Cold planer

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A cold planer removing asphalt from a street at Sestri Ponente (Genoa)

A cold planer (also known as a pavement planer, pavement recycler, asphalt milling machine or roto-mill) is a construction machine used to remove bituminous pavement or asphalt concrete from roadways, resulting in a somewhat rough, even surface that can be immediately opened to traffic. This is accomplished by bringing a rotating mandrel or "head" into contact with the pavement at an exact depth or slope. The mandrel has hundreds of hardened spikes on its surface, which bite and tear away at the roadway's surface. The surface material that is removed is normally fed by conveyor into a dump truck or semi trailer, but can be left in place or windrowed to be removed at a later date or recycled. A water spray system provides cooling for the mandrel, as well as dust management.

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Asphalt milling machines have been around for over 30 years. Asphalt milling is the process of grinding up asphalt that can then be recycled. The process came about because many streets were getting higher and higher on curbs, and therefore drainage of the roadway was becoming an increasingly bad problem. The first production milling machines were called Galions after their manufacturer, Galion Iron Works. These machines resembled graders in shape and size. The difference was there was a 30-inch-wide (760 mm) milling head where the scraper blade would normally be. The cutter drum was set into action by a rather large hydraulic pump.

Today's machines are much larger. They also have elaborate conveyor systems to reduce the labor of picking up the material from the roadway. With many new types of asphalt aggregates in use today the asphalt cold milling machines are often used. These new production machines are designed to tackle any mix design they chew into. Some of the larger machines, depending on the depth of the cut, can cut close to 15,000 square yards (13,000 m2) a day, at 75 feet per minute.

Operating an asphalt milling machine requires specialized training. Typically newer machines require two or more people to operate safely and efficiently. The operator stands on the deck of the machine and controls most of the machine's functions, while another person on the ground controls the depth of the cut and keeps an eye out for obstructions in the roadway such as manholes and/or water valves. Operators typically learn by on-the-job training, making the transition from operating on the ground to running the machine on top.

Diamond grinding of pavement is a process to work the surface of asphalt or concrete pavement.