Dynamic Modulus and Repeated Load Tests of Cold In-Place Recycling Mixtures Using Foamed Asphalt
As part of the validation effort to evaluate the consistency of a new cold in-place recycling using foamed asphalt (CIR — foam) mix design process for the Iowa Department of Transportation, the dynamic modulus and repeated load tests were conducted to evaluate the performance characteristics of CIR — foam mixtures over a wide range of loading and temperature conditions. The main objective of this research is to study the impacts of the foamed asphalt contents and reclaimed asphalt pavement (RAP) material characteristics on dynamic modulus and flow number.
Dynamic modulus and repeated load tests were conducted on CIR — foam mixtures with RAP materials collected from seven different CIR project sites located throughout Iowa. Dynamic modulus values of the RAP materials varied depending on the sources and foamed asphalt contents. Coarse RAP materials with a small amount of residual asphalt content exhibited a higher modulus value at 4.4°C but exhibited a lower dynamic modulus value at 37.8°C than fine RAP materials with a large amount of residual asphalt content. Flow numbers were varied significantly depending on their RAP sources and foamed asphalt contents. Fine RAP materials with a hard residual asphalt binder exhibited a higher flow number than coarse RAP materials with a soft residual binder.
The relative rankings of RAP materials in terms of the flow number did not change when the foamed asphalt was increased from 1.0 to 3.0%, which supports the repeated load test being consistent in evaluating a rutting potential of RAP materials.