Characterisation of foam bitumen mixes with diffrent RAP content at elevated mixing temperature using design of experiment (DOE) approach.

Cold recycling using foam bitumen is one of the most popular rehabilitation techniques for bituminous pavements. Effect on mixing temperature reclaimed asphalt pavement (RAP) material content and foam binder content on the performance of foam bitumen mix (FBM) has been evaluated in the present study. This paper discusses the statistical approach adopted for FBM design and the development of the model consisting of three factors which are mixing temperature, foam bitumen content, and RAP material content. The experiment was designed according to the 23 factorial design using the central composite design (CCD) method and the desirability approach was adopted for determining the optimum parameter. Dry and wet indirect tensile strength parameters were considered as responses to optimise the input parameters. Results show that with increasing the mixing temperature of FBM, the performance of FBM improves at lesser binder content. The developed quadratic models using the response surface methodology (RSM) optimisation tool have higher determination coefficients for dry IDT and wet IDT indicating a good model fit between the actual and predicted values. A scanning electron microscope analysis was conducted to evaluate the impact of RAP content and mixing temperature on the dispersion of bitumen in the FBM matrix. [ABSTRACT FROM AUTHOR]