield that minimizes radiant heat from hitting the drum shell, to keep it from overheating. The overlapping also reduces the opportunity for aggregate to get behind the flights and cause additional drum wear.


Achieving a quality asphalt pavement requires mixing materials correctly, with consideration given to providing sufficient time for blending. The superheated virgin materials must have adequate mixing time with the recycled asphalt to bring it to temperature. The virgin aggregate, recycled asphalt and shingles, additives, baghouse fines, and virgin liquid AC must all be blended thoroughly to ensure everything is well coated and the gradation is uniform. The mixing chamber in the UniDrum mixer is an excellent mechanism to ensure adequate blending to achieve a quality mix.

1.) Burner Nose

The burner nose restricts the cross sectional area of the mixing chamber. This smaller area means more particles come in contact with one another, providing better heat exchange, and better blending of materials. A deflector hood prevents mix from contacting the long burner nozzle.

2.) Recycle Inlet

A collar around the drum allows entry of recycled asphalt (RAP), additives/filler, and baghouse dust into the mixing chamber, where they are blended with the virgin material.

  1. ) Recycle
  2. ) Additives

RAP, recycled asphalt shingles (RAS), baghouse dust, and any additive/fillers enter the mixing chamber directly behind the burner tip, minimizing oxidation of the liquid asphalt from the burner flame allowing preliminary blending before the virgin liquid asphalt is added.

3.) Liquid Asphalt Inlet

Liquid asphalt is injected after the virgin aggregate, the recycled material, and baghouse dust are mixed. Pre-mixing these materials allows a more even distribution of the liquid asphalt cement.

  1. ) Liquid Asphalt Cement Entry
  2. ) Warm Mix System

Liquid asphalt is accurately pumped from the storage tanks directly to the liquid asphalt inlet inside the mixing zone, or it can be redirected to the Astec Warm Mix System to produce foamed asphalt before being injected in the mixing zone.

4.) Mixing Flights

After virgin and recycled materials are combined and brought up to the proper temperature, liquid asphalt is injected. Mixing flights provide increased agitation for improved mix quality.

UniDrum mixing flights are engineered to comb through virgin and recycled materials to give thorough blending before the mix exits the drum.


The key to a long-lasting and reliable drum is the drive system. From massive trunnions to heavy-duty drum tires, the UniDrum dryer/mixer uses drive components that are made to last. The unique tire spoke design keeps heat from warping the tire. A single point trunnion adjustment system keeps the drum spinning smoothly and minimizes wear.

Industrial duty thrust rollers support the drum and keep it from riding up or down while spinning. With single point trunnion alignment, finding the sweet spot between the thrust rollers is simple.


The drum is centered on four heavy-duty trunnions, fitted with adjustable, double-row Timken™ bearings and ring fitters that ensure reliable operation; the drum can continue operating even if one drive breaks down.


Single point trunnion adjustment eliminates the time-consuming procedure of trunnion alignment and ensures proper equipment operation. The key to this industry exclusive feature is the unique pivot pin system, which allows an operator to easily dial in the dryer in a matter of minutes without the need of any specialized equipment. The end result is a properly rotating dryer without excess wear to the tires, trunnions, and thrust roller assemblies. The single point trunnion adjustment significantly reduces excess trunnion wear, premature deterioration of hardened tire surfaces, broken trunnion shafts, bearing failures, and thrust roller assembly damage.


The UniDrum dryer/mixer rotates on two heavy-duty drum tires. The tires are forged and then hardened to take the beating of everyday use. Single point trunnion alignment minimizes tire wear.


Each drum tire is mounted to the UniDrum dryer/mixer with suspension bars. These bars not only keep the drum tire in place, but also allow some flexibility from heat expansion to prevent warping the tire.


While the internal components of a drum are what make the plant work, the external components support and protect the drum. Asphalt plants face harsh environments, so tough skin is crucial. The drum collar must be well-designed for reliable introduction of virgin aggregates, liquid asphalt cement, recycled asphalt pavement, and baghouse dust that must enter mid-drum to be blended together behind the burner flame. All of these components must also be easily accessible.

1.) RAP Inlet

The extra wide RAP inlet design has an access door for easy entry. It also has replaceable wear edges and diggers for simple service.

2.) Dust Inlet

A screw auger returns baghouse fines to the RAP collar. This is done behind the burner to keep the dust from being sucked back out into the baghouse.

*Dust metering systems also available.
† Not shown on illustration

3.) Insulation

The drum is wrapped with 4” of fiberglass insulation greatly reducing heat (energy) loss. The drum is then wrapped in stainless steel to protect the insulation.

4.) Frames

Astec offers two styles of heavy-duty, industrial steel frames: relocatable frames feature foundation plates to support the drum, and portable models are supported by axles to make moving the drum simple.

5.) Access

The interior of the dryer drum and mixer is reached through an access door at the inlet breeching.