Understanding Asphalt Milling: Definition And Purpose
Asphalt milling is the process of removing one or more layers of asphalt using a milling machine. It is the most common form of cold planing, a broader concept that involves removing layers from paved surfaces without the use of heat.
The purpose of asphalt milling is twofold: To remove part of an asphalt surface to create an easy-to-work-with, uniform layer and to reclaim asphalt for reuse in other projects.
Business owners who need paved surfaces overlaid or refinished should consider asphalt milling because it’s one of the fastest, most cost-effective ways to prepare surfaces for new asphalt.
The Complete Asphalt Milling Process
Asphalt milling is one of the quickest ways to remove asphalt. The process involves four steps:
- Assessment: Will the asphalt surface you’re working on benefit from milling? Typically, you’ll only want to remove the top layer of asphalt through milling (though in some cases, sub-layers can also be removed). When the project requires all of the asphalt to be removed, full-depth reclamation (FDR) is typically used instead of asphalt milling.
- Milling: Specialized milling machines precisely grind and break up the asphalt layers being milled. These machines feature carbide cutters on a rotating drum and conveyor belts that pick up the milled pieces of asphalt.
- Reclaiming: The milled pieces of asphalt picked up by the machine are deposited into a dump truck to be transported to a recycling facility.
- Cleaning: Loose pieces of asphalt and dust that remain on the surface are cleaned away with sweeping machines and water.
Equipment Used In Professional Asphalt Milling
Asphalt milling machines are the most important pieces of equipment used in the milling process; dump trucks are also essential to carry the milled asphalt. These are not the only useful pieces of equipment, however; several other tools and pieces of machinery may be used, including:
- Truck brooms/power brooms
- Water trucks
- Skid steers
- Loaders
- Walk-behind milling machines
- Asphalt cutoff saws
These tools help to clear asphalt and keep other machinery running; they also allow contractors to access areas that larger asphalt milling machines are too big to pass over.
When Is Asphalt Milling Necessary?
Asphalt milling is used when a paved surface is compromised – especially when the damage only extends to the top layer of asphalt. Milling prepares a surface for resurfacing or overlays. Your contractor may recommend asphalt milling to restore asphalt that’s been seriously compromised by:
- Cracks
- Potholes
- Ruts
- Poor drainage
- Raveling
- Bleeding
- And other damage
Roads, parking lots, driveways, sidewalks, and other asphalt-paved surfaces can all benefit from asphalt milling.
Common Issues Addressed By Milling
When asphalt pavement is milled, the top few inches are removed without compromising the structural integrity of the base. The depth at which the machines mill can be adjusted, which allows operators to fix drainage problems by adjusting slopes. Finally, the surface left behind is rough; this textured surface is easier for new asphalt to adhere to.
Thanks to these qualities, milling can be used to:
- Resurface parking lots
- Resurface roads
- Prepare surfaces for treatments
- Adjust the elevation of a paved surface
Benefits Of Asphalt Milling For Phoenix Properties
Asphalt milling is one of the most commonly used techniques to prepare large asphalt surfaces for resurfacing. The speed at which milling can be performed reduces downtime, so municipalities and businesses can get their roads, parking lots, and other paved surfaces back in working order faster.
Another core benefit of asphalt milling is that the collected material (known as asphalt millings) can be reused in other projects. Though this does not directly benefit Phoenix property owners, there are a number of indirect benefits. The most important among those benefits is that collecting asphalt millings makes this type of work more cost-effective for contractors; consequently, the price of asphalt milling is lower than it would be if the recovered materials could not be reused.
Cost-Effectiveness & Sustainability
Asphalt milling is cost-effective for two reasons:
- Massive volumes of asphalt can be milled; tens of thousands of square feet per hour per machine.
- The collected asphalt millings can be reused or sold by the asphalt milling contractors.
Volume here is a key detail; asphalt milling is not typically cost-effective for small areas that need to be resurfaced. You’re more likely to see milling for surface damage across an entire parking lot or a section of road, rather than milling on a small pathway (though walk-behind mills do exist – and they are cost-effective for smaller jobs).
Sustainability is the other key advantage of asphalt milling. As we’ll explore further in a later section, asphalt millings can be used almost anywhere that you could use traditional asphalt – it just needs to be processed first. This can help business owners and municipalities meet sustainability goals; we encourage our readers to look into using reclaimed asphalt pavement (RAP) in future projects.
Types Of Asphalt Milling Techniques
There are a number of different asphalt milling techniques; the technique we’ve covered so far is standard asphalt milling, which removes inches of paved material to prepare the surface for fresh asphalt material. The technique that contractors will use depends on the nature of your asphalt paving project. Milling techniques include:
- Standard milling
- Micro-milling
- Fine milling
- Deep milling
- Edge milling
These milling techniques use different sizes of machines and varied tooth spacing to remove specific depths; they also produce different textures on the remaining surface.
Standard Milling Vs. Micro-Milling
Two of the most common milling techniques are standard milling and micro-milling.
Standard milling removes 1 to 3 inches of asphalt, leaving rough grooves. This is the technique that’s used for the resurfacing of parking lots and roads; it’s great for fixing drainage issues caused by improper slopes and removing heavily damaged top layers.
Micro-milling removes ½” or less of asphalt; it’s used to prepare surfaces for treatments like slurry seal or to improve the smoothness of paved surfaces.
Preparing Your Property For Asphalt Milling
Preparing for asphalt milling is a relatively straightforward process. You’ll want to remove any obstacles from the area being milled. Contractors can work around structures like concrete barriers and light poles, but you should move any traffic cones, vehicles, and other potential obstructions.
Your contractor will tell you what you’ll need to do to prepare and how long the asphalt milling process will take. In almost all cases, new asphalt will be applied to the milled surface, so the downtime for your paved surfaces will be longer than the time it takes to just complete the milling process.
What To Expect During The Process
Expect a lot of machinery and people on your property – machinery and people that will use defined entrance and exit points. You’ll need to close affected areas off to traffic to leave space for your contractor to operate. They’ll give you a timeframe in which the surfaces need to remain closed.
Noise pollution and dust are to be expected during the process; this can create some disruptions, so depending on your line of business, you may want to close temporarily during the asphalt milling process.
Recycling And Reusing Asphalt Millings
Asphalt millings are recycled and reused; this reused product is known as reclaimed asphalt pavement (RAP). To create RAP, plants use a multistep process:
- Milled asphalt is hauled to the plant.
- The milled asphalt is then crushed and screened to separate it into different aggregate sizes and remove oversized pieces.
- The crushed asphalt is mixed with new aggregates and bitumen.
- The combined mixture is carefully heated and mixed to create new asphalt pavement; this hot mix asphalt can then be used like regular asphalt pavement.
Applications For Reclaimed Asphalt Pavement
Reclaimed asphalt pavement can be used almost anywhere you could use standard asphalt pavement. In most cases, asphalt pavement blends that use RAP contain about 15-30% reclaimed product and 70-85% new (virgin) asphalt. Mixes that use higher percentages of RAP tend to gray much faster than new asphalt, and can have performance issues; as such, they’re more rarely used – especially in extremely hot environments like Phoenix.
Japan has one of the highest uses of recycled asphalt pavement in the world; in that country, the average level of RAP in asphalt pavements is 47%. Context is extremely important when it comes to RAP percentages in pavement.
Asphalt Milling Vs. Complete Replacement
Asphalt milling removes the top layers of asphalt, only penetrating 1 to 3 inches deep. Complete replacement, on the other hand, removes all of the asphalt pavement layers; it may even involve removing the concrete base to fix structural issues.
Making The Right Choice For Your Project
The type of restoration that your paved surface will need depends on the issues at hand. Structural issues that stem from deep within the asphalt pavement or its concrete substrate will require complete replacement. Surface-level defects, on the other hand, can be removed by milling machines.
Unless you’re an asphalt contractor, you will not have the knowledge needed to determine whether milling or complete replacement is right for you. Fortunately, our team can handle the job – just like we’ve handled over a thousand others.
Choosing Professional Asphalt Milling Services In Phoenix
Choosing a company to provide asphalt milling surfaces is the same as choosing any contractor for paving work. Look at the projects they’ve done and the size of their team. Look at testimonials and reviews from customers. Contact them for quotes and more information. Using all of that information, you can make a decision on which contractor is right for you.
Having read this article, you’re already more informed than most about the nitty-gritty of asphalt milling. As a contractor that offers asphalt paving in Phoenix, AZ – including asphalt milling services – we’re happy to answer any questions you might have about processes and price. Get in touch with us!