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There are few people with as much experience in Cold In-Place Recycling (CIR) as Jeff Blue. Well-known in the industry, Blue began his career as a county engineer in 1989. During his 10-year tenure in Minnesota, he had a front-row seat to the leading edge of CIR techniques, where his county, Waseca County, completed 30–40 miles of projects.
In 2004, Blue became County Engineer for the Champaign County, Illinois Highway Department, where he began leveraging CIR throughout the road network. Twenty-five years after first encountering the technique, he has become one of its most vocal champions, eager to share lessons learned.
We spoke with Jeff Blue to hear firsthand how CIR has worked for him, and what advice he would give other engineers and agencies.
Over the past 20 years, Champaign County has completed 12 CIR projects covering roughly 80–100 miles. Many of the county’s roads are built-up state routes they have inherited, with 8–12 inches of asphalt over rock or old concrete pavements.
Why does that matter? As Blue explains:
“Success with CIR starts with picking the right road.”
Blue’s team takes a rigorous approach to road assessment. They core the pavement about every half mile in both lanes to determine the layers of the road structure. The ideal candidate must have a strong sub-base—whether heavy aggregate, concrete, or asphalt—that can absorb impact and support the flexible CIR layer.
Surface condition of CH-15 in Champaign County just prior to CIR
The team also uses pavement condition index (PCI) scores to guide treatment decisions. PCI runs from 0 to 100:
If a road scores between 40 and 70 and cores confirm a solid sub-base, CIR with an asphalt overlay is the top choice.
Blue has found that a 4-inch CIR depth is the sweet spot—deep enough to break up the crack matrix without being too thick for proper compaction coming out of the screed. For the wearing course, Champaign County applies a 3-inch asphalt overlay, though some agencies prefer micro surfacing or chip seals.
4” thick CIR before rolling operation
How does CIR with an asphalt overlay compare to a standard hot mix asphalt (HMA) overlay? Blue attests that CIR adds 7–10 years to the life expectancy of a road.
Most old asphalt pavements contain deep thermal cracks that make their way up to the surface and inevitably crack the wearing course. CIR disrupts that crack matrix, turning brittle layers into a flexible interstitial asphalt layer that delays cracks from re-emerging. While a straight HMA overlay may require crack sealing within a few years, Blue reports that CIR allows him to go 6–8 years without crack sealing.
Hot In-Place Recycling (HIR) can look appealing for the same reasons as CIR: they are both cost-effective, reduce trucking, and reuse 100% of existing materials. But HIR cannot go deep enough to solve major cracking.
HIR mills only 1.5–2 inches, making it effective for rutting or shallow distress, but it ultimately yields similar results to a traditional mill-and-fill. As Blue puts it, CIR remains the more durable choice when cracking runs deep.
Champaign County partners with a local transportation infrastructure company that has tracked CIR performance from the beginning.
“The CIR pavements are performing way above the traditional deterioration curve that you see for an asphalt pavement,” Blue shares.
Where conventional pavements last about 15 years before sharp decline, Blue expects 25 years of solid performance with CIR.
Most recently, Evergreen Roadworks completed a 7.8-mile CIR project on County Highway 15 from the Village of Sidney to Vermilion County. In addition to the 4-inch CIR, this project addressed aggregate shoulders that required annual maintenance due to heavy agricultural traffic.
The solution: widen the shoulders by milling out the rock and dirt, laying recycled asphalt pavement, and pulling 15 feet wide with the CIR train to capture the full width of the expanded structure. In the process, the road was widened by 6 feet.
The road with the wearing course milled off and shoulder prepared, ready for CIR train to follow
CIR Train: water truck, asphalt truck, CIR machine, paver
“This job has gone really well for us,” says Blue. “Open Road Paving, Evergreen Roadworks—the whole group has been a very good partner for Champaign County for many years.”
Evergreen Roadworks team on CH-15 CIR job ………. Rolling the CIR mat
CIR is best understood within a broader pavement preservation strategy—maintaining pavements throughout their service life at lower cost.
In Champaign County, projects are typically seal coated with a polymer-modified emulsion 2–3 years after CIR.
“This way,” Blue says, “[the CIR pavement] will last another 8–10 years before you even have to touch the top of it.”
Waiting too long reduces effectiveness:
“If you wait until your pavement is 6–8 years old, the seal coat won’t last as long, and you won’t get the same benefit. So you might as well do it early in the pavement life so it will ride better and look better for longer.”
For agencies new to CIR, Blue recommends starting simple:
“Go out and core your roadways, see what’s there, and then develop a program. A Milwaukee Coring machine on the back of your utility truck will only cost about $1,500. And if you have a good base and a decent asphalt layer, then 100% go out there and do CIR with whatever kind of treatment you want to put on top.”
For counties without the capital to invest, Blue advises patience and planning:
“Save up your money for a couple more years and do it. You know if a pavement is in bad shape and gets a mill and overlay on it, it’s going to be in bad shape again in 10–12 years. Save your money up. Go deeper, do CIR, and get 20 years of life.”
CIR consistently pays off for Champaign County, delivering 7–10 years of added life at about a quarter of the cost of a traditional HMA overlay.
“It is a really cheap investment for the longevity that you’re going to get out of your pavements,” Blue concludes.
Ready to discuss the possibilities for your roads? We are happy to talk through your options so you can find the right treatment for the right road at the right time. Reach out today.
