New York State DOT Evaluation of Cold In-Place Recycling

By Dr. Stephen Cross

June 13, 2011

The New York State DOT, in cooperation with the NY State Energy Research and Development Authority, funded a two-year evaluation of cold in-place recycled pavements in New York. The study was completed by Chesner Engineering, P.C. of Long Beach, NY.

The study was composed of six tasks or deliverables that consisted of: 1) a literature review, 2) a survey of state practice, 3) development of a data base of CIR projects in NY, 4) a comparative assessment of CIR field performance compared to other maintenance options and an environmental life cycle analysis of CIR compared to other maintenance options, 5) analysis of CIR service life, and 6) a final report consisting of a summary of the tasks and a Best Practice Guideline. The reports are available on the NYSDOT web page.

The authors of the study presented their findings on CIR service life at the 89th Annual Meeting of the Transportation Research Board in January. The paper is scheduled for publication in the Journal of TRB.

The authors reported on performance data in the form of serviceability ratings (SR) obtained from the NYSDOT Highway Sufficiency Ratings Database. The SR scale is a 10 to 1 point scale with 10 indicating the best condition and 6 indicating corrective action is required. The data was from 163 CIR projects constructed between 1992 and 2008. The authors evaluated the data to determine what factors affected CIR service life, measured as the time in years to an SR of 6. Factors evaluated included traffic measured in AADT and ESALs, base thickness, subbase thickness and total base plus subbase thickness, region and condition prior to CIR rehabilitation.

Significant findings included:

  1. CIR in NY had an average service life of 11years.       
  2. CIR pavements constructed with thicker pavement base, base plus subbase and total pavement thickness exceeded the average service life by 2-4 years.
  3. CIR pavements subjected to higher AADT and higher truck traffic exceeded the average service life by 2-3 years.
  4. Environment and climate did not significantly affect the expected service of CIR pavements.
  5. The service life of pavements that were rehabilitated with CIR prior to severe deterioration (SR ≥ 6.5) was approximately 50 percent longer than CIR rehabilitated pavements with severe pavement deterioration (SR< 6.5).

Major conclusions included:

  • When CIR is used on better-designed pavements that have thicker supporting bases and subbases, CIPR performance will benefit and the service life of the pavement will be extended. This could significantly expand the locations that CIPR can be employed.
  • When CIPR is used on poorly supported pavements the service life of the pavement can be expected to decrease.
  • When pavement rehabilitation is implemented prior to severe pavement deterioration the service life of the pavement can be expected to increase.
  •  It is also concluded that a general policy of employing CIPR as a rehabilitation strategy on low AADT and lightly traveled pavements with low truck traffic may be misleading. The data generated in the study tends to support the opposite conclusion. CIPR pavements last longer if applied on pavements with higher AADT and higher levels of truck traffic. It is concluded, however, that the primary factor is not traffic but the pavement support structure. Higher trafficked pavements tend to be designed with greater base and subbase thickness, thereby providing enhanced support to the CIPR section, which increases the service life of the pavement.

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