When an asphalt pavement’s deficiencies are primarily surface distresses, milling (also known as cold planning) may offer an effective solution. Surface distress may include raveling (aggregate becoming separated from the binder), rutting (formation of low spots), shoving (a washboard-like effect), bleeding (asphalt binder coming up to the surface) and minor cracking.
A milling machine is designed to remove a selected, precise thickness of asphalt pavement. These machines use a large, rotating drum that grinds and removes the pavement surface without penetrating the base. Water is generally applied to the drum as it spins for heat and dust control.
As part of the process, the milled material is moved by conveyor belt from the machine and loaded into trucks. This material is then transported to an approved recycling site where it is screened and mixed with stone to produce high quality base material.
The asphalt pavement remaining after the milling process is thoroughly cleaned utilizing high-speed air blowers and/or mechanical sweepers. An asphalt emulsion tack coat is then sprayed over the entire area to improve bonding.
A new layer of hot mix asphalt is placed using conventional paving equipment. Generally, asphalt is replaced at the same thickness as was removed. Thickness may be varied to meet special requirements. Compaction is completed with steel wheeled, vibratory rollers.
A major advantage of asphalt milling is that there need not be any elevation changes. The completed new pavement should match existing structures and should not change the drainage in any way. Milling is also cost effective, environmentally friendly, and has a faster completion time compared to many other systems.
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