Cold In-Place Recycling in Nevada

Abstract

The Nevada Department of Transportation has long used CMS-2S emulsion for cold in-place recycling (CIR) projects and has recently introduced solvent-free (Reflex) emulsion and polymerized asphalt surface sealer (PASS) emulsion. An observed difference in CIR performance with changing emulsion technology prompted the assessment of long-term performance of CIR pavements throughout Nevada. The evaluated CIR projects were divided on the basis of rehabilitation type and then subdivided on the basis of emulsion technology. 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 did CIR with surface treatment on low-volume roads. Transverse and longitudinal cracking were the major types of distresses in CIR pavements. Approximately 50% of pavements constructed with HMA overlay and surface treatment and 95% of pavements constructed with only surface treatment experienced transverse cracking during service life. About 30% of pavements constructed with HMA overlay and surface treatment and 70% of pavements constructed with only surface treatment experienced longitudinal cracking. The CIR technology with HMA overlay and surface treatment significantly improved rutting resistance and pavement roughness. Climatic condition, CIR layer thickness, and surface treatment types were found not to affect performance of roads with CIR. The CMS-2S projects constructed with surface treatment and 1.5- to 2.5-in. HMA overlay were predicted to reach a pavement condition index value of 60 for rehabilitation in 15 years. The CMS-2S projects constructed with 3 to 4 in. of HMA overlay performed excellently up to 9 years and were 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 the index value of 60 after 15 and 19 years, respectively. However, Reflex emulsion was predicted to need rehabilitation after only 6 years.