The Essential Guide to Understanding Millings in Construction and Roadwork

Millings play a crucial role in construction and roadwork projects, yet many people outside the industry may not fully understand what they are or why they matter. This guide breaks down the basics of millings, how they are used, and why they are an important part of maintaining and building roads and other surfaces.

Freshly milled asphalt surface on a city road

What Are Millings?

Millings refer to the material that results from grinding or removing the top layer of asphalt or concrete from a road or pavement surface. This process is often called cold planing or pavement milling. The machine used for this task scrapes off the old surface, creating a rough texture that can be reused or disposed of.

Millings consist mainly of crushed asphalt pieces mixed with some aggregate and fines. They vary in size and quality depending on the milling depth and the condition of the original pavement.

Why Are Millings Important?

Millings serve several purposes in construction and roadwork:

• Recycling material: Instead of discarding old asphalt, millings can be reused in new pavement layers or as base material. This reduces waste and lowers costs.

• Surface preparation: Milling removes damaged or uneven pavement, creating a clean, textured surface for new asphalt to bond properly.

• Improving road safety: Milling can restore proper road profiles, improve drainage, and reduce surface irregularities that cause hazards.

• Cost efficiency: Using millings reduces the need for new raw materials and speeds up construction by recycling on-site materials.

  
  

How Are Millings Created?

The milling process involves specialized equipment called milling machines or cold planers. These machines have rotating drums fitted with sharp teeth that grind the pavement surface. The depth of milling can be adjusted depending on the project needs, typically ranging from a few millimeters to several inches.

The removed material is collected by conveyors and loaded into trucks for transport. Depending on the project, millings may be taken to a recycling plant or reused directly on-site.

Common Uses of Millings in Roadwork

Millings have versatile applications in construction and road maintenance:

• Base layers for new roads: Millings can be compacted to form a stable base layer before laying fresh asphalt.

• Temporary road surfaces: In some cases, millings are spread and compacted to create temporary driving surfaces during construction.

• Driveways and parking lots: Millings provide a cost-effective and durable surface option for private driveways and parking areas.

• Pothole and crack repair: Mixed with binders, millings can be used to patch damaged pavement sections.

• Shoulder and trail surfaces: Millings offer a firm, permeable surface for road shoulders and walking trails.

  
  

Benefits of Using Millings

Using millings offers several advantages for contractors and municipalities:

• Environmental impact: Recycling asphalt reduces the demand for new materials and lowers landfill waste.

• Cost savings: Millings are often less expensive than new asphalt or concrete.

• Durability: When properly compacted and maintained, millings provide a long-lasting surface.

• Quick installation: Millings can be laid and compacted faster than traditional paving materials.

• Flexibility: They can be used in various applications, from base layers to finished surfaces.

  
  

Challenges and Considerations

While millings are valuable, there are some challenges to keep in mind:

• Quality control: The condition of millings depends on the original pavement and milling process. Poor-quality millings may contain contaminants or excessive fines.

• Compaction requirements: Proper compaction is essential to avoid loose surfaces and ensure durability.

• Surface texture: Millings may create a rougher surface compared to new asphalt, which can affect ride comfort.

• Weather sensitivity: Millings can be sensitive to moisture during installation and may require proper drainage.

  
  

Best Practices for Working with Millings

To get the most out of millings, follow these guidelines:

• Inspect millings before use: Check for contaminants and particle size distribution.

• Control moisture: Keep millings dry during storage and apply water as needed during compaction.

• Use proper equipment: Employ rollers and compactors suitable for millings.

• Apply binders if needed: For some applications, adding asphalt emulsion or other binders improves stability.

• Plan for drainage: Ensure the surface has adequate slope to prevent water pooling.

  
  

Real-World Example

A city in the Midwest faced frequent potholes and pavement deterioration on its residential streets. Instead of full reconstruction, the public works department chose to mill the existing asphalt and reuse the millings as a base layer topped with a thin asphalt overlay. This approach saved the city over 30% in costs and reduced construction time by several weeks. The streets now have improved durability and smoother surfaces, demonstrating the practical benefits of millings.