The RT-500 mobile recycling trailer can be used either for cold in-place recycling (CIR) of asphalt pavement or as a central, on-site cold-mix plant. When used in the CIR application, the RT-500 is pulled and supplied with material by the Roadtec RX-900 milling machine.
The CIR concept involves removing a pavement’s damaged layers, processing the material removed, and then placing and compacting the processed material on the newly milled roadway. Typically, a thin lift of hot-mix asphalt (or other preservation treatment) is placed on top of the CIR material to serve as the wearing surface.
The CIR process, says Roadtec, can allow repairing a damaged roadway in a single pass, while using up to 100 percent of the roadway’s existing material. With CIR technology, says the company, the new paving mix is prepared as the recycling train advances, eliminating the need for haul trucks, and in most instances, the need for virgin materials.
As the CIR train advances, the cold planer mills the damaged layers of the existing pavement and conveys the resulting material to the entry chute of the RT-500, where the material moves onto the double-deck vibratory screen that separates the milled material by size. The low-profile flat screen measures 5x14 feet and features adjustable amplitude/frequency settings and springs/vibration isolators designed for smooth, quiet operation, says Roadtec.
The screen allows material of proper size to pass through, and oversize material is channeled to the RT-500’s horizontal-shaft impactor crusher. The crusher features a heavy-duty main shaft and bearings, says Roadtec, and uses four rows of hammer bars in its patented “hammer-and- wedge” design. Abrasion-resistant liners are designed to provide wear protection in the crusher, says the company, and a hydraulic access door facilitates maintenance. The shaft-and-rotor assembly is designed for removal without press fits or keys. Material processed by the crusher is recirculated to the top deck of the screen and then into the RT-500’s twin-shaft pugmill that uses 48-inch-diameter shafts 6 feet in length (8-foot shafts are available).
The crushing/sizing process is designed to eliminate having to pre-process recycled asphalt pavement (RAP) when the RT-500 is used as a cold-mix plant, says Roadtec. The RT-500 uses a weigh bridge to monitor the volume of material from the screen that is placed in the pugmill, thus coordinating material volume with proper amounts of additives, which are metered and injected via a computer-controlled system. Up to three additives are used, says Roadtec, such as emulsion or foamed liquid asphalt cement, slurry, and water, depending on mix design. The finished mix is then either discharged into a windrow or conveyed into a paver’s hopper.
The RT-500 computer logs all production data at desired intervals. The data then can be downloaded for a complete history report, including rates of all materials used, date, time, distance (or station), and speed. Data can be shown in either Metric or English units.