CIR vs. FDR vs. Cold Milling: How to Choose a Recycling Method

Mon October 20, 2025
Dennis Howard — Special to CEG

Grit isn't just a trait of most people in the roadbuilding industry, but also the texture of one of the most recycled materials in the world: asphalt.

In a year when "doing more with less" has become the rule rather than the exception, contractors are watching building costs more closely than ever. Dennis Howard of RDO Equipment Co. spoke with emerging leaders in the asphalt industry to learn how today's machines are reclaiming and renewing old roads — transforming yesterday's infrastructure into tomorrow's foundation.

"Asphalt recycling is like rebuilding a road with its original grit and DNA," said Jessie Boone, Wirtgen Group's market development manager of recycling products. "Some machines and processes, like cold in-place recycling (CIR) or full depth reclamation or paver laid recycling, can reuse existing materials, reinforce the surface and put it to work without hauling in new resources."

Bonne and Casey Bovkoon, general manager of Allstates Pavement Recycling and Stabilization, both agree that asphalt recycling can significantly increase efficiency without increasing overall project costs while reducing impacts to traffic.

"With a single W 380 CRi (cold recycler) our team has been able to increase efficiency and quickly re-use asphalt in the urban area projects in Minnesota," Bovkoon said. "We've focused on partnering with equipment providers like RDO Equipment Co. to ensure that we have the right equipment and training to create new base materials to be paved on."

Bovkoon explained that the Allstates team works on projects from Minnesota to Texas and relies on support from RDO from the Midwest to southern Texas to Utah

"When we partner with agencies like a state or county's DOT and work together to provide the best solution for each individual project," he said "Weather its CIR, asphalt milling, soil stabilization or full depth reclamation (FDR), Allstates has a solution to solve any base issue."

Bovkoon explains that different states may specify what they'd prefer in the bidding process. He further defines some of the work his team specializes in:

• Asphalt milling: Removes the top layer of asphalt to smooth imperfections or recycle it for new pavement.

• Full depth reclamation (FDR): Pulverizes the existing road surface to create a new base layer.

• Soil stabilization: Mixes in additives like cement or lime to alter soil to enhance its physical strength.

Contractors like Allstates understand that asphalt usually still retains its resilient fighting spirit. And with the many ways to grind it up and mix materials before laying it back down, we in industry can build stronger roads ready to handle the weight of busy traffic. Let's take a closer look at each cold milling, CIR and FDR application process.

Cold Milling Vs. CIR Vs. FDR

Cold milling and cold recycling serve very different purposes but are sometimes referred to interchangeably. Cold milling, also known as asphalt milling, is a surface-level process that removes the top layer of asphalt using a milling machine. As a "mill and fill operation," where the milled surface is overlaid with new asphalt, cold milling is ideal when the underlying base is still structurally sound.

Cold Milling's Key Characteristics:

• Depth: 1-4 inches.

• Purpose: Prepares surface for overlays, corrects profile and drainage.

• Output: Reclaimed Asphalt Pavement (RAP), which can be reused.

• Best for: Roads with surface distress but stable subgrade.

"Cold milling can be great option to quickly resurface roads," Boone said. "Although, it can act as a ‘Band Aid' if an underlying issue like a subgrade failure isn't addressed."

CIR, or cold in-place recycling, involves milling the existing asphalt layer up to 6 in. and then reusing all that material on site. DOT engineers and contractors may opt for CIR when the top asphalt layer has reached the end of its life but its underlying base remains intact. Ideal for roads with surface cracking that does not extend to its subgrade layer, CIR mills the existing asphalt layer, then mixes it with stabilizers like applies in emulsion or foamed format before laying it back down.

Cold In-Place Recycling's Key Characteristics:

• Depth: 3-6 in. (asphalt layer only).

• Stabilizers: Asphalt emulsion or foamed asphalt which are sometimes coupled with an active filler like cement or lime.

• Equipment: Reclaimer/stabilizer (e.g., Vögele S2100-2 for example), high-density paver.

• Best for: Roads with surface cracking that hasn't penetrated the base.

Boone said CIR is gaining popularity among DOTs due to its reduced hauling costs and potential environmental benefits. For rural roads, when asphalt plants and aggregate sources are far apart, CIR can be especially effective. Some states' DOTs like California or Viriginia could be especially interested in CIR to reduce RAP stockpiles.

FDR revitalizes a road's structural base and can be used when the subgrade layer has failed. FDR pulverizes the entire pavement structure and blends it with stabilizers to create a new, stronger base.

FDR's Key Characteristics:

• Depth: Six to 14 in., but can achieve a thicker depth with proper equipment and expertise.

• Stabilizers: Cement, lime or asphalt emulsion.

• Variants: Traditional FDR or Paver-Laid FDR using high-density pavers.

• Best for: Roads with deep structural issues.

"FDR allows contractors to address the ‘mashed potatoes' under a road's asphalt," Boone said. "FDR can create a longer-lasting solution by addressing pavement's root causes of deterioration."

FDR can extend the life of the road significantly and reduce the need for repeated mill-and-fill cycles. Boone shared that some are opting for Paver Laid FDR, a recently developed method that uses a high-density paver instead of grader and pad foot roller to create a single-pass operation, eliminating the need for more compaction passes.

How to Choose Right Method

DOT engineers and contractors always begin with a thorough analysis of pavement conditions, including core sampling and deflectometer testing. When the asphalt layer's damage is minimal, CIR might be best, but when structural issues exist, FDR may be necessary.

Bonne explained mill and fill operations are used more often than CIR or FDR. Although she expects CIR, FDR or Paver Laid FDR, to grow in popularity in the coming years.

"When we all can understand the differences among cold milling, CIR and FDR, we can work together to make smarter decisions," Boone said. "DOT engineers, county planners or contractors know that they will get better results when a failing road's root cause is treated and not just the symptoms."

For more information, visit ColdRecyclingInfo.com.

*Article reprinted with permission of RDO Equipment Co. Dennis Howard is the senior vice president of roadbuilding and materials of RDO Equipment Co.