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What Is Road Milling?

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Have you ever wondered how old, cracked roads are transformed into smooth highways without tearing everything apart? The answer lies in a powerful process called road milling — also known as pavement milling, asphalt milling, or cold planing. It's one of the most efficient ways to give damaged pavement a new life without starting from scratch.

Road milling plays a key role in modern construction and maintenance. Instead of rebuilding entire roads, it removes just the top layer of asphalt, fixing surface damage and preparing the ground for fresh pavement. This not only saves time and money, but also helps protect the environment by recycling old materials.

In this post, you'll learn what road milling is, how it works, why it's used, and what makes it such an essential technique in today's roadwork. We'll also explore the equipment involved, different milling methods, and the many benefits this process offers — from cost-efficiency to sustainability and longer-lasting roads.

What Is Road Milling?

Imagine taking off just the top layer of a road instead of digging everything up and starting over. That's what road milling does. It's a process that removes a portion of the paved surface — usually the damaged or worn-out part — without disturbing what's underneath. The goal? A smoother, safer road ready for fresh asphalt.

You'll hear people call it by different names:

  • Asphalt milling

  • Cold milling

  • Pavement milling

  • Or the more technical term: cold planing

They all mean pretty much the same thing — using a big machine to scrape away the top of the road.

Unlike complete road replacement, which tears out everything down to the base, road milling is quicker and more budget-friendly. It only targets the surface layer. That means fewer materials, less construction time, and fewer traffic delays. The original foundation stays in place, so crews can lay new asphalt directly over it.

Let's break it down with a quick comparison:

Feature Road Milling Complete Road Replacement
Process Removes surface layer only Digs out full pavement structure
Time Required Short Long
Cost Lower Higher
Environmental Impact Reuses old asphalt (recycling) Creates more waste
Subbase Disturbance Minimal or none Full removal
Typical Uses Surface repair, overlay prep Structural damage, base issues

Think of road milling as a clean shave — it smooths out bumps, cracks, and ruts so the next layer can go on cleanly. And thanks to this method, roads last longer and drive better — all without starting from zero.

Why Is Road Milling Used?

Roads age. Cracks open, ruts sink, bumps rise. Instead of ripping out every layer, crews run a milling machine across the surface. It slices off the worn asphalt so new pavement sticks like glue.

Prepares Surface for Repaving

  • Rough, oxidized asphalt gets shaved away.

  • Fresh aggregate shows, creating a textured "tooth" the new mix can grip.

  • No need to tack more layers on top; we keep the road at its original elevation.

Fixes Surface Damage—Subbase Stays Put

  • Milling targets only the trouble spots: potholes, bleeding binder, raveling aggregate.

  • The rock-solid base stays untouched, saving time and money.

  • Less excavation means fewer lane closures and faster reopenings.

Lets Crews Adjust Height for Curbs, Drains, Bridges

Structure Affected Typical Issue Milling Advantage
Curbs & Gutters Pavement sits higher than curb, blocks runoff Mill a thin layer, restore proper curb reveal
Manholes & Catch Basins Covers sit low after overlays Trim surrounding pavement, lids sit flush
Bridge Decks New overlay adds weight, reduces clearance Remove old asphalt first, maintain design height
Guardrails/Barriers Road layers creep up over years Lower surface so posts meet safety spec

By dialing depth in fractions of an inch, crews fine-tune slopes for drainage or match adjacent slabs. It's a simple shave that keeps the whole system in balance.

How Does Road Milling Work?

Road milling might look like a giant machine scraping the ground — and that's exactly what it is. But there's a smart system behind it. Each part works together to turn rough asphalt into reusable material.

Step-by-Step: The Milling Process

  1. Site setup begins
    Crews block off the area, set safety signs, and prep the work zone.

  2. Milling machine rolls in
    This big machine — also called a cold planer — lowers a rotating drum onto the pavement.

  3. Cutting starts
    Sharp carbide teeth dig into the asphalt, peeling off the top layer bit by bit.

  4. Material moves forward
    The crushed pieces drop onto a built-in conveyor belt.

  5. Transfer to dump truck
    The belt launches the material into a truck just ahead of the milling machine.

  6. Dust gets handled
    A water spray system keeps things cool and cuts down dust clouds.

  7. Final cleanup
    Sweepers roll in, clearing leftover bits so the surface is ready for paving.

How It Removes Pavement Layers

The milling drum spins against the direction of travel. This creates a scraping effect, not a rolling one. The drum holds rows of teeth spaced to control depth and texture. By changing the spacing, crews decide how smooth or rough the surface will be.

Depth Type Use Case Teeth Spacing
Full-depth (2"+) Complete surface removal Wide spacing
Surface-level Repaving prep, smooth finish Tight (micro-milling)

More teeth = smoother results.

Recycled Material Collection and Reuse

Once asphalt gets milled, it's not trash — it's gold. Here's what happens next:

  • Milled chunks go to a Reclaimed Asphalt Pavement (RAP) facility.

  • There, they're crushed into gravel-sized pieces.

  • These are mixed with bitumen, sand, and stone to make new asphalt.

Instead of sending old pavement to landfills, crews reuse it. That means fewer raw materials, lower costs, and a much greener process.

What Equipment Is Used in Road Milling?

To turn rough pavement into a clean, reusable surface, you need more than just one big machine. Road milling relies on a whole team of tools — each doing a specific job to keep the process fast, safe, and efficient.

1. Milling Machine (Cold Planer)

This is the star of the show. A cold planer rolls in, drops its spinning drum, and begins grinding asphalt.

Key Components:

  • Milling Drum: The rotating cylinder covered in rows of tool holders. These tool holders grip the cutting teeth that slice through asphalt like butter.

  • Cutting Teeth: Made of carbide, these sharp tips do the actual cutting. They wear out over time, so crews replace them often.

  • Conveyor System: A belt that lifts the milled asphalt and tosses it into a truck. It's quick, clean, and keeps the job moving.

Front-Loading vs. Rear-Loading:

Type Material Exit Point Common Use Benefit
Front-Loading Conveyor shoots forward Most modern jobsites Easier coordination
Rear-Loading Conveyor dumps behind Older or tight road setups Works in narrow zones

Front-loaders pair easily with dump trucks. Rear-loaders need more planning but can work in smaller spaces.

2. Support Equipment

A milling machine can't do it all. It needs backup from a few key players.

  • Dump Trucks
    These follow close behind, ready to catch the milled material as it's shot out from the conveyor. Once full, they haul it to recycling facilities or temporary storage.

  • Water Trucks
    Milling kicks up dust and creates heat. Water trucks spray a steady mist during the job to cool down the drum and keep the air clear.

  • Sweepers
    After milling, dust and loose chunks remain. Sweepers roll through to clean the site, leaving a fresh, textured surface ready for new asphalt.


Here's a quick overview:

Equipment Job Role Why It Matters
Cold Planer Cuts and mills asphalt surface Core machine for road milling
Dump Truck Carries away milled material Keeps the site clean and moving
Water Truck Controls dust and heat Improves safety and visibility
Sweeper Cleans remaining debris Prepares surface for overlay

Different Types of Road Milling

Not all road surfaces need the same fix. That's why milling comes in different styles — each designed to match the depth, purpose, and condition of the pavement. Whether we're smoothing the surface or stripping it down, there's a method for it.

1. Fine Milling

Use: Touch-ups for the top layer

Fine milling targets surface issues — shallow cracks, rough textures, or early wear. It's perfect when the road base is still strong. The milling machine removes just enough material to make the road even again. Then we can apply a thin overlay without raising the height too much.

Benefits:

  • Improves skid resistance

  • Prepares surface for a smooth overlay

  • Keeps drainage working right

Key Features:

  • Medium-depth cuts

  • Balanced texture

  • Common in urban road maintenance

2. Planing

Use: Full-depth removal for large-scale repaving

Planing is the heavy-duty version. Crews dig deeper — right through damaged layers — to completely rebuild high-traffic areas like highways or industrial zones. It's not just a repair; it's a reset.

Planing Process:

  • Cut down to the base

  • Remove all damaged material

  • Reuse milled pieces as aggregate

  • Repave from the ground up

Best For:

  • Roads with base failure

  • Widespread cracking or rutting

  • Projects needing structural upgrades

3. Micro-Milling

Use: Preventive maintenance on light wear

Micro-milling takes off just a paper-thin layer — usually an inch or less. What makes it special? The milling drum has more cutting teeth packed closely together. That means it leaves behind a smoother finish.

Why It Works:

  • Slows down road wear

  • Reduces need for overlays

  • Fixes minor surface distress early

Where It Helps Most:

  • Roads showing early raveling

  • Surfaces with minor bumps or bleeding

  • Areas needing texture improvement for safety

Feature Fine Milling Planing Micro-Milling
Depth of Cut Medium Deep Very shallow
Surface Texture Moderate New surface Very smooth
Main Purpose Repair Rebuild Prevent damage
Cost Efficiency High Medium Very high

Where Is Road Milling Commonly Used?

You don't need to dig up an entire road to make it better — just mill the part that's worn out. Road milling shows up all over our cities, highways, and even airports. Here's where it does the most work.

Highways and Main Roads

Heavy traffic wears roads down fast. Trucks, buses, and weather all leave their mark. Milling helps fix ruts, cracks, and surface wear without replacing the whole road. Crews mill long stretches, smooth things out, and lay fresh asphalt — all while keeping traffic flowing in nearby lanes.

Parking Lots

Businesses want smooth parking lots that look clean and feel safe. When cracks, bumps, or drainage problems show up, milling machines step in. They grind the top layer, remove damage, and make the lot ready for new pavement. It's faster and cheaper than a full rebuild.

Driveways and Sidewalks

Milling isn't just for highways. Residential and commercial driveways use it to remove surface defects or prepare for overlays. Sidewalks with trip hazards or height differences? A quick mill can even out the slab without breaking concrete apart.

Intersections and Ramps

These areas take a beating. Cars brake, stop, and turn constantly — which leads to rapid wear. Milling helps correct rough transitions and surface irregularities. It also allows crews to level out grade changes between intersecting roads or adjust slope for better drainage.

Airports and Bridge Decks

Planes land hard, and bridge decks shift with traffic and temperature. Both need precision repair. Milling gives engineers a way to fix surface damage, remove bumps, and restore safety — without damaging the underlying structure.

Application Area Common Issues Milling Solution
Highways/Main Roads Rutting, cracking Smooths surface, prep for overlay
Parking Lots Potholes, poor drainage Levels surface, enhances appearance
Driveways/Sidewalks Unevenness, minor cracking Removes thin layer, safe to walk/drive
Intersections/Ramps Bumps, misaligned pavement Adjusts slope, improves transitions
Airports/Bridge Decks Impact damage, uneven joints Precision milling without base harm

Common Problems Road Milling Solves

When pavement starts breaking down, it shows up in different ways — some obvious, some not so much. Road milling steps in to fix these issues fast without a full rebuild. Here's what it takes care of.

Cracks and Potholes

Cracks let water in. Water weakens the layers underneath. That's how potholes form. Milling removes the cracked surface and gives new asphalt a fresh base to bond with — sealing out future damage.

Rutting (Wheel Path Grooves)

You've seen it — tire tracks carved into the road from heavy trucks. These grooves collect water and mess up driving. A milling machine grinds down the ruts and levels the lane for safer travel.

Raveling (Loose Surface Aggregate)

When asphalt loses its grip, tiny rocks break free. It starts feeling rough, then slippery. Milling gets rid of the loose top layer and replaces it with fresh, tightly bound asphalt.

Bleeding (Bitumen Rising to the Surface)

Too much binder, hot weather, or heavy traffic can push oily asphalt to the top. This slick film is dangerous. Milling takes off the top layer so new material sticks better and stays safe.

Shoving (Waves in Pavement)

When cars or trucks push soft asphalt, it ripples like a wave. It happens at stops, curves, or steep hills. Milling cuts through the shove and flattens the surface before it gets worse.

Poor Ride Quality (Bumps, Sags, Depressions)

A road full of dips and humps doesn't just feel bad — it's unsafe. Milling smooths out rough spots so vehicles glide over instead of bouncing or bottoming out.

Drainage Issues (Surface Too High)

Every time a new layer is added, roads rise a bit. Eventually, water stops draining right. Milling lowers the surface back to spec. That way, water flows into drains instead of pooling on the road.

Problem Type What You See What Milling Does
Cracks & Potholes Fractures, holes Removes damaged top layer
Rutting Grooves in tire tracks Levels the wheel path
Raveling Loose gravel-like texture Strips unstable surface
Bleeding Slick, shiny road surface Eliminates excess binder layer
Shoving Ripples or waves in asphalt Cuts and resets surface profile
Ride Quality Issues Bumps, sags, sudden jolts Smooths for safer driving
Drainage Problems Water pooling, blocked flow Restores height for runoff

Benefits of Road Milling

Road milling isn't just about grinding asphalt — it's about making pavement smarter, cleaner, and more cost-effective. Here's why cities, contractors, and engineers rely on it every day.

1. Economic Efficiency

Full reconstruction? Expensive. Milling? Not so much. Since it only targets the damaged surface, it cuts down on materials, crew size, and construction time.

Why it saves money:

  • Less asphalt needed for overlays

  • Smaller crews complete jobs faster

  • Recycled millings reduce raw material costs

2. Environmental Sustainability

When we mill a road, we don't throw the old asphalt away — we reuse it. That means less waste in landfills and fewer natural resources pulled from the earth.

How milling helps the planet:

  • Milled asphalt becomes RAP (Reclaimed Asphalt Pavement)

  • RAP gets mixed into new pavement

  • Recycling reduces carbon footprint and raw material use

3. Surface Height and Drainage Control

Piling layer after layer of asphalt can raise road height too much. That messes up curb lines, manholes, and drainage. Milling brings it back down to size.

Fixes problems like:

  • Water pooling near curbs

  • Catch basins sitting too low

  • Driveways and intersections becoming uneven

4. Time and Traffic Efficiency

Milling is fast. Instead of shutting down a road for weeks, crews can be in and out — often within a day — especially for small jobs or thin-layer milling.

Drivers stay happier because:

  • Less time waiting on road repairs

  • Partial lane closures instead of full shutdowns

  • Immediate prep for paving after milling

5. Improved Road Safety

Smoother roads mean safer roads. Milling reduces bumps, ruts, and slick spots. It also improves grip by restoring proper surface texture.

Key safety upgrades:

  • Reduces skidding on worn surfaces

  • Removes oil-slicked or bleeding asphalt

  • Creates an even base for overlays or surface treatments

Road Milling vs Full Reconstruction

When a road starts to fail, crews face a big decision: mill the surface or tear everything out? Both methods fix pavement, but they work differently — in cost, time, and purpose.

Cost Comparison

Milling is more budget-friendly. It keeps the base layer intact and focuses only on the top, saving tons of material and labor. Full reconstruction? That's a deeper investment — new base, new layers, more equipment.

Cost Factor Road Milling Full Reconstruction
Material Needed Low (uses recycled) High (all new material)
Labor Requirements Small to medium Large, multi-crew
Equipment Milling machine + few trucks Excavators, graders, rollers

Time and Equipment Differences

Milling moves fast. Machines roll in, grind the surface, and prep it for new asphalt — sometimes in just a few hours. Full reconstruction means excavation, regrading, compacting, and rebuilding. More steps, more delays.

Road Milling:

  • Requires milling machine, water truck, dump truck, sweeper

  • Often completed in one or two passes

  • Great for night work or tight schedules

Full Reconstruction:

  • Uses heavy-duty equipment like bulldozers and pavers

  • Requires subbase removal and reinstallation

  • Projects often stretch across weeks

Which Method Is Better and When?

It depends on what's wrong underneath.

Choose road milling when:

  • The base layer is still solid

  • You need to fix surface cracks, ruts, or minor bumps

  • Time and cost are critical

  • You plan to overlay with new asphalt

Go with full reconstruction when:

  • The pavement is failing from the bottom up

  • There are drainage or structural issues

  • The surface is beyond repair or heavily deformed

Situation Best Method
Surface damage only Road Milling
Deep cracks reaching subbase Full Reconstruction
Fast repair needed Road Milling
Long-term structural solution Full Reconstruction
Budget-conscious maintenance Road Milling

Road Milling vs Asphalt Overlay

Before crews add new asphalt to an old road, they face a choice: overlay directly or mill first.

What Is Overlaying?

An asphalt overlay is a fresh layer — usually 1–2 inches thick — placed straight on top of the existing pavement. It hides cracks, improves ride quality, and adds life without digging into the surface.

When to Choose Milling Before Overlay

Overlaying alone isn't always enough. We mill first when:

  • Height matters — Extra layers could block curbs, drains, or garage entrances.

  • Surface is uneven — Ruts or bumps need leveling so the overlay bonds evenly.

  • Cracks run deep — Milling removes weak material, stops cracks from reflecting through.

  • Drainage is poor — Lowering the surface restores slope toward catch basins.

Condition Overlay Only Mill + Overlay
Pavement height acceptable
Ruts or wheel paths present
Deep cracking visible
Drainage issues exist

Combined Approach Benefits

Doing both — milling first, overlaying after — gives the best of each method.

  • Even Surface: Milling flattens; overlay seals.

  • Longer Life: Fresh asphalt bonds tighter to a clean, textured base.

  • Cost Control: Less material than full reconstruction, fewer future repairs.

  • Sustainability: Milled asphalt becomes RAP, reducing waste and raw aggregate use.

Asphalt Milling vs Micro-Milling

Both asphalt milling and micro-milling use machines to remove the top layer of pavement — but they serve different purposes, reach different depths, and leave very different finishes.

Structural and Functional Differences

Asphalt milling cuts deeper. It removes damaged layers, prepares for overlays, and fixes structural issues near the surface. Great for roads that see heavy use and need a fresh start without full reconstruction.

Micro-milling goes shallow. It scrapes off a thin layer — less than an inch — with more cutting teeth. Think of it as polishing instead of grinding. It's perfect for improving texture, restoring skid resistance, or prepping for a very thin overlay.

Feature Asphalt Milling Micro-Milling
Depth 1" to several inches Usually < 1 inch
Cutting Teeth Spacing Wider Dense and closely spaced
Use Case Structural prep Surface texture, safety

Cost and Depth Differences

Milling costs more because it digs deeper and takes longer. It's used when the pavement has damage below the surface — cracks, ruts, potholes. Crews haul away more material and may need multiple passes.

Micro-milling is faster, lighter, and cheaper. Since it removes less asphalt, there's less cleanup, fewer trucks, and lower labor costs.

Cost Factor Asphalt Milling Micro-Milling
Labor Intensity Higher Lower
Hauling Required Yes Minimal
Typical Project Road resurfacing Skid correction

Surface Smoothness Results

Here's where micro-milling shines. It leaves a much finer finish — smooth enough for thin overlays or even as a final surface in low-speed areas. Milling, on the other hand, can leave ridges that require follow-up paving to even out.

Visual Difference:

  • Milled Surface: Grooved, coarse texture

  • Micro-Milled Surface: Almost polished, fine lines

Drivers feel the difference. Micro-milled surfaces reduce road noise and tire vibration — especially helpful near neighborhoods or urban areas.

Finish Quality Asphalt Milling Micro-Milling
Surface Texture Rough, needs overlay Smooth, can be left as-is
Overlay Needed Always Optional
Skid Resistance Improved after paving Improved instantly

What to Expect During a Road Milling Project

Road milling projects move fast, but they still follow a clear plan. Whether you're a nearby resident, a city planner, or a curious driver, it helps to know what's coming — and what it's going to sound and feel like.

Timeline: From Site Assessment to Final Resurfacing

  1. Site Inspection
    Engineers check the road for cracks, ruts, or bumps. They measure depths, mark utilities, and decide how much asphalt to remove.

  2. Traffic Control Setup
    Crews place signs, cones, and barriers. Detours go up if needed. This keeps workers and drivers safe during the process.

  3. Milling Day
    Machines roll in early. The milling drum cuts the asphalt. Conveyor belts send the material to waiting dump trucks. Water keeps dust down. Crews follow a tight path and clear lane by lane.

  4. Surface Cleanup
    Sweepers remove dust and leftover chunks. The road is now rough but level — ready for the next layer.

  5. Overlay or Resurfacing
    New asphalt is laid. In some cases, this happens the same day. Other times, it's scheduled later.


Phase Description Time Estimate
Inspection & Planning Site review, depth decision 1–2 days
Milling Operations Asphalt removal Few hours to 1–2 days
Cleanup Sweeping and surface prep Same day as milling
Resurfacing Fresh asphalt overlay Same day or scheduled

Noise, Dust, and Traffic Considerations

Noise
Expect grinding sounds from the milling drum, rumbling from trucks, and beeping from machines. It's loud — but usually lasts only a day or two in each location.

Dust
Water trucks spray the drum and road to cut down airborne particles. It still gets dusty, especially on dry or windy days. Nearby cars and buildings might catch light dust.

Traffic Flow
Crews try to leave one lane open. If that's not possible, detours are set up. Flaggers guide vehicles during the day. In busy zones, work may happen at night to avoid rush hour.

Post-Milling Inspection and Surface Prep

After milling, crews don't jump straight to paving. They inspect the surface for:

  • Loose debris

  • Uncut sections

  • Damage to curbs, drains, or edges

Sweepers and sometimes vacuums come through again. The road must be clean and dry before hot mix asphalt sticks properly.

Post-Milling Task Why It Matters
Sweeping debris Prevents bumps under overlay
Final inspection Catches missed problem areas
Surface drying Ensures proper asphalt bond

Conclusion

Road milling is a smart, efficient way to remove the top layer of old or damaged pavement without tearing up the entire road. It helps fix surface problems like cracks, bumps, and drainage issues while keeping the strong base underneath in place.

This process matters because it's better for the environment, safer for drivers, and faster for construction crews. By recycling old asphalt and reducing waste, road milling supports sustainable building. It also makes roads smoother and safer, with less disruption to traffic.

If you're looking for a cost-effective, eco-friendly way to repair or upgrade pavement, road milling is a solution worth considering.

FAQ

Q: How deep can road milling go?

A: Road milling can remove anywhere from a thin surface layer (less than 1 inch with micro-milling) to several inches deep for full-depth repair, depending on project needs.

Q: Is it safe to drive on a milled road?

A: Yes, it's generally safe to drive on a milled road, though the surface may feel rough and create more tire noise until repaving is complete.

Q: How long does milling take?

A: Milling typically takes a few hours to a couple of days, depending on the road size, depth of cut, and weather conditions.

Q: Can I reuse the asphalt millings?

A: Yes, asphalt millings are recyclable and can be reused as reclaimed asphalt pavement (RAP) in new paving projects.

Q: How often should roads be milled?

A: Roads are usually milled every 10–15 years or as needed, depending on traffic wear, climate, and maintenance goals.


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