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Concrete Milling 101: The Ultimate Guide

Concrete Milling 101: The Ultimate Guide

A Concreate worker operating a milling machine.

Unsure of what concrete milling is and when it’s recommended? Here’s everything to know about this surface preparation technique.

Key Takeaways:

  • Milling involves removing the top layer of concrete
  • It’s necessary when there’s a thick coating on the floor
  • Extremely rough concrete could also require milling
  • The process can prepare the floor for polishing in the future

If you’re considering updating or revamping your residential or commercial concrete floor, milling is one of the surface preparation techniques you may have encountered. Surface preparation is key to ensuring your new flooring finish will last, and milling is a popular way to create a smooth, level surface ready for polishing or resurfacing. But what is milling, and when should you use this technique? Read on for everything you need to know about concrete milling.

What is milling?

Like many surface preparation techniques, milling involves removing the top layers of concrete until you reach the desired depth. The job is typically done with a scarifying machine, which uses diamond-tipped blades to grind the top layers of concrete. 

As the machine passes over the concrete, the blades abrade the top layers between 5 mm and 50 mm deep, leaving behind a smooth surface.

Irregular or uneven concrete surfaces hamper concrete polishing, sealing, and other resurfacing treatments. Milling helps to smooth out the inconsistencies and create a level surface, allowing for a better finish with excellent adhesion.

Types of milling

Milling varies in depth and aggressiveness and is classified as either light, medium, or heavy milling, depending on how much material needs to be removed.

  • Light milling is perfect for removing thin coatings such as sealers, paint, or adhesives from concrete surfaces. The process is gentle and doesn’t require too much heavy equipment, making it ideal for small jobs.
  • Medium milling removes thicker coatings and lippage (unevenness or protrusions) from concrete floors. It requires more aggressive machinery than light milling but is still a relatively non-invasive process.
  • Heavy milling is the most aggressive form and is used to remove large amounts of concrete quickly. This type of milling is often used on very thick coatings or to level out extremely uneven surfaces. Heavy milling should only be done by experienced professionals with the proper equipment.

There are also four categories of concrete milling based on application:

  • Concrete floor milling: Involves bulk removal of materials from a concrete floor to prepare the surface for new coatings, epoxies, or polishing. It’s slightly different from concrete scarifying, a less aggressive milling form that leaves a rougher profile.
  • Asphalt milling: Over time, roads, pavements, parking lots, and other asphalt surfaces can become worn down and need repair or replacement. Asphalt milling involves removing the top layer of asphalt to the desired depth using heavy machinery. Concrete specialists can use it to level out a surface, repair damage, or prepare the asphalt for a new pavement layer.
  • Airport milling: Airports require smooth, level surfaces for safe take-offs and landings. Irregularities, potholes, and other damage can cause plane wheels to skid or bounce, leading to accidents. Airport milling helps grind down these uneven surfaces to create a safe runway with better traction.
  • Vertical milling: Sometimes called “profiling,” vertical milling removes damaged or deteriorated concrete on walls or columns. The process involves using a large machine to grind down the concrete to the desired level, being careful not to damage any structural supports.

When milling is the right choice

While milling is a popular surface preparation technique, it’s not always the best choice. In some cases, other methods like shot blasting or grinding may be more appropriate. Here are a few instances where milling is the best option:

You need to remove a very thick coating

Adequate surface preparation is essential for the success of any polishing or re-coating project. Dirt, debris, and existing coating layers can all prevent new treatments from adhering correctly. 

If you’re dealing with a very thick coating like elastomeric membranes, epoxy, or paint, milling is often the best way to remove it. The abrasive action of the blades will quickly strip away the coating without damaging the concrete underneath.

You need to level an extremely rough surface

Concrete surfaces fall into 10 Concrete Surface Profiles (CSPs) based on their level of roughness. CSP helps concrete installers achieve proper texture for successful bonding, polishing, and coating projects. 

If your surface is a 9 or 10 on the CSP scale (very rough), milling is the best way to level it out. Milling machines abrade the existing concrete surface, creating a more even texture ideal for bonding and polishing.

You need to remove large areas of concrete quickly

Milling is a surface preparation technique on steroids. It is fast, efficient, and can quickly remove large areas of concrete. This makes it ideal for projects that require a lot of surface prep, like airport runways and parking lots.

You’re working on a vertical surface

Vertical surfaces like walls and columns can be challenging to prepare for bonding, polishing, or coating. You might be able to use a hand grinder in some cases, but milling is often the best way to achieve a smooth, even surface. The blades on a milling machine can quickly remove concrete from vertical surfaces without damaging the underlying structure.

These are just a few instances where concrete milling can be the right choice. If you’re unsure whether milling suits your project, a concrete specialist will assess your needs and recommend the best surface preparation method.

Partner with experienced concrete specialists and get the job done right

Concrete milling is a versatile, cost-effective way to create smooth, level surfaces. However, it is a sensitive process that requires heavy machinery and experienced operators. Done incorrectly, it can damage your concrete or create an unsafe work environment. Partnering with a professional concrete contractor is the best way to ensure a successful milling job. 

Concreate is a leading expert and can help with all things concrete (except pouring), from assessment and repair to milling and polishing. With a decade of experience, our team has the knowledge and equipment to handle any concrete project, big or small. Visit our website thisisconcrete.com to learn more about our services.