Asphalt Recycler

Overview

An asphalt recycler turns old road material back into usable hot mix on site. When a road is milled or dug up, the broken pavement, called reclaimed asphalt pavement or RAP, still contains good aggregate and bitumen, but the bitumen has hardened with age and the material has cooled. The recycler reheats it, softens and supplements the binder, and discharges a hot mix that can be laid straight back into patches, utility cuts, and small overlays. This avoids buying fresh hot mix and hauling waste away, which matters most for maintenance crews working far from a fixed asphalt plant.

The machine rides on a Trailer Chassis to the job. RAP goes in through the RAP Feed Hopper, is heated and tumbled in the Heating Drum fired by the Burner System, and is dosed with Binder Dosing to restore the mix. Finished material collects in the Discharge and Storage bin, the Exhaust and Dust Control cleans the gas, and the Control System ties the whole process together.

Feeding the reclaimed material

Consistent output needs a steady, screened feed. The RAP Feed Hopper starts with a Feed Bin holding a charge of milled or crushed RAP. A Grizzly Screen bar screen rejects lumps too large to heat through, and the Feed Conveyor carries the rest to the drum inlet, driven by a Feed Drive whose speed the controller sets. A Belt Weigh Cell under the belt weighs the feed continuously, which matters because the binder is dosed by feed mass rather than by guesswork.

Reheating in the drum

The Heating Drum is the heart of the machine. It is a Drum Shell mounted at a slight slope on Trunnion Roller rollers, with Thrust Roller units that stop it sliding downhill. A Drum Drive rotates it slowly while internal Lifting Flight vanes lift the material and shower it through the hot gas, so every particle is heated evenly instead of being scorched on the outside and cold in the core. Asphalt is easy to ruin: too much direct flame burns the bitumen and ruins the mix, so the drum is run so the material sees hot gas more than open flame. Outer Drum Insulation keeps the heat in the load and the skin safe.

Burner and binder restoration

Heat comes from the Burner System. A Burner Head fires diesel or gas, a Combustion Fan supplies air, a Fuel Pump feeds the nozzle from the Fuel Tank, and a Flame Sensor cuts fuel the instant the flame is lost. Heating alone is not enough, because aged bitumen is too stiff to bind. The Binder Dosing subsystem corrects this. A Rejuvenator Tank holds a recycling agent that re-softens the old binder, kept pumpable by a Tank Heater and metered by a Metering Pump in proportion to the weighed feed. A Spray Bar injects it into the drum, and a Flow Meter confirms the dose.

Discharge, storage, and emissions

Finished mix leaves through the Discharge and Storage subsystem. A heated Discharge Chute feeds an insulated Storage Bin that holds the mix hot and unsegregated until a Discharge Gate loads it out, while Temperature Probe thermocouples log the temperature. Heating asphalt makes dust and blue smoke that cannot go straight up the stack, so the Exhaust and Dust Control subsystem cleans it. A Induced-Draft Fan draws gas through the drum and holds it under slight vacuum, a Cyclone Separator drops coarse dust back into the mix, and a Baghouse Filter captures fine particulate before the Exhaust Stack releases the cleaned gas. Returning the cyclone fines to the drum keeps the mineral filler in the mix rather than wasting it, which helps the recycled material meet its gradation.

Control and field use

The Control System panel runs the plant as one loop. The Mix Controller reads the feed weight, mix temperature, and binder flow and trims burner output, feed speed, and binder dosing to hold the recipe, while the operator sets targets and watches the run on the Operator Panel. In service the crew levels the Trailer Chassis on its jacks, loads RAP, sets a recipe, and runs the drum until the bin holds enough hot mix to patch a stretch of road. Smaller trailer units suit utility and pothole crews; larger ones approach the output of a small fixed plant. Because mix quality depends on holding temperature and dose within a narrow band, the controller and the weigh-based dosing do most of the work of keeping the recycled material on specification. The proportion of RAP a recycler can use depends on how aged the old binder is and how much fresh binder and rejuvenator are added, so a job mix is set from a test of the reclaimed stock before production begins. Where the recycled material is used for a structural layer rather than a patch, agencies sample the drum output and check its binder content and gradation against the design, and the recycler is run to hold those targets pass after pass.