LONG TERM PERFORMANCE EVALUATION OF COLD IN-PLACE RECYCLING (CIR) TECHNIQUE IN NEVADA
AdvisorHajj, Elie Y
Civil and Environmental Engineering
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Cold in-place recycling (CIR) is one of the commonly used rehabilitation technique for asphalt pavements in Nevada. Nevada Department of Transportation (NDOT) has long been using CMS-2S emulsion for CIR projects and recently has introduced Reflex emulsion and PASS emulsion for CIR. A difference in the performance of the CIR with changing emulsion technology has been observed which warranted the need for this study to assess the long-term performance of CIR pavements throughout Nevada. The long term performance of 67 CIR projects was evaluated in this study. The evaluated CIR projects were divided based on the rehabilitation type and then sub-divided based on the emulsion technology. Performances of the various projects were analyzed by individual distresses such as longitudinal cracking, fatigue cracking, transverse cracking, block cracking, roughness and rutting using NDOT's pavement management system data. In addition, overall condition of the pavement was evaluated using PCI values. A statistical approach called principal component analysis also used to evaluate the effectiveness of CIR in Nevada.The study revealed that CIR followed by a HMA overlay and a surface treatment performed much better on high volume roads than CIR with surface treatment on low volume roads. Transverse and longitudinal cracking were the two major types of distresses in CIR pavements. About 50% of the pavements constructed with HMA overlay and surface treatment and 95% of the pavements constructed with only surface treatment experienced transverse cracking during their service life. About 30% of the pavements constructed with HMA overlay and surface treatment and 70% of the pavements constructed with only surface treatment experienced longitudinal cracking. The CIR technology with HMA overlay and surface treatment significantly improved the rutting resistance and roughness of the pavement. The climatic condition, CIR layer thickness, and surface treatment types were not found to affect the performance of CIR roads. The CMS-2S projects without HMA overlay and 1.5 to 2.5 inches HMA overlay were predicted to reach a PCI value of 60 for rehabilitation 15 years after construction. The CMS-2S projects constructed with 3 to 4 inches of HMA overlay performed excellent up to 9 years and expected to last more than 20 years before rehabilitation. The CIR with CMS-2S and PASS emulsions constructed with surface treatment were predicted to reach a PCI level of 60 after 15 and 19 years, respectively. However, Reflex emulsion was predicted to be due for rehabilitation only after 6 years from construction.