Evaluation of Long-term Performance of Cold In-Place Recycling Pavements in Nevada
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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 solvent free (ReflexTM) emulsion and polymer-modified (PASS) emulsion for CIR. The long-term performances of 67 CIR projects were evaluated in this study. The evaluated CIR projects were divided based on the rehabilitation type and further sub-divided based on the emulsion technology. The performance 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 (PMS) data. In addition, the overall condition of the pavement was evaluated using the pavement condition index (PCI) values calculated from NDOT PMS measurements. The study revealed that CIR followed by a hot mix asphalt (HMA) overlay and a surface treatment performed much better on high volume roads than CIR with a 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 environment variations within the state, the CIR layer thickness, and the surface treatment types were not found to affect the performance of the evaluated 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, 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 constructed with surface treatment were predicted to reach a PCI level of 60 after 15 and 19 years, respectively. However, the CIR projects with Reflex were predicted to be due for rehabilitation only after 10 years from construction.