Asphalt milling (cold planing, asphalt milling, or profiling) is the process of removing at least part of the surface of a paved area such as a road or parking lot. Milling removes anywhere from just enough thickness to level and smooth the surface to a full depth removal. There are a number of different reasons for milling a paved area instead of simply repaving over the existing surface.
Milling allows new asphalt to be laid down without increasing the height of the pavement and saves you time if the sub-base doesn't need to be fixed. Thanks to the milling process curbs, drainage and other existing structures remain undisturbed.
Asphalt milling is done using a milling machine. The first production milling machines were called Galions because Gilion Iron Works manufactured them. They now come in various sizes to handle small or big jobs. Some of the larger machines, depending on the depth of the cut, can cut close to 15,000 square yards (13,000 square meters) a day, at 75 feet per minute.
The cutting drum rotates cutting heads across the surface, chewing up the existing asphalt to the depth of the cutting heads. The vacuum sucks up the milled material and deposits it where the conveyance system can then move it to a dump truck. The dump truck and the milling machine move together so the material is collected as it is removed from the surface, saving a lot of the time and effort that would be needed to collected later. The milled asphalt is recycled and reused in future paving projects.
Once the milling machine has removed the asphalt to the desired width and depth, the surface is swept and cleaned. This removes dust and debris that might cause problems with the new asphalt bonding to the surface. Once clean, the bond between the old and new asphalt should be very good, particularly as the old asphalt has a rough surface from the milling that will bond to the new better.
Proper milling allows new layers of asphalt to be laid evenly and at the same depth as the old surface, ensuring other structures like curbs and drainage ditches are not negatively affected. It also allows for the easy collection of old asphalt to be recycled for new applications.
1. Because just the affected layers can be removed, it will be less expensive to repave.
2. Trucking charges will be less to deliver the reduced amount of asphalt as well as to haul the old asphalt away.
3. It is sometimes possible to recycle the milled asphalt on-site, reducing costs even more.
4. Contractors can often charge lower labor costs due to the reduced time that the crew must spend on the job.