The milling process is the controlled removal of asphalt pavement to a predetermined depth, slope and/or specified thickness. As one can see by the pictures the milling machine actually grinds down the existing pavement, and the ground down pavement particles are hauled off to the asphalt plant to be used as recycled raw materials in the manufacturing of new asphalt.
There are many applications where the milling machine is used, most notably: edge milling in asphalt overlays, full depth removal of asphalt down to the base, correction of drainage problems in existing pavement prior to overlay, removal of asphalt prior to a full depth reclamation/pulverization, and full width milling in total asphalt overlays. In cases where the asphalt is removed down to the base in a full depth repair and/or total asphalt excavation, the milling machine can complete the task much faster than conventional excavation with front end loaders and excavators, thus saving the customer money. The milling machine can also remove the existing base and sub-base material if needed.
As noted in the pictures, there are many different sized milling machines that can be used on a project, with the size of the project and milling thickness being the determining factor.