Asphalt milling, also called cold milling or cold planing, is the process of removing a part of the existing pavement surface to help restore it to a uniform texture to use or repave. Specially designed milling equipment can reach various depths, from removing just enough to make the surface level and smooth out any irregularities to a full-depth removal.
Asphalt milling makes it possible to repair or replace the top layer of existing asphalt, like a road surface or parking lot, without having to demolish and redo the entire structure. It also allows for the discarded asphalt pieces, called millings, to be recycled in resurfacing the pavement.
In this article, we go over the process of asphalt milling, what equipment you need, the different types of asphalt milling, and how it can benefit your project.
The Asphalt Milling Process
The asphalt milling process is comprised of several steps:
- Determine if the asphalt condition could benefit from asphalt milling. You get the best results with asphalt milling if you only intend to remove the top layer of asphalt and not the underlying sub-base materials.
- Use a milling machine to grind up the top layer of asphalt, adjusting to the depth you need, depending on your project and how damaged the asphalt is.
- Put asphalt millings into a dump truck to be reused. The crushed asphalt can be as useful of an aggregate as concrete, gravel, or fresh asphalt in resurfacing.
- Clean up the milled surface by sweeping up or washing away dust and loose millings.
- Lay new asphalt material.
What Projects Need Asphalt Milling?
Asphalt milling offers a great solution for restoring uneven and bumpy pavement, pavement with irregularities like ruts or potholes, pavement damaged by accidents or fires, or any other damage that compromises a paved surface. You can use asphalt milling for projects like:
- Parking lots
Some of the main issues asphalt milling addresses include:
- Cracking: Asphalt milling is very effective at fixing surface flaws. Using it to eliminate cracks, or other areas where water and debris could penetrate your pavement protects both the surface and the layers underneath from deterioration.
- Raveling: When an asphalt surface ravels, or begins to disintegrate, its aggregate materials are dislodged, making it rougher, more easily damaged, and more dangerous to use. Asphalt milling removes the compromised surface and turns the old asphalt into new aggregate for repaving.
- Bleeding: Bleeding, or flushing, happens when an oil-based asphalt binder fills the aggregate voids, usually during hot weather or because of traffic compaction, causing an oily film to appear on an asphalt surface. It’s often the result of overasphalting. Asphalt milling can remove the layer of asphalt prone to bleeds so that it can be replaced.
What Are the Benefits of Asphalt Milling?
When you need to repair an asphalt surface, asphalt milling can be a great option as compared to other methods you might use. Some of the benefits of asphalt milling include:
- Environmentally-friendly: The milling process doesn’t create smoke or flame, and creates aggregate that can be reused, either in your paving project as recycled asphalt pavement or in new hot mix asphalt. Asphalt milling requires less processing than other options, which means it uses less energy and fewer resources.
- Recycled materials for current or future projects: Millings can be used as a new material in most pavement projects.
- Improves the surface to prevent skidding: Asphalt milling eliminates bumps, ruts, and other surface irregularities that can impact the safety of a paved surface.
- Less expensive. It’s more cost-effective to resurface pavement than to replace the entire structure. If your problem is contained in the top layer of asphalt, asphalt milling allows you to address that without disturbing the sub-base at all, at a much lower cost.
- Minimal traffic disruption. Milling is a quick process, minimizing the amount of time it takes to repave. In addition, you can move traffic into the milled lane to reduce the impact and length of lane closures.
What Equipment is Needed For Asphalt Milling?
Asphalt milling uses specially designed equipment to pick up, compact, and redistribute asphalt. You need these key pieces of equipment:
- Milling machines
- Haul trucks
- Water trucks
- Sweepers or power brooms
Asphalt Milling vs. Micro Milling
Micro milling uses the same basic equipment as asphalt milling and serves a similar function: to adjust the grade, elevation, and smoothness of a paved surface or road. However, micro milling uses more cutting teeth, pulverizing the asphalt, and creating a finer surface texture.
A finer surface can result in a better foundation for repaving after milling, but micro milling only works at depths of two inches or less — anything deeper than that requires asphalt milling.
How Are Asphalt Millings Reused?
The new material generated by asphalt milling, reclaimed asphalt pavement, or RAP, is almost always returned back into the roadway structure in some way. It can be incorporated into asphalt paving through hot or cold recycling or used as an aggregate in base or sub-base construction.
Outside of roadways, RAP isn’t typically used in high-traffic areas. It can, however, also be used in other construction applications, like as an aggregate substitute or supplement in recycled asphalt paving, a granular base or sub-base, a stabilized base aggregate, or an embankment or fill material.
If you’re dealing with a road, driveway, or other paved surfaces with pesky bumps or ruts and need a quick, cost-effective solution, asphalt milling might be the right choice for you. Check out our compaction equipment rental options for your next surfacing or paving project.