Long-Term Field Performance of Cold In-Place Recycled Roads in Iowa

Cold in-place recycling (CIR) is one of the most effective methods to rehabilitate asphalt pavements. In fact, most CIR roads have performed well at low cost in Iowa since the first CIR road was constructed in 1986. However, some CIR roads have reached failures earlier than their expected design lives because there is no design standard for designing CIR roads with a limited amount of past performance information. Some of the most prominent problems seemed to have come from selecting CIR in areas where there are poor subgrades. Therefore, it is critical to collect CIR performance data along with falling weight deflectometer (FWD) data in order to develop performance models. The main purpose of this paper is to document that effort. The performance models were developed on the basis of historical data collected from CIR roads in Iowa. First, an inventory of CIR roads was created which includes construction information, subgrade and base characteristics, and traffic levels. In consideration of pavement age,...