Since 1984, the Oregon State Highway Division has constructed 724 km (450 centerline miles) of cold in-place recycled pavements. During this period, an intensive study was undertaken by the Oregon Department of Transportation (ODOT) and Oregon State University (OSU) with the following purposes: 1. To develop an improved mix design procedure for cold in-place recycled pavements. 2. To evaluate the structural contribution of cold in-place recycled pavements. 3. To develop improved guidelines and specifications for the construction of cold in-place recycled pavements.
This paper summarizes the development of a mix design process and describes the early procedures used and their limitations.
The first section of the paper describes the recycling process used during the 1984–1988 period. The second part of the paper describes the evolution of the mix design process used during this period. It describes the steps needed to estimate the emulsion content from properties such as RAP gradation, residual asphalt content, and asphalt properties (penetration and viscosity). Also described are the mix design criteria developed to date (stability, modulus, etc.). The third part describes the expected ranges in strength properties (stability, modulus, etc.) for cold recycled mixes.
The last part of the paper presents significant conclusions from the work performed to date as well as recommendations for further study.