Is cold in-place recycling (CIR) the same as cold central plant recycling (CCPR)?

No. CIR refers to recycling the existing road in-place, adding ingredients in-place to achieve the mix design, screeding the material back in-place for compaction and to make ready for a final wearing course such as HMA, CCPR asphalt, or chip and seal.

CCPR, is the process of using a plant to create asphalt from recycled material at a cooler temperature which is then transported to the jobsite or laydown area. CCPR asphalt mix could be used for a final overlay on a CIR project or as a substitute for HMA, providing it achieves final design.

How do I select candidates for cold in-place recycling?

In general, cold in-place recycling is a rehabilitation method that should be used for roads where you expect asphalt base failure rates across more than 13% - 15% of the road. Single pass cold in-place recycling should be used in your portfolio where a 2 to 4 inch mill/fill would not be sufficient, but you don’t require a full depth asphalt base repair.

How do I select a contractor for cold in-place recycling?

The current leader in cold in-place rehabilitation is Specialized Construction Incorporated from Cuyahoga Heights, Ohio. They have been using cold in-place recycling successfully in the Midwest since 1998. Cold in-place recycling requires special equipment and know-how to ensure the best outcomes for your taxpayers. Find an agency that has used cold in-place recycling and ask for their perspectives or call Specialized Construction for an educational overview and case studies.

Can cold in-place recycling be used on roads with curbs and gutters?

Yes. Curbs and gutters are acceptable, but you will need to do an elevation milling prior to the recycling to compensate for the 1 to 1.5 inch of lift that will occur with the asphalt base from recycling. The single pass recycling machine can also do cul de sacs in suburban developments, however, as the number of cul de sacs increases per linear foot of roadway, so will the labor costs. An experienced contractor can quickly assess whether the frequency of cul de sacs on your road make it a candidate for CIR.

Must core testing occur on every candidate prior to using cold in-place recycling?

Yes, unless you have very strong documentation from previous testing and work performed which indicate the minimum requirements are met. Viable road candidates include an asphalt base with bituminous material of at least 3 to 4 inches. An experienced contractor can help you ensure road candidates selected have a high probability of remaining a viable candidate after testing results are received.

If testing is conducted before the project bid is awarded how should testing be handled?

Common practice is for the agency to issue a PO to a CIR contractor to coordinate testing with an independent lab. These costs typically do not exceed a few thousand dollars ($1,000 to $3,000 as of March 2022). The initial testing objective is to confirm the road candidate meets minimum requirements not to finalize the mix design. The mix design can be finalized at a later date, once the bid is awarded. Again, if you have sufficient documented evidence about the asphalt base of the road, testing may not be necessary.

How should I budget for cold in-place recycling?

You should plan to invest slightly higher costs, but add several years of life by using CIR. In 2021, typical market costs for Ohio CIR projects of less than 2 miles were around $14 to $16 per square yard, $13 to $14 per square yard when projects are greater than 2 miles but less than 5 and $10 to $13 per square yard for projects greater than 5 miles. You will also be able to significantly reduce your asphalt base repair contingency as compared to mill and overlay budgeting since CIR rehabilitates a higher portion of the asphalt base. You can also add a significant amount of asset life (7 to 15 years or more) which in turn, decreases the whole-life asset cost. For more on service life for CIR refer to “Energy, Emissions, Material Conservation, and Prices Associated with Construction, Rehabilitation, and Material Alternatives for Flexible Pavement, Robinette and Epps, 2010.”

Is a carbon neutral project really economical or is it just hype?

It is truly economical. Carbon neutrality works well for single pass cold in-place recycling because of how it simplifies the construction process. Because the asphalt is being recycled, the amount of trucks hauling material in or out is significantly reduced. This is true even if you add aggregate to improve the coefficient of the asphalt base. Credits for a metric tonne CO2 equivalent (MTCO2e) can be purchase for around $16 (as of February 2022) and offset burning approximately 89.1 gallons of diesel. Given the low amount of fuel consumed on a CIR project compared to traditional mill and fill projects (due to the significant reduction in hauling and production of asphalt base) carbon neutrality is within reach.

Can you help me understand the curing process for the recycled mat?

The recycled mat requires a curing period to achieve the design intent for the material structure properties. Traditional approaches to the curing include testing for density and water content or simply waiting a few days to 2 weeks for the curing process to complete. A proven, common practice in Northeast Ohio is to open the road to traffic immediately, but wait 2 weeks before applying the final surface treatment. For more information refer to “NCHRP Research Report 960, Proposed AASHTO Practice and Tests for Process Control and Product Acceptance of Asphalt-Treated Cold Recycled Pavements, Diefenderfer et al, 2021.”

Will the recycled mat have loose material that causes problems for drivers?

The recycled mat is drivable immediately after compaction during the cure time and prior to application of final overlay. It is common for drivers to assume the recycled mat is the final road surface given its look and feel compared the road prior to rehabilitation. The occurrence of loose material remaining on the recycled mat which causes problems for drivers has a low probability, based on experience. You can ask the contractor to vacuum and sweep the mat to reduce any loose fines or pieces of aggregate, however, this is not commonly used in Ohio. You may also have a light fog seal applied.

Can roads with a Portland cement concrete base be recycled with single pass machines?

Typically no - not yet, at least. However, if small amounts of cementitious materials such as lime or fly ash were added to an asphalt concrete base for rigidity, a single machine recycler remains appropriate.