Incorporating CIR Into Your
Pavement Management Program

If your most common pavement maintenance tactics are mill/fill or full reconstruction, single pass CIR (partial depth) is a maintenance tactic that can help you drive savings over a 40 year Life Cycle Assessment when compared to mill/fill or full reconstruction.

  • CIR fits into your pavement management program where a mill and overlay method won’t provide enough asphalt base repair and you can avoid doing a full depth reclamation or full road replacement.

  • CIR candidates are those in the middle to later part of their product life or have a Pavement Condition Index rating of 60 or lower.

  • CIR is a rehabilitation methodology that can provide 20+ years of service life or more to your roads and reduce whole-life total cost.

  • Resulting structural coefficients from CIR range from 0.20 to 0.44 with 0.30 being the representative value (although higher values are reported, but not published).

  • When your mill and overlay project plan is expected to include an asphalt base repair contingency of 15% or higher, CIR should be considered

Data above are from Specialized Construction Incorporated own observations and experience and “Energy, Emissions, Material Conservation, and Prices Associated with Construction, Rehabilitation, and Material Alternatives for Flexible Pavement”, Robinette and Epps, 2010.

Overview of How a CIR Project Comes to Life

  • Step 0. Identify Candidates

    Ideal candidates are roads aging from 7 to 15+ years or a PCI of 60 or less. Candidates should require more structural improvement than an additional mill/fill. but not require a full reconstruction.

    Consider using CIR on roads where you plan to use a 3” mill/fill and your model includes an asphalt base repair contingency of greater than 15%.

    Candidates can include curbs and gutters, but should not include Portland cement concrete base.

    Sub-base issues will not be corrected with CIR.

  • Step 1. Test

    CIR requires a minimum of 3 - 4 inches of bituminous material in the asphalt base. Therefore, it is critical to perform core testing to confirm the nature of the asphalt base, unless you have strong historical documentation that indicates the asphalt base meets all CIR requirements.

    An experienced contractor can help you navigate this process and ensure testing costs are only spent on roads with a very high probability of being a viable CIR candidate.

  • Step 2. Design

    The mix design should be co-created by the testing lab and the contractor. It is important the contractor take the lead to provide historical evidence and perspective on what will work best with the machinery and the road candidate.

    Labs providing mix designs must be ODOT Level 2 Technician certified.

  • Step 3. Prep

    The recycling process usually generates a 1” to 1.5” lift in the recycled mat. This means an elevation milling may need to occur to ensure the final product matches curb, gutter and concrete apron elevations.

    Even with elevation milling, CIR projects can still provide a better ROI on investment for candidates where your base repair contingency is greater than 15%.

  • Step 4. Recycle

    Recycling occurs at the rate of 12 to 15 foot per minute and is drivable immediately after compaction. The recycling occurs in a single pass of the machine.

    A pneumatic roller and vibratory steel drum roller is used to achieve desired density growth curves.

  • Step 5. Cure

    The recycled mat undergoes a curing process and requires some time to reach peak ruggedness. Current practice in Ohio is to monitor density and moisture content or simply wait up to 2 weeks prior to application of the final overlay.

    Two new testing standards have been proposed by AASHTO to test for ruggedness beyond density and moisture. This is ultimately expected to shorten the wait times for full cure.

    Refer to NCHRP Research Report 960: Proposed AASHTO Practice and Tests for Process Control and Product Acceptance of Asphalt-Treated Cold Recycled Pavements.

  • Step 6. Overlay

    A cured recycled mat can be treated with any common wearing course. Common applications include a single lift of HMA or chip and seal.