Asphalt is a great paving material, especially when you need to cover large areas (e.g. parking lots). It's not indestructible, though, and you need to know when to draw the line between resurfacing a worn lot and replacing it entirely. When a quarter or more of the exposed surface is showing clear signs of damage it's time to start asking these questions.
Ultimately, the deciding factor between resurfacing and full replacement is what sort of shape the lot's base course is in. If you've been through multiple rounds of surface repair (i.e. hot-mix asphalt resurfacing) in a short span of time, the odds are good that there's a fundamental foundation problem down below.
There are a lot of worn asphalt lots that are in sound shape once you go one or two inches down beneath the surface. These properties are perfect candidates for asphalt milling.
Asphalt Milling Defined
The best asphalt resurfacing companies will provide this service first. In asphalt milling, an industrial grinder is brought in to scrape away one or two layers of asphalt pavement. The resulting surface is ready for immediate resurfacing or the installation of a new finish surface. Milling is less expensive than complete replacement of asphalt paving.
Key Signs That A Lot Is Ready For Milling:
Pavement is "unraveling" down from the finish surface
Pavement is suffering from top-down water penetration
Waves are appearing in the topmost layer of asphalt perpendicular to the normal direction of traffic. These waves are especially common in areas where vehicles break frequently and abruptly. Examples include exits and bus lines.
Surface reshaping is required for proper drainage, i.e. swales need to be cut so that precipitation runs off properly.
Low to moderate "alligator" cracking - these are interconnected perpendicular cracks caused by a combination of insufficient support and heavy traffic.
Asphalt Milling - The Benefits
Improved paving surface
Your pavement's longitudinal profile (cross-section) is restored to uniformity - ruts, bumps, and other irregularities are removed.
Drainage is improved.
Better texture for controlling skids.
Parking areas that have suffered repeated overlays are returned to a clean curb profile.
The process is time efficient. Industrial milling machines can cut 15,000 square yards a day.
Less interruption of traffic. In most cases, the surface can be utilized immediately for vehicular traffic as soon as milling is complete.
Sustainability. Milling creates Recycled Asphalt Pavement, or RAP. This material can be used to replace aggregate in fresh asphalt pours; the RAP generated in milling therefore has a significant monetary value.
Low environmental impact. Milling creates no smoke or hazardous materials; the minor amount of dust created can easily be mitigated.
Saving and reusing the RAP generated during milling reduces the environmental impact in projects where it is used.
Cost savings. Milling a parking lot costs less than reconstructing or replacing the asphalt. This can significantly expand the amount of work that will fit into a given maintenance budget.