USE OF ASPHALT EMULSIONS FOR IN-PLACE RECYCLING: OREGON EXPERIENCE

An overview of the use of emulsified asphalts for cold in-place recycling (CIR) of asphalt pavements by the Oregon Department of Transportation (ODOT) is presented. Project selection, design, construction, and inspection considerations are presented. ODOT has successfully used both CMS-2S (now called CMS-2RA) and high-float emulsions for recycling. Typical projects have been recycled to depths of 2 to 4 in. followed by either a chip seal or an open-graded emulsion mix. A brief overview of the CIR process is followed by a discussion of project selection--where to use and where not to use CIR. Procedures for estimating required water and emulsion additions to recycled asphalt pavement are presented. Procedures for field adjustments of emulsion and water content and for proper compaction of CIR pavements are presented. Finally, a discussion of problems experienced and appropriate preventive and remedial measures is presented. Significant findings include the following: (a) careful project selection is important to CIR project success; (b) the maintenance of proper proportions of emulsion and mix water is the biggest challenge in the field (the estimation procedure presented provides a good starting point and the discussion of construction control provides criteria for adjustments to meet changing field conditions); and (c) excess moisture from construction must be allowed to leave the mat before sealing, which should take place before winter conditions.